text: // This is an open source non-commercial project. Dear PVS-Studio, please check
  // it. PVS-Studio Static Code Analyzer for C, C++ and C#: http://www.viva64.com
  
  /*
   * eval.c: Expression evaluation.
   */
  
  #include <math.h>
  
  #ifdef HAVE_LOCALE_H
  # include <locale.h>
  #endif
  
  #include "nvim/ascii.h"
  #include "nvim/buffer.h"
  #include "nvim/change.h"
  #include "nvim/channel.h"
  #include "nvim/charset.h"
  #include "nvim/cursor.h"
  #include "nvim/edit.h"
  #include "nvim/eval/userfunc.h"
  #include "nvim/eval.h"
  #include "nvim/eval/encode.h"
  #include "nvim/eval/executor.h"
  #include "nvim/eval/gc.h"
  #include "nvim/eval/typval.h"
  #include "nvim/ex_cmds2.h"
  #include "nvim/ex_docmd.h"
  #include "nvim/ex_getln.h"
  #include "nvim/ex_session.h"
  #include "nvim/fileio.h"
  #include "nvim/getchar.h"
  #include "nvim/lua/executor.h"
  #include "nvim/mark.h"
  #include "nvim/memline.h"
  #include "nvim/misc1.h"
  #include "nvim/move.h"
  #include "nvim/ops.h"
  #include "nvim/option.h"
  #include "nvim/os/input.h"
  #include "nvim/os/os.h"
  #include "nvim/os/shell.h"
  #include "nvim/path.h"
  #include "nvim/quickfix.h"
  #include "nvim/regexp.h"
  #include "nvim/screen.h"
  #include "nvim/search.h"
  #include "nvim/sign.h"
  #include "nvim/syntax.h"
  #include "nvim/ui.h"
  #include "nvim/undo.h"
  #include "nvim/version.h"
  #include "nvim/window.h"
  
  
  // TODO(ZyX-I): Remove DICT_MAXNEST, make users be non-recursive instead
  
  #define DICT_MAXNEST 100        // maximum nesting of lists and dicts
  
  
  static char *e_letunexp = N_("E18: Unexpected characters in :let");
  static char *e_missbrac = N_("E111: Missing ']'");
  static char *e_dictrange = N_("E719: Cannot use [:] with a Dictionary");
  static char *e_illvar = N_("E461: Illegal variable name: %s");
  static char *e_cannot_mod = N_("E995: Cannot modify existing variable");
  static char *e_invalwindow = N_("E957: Invalid window number");
  
  // TODO(ZyX-I): move to eval/executor
  static char *e_letwrong = N_("E734: Wrong variable type for %s=");
  
  static char_u * const namespace_char = (char_u *)"abglstvw";
  
  /// Variable used for g:
  static ScopeDictDictItem globvars_var;
  
  /// g: value
  #define globvarht globvardict.dv_hashtab
  
  /*
   * Old Vim variables such as "v:version" are also available without the "v:".
   * Also in functions.  We need a special hashtable for them.
   */
  static hashtab_T compat_hashtab;
  
  /// Used for checking if local variables or arguments used in a lambda.
  bool *eval_lavars_used = NULL;
  
  /*
   * Array to hold the hashtab with variables local to each sourced script.
   * Each item holds a variable (nameless) that points to the dict_T.
   */
  typedef struct {
    ScopeDictDictItem sv_var;
    dict_T sv_dict;
  } scriptvar_T;
  
  static garray_T ga_scripts = {0, 0, sizeof(scriptvar_T *), 4, NULL};
  #define SCRIPT_SV(id) (((scriptvar_T **)ga_scripts.ga_data)[(id) - 1])
  #define SCRIPT_VARS(id) (SCRIPT_SV(id)->sv_dict.dv_hashtab)
  
  static int echo_attr = 0;   // attributes used for ":echo"
  
  // The names of packages that once were loaded are remembered.
  static garray_T ga_loaded = { 0, 0, sizeof(char_u *), 4, NULL };
  
  /*
   * Info used by a ":for" loop.
   */
  typedef struct {
    int fi_semicolon;             // TRUE if ending in '; var]'
    int fi_varcount;              // nr of variables in the list
    listwatch_T fi_lw;            // keep an eye on the item used.
    list_T      *fi_list;         // list being used
  } forinfo_T;
  
  // values for vv_flags:
  #define VV_COMPAT       1       // compatible, also used without "v:"
  #define VV_RO           2       // read-only
  #define VV_RO_SBX       4       // read-only in the sandbox
  
  #define VV(idx, name, type, flags) \
    [idx] = { \
      .vv_name = name, \
      .vv_di = { \
        .di_tv = { .v_type = type }, \
        .di_flags = 0, \
        .di_key = { 0 }, \
      }, \
      .vv_flags = flags, \
    }
  
  // Array to hold the value of v: variables.
  // The value is in a dictitem, so that it can also be used in the v: scope.
  // The reason to use this table anyway is for very quick access to the
  // variables with the VV_ defines.
  static struct vimvar {
    char        *vv_name;  ///< Name of the variable, without v:.
    TV_DICTITEM_STRUCT(17) vv_di;  ///< Value and name for key (max 16 chars).
    char vv_flags;  ///< Flags: #VV_COMPAT, #VV_RO, #VV_RO_SBX.
  } vimvars[] =
  {
    // VV_ tails differing from upcased string literals:
    // VV_CC_FROM "charconvert_from"
    // VV_CC_TO "charconvert_to"
    // VV_SEND_SERVER "servername"
    // VV_REG "register"
    // VV_OP "operator"
    VV(VV_COUNT,          "count",            VAR_NUMBER, VV_RO),
    VV(VV_COUNT1,         "count1",           VAR_NUMBER, VV_RO),
    VV(VV_PREVCOUNT,      "prevcount",        VAR_NUMBER, VV_RO),
    VV(VV_ERRMSG,         "errmsg",           VAR_STRING, 0),
    VV(VV_WARNINGMSG,     "warningmsg",       VAR_STRING, 0),
    VV(VV_STATUSMSG,      "statusmsg",        VAR_STRING, 0),
    VV(VV_SHELL_ERROR,    "shell_error",      VAR_NUMBER, VV_RO),
    VV(VV_THIS_SESSION,   "this_session",     VAR_STRING, 0),
    VV(VV_VERSION,        "version",          VAR_NUMBER, VV_COMPAT+VV_RO),
    VV(VV_LNUM,           "lnum",             VAR_NUMBER, VV_RO_SBX),
    VV(VV_TERMRESPONSE,   "termresponse",     VAR_STRING, VV_RO),
    VV(VV_FNAME,          "fname",            VAR_STRING, VV_RO),
    VV(VV_LANG,           "lang",             VAR_STRING, VV_RO),
    VV(VV_LC_TIME,        "lc_time",          VAR_STRING, VV_RO),
    VV(VV_CTYPE,          "ctype",            VAR_STRING, VV_RO),
    VV(VV_CC_FROM,        "charconvert_from", VAR_STRING, VV_RO),
    VV(VV_CC_TO,          "charconvert_to",   VAR_STRING, VV_RO),
    VV(VV_FNAME_IN,       "fname_in",         VAR_STRING, VV_RO),
    VV(VV_FNAME_OUT,      "fname_out",        VAR_STRING, VV_RO),
    VV(VV_FNAME_NEW,      "fname_new",        VAR_STRING, VV_RO),
    VV(VV_FNAME_DIFF,     "fname_diff",       VAR_STRING, VV_RO),
    VV(VV_CMDARG,         "cmdarg",           VAR_STRING, VV_RO),
    VV(VV_FOLDSTART,      "foldstart",        VAR_NUMBER, VV_RO_SBX),
    VV(VV_FOLDEND,        "foldend",          VAR_NUMBER, VV_RO_SBX),
    VV(VV_FOLDDASHES,     "folddashes",       VAR_STRING, VV_RO_SBX),
    VV(VV_FOLDLEVEL,      "foldlevel",        VAR_NUMBER, VV_RO_SBX),
    VV(VV_PROGNAME,       "progname",         VAR_STRING, VV_RO),
    VV(VV_SEND_SERVER,    "servername",       VAR_STRING, VV_RO),
    VV(VV_DYING,          "dying",            VAR_NUMBER, VV_RO),
    VV(VV_EXCEPTION,      "exception",        VAR_STRING, VV_RO),
    VV(VV_THROWPOINT,     "throwpoint",       VAR_STRING, VV_RO),
    VV(VV_STDERR,         "stderr",           VAR_NUMBER, VV_RO),
    VV(VV_REG,            "register",         VAR_STRING, VV_RO),
    VV(VV_CMDBANG,        "cmdbang",          VAR_NUMBER, VV_RO),
    VV(VV_INSERTMODE,     "insertmode",       VAR_STRING, VV_RO),
    VV(VV_VAL,            "val",              VAR_UNKNOWN, VV_RO),
    VV(VV_KEY,            "key",              VAR_UNKNOWN, VV_RO),
    VV(VV_PROFILING,      "profiling",        VAR_NUMBER, VV_RO),
    VV(VV_FCS_REASON,     "fcs_reason",       VAR_STRING, VV_RO),
    VV(VV_FCS_CHOICE,     "fcs_choice",       VAR_STRING, 0),
    VV(VV_BEVAL_BUFNR,    "beval_bufnr",      VAR_NUMBER, VV_RO),
    VV(VV_BEVAL_WINNR,    "beval_winnr",      VAR_NUMBER, VV_RO),
    VV(VV_BEVAL_WINID,    "beval_winid",      VAR_NUMBER, VV_RO),
    VV(VV_BEVAL_LNUM,     "beval_lnum",       VAR_NUMBER, VV_RO),
    VV(VV_BEVAL_COL,      "beval_col",        VAR_NUMBER, VV_RO),
    VV(VV_BEVAL_TEXT,     "beval_text",       VAR_STRING, VV_RO),
    VV(VV_SCROLLSTART,    "scrollstart",      VAR_STRING, 0),
    VV(VV_SWAPNAME,       "swapname",         VAR_STRING, VV_RO),
    VV(VV_SWAPCHOICE,     "swapchoice",       VAR_STRING, 0),
    VV(VV_SWAPCOMMAND,    "swapcommand",      VAR_STRING, VV_RO),
    VV(VV_CHAR,           "char",             VAR_STRING, 0),
    VV(VV_MOUSE_WIN,      "mouse_win",        VAR_NUMBER, 0),
    VV(VV_MOUSE_WINID,    "mouse_winid",      VAR_NUMBER, 0),
    VV(VV_MOUSE_LNUM,     "mouse_lnum",       VAR_NUMBER, 0),
    VV(VV_MOUSE_COL,      "mouse_col",        VAR_NUMBER, 0),
    VV(VV_OP,             "operator",         VAR_STRING, VV_RO),
    VV(VV_SEARCHFORWARD,  "searchforward",    VAR_NUMBER, 0),
    VV(VV_HLSEARCH,       "hlsearch",         VAR_NUMBER, 0),
    VV(VV_OLDFILES,       "oldfiles",         VAR_LIST, 0),
    VV(VV_WINDOWID,       "windowid",         VAR_NUMBER, VV_RO_SBX),
    VV(VV_PROGPATH,       "progpath",         VAR_STRING, VV_RO),
    VV(VV_COMPLETED_ITEM, "completed_item",   VAR_DICT, VV_RO),
    VV(VV_OPTION_NEW,     "option_new",       VAR_STRING, VV_RO),
    VV(VV_OPTION_OLD,     "option_old",       VAR_STRING, VV_RO),
    VV(VV_OPTION_TYPE,    "option_type",      VAR_STRING, VV_RO),
    VV(VV_ERRORS,         "errors",           VAR_LIST, 0),
    VV(VV_MSGPACK_TYPES,  "msgpack_types",    VAR_DICT, VV_RO),
    VV(VV_EVENT,          "event",            VAR_DICT, VV_RO),
    VV(VV_FALSE,          "false",            VAR_BOOL, VV_RO),
    VV(VV_TRUE,           "true",             VAR_BOOL, VV_RO),
    VV(VV_NULL,           "null",             VAR_SPECIAL, VV_RO),
    VV(VV__NULL_LIST,     "_null_list",       VAR_LIST, VV_RO),
    VV(VV__NULL_DICT,     "_null_dict",       VAR_DICT, VV_RO),
    VV(VV_VIM_DID_ENTER,  "vim_did_enter",    VAR_NUMBER, VV_RO),
    VV(VV_TESTING,        "testing",          VAR_NUMBER, 0),
    VV(VV_TYPE_NUMBER,    "t_number",         VAR_NUMBER, VV_RO),
    VV(VV_TYPE_STRING,    "t_string",         VAR_NUMBER, VV_RO),
    VV(VV_TYPE_FUNC,      "t_func",           VAR_NUMBER, VV_RO),
    VV(VV_TYPE_LIST,      "t_list",           VAR_NUMBER, VV_RO),
    VV(VV_TYPE_DICT,      "t_dict",           VAR_NUMBER, VV_RO),
    VV(VV_TYPE_FLOAT,     "t_float",          VAR_NUMBER, VV_RO),
    VV(VV_TYPE_BOOL,      "t_bool",           VAR_NUMBER, VV_RO),
    VV(VV_ECHOSPACE,      "echospace",        VAR_NUMBER, VV_RO),
    VV(VV_EXITING,        "exiting",          VAR_NUMBER, VV_RO),
    VV(VV_LUA,            "lua",              VAR_PARTIAL, VV_RO),
    VV(VV_ARGV,           "argv",             VAR_LIST, VV_RO),
  };
  #undef VV
  
  // shorthand
  #define vv_type         vv_di.di_tv.v_type
  #define vv_nr           vv_di.di_tv.vval.v_number
  #define vv_bool         vv_di.di_tv.vval.v_bool
  #define vv_special      vv_di.di_tv.vval.v_special
  #define vv_float        vv_di.di_tv.vval.v_float
  #define vv_str          vv_di.di_tv.vval.v_string
  #define vv_list         vv_di.di_tv.vval.v_list
  #define vv_dict         vv_di.di_tv.vval.v_dict
  #define vv_partial      vv_di.di_tv.vval.v_partial
  #define vv_tv           vv_di.di_tv
  
  /// Variable used for v:
  static ScopeDictDictItem vimvars_var;
  
  static partial_T *vvlua_partial;
  
  /// v: hashtab
  #define vimvarht  vimvardict.dv_hashtab
  
  #ifdef INCLUDE_GENERATED_DECLARATIONS
  # include "eval.c.generated.h"
  #endif
  
  static uint64_t last_timer_id = 1;
  static PMap(uint64_t) *timers = NULL;
  
  static const char *const msgpack_type_names[] = {
    [kMPNil] = "nil",
    [kMPBoolean] = "boolean",
    [kMPInteger] = "integer",
    [kMPFloat] = "float",
    [kMPString] = "string",
    [kMPBinary] = "binary",
    [kMPArray] = "array",
    [kMPMap] = "map",
    [kMPExt] = "ext",
  };
  const list_T *eval_msgpack_type_lists[] = {
    [kMPNil] = NULL,
    [kMPBoolean] = NULL,
    [kMPInteger] = NULL,
    [kMPFloat] = NULL,
    [kMPString] = NULL,
    [kMPBinary] = NULL,
    [kMPArray] = NULL,
    [kMPMap] = NULL,
    [kMPExt] = NULL,
  };
  
  // Return "n1" divided by "n2", taking care of dividing by zero.
  varnumber_T num_divide(varnumber_T n1, varnumber_T n2)
    FUNC_ATTR_CONST FUNC_ATTR_WARN_UNUSED_RESULT
  {
    varnumber_T result;
  
    if (n2 == 0) {  // give an error message?
      if (n1 == 0) {
        result = VARNUMBER_MIN;  // similar to NaN
      } else if (n1 < 0) {
        result = -VARNUMBER_MAX;
      } else {
        result = VARNUMBER_MAX;
      }
    } else {
      result = n1 / n2;
    }
  
    return result;
  }
  
  // Return "n1" modulus "n2", taking care of dividing by zero.
  varnumber_T num_modulus(varnumber_T n1, varnumber_T n2)
    FUNC_ATTR_CONST FUNC_ATTR_WARN_UNUSED_RESULT
  {
    // Give an error when n2 is 0?
    return (n2 == 0) ? 0 : (n1 % n2);
  }
  
  /*
   * Initialize the global and v: variables.
   */
  void eval_init(void)
  {
    vimvars[VV_VERSION].vv_nr = VIM_VERSION_100;
  
    timers = pmap_new(uint64_t)();
    struct vimvar   *p;
  
    init_var_dict(&globvardict, &globvars_var, VAR_DEF_SCOPE);
    init_var_dict(&vimvardict, &vimvars_var, VAR_SCOPE);
    vimvardict.dv_lock = VAR_FIXED;
    hash_init(&compat_hashtab);
    func_init();
  
    for (size_t i = 0; i < ARRAY_SIZE(vimvars); i++) {
      p = &vimvars[i];
      assert(STRLEN(p->vv_name) <= 16);
      STRCPY(p->vv_di.di_key, p->vv_name);
      if (p->vv_flags & VV_RO)
        p->vv_di.di_flags = DI_FLAGS_RO | DI_FLAGS_FIX;
      else if (p->vv_flags & VV_RO_SBX)
        p->vv_di.di_flags = DI_FLAGS_RO_SBX | DI_FLAGS_FIX;
      else
        p->vv_di.di_flags = DI_FLAGS_FIX;
  
      // add to v: scope dict, unless the value is not always available
      if (p->vv_type != VAR_UNKNOWN) {
        hash_add(&vimvarht, p->vv_di.di_key);
      }
      if (p->vv_flags & VV_COMPAT) {
        // add to compat scope dict
        hash_add(&compat_hashtab, p->vv_di.di_key);
      }
    }
    vimvars[VV_VERSION].vv_nr = VIM_VERSION_100;
  
    dict_T *const msgpack_types_dict = tv_dict_alloc();
    for (size_t i = 0; i < ARRAY_SIZE(msgpack_type_names); i++) {
      list_T *const type_list = tv_list_alloc(0);
      tv_list_set_lock(type_list, VAR_FIXED);
      tv_list_ref(type_list);
      dictitem_T *const di = tv_dict_item_alloc(msgpack_type_names[i]);
      di->di_flags |= DI_FLAGS_RO|DI_FLAGS_FIX;
      di->di_tv = (typval_T) {
        .v_type = VAR_LIST,
        .vval = { .v_list = type_list, },
      };
      eval_msgpack_type_lists[i] = type_list;
      if (tv_dict_add(msgpack_types_dict, di) == FAIL) {
        // There must not be duplicate items in this dictionary by definition.
        assert(false);
      }
    }
    msgpack_types_dict->dv_lock = VAR_FIXED;
  
    set_vim_var_dict(VV_MSGPACK_TYPES, msgpack_types_dict);
    set_vim_var_dict(VV_COMPLETED_ITEM, tv_dict_alloc());
  
    dict_T *v_event = tv_dict_alloc();
    v_event->dv_lock = VAR_FIXED;
    set_vim_var_dict(VV_EVENT, v_event);
    set_vim_var_list(VV_ERRORS, tv_list_alloc(kListLenUnknown));
    set_vim_var_nr(VV_STDERR,   CHAN_STDERR);
    set_vim_var_nr(VV_SEARCHFORWARD, 1L);
    set_vim_var_nr(VV_HLSEARCH, 1L);
    set_vim_var_nr(VV_COUNT1, 1);
    set_vim_var_nr(VV_TYPE_NUMBER, VAR_TYPE_NUMBER);
    set_vim_var_nr(VV_TYPE_STRING, VAR_TYPE_STRING);
    set_vim_var_nr(VV_TYPE_FUNC,   VAR_TYPE_FUNC);
    set_vim_var_nr(VV_TYPE_LIST,   VAR_TYPE_LIST);
    set_vim_var_nr(VV_TYPE_DICT,   VAR_TYPE_DICT);
    set_vim_var_nr(VV_TYPE_FLOAT,  VAR_TYPE_FLOAT);
    set_vim_var_nr(VV_TYPE_BOOL,   VAR_TYPE_BOOL);
  
    set_vim_var_bool(VV_FALSE, kBoolVarFalse);
    set_vim_var_bool(VV_TRUE, kBoolVarTrue);
    set_vim_var_special(VV_NULL, kSpecialVarNull);
    set_vim_var_special(VV_EXITING, kSpecialVarNull);
  
    set_vim_var_nr(VV_ECHOSPACE,    sc_col - 1);
  
    vimvars[VV_LUA].vv_type = VAR_PARTIAL;
    vvlua_partial = xcalloc(1, sizeof(partial_T));
    vimvars[VV_LUA].vv_partial = vvlua_partial;
    // this value shouldn't be printed, but if it is, do not crash
    vvlua_partial->pt_name = xmallocz(0);
    vvlua_partial->pt_refcount++;
  
    set_reg_var(0);  // default for v:register is not 0 but '"'
  }
  
  #if defined(EXITFREE)
  void eval_clear(void)
  {
    struct vimvar   *p;
  
    for (size_t i = 0; i < ARRAY_SIZE(vimvars); i++) {
      p = &vimvars[i];
      if (p->vv_di.di_tv.v_type == VAR_STRING) {
        XFREE_CLEAR(p->vv_str);
      } else if (p->vv_di.di_tv.v_type == VAR_LIST) {
        tv_list_unref(p->vv_list);
        p->vv_list = NULL;
      }
    }
    hash_clear(&vimvarht);
    hash_init(&vimvarht);    // garbage_collect() will access it
    hash_clear(&compat_hashtab);
  
    free_scriptnames();
    free_locales();
  
    // global variables
    vars_clear(&globvarht);
  
    // autoloaded script names
    ga_clear_strings(&ga_loaded);
  
    /* Script-local variables. First clear all the variables and in a second
     * loop free the scriptvar_T, because a variable in one script might hold
     * a reference to the whole scope of another script. */
    for (int i = 1; i <= ga_scripts.ga_len; ++i)
      vars_clear(&SCRIPT_VARS(i));
    for (int i = 1; i <= ga_scripts.ga_len; ++i)
      xfree(SCRIPT_SV(i));
    ga_clear(&ga_scripts);
  
    // unreferenced lists and dicts
    (void)garbage_collect(false);
  
    // functions not garbage collected
    free_all_functions();
  }
  
  #endif
  
  /*
   * Set an internal variable to a string value. Creates the variable if it does
   * not already exist.
   */
  void set_internal_string_var(char_u *name, char_u *value)
  {
    const typval_T tv = {
      .v_type = VAR_STRING,
      .vval.v_string = value,
    };
  
    set_var((const char *)name, STRLEN(name), (typval_T *)&tv, true);
  }
  
  static lval_T   *redir_lval = NULL;
  static garray_T redir_ga;  // Only valid when redir_lval is not NULL.
  static char_u *redir_endp = NULL;
  static char_u   *redir_varname = NULL;
  
  /*
   * Start recording command output to a variable
   * Returns OK if successfully completed the setup.  FAIL otherwise.
   */
  int
  var_redir_start(
      char_u *name,
      int append                     // append to an existing variable
  )
  {
    int save_emsg;
    int err;
    typval_T tv;
  
    // Catch a bad name early.
    if (!eval_isnamec1(*name)) {
      EMSG(_(e_invarg));
      return FAIL;
    }
  
    // Make a copy of the name, it is used in redir_lval until redir ends.
    redir_varname = vim_strsave(name);
  
    redir_lval = xcalloc(1, sizeof(lval_T));
  
    // The output is stored in growarray "redir_ga" until redirection ends.
    ga_init(&redir_ga, (int)sizeof(char), 500);
  
    // Parse the variable name (can be a dict or list entry).
    redir_endp = (char_u *)get_lval(redir_varname, NULL, redir_lval, false, false,
                                    0, FNE_CHECK_START);
    if (redir_endp == NULL || redir_lval->ll_name == NULL
        || *redir_endp != NUL) {
      clear_lval(redir_lval);
      if (redir_endp != NULL && *redir_endp != NUL) {
        // Trailing characters are present after the variable name
        EMSG(_(e_trailing));
      } else {
        EMSG(_(e_invarg));
      }
      redir_endp = NULL;      // don't store a value, only cleanup
      var_redir_stop();
      return FAIL;
    }
  
    /* check if we can write to the variable: set it to or append an empty
     * string */
    save_emsg = did_emsg;
    did_emsg = FALSE;
    tv.v_type = VAR_STRING;
    tv.vval.v_string = (char_u *)"";
    if (append) {
      set_var_lval(redir_lval, redir_endp, &tv, true, false, (char_u *)".");
    } else {
      set_var_lval(redir_lval, redir_endp, &tv, true, false, (char_u *)"=");
    }
    clear_lval(redir_lval);
    err = did_emsg;
    did_emsg |= save_emsg;
    if (err) {
      redir_endp = NULL;      // don't store a value, only cleanup
      var_redir_stop();
      return FAIL;
    }
  
    return OK;
  }
  
  /*
   * Append "value[value_len]" to the variable set by var_redir_start().
   * The actual appending is postponed until redirection ends, because the value
   * appended may in fact be the string we write to, changing it may cause freed
   * memory to be used:
   *   :redir => foo
   *   :let foo
   *   :redir END
   */
  void var_redir_str(char_u *value, int value_len)
  {
    int len;
  
    if (redir_lval == NULL)
      return;
  
    if (value_len == -1) {
      len = (int)STRLEN(value);           // Append the entire string
    } else {
      len = value_len;                    // Append only "value_len" characters
    }
  
    ga_grow(&redir_ga, len);
    memmove((char *)redir_ga.ga_data + redir_ga.ga_len, value, len);
    redir_ga.ga_len += len;
  }
  
  /*
   * Stop redirecting command output to a variable.
   * Frees the allocated memory.
   */
  void var_redir_stop(void)
  {
    typval_T tv;
  
    if (redir_lval != NULL) {
      // If there was no error: assign the text to the variable.
      if (redir_endp != NULL) {
        ga_append(&redir_ga, NUL);        // Append the trailing NUL.
        tv.v_type = VAR_STRING;
        tv.vval.v_string = redir_ga.ga_data;
        // Call get_lval() again, if it's inside a Dict or List it may
        // have changed.
        redir_endp = (char_u *)get_lval(redir_varname, NULL, redir_lval,
                                        false, false, 0, FNE_CHECK_START);
        if (redir_endp != NULL && redir_lval->ll_name != NULL) {
          set_var_lval(redir_lval, redir_endp, &tv, false, false, (char_u *)".");
        }
        clear_lval(redir_lval);
      }
  
      // free the collected output
      XFREE_CLEAR(redir_ga.ga_data);
  
      XFREE_CLEAR(redir_lval);
    }
    XFREE_CLEAR(redir_varname);
  }
  
  int eval_charconvert(const char *const enc_from, const char *const enc_to,
                       const char *const fname_from, const char *const fname_to)
  {
    bool err = false;
  
    set_vim_var_string(VV_CC_FROM, enc_from, -1);
    set_vim_var_string(VV_CC_TO, enc_to, -1);
    set_vim_var_string(VV_FNAME_IN, fname_from, -1);
    set_vim_var_string(VV_FNAME_OUT, fname_to, -1);
    if (eval_to_bool(p_ccv, &err, NULL, false)) {
      err = true;
    }
    set_vim_var_string(VV_CC_FROM, NULL, -1);
    set_vim_var_string(VV_CC_TO, NULL, -1);
    set_vim_var_string(VV_FNAME_IN, NULL, -1);
    set_vim_var_string(VV_FNAME_OUT, NULL, -1);
  
    if (err) {
      return FAIL;
    }
    return OK;
  }
  
  int eval_printexpr(const char *const fname, const char *const args)
  {
    bool err = false;
  
    set_vim_var_string(VV_FNAME_IN, fname, -1);
    set_vim_var_string(VV_CMDARG, args, -1);
    if (eval_to_bool(p_pexpr, &err, NULL, false)) {
      err = true;
    }
    set_vim_var_string(VV_FNAME_IN, NULL, -1);
    set_vim_var_string(VV_CMDARG, NULL, -1);
  
    if (err) {
      os_remove(fname);
      return FAIL;
    }
    return OK;
  }
  
  void eval_diff(const char *const origfile, const char *const newfile,
                 const char *const outfile)
  {
    bool err = false;
  
    set_vim_var_string(VV_FNAME_IN, origfile, -1);
    set_vim_var_string(VV_FNAME_NEW, newfile, -1);
    set_vim_var_string(VV_FNAME_OUT, outfile, -1);
    (void)eval_to_bool(p_dex, &err, NULL, FALSE);
    set_vim_var_string(VV_FNAME_IN, NULL, -1);
    set_vim_var_string(VV_FNAME_NEW, NULL, -1);
    set_vim_var_string(VV_FNAME_OUT, NULL, -1);
  }
  
  void eval_patch(const char *const origfile, const char *const difffile,
                  const char *const outfile)
  {
    bool err = false;
  
    set_vim_var_string(VV_FNAME_IN, origfile, -1);
    set_vim_var_string(VV_FNAME_DIFF, difffile, -1);
    set_vim_var_string(VV_FNAME_OUT, outfile, -1);
    (void)eval_to_bool(p_pex, &err, NULL, FALSE);
    set_vim_var_string(VV_FNAME_IN, NULL, -1);
    set_vim_var_string(VV_FNAME_DIFF, NULL, -1);
    set_vim_var_string(VV_FNAME_OUT, NULL, -1);
  }
  
  /*
   * Top level evaluation function, returning a boolean.
   * Sets "error" to TRUE if there was an error.
   * Return TRUE or FALSE.
   */
  int
  eval_to_bool(
      char_u *arg,
      bool *error,
      char_u **nextcmd,
      int skip                   // only parse, don't execute
  )
  {
    typval_T tv;
    bool retval = false;
  
    if (skip) {
      emsg_skip++;
    }
    if (eval0(arg, &tv, nextcmd, !skip) == FAIL) {
      *error = true;
    } else {
      *error = false;
      if (!skip) {
        retval = (tv_get_number_chk(&tv, error) != 0);
        tv_clear(&tv);
      }
    }
    if (skip) {
      emsg_skip--;
    }
  
    return retval;
  }
  
  // Call eval1() and give an error message if not done at a lower level.
  static int eval1_emsg(char_u **arg, typval_T *rettv, bool evaluate)
    FUNC_ATTR_NONNULL_ARG(1, 2)
  {
    const char_u *const start = *arg;
    const int did_emsg_before = did_emsg;
    const int called_emsg_before = called_emsg;
  
    const int ret = eval1(arg, rettv, evaluate);
    if (ret == FAIL) {
      // Report the invalid expression unless the expression evaluation has
      // been cancelled due to an aborting error, an interrupt, or an
      // exception, or we already gave a more specific error.
      // Also check called_emsg for when using assert_fails().
      if (!aborting()
          && did_emsg == did_emsg_before
          && called_emsg == called_emsg_before) {
        emsgf(_(e_invexpr2), start);
      }
    }
    return ret;
  }
  
  int eval_expr_typval(const typval_T *expr, typval_T *argv,
                       int argc, typval_T *rettv)
    FUNC_ATTR_NONNULL_ARG(1, 2, 4)
  {
    int dummy;
  
    if (expr->v_type == VAR_FUNC) {
      const char_u *const s = expr->vval.v_string;
      if (s == NULL || *s == NUL) {
        return FAIL;
      }
      if (call_func(s, (int)STRLEN(s), rettv, argc, argv, NULL,
                    0L, 0L, &dummy, true, NULL, NULL) == FAIL) {
        return FAIL;
      }
    } else if (expr->v_type == VAR_PARTIAL) {
      partial_T *const partial = expr->vval.v_partial;
      const char_u *const s = partial_name(partial);
      if (s == NULL || *s == NUL) {
        return FAIL;
      }
      if (call_func(s, (int)STRLEN(s), rettv, argc, argv, NULL,
                    0L, 0L, &dummy, true, partial, NULL) == FAIL) {
        return FAIL;
      }
    } else {
      char buf[NUMBUFLEN];
      char_u *s = (char_u *)tv_get_string_buf_chk(expr, buf);
      if (s == NULL) {
        return FAIL;
      }
      s = skipwhite(s);
      if (eval1_emsg(&s, rettv, true) == FAIL) {
        return FAIL;
      }
      if (*s != NUL) {  // check for trailing chars after expr
        tv_clear(rettv);
        emsgf(_(e_invexpr2), s);
        return FAIL;
      }
    }
    return OK;
  }
  
  /// Like eval_to_bool() but using a typval_T instead of a string.
  /// Works for string, funcref and partial.
  bool eval_expr_to_bool(const typval_T *expr, bool *error)
    FUNC_ATTR_NONNULL_ARG(1, 2)
  {
    typval_T argv, rettv;
  
    if (eval_expr_typval(expr, &argv, 0, &rettv) == FAIL) {
      *error = true;
      return false;
    }
    const bool res = (tv_get_number_chk(&rettv, error) != 0);
    tv_clear(&rettv);
    return res;
  }
  
  /// Top level evaluation function, returning a string
  ///
  /// @param[in]  arg  String to evaluate.
  /// @param  nextcmd  Pointer to the start of the next Ex command.
  /// @param[in]  skip  If true, only do parsing to nextcmd without reporting
  ///                   errors or actually evaluating anything.
  ///
  /// @return [allocated] string result of evaluation or NULL in case of error or
  ///                     when skipping.
  char *eval_to_string_skip(const char *arg, const char **nextcmd,
                            const bool skip)
    FUNC_ATTR_MALLOC FUNC_ATTR_NONNULL_ARG(1) FUNC_ATTR_WARN_UNUSED_RESULT
  {
    typval_T tv;
    char *retval;
  
    if (skip) {
      emsg_skip++;
    }
    if (eval0((char_u *)arg, &tv, (char_u **)nextcmd, !skip) == FAIL || skip) {
      retval = NULL;
    } else {
      retval = xstrdup(tv_get_string(&tv));
      tv_clear(&tv);
    }
    if (skip) {
      emsg_skip--;
    }
  
    return retval;
  }
  
  /*
   * Skip over an expression at "*pp".
   * Return FAIL for an error, OK otherwise.
   */
  int skip_expr(char_u **pp)
  {
    typval_T rettv;
  
    *pp = skipwhite(*pp);
    return eval1(pp, &rettv, FALSE);
  }
  
  /*
   * Top level evaluation function, returning a string.
   * When "convert" is TRUE convert a List into a sequence of lines and convert
   * a Float to a String.
   * Return pointer to allocated memory, or NULL for failure.
   */
  char_u *eval_to_string(char_u *arg, char_u **nextcmd, int convert)
  {
    typval_T tv;
    char *retval;
    garray_T ga;
  
    if (eval0(arg, &tv, nextcmd, true) == FAIL) {
      retval = NULL;
    } else {
      if (convert && tv.v_type == VAR_LIST) {
        ga_init(&ga, (int)sizeof(char), 80);
        if (tv.vval.v_list != NULL) {
          tv_list_join(&ga, tv.vval.v_list, "\n");
          if (tv_list_len(tv.vval.v_list) > 0) {
            ga_append(&ga, NL);
          }
        }
        ga_append(&ga, NUL);
        retval = (char *)ga.ga_data;
      } else if (convert && tv.v_type == VAR_FLOAT) {
        char numbuf[NUMBUFLEN];
        vim_snprintf(numbuf, NUMBUFLEN, "%g", tv.vval.v_float);
        retval = xstrdup(numbuf);
      } else {
        retval = xstrdup(tv_get_string(&tv));
      }
      tv_clear(&tv);
    }
  
    return (char_u *)retval;
  }
  
  /*
   * Call eval_to_string() without using current local variables and using
   * textlock.  When "use_sandbox" is TRUE use the sandbox.
   */
  char_u *eval_to_string_safe(char_u *arg, char_u **nextcmd, int use_sandbox)
  {
    char_u      *retval;
    funccal_entry_T funccal_entry;
  
    save_funccal(&funccal_entry);
    if (use_sandbox) {
      sandbox++;
    }
    textlock++;
    retval = eval_to_string(arg, nextcmd, false);
    if (use_sandbox) {
      sandbox--;
    }
    textlock--;
    restore_funccal();
    return retval;
  }
  
  /*
   * Top level evaluation function, returning a number.
   * Evaluates "expr" silently.
   * Returns -1 for an error.
   */
  varnumber_T eval_to_number(char_u *expr)
  {
    typval_T rettv;
    varnumber_T retval;
    char_u      *p = skipwhite(expr);
  
    ++emsg_off;
  
    if (eval1(&p, &rettv, true) == FAIL) {
      retval = -1;
    } else {
      retval = tv_get_number_chk(&rettv, NULL);
      tv_clear(&rettv);
    }
    --emsg_off;
  
    return retval;
  }
  
  
  /*
   * Prepare v: variable "idx" to be used.
   * Save the current typeval in "save_tv".
   * When not used yet add the variable to the v: hashtable.
   */
  void prepare_vimvar(int idx, typval_T *save_tv)
  {
    *save_tv = vimvars[idx].vv_tv;
    if (vimvars[idx].vv_type == VAR_UNKNOWN)
      hash_add(&vimvarht, vimvars[idx].vv_di.di_key);
  }
  
  /*
   * Restore v: variable "idx" to typeval "save_tv".
   * When no longer defined, remove the variable from the v: hashtable.
   */
  void restore_vimvar(int idx, typval_T *save_tv)
  {
    hashitem_T  *hi;
  
    vimvars[idx].vv_tv = *save_tv;
    if (vimvars[idx].vv_type == VAR_UNKNOWN) {
      hi = hash_find(&vimvarht, vimvars[idx].vv_di.di_key);
      if (HASHITEM_EMPTY(hi)) {
        internal_error("restore_vimvar()");
      } else {
        hash_remove(&vimvarht, hi);
      }
    }
  }
  
  /// If there is a window for "curbuf", make it the current window.
  void find_win_for_curbuf(void)
  {
    for (wininfo_T *wip = curbuf->b_wininfo; wip != NULL; wip = wip->wi_next) {
      if (wip->wi_win != NULL) {
        curwin = wip->wi_win;
        break;
      }
    }
  }
  
  /*
   * Evaluate an expression to a list with suggestions.
   * For the "expr:" part of 'spellsuggest'.
   * Returns NULL when there is an error.
   */
  list_T *eval_spell_expr(char_u *badword, char_u *expr)
  {
    typval_T save_val;
    typval_T rettv;
    list_T      *list = NULL;
    char_u      *p = skipwhite(expr);
  
    // Set "v:val" to the bad word.
    prepare_vimvar(VV_VAL, &save_val);
    vimvars[VV_VAL].vv_type = VAR_STRING;
    vimvars[VV_VAL].vv_str = badword;
    if (p_verbose == 0)
      ++emsg_off;
  
    if (eval1(&p, &rettv, true) == OK) {
      if (rettv.v_type != VAR_LIST) {
        tv_clear(&rettv);
      } else {
        list = rettv.vval.v_list;
      }
    }
  
    if (p_verbose == 0)
      --emsg_off;
    restore_vimvar(VV_VAL, &save_val);
  
    return list;
  }
  
  /// Get spell word from an entry from spellsuggest=expr:
  ///
  /// Entry in question is supposed to be a list (to be checked by the caller)
  /// with two items: a word and a score represented as an unsigned number
  /// (whether it actually is unsigned is not checked).
  ///
  /// Used to get the good word and score from the eval_spell_expr() result.
  ///
  /// @param[in]  list  List to get values from.
  /// @param[out]  ret_word  Suggested word. Not initialized if return value is
  ///                        -1.
  ///
  /// @return -1 in case of error, score otherwise.
  int get_spellword(list_T *const list, const char **ret_word)
  {
    if (tv_list_len(list) != 2) {
      EMSG(_("E5700: Expression from 'spellsuggest' must yield lists with "
             "exactly two values"));
      return -1;
    }
    *ret_word = tv_list_find_str(list, 0);
    if (*ret_word == NULL) {
      return -1;
    }
    return tv_list_find_nr(list, -1, NULL);
  }
  
  
  // Call some vim script function and return the result in "*rettv".
  // Uses argv[0] to argv[argc-1] for the function arguments. argv[argc]
  // should have type VAR_UNKNOWN.
  //
  // Return OK or FAIL.
  int call_vim_function(
      const char_u *func,
      int argc,
      typval_T *argv,
      typval_T *rettv
  )
    FUNC_ATTR_NONNULL_ALL
  {
    int doesrange;
    int ret;
    int len = (int)STRLEN(func);
    partial_T *pt = NULL;
  
    if (len >= 6 && !memcmp(func, "v:lua.", 6)) {
      func += 6;
      len = check_luafunc_name((const char *)func, false);
      if (len == 0) {
        ret = FAIL;
        goto fail;
      }
      pt = vvlua_partial;
    }
  
    rettv->v_type = VAR_UNKNOWN;  // tv_clear() uses this.
    ret = call_func(func, len, rettv, argc, argv, NULL,
                    curwin->w_cursor.lnum, curwin->w_cursor.lnum,
                    &doesrange, true, pt, NULL);
  
  fail:
    if (ret == FAIL) {
      tv_clear(rettv);
    }
  
    return ret;
  }
  /// Call Vim script function and return the result as a number
  ///
  /// @param[in]  func  Function name.
  /// @param[in]  argc  Number of arguments.
  /// @param[in]  argv  Array with typval_T arguments.
  ///
  /// @return -1 when calling function fails, result of function otherwise.
  varnumber_T call_func_retnr(const char_u *func, int argc,
                              typval_T *argv)
    FUNC_ATTR_NONNULL_ALL
  {
    typval_T rettv;
    varnumber_T retval;
  
    if (call_vim_function(func, argc, argv, &rettv) == FAIL) {
      return -1;
    }
    retval = tv_get_number_chk(&rettv, NULL);
    tv_clear(&rettv);
    return retval;
  }
  /// Call Vim script function and return the result as a string
  ///
  /// @param[in]  func  Function name.
  /// @param[in]  argc  Number of arguments.
  /// @param[in]  argv  Array with typval_T arguments.
  ///
  /// @return [allocated] NULL when calling function fails, allocated string
  ///                     otherwise.
  char *call_func_retstr(const char *const func, int argc,
                         typval_T *argv)
    FUNC_ATTR_NONNULL_ALL FUNC_ATTR_WARN_UNUSED_RESULT FUNC_ATTR_MALLOC
  {
    typval_T rettv;
    // All arguments are passed as strings, no conversion to number.
    if (call_vim_function((const char_u *)func, argc, argv, &rettv)
        == FAIL) {
      return NULL;
    }
  
    char *const retval = xstrdup(tv_get_string(&rettv));
    tv_clear(&rettv);
    return retval;
  }
  /// Call Vim script function and return the result as a List
  ///
  /// @param[in]  func  Function name.
  /// @param[in]  argc  Number of arguments.
  /// @param[in]  argv  Array with typval_T arguments.
  ///
  /// @return [allocated] NULL when calling function fails or return tv is not a
  ///                     List, allocated List otherwise.
  void *call_func_retlist(const char_u *func, int argc, typval_T *argv)
    FUNC_ATTR_NONNULL_ALL
  {
    typval_T rettv;
  
    // All arguments are passed as strings, no conversion to number.
    if (call_vim_function(func, argc, argv, &rettv) == FAIL) {
      return NULL;
    }
  
    if (rettv.v_type != VAR_LIST) {
      tv_clear(&rettv);
      return NULL;
    }
  
    return rettv.vval.v_list;
  }
  
  /*
   * Prepare profiling for entering a child or something else that is not
   * counted for the script/function itself.
   * Should always be called in pair with prof_child_exit().
   */
  void prof_child_enter(
      proftime_T *tm  // place to store waittime
  )
  {
    funccall_T *fc = get_current_funccal();
  
    if (fc != NULL && fc->func->uf_profiling) {
      fc->prof_child = profile_start();
    }
  
    script_prof_save(tm);
  }
  
  /*
   * Take care of time spent in a child.
   * Should always be called after prof_child_enter().
   */
  void prof_child_exit(
      proftime_T *tm  // where waittime was stored
  )
  {
    funccall_T *fc = get_current_funccal();
  
    if (fc != NULL && fc->func->uf_profiling) {
      fc->prof_child = profile_end(fc->prof_child);
      // don't count waiting time
      fc->prof_child = profile_sub_wait(*tm, fc->prof_child);
      fc->func->uf_tm_children =
        profile_add(fc->func->uf_tm_children, fc->prof_child);
      fc->func->uf_tml_children =
        profile_add(fc->func->uf_tml_children, fc->prof_child);
    }
    script_prof_restore(tm);
  }
  
  
  /*
   * Evaluate 'foldexpr'.  Returns the foldlevel, and any character preceding
   * it in "*cp".  Doesn't give error messages.
   */
  int eval_foldexpr(char_u *arg, int *cp)
  {
    typval_T tv;
    varnumber_T retval;
    int use_sandbox = was_set_insecurely((char_u *)"foldexpr",
        OPT_LOCAL);
  
    ++emsg_off;
    if (use_sandbox)
      ++sandbox;
    ++textlock;
    *cp = NUL;
    if (eval0(arg, &tv, NULL, true) == FAIL) {
      retval = 0;
    } else {
      // If the result is a number, just return the number.
      if (tv.v_type == VAR_NUMBER) {
        retval = tv.vval.v_number;
      } else if (tv.v_type != VAR_STRING || tv.vval.v_string == NULL) {
        retval = 0;
      } else {
        // If the result is a string, check if there is a non-digit before
        // the number.
        char_u *s = tv.vval.v_string;
        if (!ascii_isdigit(*s) && *s != '-') {
          *cp = *s++;
        }
        retval = atol((char *)s);
      }
      tv_clear(&tv);
    }
    --emsg_off;
    if (use_sandbox)
      --sandbox;
    --textlock;
  
    return (int)retval;
  }
  
  // ":cons[t] var = expr1" define constant
  // ":cons[t] [name1, name2, ...] = expr1" define constants unpacking list
  // ":cons[t] [name, ..., ; lastname] = expr" define constants unpacking list
  void ex_const(exarg_T *eap)
  {
    ex_let_const(eap, true);
  }
  
  // Get a list of lines from a HERE document. The here document is a list of
  // lines surrounded by a marker.
  //     cmd << {marker}
  //       {line1}
  //       {line2}
  //       ....
  //     {marker}
  //
  // The {marker} is a string. If the optional 'trim' word is supplied before the
  // marker, then the leading indentation before the lines (matching the
  // indentation in the 'cmd' line) is stripped.
  // Returns a List with {lines} or NULL.
  static list_T *
  heredoc_get(exarg_T *eap, char_u *cmd)
  {
    char_u *marker;
    char_u *p;
    int marker_indent_len = 0;
    int text_indent_len = 0;
    char_u *text_indent = NULL;
  
    if (eap->getline == NULL) {
      EMSG(_("E991: cannot use =<< here"));
      return NULL;
    }
  
    // Check for the optional 'trim' word before the marker
    cmd = skipwhite(cmd);
    if (STRNCMP(cmd, "trim", 4) == 0
        && (cmd[4] == NUL || ascii_iswhite(cmd[4]))) {
      cmd = skipwhite(cmd + 4);
  
      // Trim the indentation from all the lines in the here document.
      // The amount of indentation trimmed is the same as the indentation of
      // the first line after the :let command line.  To find the end marker
      // the indent of the :let command line is trimmed.
      p = *eap->cmdlinep;
      while (ascii_iswhite(*p)) {
        p++;
        marker_indent_len++;
      }
      text_indent_len = -1;
    }
  
    // The marker is the next word.
    if (*cmd != NUL && *cmd != '"') {
      marker = skipwhite(cmd);
      p = skiptowhite(marker);
      if (*skipwhite(p) != NUL && *skipwhite(p) != '"') {
        EMSG(_(e_trailing));
        return NULL;
      }
      *p = NUL;
      if (islower(*marker)) {
        EMSG(_("E221: Marker cannot start with lower case letter"));
        return NULL;
      }
    } else {
      EMSG(_("E172: Missing marker"));
      return NULL;
    }
  
    list_T *l = tv_list_alloc(0);
    for (;;) {
      int mi = 0;
      int ti = 0;
  
      char_u *theline = eap->getline(NUL, eap->cookie, 0, false);
      if (theline == NULL) {
        EMSG2(_("E990: Missing end marker '%s'"), marker);
        break;
      }
  
      // with "trim": skip the indent matching the :let line to find the
      // marker
      if (marker_indent_len > 0
          && STRNCMP(theline, *eap->cmdlinep, marker_indent_len) == 0) {
          mi = marker_indent_len;
      }
      if (STRCMP(marker, theline + mi) == 0) {
        xfree(theline);
        break;
      }
      if (text_indent_len == -1 && *theline != NUL) {
          // set the text indent from the first line.
          p = theline;
          text_indent_len = 0;
          while (ascii_iswhite(*p)) {
              p++;
              text_indent_len++;
          }
          text_indent = vim_strnsave(theline, text_indent_len);
      }
      // with "trim": skip the indent matching the first line
      if (text_indent != NULL) {
          for (ti = 0; ti < text_indent_len; ti++) {
              if (theline[ti] != text_indent[ti]) {
                  break;
              }
          }
      }
  
      tv_list_append_string(l, (char *)(theline + ti), -1);
      xfree(theline);
    }
    xfree(text_indent);
  
    return l;
  }
  
  // ":let" list all variable values
  // ":let var1 var2" list variable values
  // ":let var = expr" assignment command.
  // ":let var += expr" assignment command.
  // ":let var -= expr" assignment command.
  // ":let var *= expr" assignment command.
  // ":let var /= expr" assignment command.
  // ":let var %= expr" assignment command.
  // ":let var .= expr" assignment command.
  // ":let var ..= expr" assignment command.
  // ":let [var1, var2] = expr" unpack list.
  // ":let [name, ..., ; lastname] = expr" unpack list.
  void ex_let(exarg_T *eap)
  {
    ex_let_const(eap, false);
  }
  
  static void ex_let_const(exarg_T *eap, const bool is_const)
  {
    char_u      *arg = eap->arg;
    char_u      *expr = NULL;
    typval_T rettv;
    int i;
    int var_count = 0;
    int semicolon = 0;
    char_u op[2];
    char_u      *argend;
    int first = TRUE;
  
    argend = (char_u *)skip_var_list(arg, &var_count, &semicolon);
    if (argend == NULL) {
      return;
    }
    if (argend > arg && argend[-1] == '.') {  // For var.='str'.
      argend--;
    }
    expr = skipwhite(argend);
    if (*expr != '=' && !((vim_strchr((char_u *)"+-*/%.", *expr) != NULL
                           && expr[1] == '=') || STRNCMP(expr, "..=", 3) == 0)) {
      // ":let" without "=": list variables
      if (*arg == '[') {
        EMSG(_(e_invarg));
      } else if (!ends_excmd(*arg)) {
        // ":let var1 var2"
        arg = (char_u *)list_arg_vars(eap, (const char *)arg, &first);
      } else if (!eap->skip) {
        // ":let"
        list_glob_vars(&first);
        list_buf_vars(&first);
        list_win_vars(&first);
        list_tab_vars(&first);
        list_script_vars(&first);
        list_func_vars(&first);
        list_vim_vars(&first);
      }
      eap->nextcmd = check_nextcmd(arg);
    } else if (expr[0] == '=' && expr[1] == '<' && expr[2] == '<') {
      // HERE document
      list_T *l = heredoc_get(eap, expr + 3);
      if (l != NULL) {
        tv_list_set_ret(&rettv, l);
        if (!eap->skip) {
          op[0] = '=';
          op[1] = NUL;
          (void)ex_let_vars(eap->arg, &rettv, false, semicolon, var_count,
                            is_const, op);
        }
        tv_clear(&rettv);
      }
    } else {
      op[0] = '=';
      op[1] = NUL;
      if (*expr != '=') {
        if (vim_strchr((char_u *)"+-*/%.", *expr) != NULL) {
          op[0] = *expr;  // +=, -=, *=, /=, %= or .=
          if (expr[0] == '.' && expr[1] == '.') {  // ..=
            expr++;
          }
        }
        expr = skipwhite(expr + 2);
      } else {
        expr = skipwhite(expr + 1);
      }
  
      if (eap->skip)
        ++emsg_skip;
      i = eval0(expr, &rettv, &eap->nextcmd, !eap->skip);
      if (eap->skip) {
        if (i != FAIL) {
          tv_clear(&rettv);
        }
        emsg_skip--;
      } else if (i != FAIL) {
        (void)ex_let_vars(eap->arg, &rettv, false, semicolon, var_count,
                          is_const, op);
        tv_clear(&rettv);
      }
    }
  }
  
  /*
   * Assign the typevalue "tv" to the variable or variables at "arg_start".
   * Handles both "var" with any type and "[var, var; var]" with a list type.
   * When "nextchars" is not NULL it points to a string with characters that
   * must appear after the variable(s).  Use "+", "-" or "." for add, subtract
   * or concatenate.
   * Returns OK or FAIL;
   */
  static int
  ex_let_vars(
      char_u *arg_start,
      typval_T *tv,
      int copy,                       // copy values from "tv", don't move
      int semicolon,                  // from skip_var_list()
      int var_count,                  // from skip_var_list()
      int is_const,                   // lock variables for :const
      char_u *nextchars
  )
  {
    char_u *arg = arg_start;
    typval_T ltv;
  
    if (*arg != '[') {
      /*
       * ":let var = expr" or ":for var in list"
       */
      if (ex_let_one(arg, tv, copy, is_const, nextchars, nextchars) == NULL) {
        return FAIL;
      }
      return OK;
    }
  
    // ":let [v1, v2] = list" or ":for [v1, v2] in listlist"
    if (tv->v_type != VAR_LIST) {
      EMSG(_(e_listreq));
      return FAIL;
    }
    list_T *const l = tv->vval.v_list;
  
    const int len = tv_list_len(l);
    if (semicolon == 0 && var_count < len) {
      EMSG(_("E687: Less targets than List items"));
      return FAIL;
    }
    if (var_count - semicolon > len) {
      EMSG(_("E688: More targets than List items"));
      return FAIL;
    }
    // List l may actually be NULL, but it should fail with E688 or even earlier
    // if you try to do ":let [] = v:_null_list".
    assert(l != NULL);
  
    listitem_T *item = tv_list_first(l);
    size_t rest_len = tv_list_len(l);
    while (*arg != ']') {
      arg = skipwhite(arg + 1);
      arg = ex_let_one(arg, TV_LIST_ITEM_TV(item), true, is_const,
                       (const char_u *)",;]", nextchars);
      if (arg == NULL) {
        return FAIL;
      }
      rest_len--;
  
      item = TV_LIST_ITEM_NEXT(l, item);
      arg = skipwhite(arg);
      if (*arg == ';') {
        /* Put the rest of the list (may be empty) in the var after ';'.
         * Create a new list for this. */
        list_T *const rest_list = tv_list_alloc(rest_len);
        while (item != NULL) {
          tv_list_append_tv(rest_list, TV_LIST_ITEM_TV(item));
          item = TV_LIST_ITEM_NEXT(l, item);
        }
  
        ltv.v_type = VAR_LIST;
        ltv.v_lock = VAR_UNLOCKED;
        ltv.vval.v_list = rest_list;
        tv_list_ref(rest_list);
  
        arg = ex_let_one(skipwhite(arg + 1), &ltv, false, is_const,
                         (char_u *)"]", nextchars);
        tv_clear(&ltv);
        if (arg == NULL) {
          return FAIL;
        }
        break;
      } else if (*arg != ',' && *arg != ']') {
        internal_error("ex_let_vars()");
        return FAIL;
      }
    }
  
    return OK;
  }
  
  /*
   * Skip over assignable variable "var" or list of variables "[var, var]".
   * Used for ":let varvar = expr" and ":for varvar in expr".
   * For "[var, var]" increment "*var_count" for each variable.
   * for "[var, var; var]" set "semicolon".
   * Return NULL for an error.
   */
  static const char_u *skip_var_list(const char_u *arg, int *var_count,
                                     int *semicolon)
  {
    const char_u *p;
    const char_u *s;
  
    if (*arg == '[') {
      // "[var, var]": find the matching ']'.
      p = arg;
      for (;; ) {
        p = skipwhite(p + 1);             // skip whites after '[', ';' or ','
        s = skip_var_one(p);
        if (s == p) {
          EMSG2(_(e_invarg2), p);
          return NULL;
        }
        ++*var_count;
  
        p = skipwhite(s);
        if (*p == ']')
          break;
        else if (*p == ';') {
          if (*semicolon == 1) {
            EMSG(_("Double ; in list of variables"));
            return NULL;
          }
          *semicolon = 1;
        } else if (*p != ',') {
          EMSG2(_(e_invarg2), p);
          return NULL;
        }
      }
      return p + 1;
    } else
      return skip_var_one(arg);
  }
  
  /*
   * Skip one (assignable) variable name, including @r, $VAR, &option, d.key,
   * l[idx].
   */
  static const char_u *skip_var_one(const char_u *arg)
  {
    if (*arg == '@' && arg[1] != NUL)
      return arg + 2;
    return find_name_end(*arg == '$' || *arg == '&' ? arg + 1 : arg,
        NULL, NULL, FNE_INCL_BR | FNE_CHECK_START);
  }
  
  /*
   * List variables for hashtab "ht" with prefix "prefix".
   * If "empty" is TRUE also list NULL strings as empty strings.
   */
  void list_hashtable_vars(hashtab_T *ht, const char *prefix, int empty,
                           int *first)
  {
    hashitem_T  *hi;
    dictitem_T  *di;
    int todo;
  
    todo = (int)ht->ht_used;
    for (hi = ht->ht_array; todo > 0 && !got_int; ++hi) {
      if (!HASHITEM_EMPTY(hi)) {
        todo--;
        di = TV_DICT_HI2DI(hi);
        char buf[IOSIZE];
  
        // apply :filter /pat/ to variable name
        xstrlcpy(buf, prefix, IOSIZE - 1);
        xstrlcat(buf, (char *)di->di_key, IOSIZE);
        if (message_filtered((char_u *)buf)) {
          continue;
        }
  
        if (empty || di->di_tv.v_type != VAR_STRING
            || di->di_tv.vval.v_string != NULL) {
          list_one_var(di, prefix, first);
        }
      }
    }
  }
  
  /*
   * List global variables.
   */
  static void list_glob_vars(int *first)
  {
    list_hashtable_vars(&globvarht, "", true, first);
  }
  
  /*
   * List buffer variables.
   */
  static void list_buf_vars(int *first)
  {
    list_hashtable_vars(&curbuf->b_vars->dv_hashtab, "b:", true, first);
  }
  
  /*
   * List window variables.
   */
  static void list_win_vars(int *first)
  {
    list_hashtable_vars(&curwin->w_vars->dv_hashtab, "w:", true, first);
  }
  
  /*
   * List tab page variables.
   */
  static void list_tab_vars(int *first)
  {
    list_hashtable_vars(&curtab->tp_vars->dv_hashtab, "t:", true, first);
  }
  
  /*
   * List Vim variables.
   */
  static void list_vim_vars(int *first)
  {
    list_hashtable_vars(&vimvarht, "v:", false, first);
  }
  
  // List script-local variables, if there is a script.
  static void list_script_vars(int *first)
  {
    if (current_sctx.sc_sid > 0 && current_sctx.sc_sid <= ga_scripts.ga_len) {
      list_hashtable_vars(&SCRIPT_VARS(current_sctx.sc_sid), "s:", false, first);
    }
  }
  
  /*
   * List variables in "arg".
   */
  static const char *list_arg_vars(exarg_T *eap, const char *arg, int *first)
  {
    int error = FALSE;
    int len;
    const char *name;
    const char *name_start;
    typval_T tv;
  
    while (!ends_excmd(*arg) && !got_int) {
      if (error || eap->skip) {
        arg = (const char *)find_name_end((char_u *)arg, NULL, NULL,
                                          FNE_INCL_BR | FNE_CHECK_START);
        if (!ascii_iswhite(*arg) && !ends_excmd(*arg)) {
          emsg_severe = TRUE;
          EMSG(_(e_trailing));
          break;
        }
      } else {
        // get_name_len() takes care of expanding curly braces
        name_start = name = arg;
        char *tofree;
        len = get_name_len(&arg, &tofree, true, true);
        if (len <= 0) {
          /* This is mainly to keep test 49 working: when expanding
           * curly braces fails overrule the exception error message. */
          if (len < 0 && !aborting()) {
            emsg_severe = TRUE;
            EMSG2(_(e_invarg2), arg);
            break;
          }
          error = TRUE;
        } else {
          if (tofree != NULL) {
            name = tofree;
          }
          if (get_var_tv((const char *)name, len, &tv, NULL, true, false)
              == FAIL) {
            error = true;
          } else {
            // handle d.key, l[idx], f(expr)
            const char *const arg_subsc = arg;
            if (handle_subscript(&arg, &tv, true, true) == FAIL) {
              error = true;
            } else {
              if (arg == arg_subsc && len == 2 && name[1] == ':') {
                switch (*name) {
                case 'g': list_glob_vars(first); break;
                case 'b': list_buf_vars(first); break;
                case 'w': list_win_vars(first); break;
                case 't': list_tab_vars(first); break;
                case 'v': list_vim_vars(first); break;
                case 's': list_script_vars(first); break;
                case 'l': list_func_vars(first); break;
                default:
                  EMSG2(_("E738: Can't list variables for %s"), name);
                }
              } else {
                char *const s = encode_tv2echo(&tv, NULL);
                const char *const used_name = (arg == arg_subsc
                                               ? name
                                               : name_start);
                const ptrdiff_t name_size = (used_name == tofree
                                             ? (ptrdiff_t)strlen(used_name)
                                             : (arg - used_name));
                list_one_var_a("", used_name, name_size,
                               tv.v_type, s == NULL ? "" : s, first);
                xfree(s);
              }
              tv_clear(&tv);
            }
          }
        }
  
        xfree(tofree);
      }
  
      arg = (const char *)skipwhite((const char_u *)arg);
    }
  
    return arg;
  }
  
  // TODO(ZyX-I): move to eval/ex_cmds
  
  /// Set one item of `:let var = expr` or `:let [v1, v2] = list` to its value
  ///
  /// @param[in]  arg  Start of the variable name.
  /// @param[in]  tv  Value to assign to the variable.
  /// @param[in]  copy  If true, copy value from `tv`.
  /// @param[in]  endchars  Valid characters after variable name or NULL.
  /// @param[in]  op  Operation performed: *op is `+`, `-`, `.` for `+=`, etc.
  ///                 NULL for `=`.
  ///
  /// @return a pointer to the char just after the var name or NULL in case of
  ///         error.
  static char_u *ex_let_one(char_u *arg, typval_T *const tv,
                            const bool copy, const bool is_const,
                            const char_u *const endchars, const char_u *const op)
    FUNC_ATTR_NONNULL_ARG(1, 2) FUNC_ATTR_WARN_UNUSED_RESULT
  {
    char_u *arg_end = NULL;
    int len;
    int opt_flags;
    char_u *tofree = NULL;
  
    /*
     * ":let $VAR = expr": Set environment variable.
     */
    if (*arg == '$') {
      if (is_const) {
        EMSG(_("E996: Cannot lock an environment variable"));
        return NULL;
      }
      // Find the end of the name.
      arg++;
      char *name = (char *)arg;
      len = get_env_len((const char_u **)&arg);
      if (len == 0) {
        EMSG2(_(e_invarg2), name - 1);
      } else {
        if (op != NULL && vim_strchr((char_u *)"+-*/%", *op) != NULL) {
          EMSG2(_(e_letwrong), op);
        } else if (endchars != NULL
                   && vim_strchr(endchars, *skipwhite(arg)) == NULL) {
          EMSG(_(e_letunexp));
        } else if (!check_secure()) {
          const char c1 = name[len];
          name[len] = NUL;
          const char *p = tv_get_string_chk(tv);
          if (p != NULL && op != NULL && *op == '.') {
            char *s = vim_getenv(name);
  
            if (s != NULL) {
              tofree = concat_str((const char_u *)s, (const char_u *)p);
              p = (const char *)tofree;
              xfree(s);
            }
          }
          if (p != NULL) {
            os_setenv(name, p, 1);
            if (STRICMP(name, "HOME") == 0) {
              init_homedir();
            } else if (didset_vim && STRICMP(name, "VIM") == 0) {
              didset_vim = false;
            } else if (didset_vimruntime
                       && STRICMP(name, "VIMRUNTIME") == 0) {
              didset_vimruntime = false;
            }
            arg_end = arg;
          }
          name[len] = c1;
          xfree(tofree);
        }
      }
    // ":let &option = expr": Set option value.
    // ":let &l:option = expr": Set local option value.
    // ":let &g:option = expr": Set global option value.
    } else if (*arg == '&') {
      if (is_const) {
        EMSG(_("E996: Cannot lock an option"));
        return NULL;
      }
      // Find the end of the name.
      char *const p = (char *)find_option_end((const char **)&arg, &opt_flags);
      if (p == NULL
          || (endchars != NULL
              && vim_strchr(endchars, *skipwhite((const char_u *)p)) == NULL)) {
        EMSG(_(e_letunexp));
      } else {
        int opt_type;
        long numval;
        char *stringval = NULL;
        const char *s = NULL;
  
        const char c1 = *p;
        *p = NUL;
  
        varnumber_T n = tv_get_number(tv);
        if (tv->v_type != VAR_BOOL && tv->v_type != VAR_SPECIAL) {
          s = tv_get_string_chk(tv);  // != NULL if number or string.
        }
        if (s != NULL && op != NULL && *op != '=') {
          opt_type = get_option_value(arg, &numval, (char_u **)&stringval,
                                      opt_flags);
          if ((opt_type == 1 && *op == '.')
              || (opt_type == 0 && *op != '.')) {
            EMSG2(_(e_letwrong), op);
            s = NULL;  // don't set the value
          } else {
            if (opt_type == 1) {  // number
              switch (*op) {
                case '+': n = numval + n; break;
                case '-': n = numval - n; break;
                case '*': n = numval * n; break;
                case '/': n = num_divide(numval, n); break;
                case '%': n = num_modulus(numval, n); break;
              }
            } else if (opt_type == 0 && stringval != NULL) {  // string
              char *const oldstringval = stringval;
              stringval = (char *)concat_str((const char_u *)stringval,
                                             (const char_u *)s);
              xfree(oldstringval);
              s = stringval;
            }
          }
        }
        if (s != NULL || tv->v_type == VAR_BOOL
            || tv->v_type == VAR_SPECIAL) {
          set_option_value((const char *)arg, n, s, opt_flags);
          arg_end = (char_u *)p;
        }
        *p = c1;
        xfree(stringval);
      }
    // ":let @r = expr": Set register contents.
    } else if (*arg == '@') {
      if (is_const) {
        EMSG(_("E996: Cannot lock a register"));
        return NULL;
      }
      arg++;
      if (op != NULL && vim_strchr((char_u *)"+-*/%", *op) != NULL) {
        emsgf(_(e_letwrong), op);
      } else if (endchars != NULL
                 && vim_strchr(endchars, *skipwhite(arg + 1)) == NULL) {
        EMSG(_(e_letunexp));
      } else {
        char_u      *s;
  
        char_u *ptofree = NULL;
        const char *p = tv_get_string_chk(tv);
        if (p != NULL && op != NULL && *op == '.') {
          s = get_reg_contents(*arg == '@' ? '"' : *arg, kGRegExprSrc);
          if (s != NULL) {
            ptofree = concat_str(s, (const char_u *)p);
            p = (const char *)ptofree;
            xfree(s);
          }
        }
        if (p != NULL) {
          write_reg_contents(*arg == '@' ? '"' : *arg,
                             (const char_u *)p, STRLEN(p), false);
          arg_end = arg + 1;
        }
        xfree(ptofree);
      }
    }
    /*
     * ":let var = expr": Set internal variable.
     * ":let {expr} = expr": Idem, name made with curly braces
     */
    else if (eval_isnamec1(*arg) || *arg == '{') {
      lval_T lv;
  
      char_u *const p = get_lval(arg, tv, &lv, false, false, 0, FNE_CHECK_START);
      if (p != NULL && lv.ll_name != NULL) {
        if (endchars != NULL && vim_strchr(endchars, *skipwhite(p)) == NULL) {
          EMSG(_(e_letunexp));
        } else {
          set_var_lval(&lv, p, tv, copy, is_const, op);
          arg_end = p;
        }
      }
      clear_lval(&lv);
    } else
      EMSG2(_(e_invarg2), arg);
  
    return arg_end;
  }
  
  // TODO(ZyX-I): move to eval/executor
  
  /// Get an lvalue
  ///
  /// Lvalue may be
  /// - variable: "name", "na{me}"
  /// - dictionary item: "dict.key", "dict['key']"
  /// - list item: "list[expr]"
  /// - list slice: "list[expr:expr]"
  ///
  /// Indexing only works if trying to use it with an existing List or Dictionary.
  ///
  /// @param[in]  name  Name to parse.
  /// @param  rettv  Pointer to the value to be assigned or NULL.
  /// @param[out]  lp  Lvalue definition. When evaluation errors occur `->ll_name`
  ///                  is NULL.
  /// @param[in]  unlet  True if using `:unlet`. This results in slightly
  ///                    different behaviour when something is wrong; must end in
  ///                    space or cmd separator.
  /// @param[in]  skip  True when skipping.
  /// @param[in]  flags  @see GetLvalFlags.
  /// @param[in]  fne_flags  Flags for find_name_end().
  ///
  /// @return A pointer to just after the name, including indexes. Returns NULL
  ///         for a parsing error, but it is still needed to free items in lp.
  char_u *get_lval(char_u *const name, typval_T *const rettv,
                   lval_T *const lp, const bool unlet, const bool skip,
                   const int flags, const int fne_flags)
    FUNC_ATTR_NONNULL_ARG(1, 3)
  {
    dictitem_T  *v;
    typval_T var1;
    typval_T var2;
    int empty1 = FALSE;
    listitem_T  *ni;
    hashtab_T   *ht;
    int quiet = flags & GLV_QUIET;
  
    // Clear everything in "lp".
    memset(lp, 0, sizeof(lval_T));
  
    if (skip) {
      // When skipping just find the end of the name.
      lp->ll_name = (const char *)name;
      return (char_u *)find_name_end((const char_u *)name, NULL, NULL,
                                     FNE_INCL_BR | fne_flags);
    }
  
    // Find the end of the name.
    char_u *expr_start;
    char_u *expr_end;
    char_u *p = (char_u *)find_name_end(name,
                                        (const char_u **)&expr_start,
                                        (const char_u **)&expr_end,
                                        fne_flags);
    if (expr_start != NULL) {
      // Don't expand the name when we already know there is an error.
      if (unlet && !ascii_iswhite(*p) && !ends_excmd(*p)
          && *p != '[' && *p != '.') {
        EMSG(_(e_trailing));
        return NULL;
      }
  
      lp->ll_exp_name = (char *)make_expanded_name(name, expr_start, expr_end,
                                                   (char_u *)p);
      lp->ll_name = lp->ll_exp_name;
      if (lp->ll_exp_name == NULL) {
        /* Report an invalid expression in braces, unless the
         * expression evaluation has been cancelled due to an
         * aborting error, an interrupt, or an exception. */
        if (!aborting() && !quiet) {
          emsg_severe = TRUE;
          EMSG2(_(e_invarg2), name);
          return NULL;
        }
        lp->ll_name_len = 0;
      } else {
        lp->ll_name_len = strlen(lp->ll_name);
      }
    } else {
      lp->ll_name = (const char *)name;
      lp->ll_name_len = (size_t)((const char *)p - lp->ll_name);
    }
  
    // Without [idx] or .key we are done.
    if ((*p != '[' && *p != '.') || lp->ll_name == NULL) {
      return p;
    }
  
    // Only pass &ht when we would write to the variable, it prevents autoload
    // as well.
    v = find_var(lp->ll_name, lp->ll_name_len,
                 (flags & GLV_READ_ONLY) ? NULL : &ht,
                 flags & GLV_NO_AUTOLOAD);
    if (v == NULL && !quiet) {
      emsgf(_("E121: Undefined variable: %.*s"),
            (int)lp->ll_name_len, lp->ll_name);
    }
    if (v == NULL) {
      return NULL;
    }
  
    /*
     * Loop until no more [idx] or .key is following.
     */
    lp->ll_tv = &v->di_tv;
    var1.v_type = VAR_UNKNOWN;
    var2.v_type = VAR_UNKNOWN;
    while (*p == '[' || (*p == '.' && lp->ll_tv->v_type == VAR_DICT)) {
      if (!(lp->ll_tv->v_type == VAR_LIST && lp->ll_tv->vval.v_list != NULL)
          && !(lp->ll_tv->v_type == VAR_DICT
               && lp->ll_tv->vval.v_dict != NULL)) {
        if (!quiet)
          EMSG(_("E689: Can only index a List or Dictionary"));
        return NULL;
      }
      if (lp->ll_range) {
        if (!quiet)
          EMSG(_("E708: [:] must come last"));
        return NULL;
      }
  
      int len = -1;
      char_u *key = NULL;
      if (*p == '.') {
        key = p + 1;
        for (len = 0; ASCII_ISALNUM(key[len]) || key[len] == '_'; len++) {
        }
        if (len == 0) {
          if (!quiet) {
            EMSG(_("E713: Cannot use empty key after ."));
          }
          return NULL;
        }
        p = key + len;
      } else {
        // Get the index [expr] or the first index [expr: ].
        p = skipwhite(p + 1);
        if (*p == ':') {
          empty1 = true;
        } else {
          empty1 = false;
          if (eval1(&p, &var1, true) == FAIL) {  // Recursive!
            return NULL;
          }
          if (!tv_check_str(&var1)) {
            // Not a number or string.
            tv_clear(&var1);
            return NULL;
          }
        }
  
        // Optionally get the second index [ :expr].
        if (*p == ':') {
          if (lp->ll_tv->v_type == VAR_DICT) {
            if (!quiet) {
              EMSG(_(e_dictrange));
            }
            tv_clear(&var1);
            return NULL;
          }
          if (rettv != NULL && (rettv->v_type != VAR_LIST
                                || rettv->vval.v_list == NULL)) {
            if (!quiet) {
              EMSG(_("E709: [:] requires a List value"));
            }
            tv_clear(&var1);
            return NULL;
          }
          p = skipwhite(p + 1);
          if (*p == ']') {
            lp->ll_empty2 = true;
          } else {
            lp->ll_empty2 = false;
            if (eval1(&p, &var2, true) == FAIL) {  // Recursive!
              tv_clear(&var1);
              return NULL;
            }
            if (!tv_check_str(&var2)) {
              // Not a number or string.
              tv_clear(&var1);
              tv_clear(&var2);
              return NULL;
            }
          }
          lp->ll_range = TRUE;
        } else
          lp->ll_range = FALSE;
  
        if (*p != ']') {
          if (!quiet) {
            EMSG(_(e_missbrac));
          }
          tv_clear(&var1);
          tv_clear(&var2);
          return NULL;
        }
  
        // Skip to past ']'.
        p++;
      }
  
      if (lp->ll_tv->v_type == VAR_DICT) {
        if (len == -1) {
          // "[key]": get key from "var1"
          key = (char_u *)tv_get_string(&var1);  // is number or string
        }
        lp->ll_list = NULL;
        lp->ll_dict = lp->ll_tv->vval.v_dict;
        lp->ll_di = tv_dict_find(lp->ll_dict, (const char *)key, len);
  
        /* When assigning to a scope dictionary check that a function and
         * variable name is valid (only variable name unless it is l: or
         * g: dictionary). Disallow overwriting a builtin function. */
        if (rettv != NULL && lp->ll_dict->dv_scope != 0) {
          int prevval;
          int wrong;
  
          if (len != -1) {
            prevval = key[len];
            key[len] = NUL;
          } else {
            prevval = 0;  // Avoid compiler warning.
          }
          wrong = ((lp->ll_dict->dv_scope == VAR_DEF_SCOPE
                    && tv_is_func(*rettv)
                    && !var_check_func_name((const char *)key, lp->ll_di == NULL))
                   || !valid_varname((const char *)key));
          if (len != -1) {
            key[len] = prevval;
          }
          if (wrong) {
            return NULL;
          }
        }
  
        if (lp->ll_di != NULL && tv_is_luafunc(&lp->ll_di->di_tv)
            && len == -1 && rettv == NULL) {
          tv_clear(&var1);
          EMSG2(e_illvar, "v:['lua']");
          return NULL;
        }
  
        if (lp->ll_di == NULL) {
          // Can't add "v:" or "a:" variable.
          if (lp->ll_dict == &vimvardict
              || &lp->ll_dict->dv_hashtab == get_funccal_args_ht()) {
            EMSG2(_(e_illvar), name);
            tv_clear(&var1);
            return NULL;
          }
  
          // Key does not exist in dict: may need to add it.
          if (*p == '[' || *p == '.' || unlet) {
            if (!quiet) {
              emsgf(_(e_dictkey), key);
            }
            tv_clear(&var1);
            return NULL;
          }
          if (len == -1) {
            lp->ll_newkey = vim_strsave(key);
          } else {
            lp->ll_newkey = vim_strnsave(key, len);
          }
          tv_clear(&var1);
          break;
        // existing variable, need to check if it can be changed
        } else if (!(flags & GLV_READ_ONLY) && var_check_ro(lp->ll_di->di_flags,
                                                            (const char *)name,
                                                            (size_t)(p - name))) {
          tv_clear(&var1);
          return NULL;
        }
  
        tv_clear(&var1);
        lp->ll_tv = &lp->ll_di->di_tv;
      } else {
        // Get the number and item for the only or first index of the List.
        if (empty1) {
          lp->ll_n1 = 0;
        } else {
          // Is number or string.
          lp->ll_n1 = (long)tv_get_number(&var1);
        }
        tv_clear(&var1);
  
        lp->ll_dict = NULL;
        lp->ll_list = lp->ll_tv->vval.v_list;
        lp->ll_li = tv_list_find(lp->ll_list, lp->ll_n1);
        if (lp->ll_li == NULL) {
          if (lp->ll_n1 < 0) {
            lp->ll_n1 = 0;
            lp->ll_li = tv_list_find(lp->ll_list, lp->ll_n1);
          }
        }
        if (lp->ll_li == NULL) {
          tv_clear(&var2);
          if (!quiet) {
            EMSGN(_(e_listidx), lp->ll_n1);
          }
          return NULL;
        }
  
        /*
         * May need to find the item or absolute index for the second
         * index of a range.
         * When no index given: "lp->ll_empty2" is TRUE.
         * Otherwise "lp->ll_n2" is set to the second index.
         */
        if (lp->ll_range && !lp->ll_empty2) {
          lp->ll_n2 = (long)tv_get_number(&var2);  // Is number or string.
          tv_clear(&var2);
          if (lp->ll_n2 < 0) {
            ni = tv_list_find(lp->ll_list, lp->ll_n2);
            if (ni == NULL) {
              if (!quiet)
                EMSGN(_(e_listidx), lp->ll_n2);
              return NULL;
            }
            lp->ll_n2 = tv_list_idx_of_item(lp->ll_list, ni);
          }
  
          // Check that lp->ll_n2 isn't before lp->ll_n1.
          if (lp->ll_n1 < 0) {
            lp->ll_n1 = tv_list_idx_of_item(lp->ll_list, lp->ll_li);
          }
          if (lp->ll_n2 < lp->ll_n1) {
            if (!quiet) {
              EMSGN(_(e_listidx), lp->ll_n2);
            }
            return NULL;
          }
        }
  
        lp->ll_tv = TV_LIST_ITEM_TV(lp->ll_li);
      }
    }
  
    tv_clear(&var1);
    return p;
  }
  
  // TODO(ZyX-I): move to eval/executor
  
  /*
   * Clear lval "lp" that was filled by get_lval().
   */
  void clear_lval(lval_T *lp)
  {
    xfree(lp->ll_exp_name);
    xfree(lp->ll_newkey);
  }
  
  // TODO(ZyX-I): move to eval/executor
  
  /*
   * Set a variable that was parsed by get_lval() to "rettv".
   * "endp" points to just after the parsed name.
   * "op" is NULL, "+" for "+=", "-" for "-=", "*" for "*=", "/" for "/=",
   * "%" for "%=", "." for ".=" or "=" for "=".
   */
  static void set_var_lval(lval_T *lp, char_u *endp, typval_T *rettv,
                           int copy, const bool is_const, const char_u *op)
  {
    int cc;
    listitem_T  *ri;
    dictitem_T  *di;
  
    if (lp->ll_tv == NULL) {
      cc = *endp;
      *endp = NUL;
      if (op != NULL && *op != '=') {
        typval_T tv;
  
        if (is_const) {
          EMSG(_(e_cannot_mod));
          *endp = cc;
          return;
        }
  
        // handle +=, -=, *=, /=, %= and .=
        di = NULL;
        if (get_var_tv((const char *)lp->ll_name, (int)STRLEN(lp->ll_name),
                       &tv, &di, true, false) == OK) {
          if ((di == NULL
               || (!var_check_ro(di->di_flags, (const char *)lp->ll_name,
                                 TV_CSTRING)
                   && !tv_check_lock(di->di_tv.v_lock, (const char *)lp->ll_name,
                                     TV_CSTRING)))
              && eexe_mod_op(&tv, rettv, (const char *)op) == OK) {
            set_var(lp->ll_name, lp->ll_name_len, &tv, false);
          }
          tv_clear(&tv);
        }
      } else {
        set_var_const(lp->ll_name, lp->ll_name_len, rettv, copy, is_const);
      }
      *endp = cc;
    } else if (tv_check_lock(lp->ll_newkey == NULL
                             ? lp->ll_tv->v_lock
                             : lp->ll_tv->vval.v_dict->dv_lock,
                             (const char *)lp->ll_name, TV_CSTRING)) {
    } else if (lp->ll_range) {
      listitem_T *ll_li = lp->ll_li;
      int ll_n1 = lp->ll_n1;
  
      if (is_const) {
        EMSG(_("E996: Cannot lock a range"));
        return;
      }
  
      // Check whether any of the list items is locked
      for (ri = tv_list_first(rettv->vval.v_list);
           ri != NULL && ll_li != NULL; ) {
        if (tv_check_lock(TV_LIST_ITEM_TV(ll_li)->v_lock,
                          (const char *)lp->ll_name,
                          TV_CSTRING)) {
          return;
        }
        ri = TV_LIST_ITEM_NEXT(rettv->vval.v_list, ri);
        if (ri == NULL || (!lp->ll_empty2 && lp->ll_n2 == ll_n1)) {
          break;
        }
        ll_li = TV_LIST_ITEM_NEXT(lp->ll_list, ll_li);
        ll_n1++;
      }
  
      /*
       * Assign the List values to the list items.
       */
      for (ri = tv_list_first(rettv->vval.v_list); ri != NULL; ) {
        if (op != NULL && *op != '=') {
          eexe_mod_op(TV_LIST_ITEM_TV(lp->ll_li), TV_LIST_ITEM_TV(ri),
                      (const char *)op);
        } else {
          tv_clear(TV_LIST_ITEM_TV(lp->ll_li));
          tv_copy(TV_LIST_ITEM_TV(ri), TV_LIST_ITEM_TV(lp->ll_li));
        }
        ri = TV_LIST_ITEM_NEXT(rettv->vval.v_list, ri);
        if (ri == NULL || (!lp->ll_empty2 && lp->ll_n2 == lp->ll_n1)) {
          break;
        }
        assert(lp->ll_li != NULL);
        if (TV_LIST_ITEM_NEXT(lp->ll_list, lp->ll_li) == NULL) {
          // Need to add an empty item.
          tv_list_append_number(lp->ll_list, 0);
          // ll_li may have become invalid after append, don’t use it.
          lp->ll_li = tv_list_last(lp->ll_list);  // Valid again.
        } else {
          lp->ll_li = TV_LIST_ITEM_NEXT(lp->ll_list, lp->ll_li);
        }
        lp->ll_n1++;
      }
      if (ri != NULL) {
        EMSG(_("E710: List value has more items than target"));
      } else if (lp->ll_empty2
                 ? (lp->ll_li != NULL
                    && TV_LIST_ITEM_NEXT(lp->ll_list, lp->ll_li) != NULL)
                 : lp->ll_n1 != lp->ll_n2) {
        EMSG(_("E711: List value has not enough items"));
      }
    } else {
      typval_T oldtv = TV_INITIAL_VALUE;
      dict_T *dict = lp->ll_dict;
      bool watched = tv_dict_is_watched(dict);
  
      if (is_const) {
        EMSG(_("E996: Cannot lock a list or dict"));
        return;
      }
  
      // Assign to a List or Dictionary item.
      if (lp->ll_newkey != NULL) {
        if (op != NULL && *op != '=') {
          EMSG2(_(e_letwrong), op);
          return;
        }
  
        // Need to add an item to the Dictionary.
        di = tv_dict_item_alloc((const char *)lp->ll_newkey);
        if (tv_dict_add(lp->ll_tv->vval.v_dict, di) == FAIL) {
          xfree(di);
          return;
        }
        lp->ll_tv = &di->di_tv;
      } else {
        if (watched) {
          tv_copy(lp->ll_tv, &oldtv);
        }
  
        if (op != NULL && *op != '=') {
          eexe_mod_op(lp->ll_tv, rettv, (const char *)op);
          goto notify;
        } else {
          tv_clear(lp->ll_tv);
        }
      }
  
      // Assign the value to the variable or list item.
      if (copy) {
        tv_copy(rettv, lp->ll_tv);
      } else {
        *lp->ll_tv = *rettv;
        lp->ll_tv->v_lock = 0;
        tv_init(rettv);
      }
  
  notify:
      if (watched) {
        if (oldtv.v_type == VAR_UNKNOWN) {
          assert(lp->ll_newkey != NULL);
          tv_dict_watcher_notify(dict, (char *)lp->ll_newkey, lp->ll_tv, NULL);
        } else {
          dictitem_T *di_ = lp->ll_di;
          assert(di_->di_key != NULL);
          tv_dict_watcher_notify(dict, (char *)di_->di_key, lp->ll_tv, &oldtv);
          tv_clear(&oldtv);
        }
      }
    }
  }
  
  // TODO(ZyX-I): move to eval/ex_cmds
  
  /*
   * Evaluate the expression used in a ":for var in expr" command.
   * "arg" points to "var".
   * Set "*errp" to TRUE for an error, FALSE otherwise;
   * Return a pointer that holds the info.  Null when there is an error.
   */
  void *eval_for_line(const char_u *arg, bool *errp, char_u **nextcmdp, int skip)
  {
    forinfo_T   *fi = xcalloc(1, sizeof(forinfo_T));
    const char_u *expr;
    typval_T tv;
    list_T      *l;
  
    *errp = true;  // Default: there is an error.
  
    expr = skip_var_list(arg, &fi->fi_varcount, &fi->fi_semicolon);
    if (expr == NULL)
      return fi;
  
    expr = skipwhite(expr);
    if (expr[0] != 'i' || expr[1] != 'n' || !ascii_iswhite(expr[2])) {
      EMSG(_("E690: Missing \"in\" after :for"));
      return fi;
    }
  
    if (skip)
      ++emsg_skip;
    if (eval0(skipwhite(expr + 2), &tv, nextcmdp, !skip) == OK) {
      *errp = false;
      if (!skip) {
        l = tv.vval.v_list;
        if (tv.v_type != VAR_LIST) {
          EMSG(_(e_listreq));
          tv_clear(&tv);
        } else if (l == NULL) {
          // a null list is like an empty list: do nothing
          tv_clear(&tv);
        } else {
          /* No need to increment the refcount, it's already set for the
           * list being used in "tv". */
          fi->fi_list = l;
          tv_list_watch_add(l, &fi->fi_lw);
          fi->fi_lw.lw_item = tv_list_first(l);
        }
      }
    }
    if (skip)
      --emsg_skip;
  
    return fi;
  }
  
  // TODO(ZyX-I): move to eval/ex_cmds
  
  /*
   * Use the first item in a ":for" list.  Advance to the next.
   * Assign the values to the variable (list).  "arg" points to the first one.
   * Return TRUE when a valid item was found, FALSE when at end of list or
   * something wrong.
   */
  bool next_for_item(void *fi_void, char_u *arg)
  {
    forinfo_T *fi = (forinfo_T *)fi_void;
  
    listitem_T *item = fi->fi_lw.lw_item;
    if (item == NULL) {
      return false;
    } else {
      fi->fi_lw.lw_item = TV_LIST_ITEM_NEXT(fi->fi_list, item);
      return (ex_let_vars(arg, TV_LIST_ITEM_TV(item), true,
                          fi->fi_semicolon, fi->fi_varcount, false, NULL) == OK);
    }
  }
  
  // TODO(ZyX-I): move to eval/ex_cmds
  
  /*
   * Free the structure used to store info used by ":for".
   */
  void free_for_info(void *fi_void)
  {
    forinfo_T    *fi = (forinfo_T *)fi_void;
  
    if (fi != NULL && fi->fi_list != NULL) {
      tv_list_watch_remove(fi->fi_list, &fi->fi_lw);
      tv_list_unref(fi->fi_list);
    }
    xfree(fi);
  }
  
  
  void set_context_for_expression(expand_T *xp, char_u *arg, cmdidx_T cmdidx)
  {
    int got_eq = FALSE;
    int c;
    char_u      *p;
  
    if (cmdidx == CMD_let || cmdidx == CMD_const) {
      xp->xp_context = EXPAND_USER_VARS;
      if (vim_strpbrk(arg, (char_u *)"\"'+-*/%.=!?~|&$([<>,#") == NULL) {
        // ":let var1 var2 ...": find last space.
        for (p = arg + STRLEN(arg); p >= arg; ) {
          xp->xp_pattern = p;
          MB_PTR_BACK(arg, p);
          if (ascii_iswhite(*p)) {
            break;
          }
        }
        return;
      }
    } else
      xp->xp_context = cmdidx == CMD_call ? EXPAND_FUNCTIONS
                       : EXPAND_EXPRESSION;
    while ((xp->xp_pattern = vim_strpbrk(arg,
                (char_u *)"\"'+-*/%.=!?~|&$([<>,#")) != NULL) {
      c = *xp->xp_pattern;
      if (c == '&') {
        c = xp->xp_pattern[1];
        if (c == '&') {
          ++xp->xp_pattern;
          xp->xp_context = cmdidx != CMD_let || got_eq
                           ? EXPAND_EXPRESSION : EXPAND_NOTHING;
        } else if (c != ' ') {
          xp->xp_context = EXPAND_SETTINGS;
          if ((c == 'l' || c == 'g') && xp->xp_pattern[2] == ':')
            xp->xp_pattern += 2;
  
        }
      } else if (c == '$') {
        // environment variable
        xp->xp_context = EXPAND_ENV_VARS;
      } else if (c == '=') {
        got_eq = TRUE;
        xp->xp_context = EXPAND_EXPRESSION;
      } else if (c == '#'
                 && xp->xp_context == EXPAND_EXPRESSION) {
        // Autoload function/variable contains '#'
        break;
      } else if ((c == '<' || c == '#')
                 && xp->xp_context == EXPAND_FUNCTIONS
                 && vim_strchr(xp->xp_pattern, '(') == NULL) {
        // Function name can start with "<SNR>" and contain '#'.
        break;
      } else if (cmdidx != CMD_let || got_eq) {
        if (c == '"') {               // string
          while ((c = *++xp->xp_pattern) != NUL && c != '"') {
            if (c == '\\' && xp->xp_pattern[1] != NUL) {
              xp->xp_pattern++;
            }
          }
          xp->xp_context = EXPAND_NOTHING;
        } else if (c == '\'') {     // literal string
          // Trick: '' is like stopping and starting a literal string.
          while ((c = *++xp->xp_pattern) != NUL && c != '\'') {
          }
          xp->xp_context = EXPAND_NOTHING;
        } else if (c == '|') {
          if (xp->xp_pattern[1] == '|') {
            ++xp->xp_pattern;
            xp->xp_context = EXPAND_EXPRESSION;
          } else
            xp->xp_context = EXPAND_COMMANDS;
        } else
          xp->xp_context = EXPAND_EXPRESSION;
      } else
        /* Doesn't look like something valid, expand as an expression
         * anyway. */
        xp->xp_context = EXPAND_EXPRESSION;
      arg = xp->xp_pattern;
      if (*arg != NUL) {
        while ((c = *++arg) != NUL && (c == ' ' || c == '\t')) {
        }
      }
    }
    xp->xp_pattern = arg;
  }
  
  /*
   * ":unlet[!] var1 ... " command.
   */
  void ex_unlet(exarg_T *eap)
  {
    ex_unletlock(eap, eap->arg, 0);
  }
  
  // TODO(ZyX-I): move to eval/ex_cmds
  
  /*
   * ":lockvar" and ":unlockvar" commands
   */
  void ex_lockvar(exarg_T *eap)
  {
    char_u      *arg = eap->arg;
    int deep = 2;
  
    if (eap->forceit) {
      deep = -1;
    } else if (ascii_isdigit(*arg)) {
      deep = getdigits_int(&arg, false, -1);
      arg = skipwhite(arg);
    }
  
    ex_unletlock(eap, arg, deep);
  }
  
  // TODO(ZyX-I): move to eval/ex_cmds
  
  /*
   * ":unlet", ":lockvar" and ":unlockvar" are quite similar.
   */
  static void ex_unletlock(exarg_T *eap, char_u *argstart, int deep)
  {
    char_u      *arg = argstart;
    bool error = false;
    lval_T lv;
  
    do {
      if (*arg == '$') {
        const char *name = (char *)++arg;
  
        if (get_env_len((const char_u **)&arg) == 0) {
          EMSG2(_(e_invarg2), name - 1);
          return;
        }
        os_unsetenv(name);
        arg = skipwhite(arg);
        continue;
      }
  
      // Parse the name and find the end.
      char_u *const name_end = (char_u *)get_lval(arg, NULL, &lv, true,
                                                  eap->skip || error,
                                                  0, FNE_CHECK_START);
      if (lv.ll_name == NULL) {
        error = true;  // error, but continue parsing.
      }
      if (name_end == NULL || (!ascii_iswhite(*name_end)
                               && !ends_excmd(*name_end))) {
        if (name_end != NULL) {
          emsg_severe = TRUE;
          EMSG(_(e_trailing));
        }
        if (!(eap->skip || error))
          clear_lval(&lv);
        break;
      }
  
      if (!error && !eap->skip) {
        if (eap->cmdidx == CMD_unlet) {
          if (do_unlet_var(&lv, name_end, eap->forceit) == FAIL)
            error = TRUE;
        } else {
          if (do_lock_var(&lv, name_end, deep,
                          eap->cmdidx == CMD_lockvar) == FAIL) {
            error = true;
          }
        }
      }
  
      if (!eap->skip)
        clear_lval(&lv);
  
      arg = skipwhite(name_end);
    } while (!ends_excmd(*arg));
  
    eap->nextcmd = check_nextcmd(arg);
  }
  
  // TODO(ZyX-I): move to eval/ex_cmds
  
  static int do_unlet_var(lval_T *const lp, char_u *const name_end, int forceit)
  {
    int ret = OK;
    int cc;
  
    if (lp->ll_tv == NULL) {
      cc = *name_end;
      *name_end = NUL;
  
      // Normal name or expanded name.
      if (do_unlet(lp->ll_name, lp->ll_name_len, forceit) == FAIL) {
        ret = FAIL;
      }
      *name_end = cc;
    } else if ((lp->ll_list != NULL
                // ll_list is not NULL when lvalue is not in a list, NULL lists
                // yield E689.
                && tv_check_lock(tv_list_locked(lp->ll_list),
                                 (const char *)lp->ll_name,
                                 lp->ll_name_len))
               || (lp->ll_dict != NULL
                   && tv_check_lock(lp->ll_dict->dv_lock,
                                    (const char *)lp->ll_name,
                                    lp->ll_name_len))) {
      return FAIL;
    } else if (lp->ll_range) {
      assert(lp->ll_list != NULL);
      // Delete a range of List items.
      listitem_T *const first_li = lp->ll_li;
      listitem_T *last_li = first_li;
      for (;;) {
        listitem_T *const li = TV_LIST_ITEM_NEXT(lp->ll_list, lp->ll_li);
        if (tv_check_lock(TV_LIST_ITEM_TV(lp->ll_li)->v_lock,
                          (const char *)lp->ll_name,
                          lp->ll_name_len)) {
          return false;
        }
        lp->ll_li = li;
        lp->ll_n1++;
        if (lp->ll_li == NULL || (!lp->ll_empty2 && lp->ll_n2 < lp->ll_n1)) {
          break;
        } else {
          last_li = lp->ll_li;
        }
      }
      tv_list_remove_items(lp->ll_list, first_li, last_li);
    } else {
      if (lp->ll_list != NULL) {
        // unlet a List item.
        tv_list_item_remove(lp->ll_list, lp->ll_li);
      } else {
        // unlet a Dictionary item.
        dict_T *d = lp->ll_dict;
        assert(d != NULL);
        dictitem_T *di = lp->ll_di;
        bool watched = tv_dict_is_watched(d);
        char *key = NULL;
        typval_T oldtv;
  
        if (watched) {
          tv_copy(&di->di_tv, &oldtv);
          // need to save key because dictitem_remove will free it
          key = xstrdup((char *)di->di_key);
        }
  
        tv_dict_item_remove(d, di);
  
        if (watched) {
          tv_dict_watcher_notify(d, key, NULL, &oldtv);
          tv_clear(&oldtv);
          xfree(key);
        }
      }
    }
  
    return ret;
  }
  
  // TODO(ZyX-I): move to eval/ex_cmds
  
  /// unlet a variable
  ///
  /// @param[in]  name  Variable name to unlet.
  /// @param[in]  name_len  Variable name length.
  /// @param[in]  fonceit  If true, do not complain if variable doesn’t exist.
  ///
  /// @return OK if it existed, FAIL otherwise.
  int do_unlet(const char *const name, const size_t name_len, const int forceit)
    FUNC_ATTR_NONNULL_ALL
  {
    const char *varname;
    dict_T *dict;
    hashtab_T *ht = find_var_ht_dict(name, name_len, &varname, &dict);
  
    if (ht != NULL && *varname != NUL) {
      dict_T *d = get_current_funccal_dict(ht);
      if (d == NULL) {
        if (ht == &globvarht) {
          d = &globvardict;
        } else if (ht == &compat_hashtab) {
            d = &vimvardict;
        } else {
          dictitem_T *const di = find_var_in_ht(ht, *name, "", 0, false);
          d = di->di_tv.vval.v_dict;
        }
        if (d == NULL) {
          internal_error("do_unlet()");
          return FAIL;
        }
      }
  
      hashitem_T *hi = hash_find(ht, (const char_u *)varname);
      if (HASHITEM_EMPTY(hi)) {
        hi = find_hi_in_scoped_ht((const char *)name, &ht);
      }
      if (hi != NULL && !HASHITEM_EMPTY(hi)) {
        dictitem_T *const di = TV_DICT_HI2DI(hi);
        if (var_check_fixed(di->di_flags, (const char *)name, TV_CSTRING)
            || var_check_ro(di->di_flags, (const char *)name, TV_CSTRING)
            || tv_check_lock(d->dv_lock, (const char *)name, TV_CSTRING)) {
          return FAIL;
        }
  
        if (tv_check_lock(d->dv_lock, (const char *)name, TV_CSTRING)) {
          return FAIL;
        }
  
        typval_T oldtv;
        bool watched = tv_dict_is_watched(dict);
  
        if (watched) {
          tv_copy(&di->di_tv, &oldtv);
        }
  
        delete_var(ht, hi);
  
        if (watched) {
          tv_dict_watcher_notify(dict, varname, NULL, &oldtv);
          tv_clear(&oldtv);
        }
        return OK;
      }
    }
    if (forceit)
      return OK;
    EMSG2(_("E108: No such variable: \"%s\""), name);
    return FAIL;
  }
  
  // TODO(ZyX-I): move to eval/ex_cmds
  
  /*
   * Lock or unlock variable indicated by "lp".
   * "deep" is the levels to go (-1 for unlimited);
   * "lock" is TRUE for ":lockvar", FALSE for ":unlockvar".
   */
  static int do_lock_var(lval_T *lp, char_u *const name_end, const int deep,
                         const bool lock)
  {
    int ret = OK;
  
    if (deep == 0) {  // Nothing to do.
      return OK;
    }
  
    if (lp->ll_tv == NULL) {
      // Normal name or expanded name.
      dictitem_T *const di = find_var(
          (const char *)lp->ll_name, lp->ll_name_len, NULL,
          true);
      if (di == NULL) {
        ret = FAIL;
      } else if ((di->di_flags & DI_FLAGS_FIX)
                 && di->di_tv.v_type != VAR_DICT
                 && di->di_tv.v_type != VAR_LIST) {
        // For historical reasons this error is not given for Lists and
        // Dictionaries. E.g. b: dictionary may be locked/unlocked.
        emsgf(_("E940: Cannot lock or unlock variable %s"), lp->ll_name);
      } else {
        if (lock) {
          di->di_flags |= DI_FLAGS_LOCK;
        } else {
          di->di_flags &= ~DI_FLAGS_LOCK;
        }
        tv_item_lock(&di->di_tv, deep, lock);
      }
    } else if (lp->ll_range) {
      listitem_T    *li = lp->ll_li;
  
      // (un)lock a range of List items.
      while (li != NULL && (lp->ll_empty2 || lp->ll_n2 >= lp->ll_n1)) {
        tv_item_lock(TV_LIST_ITEM_TV(li), deep, lock);
        li = TV_LIST_ITEM_NEXT(lp->ll_list, li);
        lp->ll_n1++;
      }
    } else if (lp->ll_list != NULL) {
      // (un)lock a List item.
      tv_item_lock(TV_LIST_ITEM_TV(lp->ll_li), deep, lock);
    } else {
      // (un)lock a Dictionary item.
      tv_item_lock(&lp->ll_di->di_tv, deep, lock);
    }
  
    return ret;
  }
  
  /*
   * Delete all "menutrans_" variables.
   */
  void del_menutrans_vars(void)
  {
    hash_lock(&globvarht);
    HASHTAB_ITER(&globvarht, hi, {
      if (STRNCMP(hi->hi_key, "menutrans_", 10) == 0) {
        delete_var(&globvarht, hi);
      }
    });
    hash_unlock(&globvarht);
  }
  
  /*
   * Local string buffer for the next two functions to store a variable name
   * with its prefix. Allocated in cat_prefix_varname(), freed later in
   * get_user_var_name().
   */
  
  
  static char_u   *varnamebuf = NULL;
  static size_t varnamebuflen = 0;
  
  /*
   * Function to concatenate a prefix and a variable name.
   */
  static char_u *cat_prefix_varname(int prefix, char_u *name)
  {
    size_t len = STRLEN(name) + 3;
  
    if (len > varnamebuflen) {
      xfree(varnamebuf);
      len += 10;                          // some additional space
      varnamebuf = xmalloc(len);
      varnamebuflen = len;
    }
    *varnamebuf = prefix;
    varnamebuf[1] = ':';
    STRCPY(varnamebuf + 2, name);
    return varnamebuf;
  }
  
  /*
   * Function given to ExpandGeneric() to obtain the list of user defined
   * (global/buffer/window/built-in) variable names.
   */
  char_u *get_user_var_name(expand_T *xp, int idx)
  {
    static size_t gdone;
    static size_t bdone;
    static size_t wdone;
    static size_t tdone;
    static size_t vidx;
    static hashitem_T   *hi;
    hashtab_T           *ht;
  
    if (idx == 0) {
      gdone = bdone = wdone = vidx = 0;
      tdone = 0;
    }
  
    // Global variables
    if (gdone < globvarht.ht_used) {
      if (gdone++ == 0)
        hi = globvarht.ht_array;
      else
        ++hi;
      while (HASHITEM_EMPTY(hi))
        ++hi;
      if (STRNCMP("g:", xp->xp_pattern, 2) == 0)
        return cat_prefix_varname('g', hi->hi_key);
      return hi->hi_key;
    }
  
    // b: variables
    ht = &curbuf->b_vars->dv_hashtab;
    if (bdone < ht->ht_used) {
      if (bdone++ == 0)
        hi = ht->ht_array;
      else
        ++hi;
      while (HASHITEM_EMPTY(hi))
        ++hi;
      return cat_prefix_varname('b', hi->hi_key);
    }
  
    // w: variables
    ht = &curwin->w_vars->dv_hashtab;
    if (wdone < ht->ht_used) {
      if (wdone++ == 0)
        hi = ht->ht_array;
      else
        ++hi;
      while (HASHITEM_EMPTY(hi))
        ++hi;
      return cat_prefix_varname('w', hi->hi_key);
    }
  
    // t: variables
    ht = &curtab->tp_vars->dv_hashtab;
    if (tdone < ht->ht_used) {
      if (tdone++ == 0)
        hi = ht->ht_array;
      else
        ++hi;
      while (HASHITEM_EMPTY(hi))
        ++hi;
      return cat_prefix_varname('t', hi->hi_key);
    }
  
    // v: variables
    if (vidx < ARRAY_SIZE(vimvars)) {
      return cat_prefix_varname('v', (char_u *)vimvars[vidx++].vv_name);
    }
  
    XFREE_CLEAR(varnamebuf);
    varnamebuflen = 0;
    return NULL;
  }
  
  // TODO(ZyX-I): move to eval/expressions
  
  /// Return TRUE if "pat" matches "text".
  /// Does not use 'cpo' and always uses 'magic'.
  static int pattern_match(char_u *pat, char_u *text, bool ic)
  {
    int matches = 0;
    regmatch_T regmatch;
  
    // avoid 'l' flag in 'cpoptions'
    char_u *save_cpo = p_cpo;
    p_cpo = (char_u *)"";
    regmatch.regprog = vim_regcomp(pat, RE_MAGIC + RE_STRING);
    if (regmatch.regprog != NULL) {
      regmatch.rm_ic = ic;
      matches = vim_regexec_nl(&regmatch, text, (colnr_T)0);
      vim_regfree(regmatch.regprog);
    }
    p_cpo = save_cpo;
    return matches;
  }
  
  /*
   * types for expressions.
   */
  typedef enum {
    TYPE_UNKNOWN = 0,
    TYPE_EQUAL,         // ==
    TYPE_NEQUAL,        // !=
    TYPE_GREATER,       // >
    TYPE_GEQUAL,        // >=
    TYPE_SMALLER,       // <
    TYPE_SEQUAL,        // <=
    TYPE_MATCH,         // =~
    TYPE_NOMATCH,       // !~
  } exptype_T;
  
  // TODO(ZyX-I): move to eval/expressions
  
  /*
   * The "evaluate" argument: When FALSE, the argument is only parsed but not
   * executed.  The function may return OK, but the rettv will be of type
   * VAR_UNKNOWN.  The function still returns FAIL for a syntax error.
   */
  
  /*
   * Handle zero level expression.
   * This calls eval1() and handles error message and nextcmd.
   * Put the result in "rettv" when returning OK and "evaluate" is TRUE.
   * Note: "rettv.v_lock" is not set.
   * Return OK or FAIL.
   */
  int eval0(char_u *arg, typval_T *rettv, char_u **nextcmd, int evaluate)
  {
    int ret;
    char_u      *p;
  
    p = skipwhite(arg);
    ret = eval1(&p, rettv, evaluate);
    if (ret == FAIL || !ends_excmd(*p)) {
      if (ret != FAIL) {
        tv_clear(rettv);
      }
      // Report the invalid expression unless the expression evaluation has
      // been cancelled due to an aborting error, an interrupt, or an
      // exception.
      if (!aborting()) {
        emsgf(_(e_invexpr2), arg);
      }
      ret = FAIL;
    }
    if (nextcmd != NULL)
      *nextcmd = check_nextcmd(p);
  
    return ret;
  }
  
  // TODO(ZyX-I): move to eval/expressions
  
  /*
   * Handle top level expression:
   *	expr2 ? expr1 : expr1
   *
   * "arg" must point to the first non-white of the expression.
   * "arg" is advanced to the next non-white after the recognized expression.
   *
   * Note: "rettv.v_lock" is not set.
   *
   * Return OK or FAIL.
   */
  int eval1(char_u **arg, typval_T *rettv, int evaluate)
  {
    int result;
    typval_T var2;
  
    /*
     * Get the first variable.
     */
    if (eval2(arg, rettv, evaluate) == FAIL)
      return FAIL;
  
    if ((*arg)[0] == '?') {
      result = FALSE;
      if (evaluate) {
        bool error = false;
  
        if (tv_get_number_chk(rettv, &error) != 0) {
          result = true;
        }
        tv_clear(rettv);
        if (error) {
          return FAIL;
        }
      }
  
      /*
       * Get the second variable.
       */
      *arg = skipwhite(*arg + 1);
      if (eval1(arg, rettv, evaluate && result) == FAIL) {  // recursive!
        return FAIL;
      }
  
      /*
       * Check for the ":".
       */
      if ((*arg)[0] != ':') {
        EMSG(_("E109: Missing ':' after '?'"));
        if (evaluate && result) {
          tv_clear(rettv);
        }
        return FAIL;
      }
  
      /*
       * Get the third variable.
       */
      *arg = skipwhite(*arg + 1);
      if (eval1(arg, &var2, evaluate && !result) == FAIL) {  // Recursive!
        if (evaluate && result) {
          tv_clear(rettv);
        }
        return FAIL;
      }
      if (evaluate && !result)
        *rettv = var2;
    }
  
    return OK;
  }
  
  // TODO(ZyX-I): move to eval/expressions
  
  /*
   * Handle first level expression:
   *	expr2 || expr2 || expr2	    logical OR
   *
   * "arg" must point to the first non-white of the expression.
   * "arg" is advanced to the next non-white after the recognized expression.
   *
   * Return OK or FAIL.
   */
  static int eval2(char_u **arg, typval_T *rettv, int evaluate)
  {
    typval_T var2;
    long result;
    int first;
    bool error = false;
  
    /*
     * Get the first variable.
     */
    if (eval3(arg, rettv, evaluate) == FAIL)
      return FAIL;
  
    /*
     * Repeat until there is no following "||".
     */
    first = TRUE;
    result = FALSE;
    while ((*arg)[0] == '|' && (*arg)[1] == '|') {
      if (evaluate && first) {
        if (tv_get_number_chk(rettv, &error) != 0) {
          result = true;
        }
        tv_clear(rettv);
        if (error) {
          return FAIL;
        }
        first = false;
      }
  
      /*
       * Get the second variable.
       */
      *arg = skipwhite(*arg + 2);
      if (eval3(arg, &var2, evaluate && !result) == FAIL)
        return FAIL;
  
      /*
       * Compute the result.
       */
      if (evaluate && !result) {
        if (tv_get_number_chk(&var2, &error) != 0) {
          result = true;
        }
        tv_clear(&var2);
        if (error) {
          return FAIL;
        }
      }
      if (evaluate) {
        rettv->v_type = VAR_NUMBER;
        rettv->vval.v_number = result;
      }
    }
  
    return OK;
  }
  
  // TODO(ZyX-I): move to eval/expressions
  
  /*
   * Handle second level expression:
   *	expr3 && expr3 && expr3	    logical AND
   *
   * "arg" must point to the first non-white of the expression.
   * "arg" is advanced to the next non-white after the recognized expression.
   *
   * Return OK or FAIL.
   */
  static int eval3(char_u **arg, typval_T *rettv, int evaluate)
  {
    typval_T var2;
    long result;
    int first;
    bool error = false;
  
    /*
     * Get the first variable.
     */
    if (eval4(arg, rettv, evaluate) == FAIL)
      return FAIL;
  
    /*
     * Repeat until there is no following "&&".
     */
    first = TRUE;
    result = TRUE;
    while ((*arg)[0] == '&' && (*arg)[1] == '&') {
      if (evaluate && first) {
        if (tv_get_number_chk(rettv, &error) == 0) {
          result = false;
        }
        tv_clear(rettv);
        if (error) {
          return FAIL;
        }
        first = false;
      }
  
      /*
       * Get the second variable.
       */
      *arg = skipwhite(*arg + 2);
      if (eval4(arg, &var2, evaluate && result) == FAIL)
        return FAIL;
  
      /*
       * Compute the result.
       */
      if (evaluate && result) {
        if (tv_get_number_chk(&var2, &error) == 0) {
          result = false;
        }
        tv_clear(&var2);
        if (error) {
          return FAIL;
        }
      }
      if (evaluate) {
        rettv->v_type = VAR_NUMBER;
        rettv->vval.v_number = result;
      }
    }
  
    return OK;
  }
  
  // TODO(ZyX-I): move to eval/expressions
  
  /*
   * Handle third level expression:
   *	var1 == var2
   *	var1 =~ var2
   *	var1 != var2
   *	var1 !~ var2
   *	var1 > var2
   *	var1 >= var2
   *	var1 < var2
   *	var1 <= var2
   *	var1 is var2
   *	var1 isnot var2
   *
   * "arg" must point to the first non-white of the expression.
   * "arg" is advanced to the next non-white after the recognized expression.
   *
   * Return OK or FAIL.
   */
  static int eval4(char_u **arg, typval_T *rettv, int evaluate)
  {
    typval_T var2;
    char_u      *p;
    int i;
    exptype_T type = TYPE_UNKNOWN;
    bool type_is = false;             // true for "is" and "isnot"
    int len = 2;
    varnumber_T n1, n2;
    bool ic;
  
    /*
     * Get the first variable.
     */
    if (eval5(arg, rettv, evaluate) == FAIL)
      return FAIL;
  
    p = *arg;
    switch (p[0]) {
    case '=':   if (p[1] == '=')
        type = TYPE_EQUAL;
      else if (p[1] == '~')
        type = TYPE_MATCH;
      break;
    case '!':   if (p[1] == '=')
        type = TYPE_NEQUAL;
      else if (p[1] == '~')
        type = TYPE_NOMATCH;
      break;
    case '>':   if (p[1] != '=') {
        type = TYPE_GREATER;
        len = 1;
    } else
        type = TYPE_GEQUAL;
      break;
    case '<':   if (p[1] != '=') {
        type = TYPE_SMALLER;
        len = 1;
    } else
        type = TYPE_SEQUAL;
      break;
    case 'i':   if (p[1] == 's') {
        if (p[2] == 'n' && p[3] == 'o' && p[4] == 't') {
          len = 5;
        }
        if (!isalnum(p[len]) && p[len] != '_') {
          type = len == 2 ? TYPE_EQUAL : TYPE_NEQUAL;
          type_is = true;
        }
    }
      break;
    }
  
    /*
     * If there is a comparative operator, use it.
     */
    if (type != TYPE_UNKNOWN) {
      // extra question mark appended: ignore case
      if (p[len] == '?') {
        ic = true;
        len++;
      } else if (p[len] == '#') {  // extra '#' appended: match case
        ic = false;
        len++;
      } else {  // nothing appended: use 'ignorecase'
        ic = p_ic;
      }
  
      // Get the second variable.
      *arg = skipwhite(p + len);
      if (eval5(arg, &var2, evaluate) == FAIL) {
        tv_clear(rettv);
        return FAIL;
      }
  
      if (evaluate) {
        if (type_is && rettv->v_type != var2.v_type) {
          /* For "is" a different type always means FALSE, for "notis"
           * it means TRUE. */
          n1 = (type == TYPE_NEQUAL);
        } else if (rettv->v_type == VAR_LIST || var2.v_type == VAR_LIST) {
          if (type_is) {
            n1 = (rettv->v_type == var2.v_type
                  && rettv->vval.v_list == var2.vval.v_list);
            if (type == TYPE_NEQUAL)
              n1 = !n1;
          } else if (rettv->v_type != var2.v_type
                     || (type != TYPE_EQUAL && type != TYPE_NEQUAL)) {
            if (rettv->v_type != var2.v_type) {
              EMSG(_("E691: Can only compare List with List"));
            } else {
              EMSG(_("E692: Invalid operation for List"));
            }
            tv_clear(rettv);
            tv_clear(&var2);
            return FAIL;
          } else {
            // Compare two Lists for being equal or unequal.
            n1 = tv_list_equal(rettv->vval.v_list, var2.vval.v_list, ic, false);
            if (type == TYPE_NEQUAL) {
              n1 = !n1;
            }
          }
        } else if (rettv->v_type == VAR_DICT || var2.v_type == VAR_DICT) {
          if (type_is) {
            n1 = (rettv->v_type == var2.v_type
                  && rettv->vval.v_dict == var2.vval.v_dict);
            if (type == TYPE_NEQUAL)
              n1 = !n1;
          } else if (rettv->v_type != var2.v_type
                     || (type != TYPE_EQUAL && type != TYPE_NEQUAL)) {
            if (rettv->v_type != var2.v_type)
              EMSG(_("E735: Can only compare Dictionary with Dictionary"));
            else
              EMSG(_("E736: Invalid operation for Dictionary"));
            tv_clear(rettv);
            tv_clear(&var2);
            return FAIL;
          } else {
            // Compare two Dictionaries for being equal or unequal.
            n1 = tv_dict_equal(rettv->vval.v_dict, var2.vval.v_dict,
                               ic, false);
            if (type == TYPE_NEQUAL) {
              n1 = !n1;
            }
          }
        } else if (tv_is_func(*rettv) || tv_is_func(var2)) {
          if (type != TYPE_EQUAL && type != TYPE_NEQUAL) {
            EMSG(_("E694: Invalid operation for Funcrefs"));
            tv_clear(rettv);
            tv_clear(&var2);
            return FAIL;
          }
          if ((rettv->v_type == VAR_PARTIAL
               && rettv->vval.v_partial == NULL)
              || (var2.v_type == VAR_PARTIAL
                  && var2.vval.v_partial == NULL)) {
              // when a partial is NULL assume not equal
              n1 = false;
          } else if (type_is) {
            if (rettv->v_type == VAR_FUNC && var2.v_type == VAR_FUNC) {
              // strings are considered the same if their value is
              // the same
              n1 = tv_equal(rettv, &var2, ic, false);
            } else if (rettv->v_type == VAR_PARTIAL
                       && var2.v_type == VAR_PARTIAL) {
              n1 = (rettv->vval.v_partial == var2.vval.v_partial);
            } else {
              n1 = false;
            }
          } else {
            n1 = tv_equal(rettv, &var2, ic, false);
          }
          if (type == TYPE_NEQUAL) {
            n1 = !n1;
          }
        }
        /*
         * If one of the two variables is a float, compare as a float.
         * When using "=~" or "!~", always compare as string.
         */
        else if ((rettv->v_type == VAR_FLOAT || var2.v_type == VAR_FLOAT)
                 && type != TYPE_MATCH && type != TYPE_NOMATCH) {
          float_T f1, f2;
  
          if (rettv->v_type == VAR_FLOAT) {
            f1 = rettv->vval.v_float;
          } else {
            f1 = tv_get_number(rettv);
          }
          if (var2.v_type == VAR_FLOAT) {
            f2 = var2.vval.v_float;
          } else {
            f2 = tv_get_number(&var2);
          }
          n1 = false;
          switch (type) {
            case TYPE_EQUAL:    n1 = (f1 == f2); break;
            case TYPE_NEQUAL:   n1 = (f1 != f2); break;
            case TYPE_GREATER:  n1 = (f1 > f2); break;
            case TYPE_GEQUAL:   n1 = (f1 >= f2); break;
            case TYPE_SMALLER:  n1 = (f1 < f2); break;
            case TYPE_SEQUAL:   n1 = (f1 <= f2); break;
            case TYPE_UNKNOWN:
            case TYPE_MATCH:
            case TYPE_NOMATCH:  break;
          }
        }
        /*
         * If one of the two variables is a number, compare as a number.
         * When using "=~" or "!~", always compare as string.
         */
        else if ((rettv->v_type == VAR_NUMBER || var2.v_type == VAR_NUMBER)
                 && type != TYPE_MATCH && type != TYPE_NOMATCH) {
          n1 = tv_get_number(rettv);
          n2 = tv_get_number(&var2);
          switch (type) {
            case TYPE_EQUAL:    n1 = (n1 == n2); break;
            case TYPE_NEQUAL:   n1 = (n1 != n2); break;
            case TYPE_GREATER:  n1 = (n1 > n2); break;
            case TYPE_GEQUAL:   n1 = (n1 >= n2); break;
            case TYPE_SMALLER:  n1 = (n1 < n2); break;
            case TYPE_SEQUAL:   n1 = (n1 <= n2); break;
            case TYPE_UNKNOWN:
            case TYPE_MATCH:
            case TYPE_NOMATCH:  break;
          }
        } else {
          char buf1[NUMBUFLEN];
          char buf2[NUMBUFLEN];
          const char *const s1 = tv_get_string_buf(rettv, buf1);
          const char *const s2 = tv_get_string_buf(&var2, buf2);
          if (type != TYPE_MATCH && type != TYPE_NOMATCH) {
            i = mb_strcmp_ic(ic, s1, s2);
          } else {
            i = 0;
          }
          n1 = false;
          switch (type) {
            case TYPE_EQUAL:    n1 = (i == 0); break;
            case TYPE_NEQUAL:   n1 = (i != 0); break;
            case TYPE_GREATER:  n1 = (i > 0); break;
            case TYPE_GEQUAL:   n1 = (i >= 0); break;
            case TYPE_SMALLER:  n1 = (i < 0); break;
            case TYPE_SEQUAL:   n1 = (i <= 0); break;
  
            case TYPE_MATCH:
            case TYPE_NOMATCH: {
              n1 = pattern_match((char_u *)s2, (char_u *)s1, ic);
              if (type == TYPE_NOMATCH) {
                n1 = !n1;
              }
              break;
            }
            case TYPE_UNKNOWN: break;  // Avoid gcc warning.
          }
        }
        tv_clear(rettv);
        tv_clear(&var2);
        rettv->v_type = VAR_NUMBER;
        rettv->vval.v_number = n1;
      }
    }
  
    return OK;
  }
  
  // TODO(ZyX-I): move to eval/expressions
  
  /*
   * Handle fourth level expression:
   *	+	number addition
   *	-	number subtraction
   *	.	string concatenation
   *	..	string concatenation
   *
   * "arg" must point to the first non-white of the expression.
   * "arg" is advanced to the next non-white after the recognized expression.
   *
   * Return OK or FAIL.
   */
  static int eval5(char_u **arg, typval_T *rettv, int evaluate)
  {
    typval_T var2;
    typval_T var3;
    int op;
    varnumber_T n1, n2;
    float_T f1 = 0, f2 = 0;
    char_u      *p;
  
    /*
     * Get the first variable.
     */
    if (eval6(arg, rettv, evaluate, FALSE) == FAIL)
      return FAIL;
  
    /*
     * Repeat computing, until no '+', '-' or '.' is following.
     */
    for (;; ) {
      op = **arg;
      if (op != '+' && op != '-' && op != '.')
        break;
  
      if ((op != '+' || rettv->v_type != VAR_LIST)
          && (op == '.' || rettv->v_type != VAR_FLOAT)) {
        // For "list + ...", an illegal use of the first operand as
        // a number cannot be determined before evaluating the 2nd
        // operand: if this is also a list, all is ok.
        // For "something . ...", "something - ..." or "non-list + ...",
        // we know that the first operand needs to be a string or number
        // without evaluating the 2nd operand.  So check before to avoid
        // side effects after an error.
        if (evaluate && !tv_check_str(rettv)) {
          tv_clear(rettv);
          return FAIL;
        }
      }
  
      /*
       * Get the second variable.
       */
      if (op == '.' && *(*arg + 1) == '.') {  // ..string concatenation
        (*arg)++;
      }
      *arg = skipwhite(*arg + 1);
      if (eval6(arg, &var2, evaluate, op == '.') == FAIL) {
        tv_clear(rettv);
        return FAIL;
      }
  
      if (evaluate) {
        /*
         * Compute the result.
         */
        if (op == '.') {
          char buf1[NUMBUFLEN];
          char buf2[NUMBUFLEN];
          // s1 already checked
          const char *const s1 = tv_get_string_buf(rettv, buf1);
          const char *const s2 = tv_get_string_buf_chk(&var2, buf2);
          if (s2 == NULL) {  // Type error?
            tv_clear(rettv);
            tv_clear(&var2);
            return FAIL;
          }
          p = concat_str((const char_u *)s1, (const char_u *)s2);
          tv_clear(rettv);
          rettv->v_type = VAR_STRING;
          rettv->vval.v_string = p;
        } else if (op == '+' && rettv->v_type == VAR_LIST
                   && var2.v_type == VAR_LIST) {
          // Concatenate Lists.
          if (tv_list_concat(rettv->vval.v_list, var2.vval.v_list, &var3)
              == FAIL) {
            tv_clear(rettv);
            tv_clear(&var2);
            return FAIL;
          }
          tv_clear(rettv);
          *rettv = var3;
        } else {
          bool error = false;
  
          if (rettv->v_type == VAR_FLOAT) {
            f1 = rettv->vval.v_float;
            n1 = 0;
          } else {
            n1 = tv_get_number_chk(rettv, &error);
            if (error) {
              /* This can only happen for "list + non-list".  For
               * "non-list + ..." or "something - ...", we returned
               * before evaluating the 2nd operand. */
              tv_clear(rettv);
              return FAIL;
            }
            if (var2.v_type == VAR_FLOAT)
              f1 = n1;
          }
          if (var2.v_type == VAR_FLOAT) {
            f2 = var2.vval.v_float;
            n2 = 0;
          } else {
            n2 = tv_get_number_chk(&var2, &error);
            if (error) {
              tv_clear(rettv);
              tv_clear(&var2);
              return FAIL;
            }
            if (rettv->v_type == VAR_FLOAT)
              f2 = n2;
          }
          tv_clear(rettv);
  
          // If there is a float on either side the result is a float.
          if (rettv->v_type == VAR_FLOAT || var2.v_type == VAR_FLOAT) {
            if (op == '+')
              f1 = f1 + f2;
            else
              f1 = f1 - f2;
            rettv->v_type = VAR_FLOAT;
            rettv->vval.v_float = f1;
          } else {
            if (op == '+')
              n1 = n1 + n2;
            else
              n1 = n1 - n2;
            rettv->v_type = VAR_NUMBER;
            rettv->vval.v_number = n1;
          }
        }
        tv_clear(&var2);
      }
    }
    return OK;
  }
  
  // TODO(ZyX-I): move to eval/expressions
  
  /// Handle fifth level expression:
  ///  - *  number multiplication
  ///  - /  number division
  ///  - %  number modulo
  ///
  /// @param[in,out]  arg  Points to the first non-whitespace character of the
  ///                      expression.  Is advanced to the next non-whitespace
  ///                      character after the recognized expression.
  /// @param[out]  rettv  Location where result is saved.
  /// @param[in]  evaluate  If not true, rettv is not populated.
  /// @param[in]  want_string  True if "." is string_concatenation, otherwise
  ///                          float
  /// @return  OK or FAIL.
  static int eval6(char_u **arg, typval_T *rettv, int evaluate, int want_string)
    FUNC_ATTR_NO_SANITIZE_UNDEFINED
  {
    typval_T var2;
    int op;
    varnumber_T n1, n2;
    bool use_float = false;
    float_T f1 = 0, f2 = 0;
    bool error = false;
  
    /*
     * Get the first variable.
     */
    if (eval7(arg, rettv, evaluate, want_string) == FAIL)
      return FAIL;
  
    /*
     * Repeat computing, until no '*', '/' or '%' is following.
     */
    for (;; ) {
      op = **arg;
      if (op != '*' && op != '/' && op != '%')
        break;
  
      if (evaluate) {
        if (rettv->v_type == VAR_FLOAT) {
          f1 = rettv->vval.v_float;
          use_float = true;
          n1 = 0;
        } else {
          n1 = tv_get_number_chk(rettv, &error);
        }
        tv_clear(rettv);
        if (error) {
          return FAIL;
        }
      } else {
        n1 = 0;
      }
  
      /*
       * Get the second variable.
       */
      *arg = skipwhite(*arg + 1);
      if (eval7(arg, &var2, evaluate, FALSE) == FAIL)
        return FAIL;
  
      if (evaluate) {
        if (var2.v_type == VAR_FLOAT) {
          if (!use_float) {
            f1 = n1;
            use_float = true;
          }
          f2 = var2.vval.v_float;
          n2 = 0;
        } else {
          n2 = tv_get_number_chk(&var2, &error);
          tv_clear(&var2);
          if (error) {
            return FAIL;
          }
          if (use_float) {
            f2 = n2;
          }
        }
  
        /*
         * Compute the result.
         * When either side is a float the result is a float.
         */
        if (use_float) {
          if (op == '*') {
            f1 = f1 * f2;
          } else if (op == '/') {
            // Division by zero triggers error from AddressSanitizer
            f1 = (f2 == 0
                  ? (
  #ifdef NAN
                      f1 == 0
                      ? NAN
                      :
  #endif
                      (f1 > 0
                       ? INFINITY
                       : -INFINITY)
                  )
                  : f1 / f2);
          } else {
            EMSG(_("E804: Cannot use '%' with Float"));
            return FAIL;
          }
          rettv->v_type = VAR_FLOAT;
          rettv->vval.v_float = f1;
        } else {
          if (op == '*') {
            n1 = n1 * n2;
          } else if (op == '/') {
            n1 = num_divide(n1, n2);
          } else {
            n1 = num_modulus(n1, n2);
          }
          rettv->v_type = VAR_NUMBER;
          rettv->vval.v_number = n1;
        }
      }
    }
  
    return OK;
  }
  
  // TODO(ZyX-I): move to eval/expressions
  
  // Handle sixth level expression:
  //  number  number constant
  //  "string"  string constant
  //  'string'  literal string constant
  //  &option-name option value
  //  @r   register contents
  //  identifier  variable value
  //  function()  function call
  //  $VAR  environment variable
  //  (expression) nested expression
  //  [expr, expr] List
  //  {key: val, key: val}  Dictionary
  //
  //  Also handle:
  //  ! in front  logical NOT
  //  - in front  unary minus
  //  + in front  unary plus (ignored)
  //  trailing []  subscript in String or List
  //  trailing .name entry in Dictionary
  //
  // "arg" must point to the first non-white of the expression.
  // "arg" is advanced to the next non-white after the recognized expression.
  //
  // Return OK or FAIL.
  static int eval7(
      char_u **arg,
      typval_T *rettv,
      int evaluate,
      int want_string                 // after "." operator
  )
  {
    varnumber_T n;
    int len;
    char_u      *s;
    char_u      *start_leader, *end_leader;
    int ret = OK;
    char_u      *alias;
  
    // Initialise variable so that tv_clear() can't mistake this for a
    // string and free a string that isn't there.
    rettv->v_type = VAR_UNKNOWN;
  
    // Skip '!', '-' and '+' characters.  They are handled later.
    start_leader = *arg;
    while (**arg == '!' || **arg == '-' || **arg == '+') {
      *arg = skipwhite(*arg + 1);
    }
    end_leader = *arg;
  
    switch (**arg) {
    // Number constant.
    case '0':
    case '1':
    case '2':
    case '3':
    case '4':
    case '5':
    case '6':
    case '7':
    case '8':
    case '9':
    {
      char_u *p = skipdigits(*arg + 1);
      int get_float = false;
  
      // We accept a float when the format matches
      // "[0-9]\+\.[0-9]\+\([eE][+-]\?[0-9]\+\)\?".  This is very
      // strict to avoid backwards compatibility problems.
      // Don't look for a float after the "." operator, so that
      // ":let vers = 1.2.3" doesn't fail.
      if (!want_string && p[0] == '.' && ascii_isdigit(p[1])) {
        get_float = true;
        p = skipdigits(p + 2);
        if (*p == 'e' || *p == 'E') {
          ++p;
          if (*p == '-' || *p == '+') {
            ++p;
          }
          if (!ascii_isdigit(*p)) {
            get_float = false;
          } else {
            p = skipdigits(p + 1);
          }
        }
        if (ASCII_ISALPHA(*p) || *p == '.') {
          get_float = false;
        }
      }
      if (get_float) {
        float_T f;
  
        *arg += string2float((char *) *arg, &f);
        if (evaluate) {
          rettv->v_type = VAR_FLOAT;
          rettv->vval.v_float = f;
        }
      } else {
        vim_str2nr(*arg, NULL, &len, STR2NR_ALL, &n, NULL, 0);
        *arg += len;
        if (evaluate) {
          rettv->v_type = VAR_NUMBER;
          rettv->vval.v_number = n;
        }
      }
      break;
    }
  
    // String constant: "string".
    case '"':   ret = get_string_tv(arg, rettv, evaluate);
      break;
  
    // Literal string constant: 'str''ing'.
    case '\'':  ret = get_lit_string_tv(arg, rettv, evaluate);
      break;
  
    // List: [expr, expr]
    case '[':   ret = get_list_tv(arg, rettv, evaluate);
      break;
  
    // Lambda: {arg, arg -> expr}
    // Dictionary: {key: val, key: val}
    case '{':   ret = get_lambda_tv(arg, rettv, evaluate);
                if (ret == NOTDONE) {
                  ret = dict_get_tv(arg, rettv, evaluate);
                }
      break;
  
    // Option value: &name
    case '&': {
      ret = get_option_tv((const char **)arg, rettv, evaluate);
      break;
    }
    // Environment variable: $VAR.
    case '$':   ret = get_env_tv(arg, rettv, evaluate);
      break;
  
    // Register contents: @r.
    case '@':   ++*arg;
      if (evaluate) {
        rettv->v_type = VAR_STRING;
        rettv->vval.v_string = get_reg_contents(**arg, kGRegExprSrc);
      }
      if (**arg != NUL) {
        ++*arg;
      }
      break;
  
    // nested expression: (expression).
    case '(':   *arg = skipwhite(*arg + 1);
      ret = eval1(arg, rettv, evaluate);                  // recursive!
      if (**arg == ')') {
        ++*arg;
      } else if (ret == OK) {
        EMSG(_("E110: Missing ')'"));
        tv_clear(rettv);
        ret = FAIL;
      }
      break;
  
    default:    ret = NOTDONE;
      break;
    }
  
    if (ret == NOTDONE) {
      // Must be a variable or function name.
      // Can also be a curly-braces kind of name: {expr}.
      s = *arg;
      len = get_name_len((const char **)arg, (char **)&alias, evaluate, true);
      if (alias != NULL) {
        s = alias;
      }
  
      if (len <= 0) {
        ret = FAIL;
      } else {
        if (**arg == '(') {               // recursive!
          partial_T *partial;
  
          if (!evaluate) {
            check_vars((const char *)s, len);
          }
  
          // If "s" is the name of a variable of type VAR_FUNC
          // use its contents.
          s = deref_func_name((const char *)s, &len, &partial, !evaluate);
  
          // Need to make a copy, in case evaluating the arguments makes
          // the name invalid.
          s = xmemdupz(s, len);
  
          // Invoke the function.
          ret = get_func_tv(s, len, rettv, arg,
                            curwin->w_cursor.lnum, curwin->w_cursor.lnum,
                            &len, evaluate, partial, NULL);
  
          xfree(s);
  
          // If evaluate is false rettv->v_type was not set in
          // get_func_tv, but it's needed in handle_subscript() to parse
          // what follows. So set it here.
          if (rettv->v_type == VAR_UNKNOWN && !evaluate && **arg == '(') {
            rettv->vval.v_string = (char_u *)tv_empty_string;
            rettv->v_type = VAR_FUNC;
          }
  
          // Stop the expression evaluation when immediately
          // aborting on error, or when an interrupt occurred or
          // an exception was thrown but not caught.
          if (evaluate && aborting()) {
            if (ret == OK) {
              tv_clear(rettv);
            }
            ret = FAIL;
          }
        } else if (evaluate) {
          ret = get_var_tv((const char *)s, len, rettv, NULL, true, false);
        } else {
          check_vars((const char *)s, len);
          ret = OK;
        }
      }
      xfree(alias);
    }
  
    *arg = skipwhite(*arg);
  
    // Handle following '[', '(' and '.' for expr[expr], expr.name,
    // expr(expr).
    if (ret == OK) {
      ret = handle_subscript((const char **)arg, rettv, evaluate, true);
    }
  
    // Apply logical NOT and unary '-', from right to left, ignore '+'.
    if (ret == OK && evaluate && end_leader > start_leader) {
      bool error = false;
      varnumber_T val = 0;
      float_T f = 0.0;
  
      if (rettv->v_type == VAR_FLOAT) {
        f = rettv->vval.v_float;
      } else {
        val = tv_get_number_chk(rettv, &error);
      }
      if (error) {
        tv_clear(rettv);
        ret = FAIL;
      } else {
        while (end_leader > start_leader) {
          --end_leader;
          if (*end_leader == '!') {
            if (rettv->v_type == VAR_FLOAT) {
              f = !f;
            } else {
              val = !val;
            }
          } else if (*end_leader == '-') {
            if (rettv->v_type == VAR_FLOAT) {
              f = -f;
            } else {
              val = -val;
            }
          }
        }
        if (rettv->v_type == VAR_FLOAT) {
          tv_clear(rettv);
          rettv->vval.v_float = f;
        } else {
          tv_clear(rettv);
          rettv->v_type = VAR_NUMBER;
          rettv->vval.v_number = val;
        }
      }
    }
  
    return ret;
  }
  
  // TODO(ZyX-I): move to eval/expressions
  
  /*
   * Evaluate an "[expr]" or "[expr:expr]" index.  Also "dict.key".
   * "*arg" points to the '[' or '.'.
   * Returns FAIL or OK. "*arg" is advanced to after the ']'.
   */
  static int
  eval_index(
      char_u **arg,
      typval_T *rettv,
      int evaluate,
      int verbose                    // give error messages
  )
  {
    bool empty1 = false;
    bool empty2 = false;
    long n1, n2 = 0;
    ptrdiff_t len = -1;
    int range = false;
    char_u      *key = NULL;
  
    switch (rettv->v_type) {
      case VAR_FUNC:
      case VAR_PARTIAL: {
        if (verbose) {
          EMSG(_("E695: Cannot index a Funcref"));
        }
        return FAIL;
      }
      case VAR_FLOAT: {
        if (verbose) {
          EMSG(_(e_float_as_string));
        }
        return FAIL;
      }
      case VAR_BOOL:
      case VAR_SPECIAL: {
        if (verbose) {
          EMSG(_("E909: Cannot index a special variable"));
        }
        return FAIL;
      }
      case VAR_UNKNOWN: {
        if (evaluate) {
          return FAIL;
        }
        FALLTHROUGH;
      }
      case VAR_STRING:
      case VAR_NUMBER:
      case VAR_LIST:
      case VAR_DICT: {
        break;
      }
    }
  
    typval_T var1 = TV_INITIAL_VALUE;
    typval_T var2 = TV_INITIAL_VALUE;
    if (**arg == '.') {
      /*
       * dict.name
       */
      key = *arg + 1;
      for (len = 0; ASCII_ISALNUM(key[len]) || key[len] == '_'; ++len)
        ;
      if (len == 0)
        return FAIL;
      *arg = skipwhite(key + len);
    } else {
      /*
       * something[idx]
       *
       * Get the (first) variable from inside the [].
       */
      *arg = skipwhite(*arg + 1);
      if (**arg == ':') {
        empty1 = true;
      } else if (eval1(arg, &var1, evaluate) == FAIL) {  // Recursive!
        return FAIL;
      } else if (evaluate && !tv_check_str(&var1)) {
        // Not a number or string.
        tv_clear(&var1);
        return FAIL;
      }
  
      /*
       * Get the second variable from inside the [:].
       */
      if (**arg == ':') {
        range = TRUE;
        *arg = skipwhite(*arg + 1);
        if (**arg == ']') {
          empty2 = true;
        } else if (eval1(arg, &var2, evaluate) == FAIL) {  // Recursive!
          if (!empty1) {
            tv_clear(&var1);
          }
          return FAIL;
        } else if (evaluate && !tv_check_str(&var2)) {
          // Not a number or string.
          if (!empty1) {
            tv_clear(&var1);
          }
          tv_clear(&var2);
          return FAIL;
        }
      }
  
      // Check for the ']'.
      if (**arg != ']') {
        if (verbose) {
          EMSG(_(e_missbrac));
        }
        tv_clear(&var1);
        if (range) {
          tv_clear(&var2);
        }
        return FAIL;
      }
      *arg = skipwhite(*arg + 1);         // skip the ']'
    }
  
    if (evaluate) {
      n1 = 0;
      if (!empty1 && rettv->v_type != VAR_DICT && !tv_is_luafunc(rettv)) {
        n1 = tv_get_number(&var1);
        tv_clear(&var1);
      }
      if (range) {
        if (empty2) {
          n2 = -1;
        } else {
          n2 = tv_get_number(&var2);
          tv_clear(&var2);
        }
      }
  
      switch (rettv->v_type) {
        case VAR_NUMBER:
        case VAR_STRING: {
          const char *const s = tv_get_string(rettv);
          char *v;
          len = (ptrdiff_t)strlen(s);
          if (range) {
            // The resulting variable is a substring.  If the indexes
            // are out of range the result is empty.
            if (n1 < 0) {
              n1 = len + n1;
              if (n1 < 0) {
                n1 = 0;
              }
            }
            if (n2 < 0) {
              n2 = len + n2;
            } else if (n2 >= len) {
              n2 = len;
            }
            if (n1 >= len || n2 < 0 || n1 > n2) {
              v = NULL;
            } else {
              v = xmemdupz(s + n1, (size_t)(n2 - n1 + 1));
            }
          } else {
            // The resulting variable is a string of a single
            // character.  If the index is too big or negative the
            // result is empty.
            if (n1 >= len || n1 < 0) {
              v = NULL;
            } else {
              v = xmemdupz(s + n1, 1);
            }
          }
          tv_clear(rettv);
          rettv->v_type = VAR_STRING;
          rettv->vval.v_string = (char_u *)v;
          break;
        }
        case VAR_LIST: {
          len = tv_list_len(rettv->vval.v_list);
          if (n1 < 0) {
            n1 = len + n1;
          }
          if (!empty1 && (n1 < 0 || n1 >= len)) {
            // For a range we allow invalid values and return an empty
            // list.  A list index out of range is an error.
            if (!range) {
              if (verbose) {
                EMSGN(_(e_listidx), n1);
              }
              return FAIL;
            }
            n1 = len;
          }
          if (range) {
            list_T      *l;
            listitem_T  *item;
  
            if (n2 < 0) {
              n2 = len + n2;
            } else if (n2 >= len) {
              n2 = len - 1;
            }
            if (!empty2 && (n2 < 0 || n2 + 1 < n1)) {
              n2 = -1;
            }
            l = tv_list_alloc(n2 - n1 + 1);
            item = tv_list_find(rettv->vval.v_list, n1);
            while (n1++ <= n2) {
              tv_list_append_tv(l, TV_LIST_ITEM_TV(item));
              item = TV_LIST_ITEM_NEXT(rettv->vval.v_list, item);
            }
            tv_clear(rettv);
            tv_list_set_ret(rettv, l);
          } else {
            tv_copy(TV_LIST_ITEM_TV(tv_list_find(rettv->vval.v_list, n1)), &var1);
            tv_clear(rettv);
            *rettv = var1;
          }
          break;
        }
        case VAR_DICT: {
          if (range) {
            if (verbose) {
              EMSG(_(e_dictrange));
            }
            if (len == -1) {
              tv_clear(&var1);
            }
            return FAIL;
          }
  
          if (len == -1) {
            key = (char_u *)tv_get_string_chk(&var1);
            if (key == NULL) {
              tv_clear(&var1);
              return FAIL;
            }
          }
  
          dictitem_T *const item = tv_dict_find(rettv->vval.v_dict,
                                                (const char *)key, len);
  
          if (item == NULL && verbose) {
            emsgf(_(e_dictkey), key);
          }
          if (len == -1) {
            tv_clear(&var1);
          }
          if (item == NULL || tv_is_luafunc(&item->di_tv)) {
            return FAIL;
          }
  
          tv_copy(&item->di_tv, &var1);
          tv_clear(rettv);
          *rettv = var1;
          break;
        }
        case VAR_BOOL:
        case VAR_SPECIAL:
        case VAR_FUNC:
        case VAR_FLOAT:
        case VAR_PARTIAL:
        case VAR_UNKNOWN: {
          break;  // Not evaluating, skipping over subscript
        }
      }
    }
  
    return OK;
  }
  
  // TODO(ZyX-I): move to eval/executor
  
  /// Get an option value
  ///
  /// @param[in,out]  arg  Points to the '&' or '+' before the option name. Is
  ///                      advanced to the character after the option name.
  /// @param[out]  rettv  Location where result is saved.
  /// @param[in]  evaluate  If not true, rettv is not populated.
  ///
  /// @return OK or FAIL.
  int get_option_tv(const char **const arg, typval_T *const rettv,
                    const bool evaluate)
    FUNC_ATTR_NONNULL_ARG(1)
  {
    long numval;
    char_u      *stringval;
    int opt_type;
    int c;
    bool working = (**arg == '+');  // has("+option")
    int ret = OK;
    int opt_flags;
  
    // Isolate the option name and find its value.
    char *option_end = (char *)find_option_end(arg, &opt_flags);
    if (option_end == NULL) {
      if (rettv != NULL) {
        EMSG2(_("E112: Option name missing: %s"), *arg);
      }
      return FAIL;
    }
  
    if (!evaluate) {
      *arg = option_end;
      return OK;
    }
  
    c = *option_end;
    *option_end = NUL;
    opt_type = get_option_value((char_u *)(*arg), &numval,
                                rettv == NULL ? NULL : &stringval, opt_flags);
  
    if (opt_type == -3) {                 // invalid name
      if (rettv != NULL) {
        EMSG2(_("E113: Unknown option: %s"), *arg);
      }
      ret = FAIL;
    } else if (rettv != NULL)   {
      if (opt_type == -2) {               // hidden string option
        rettv->v_type = VAR_STRING;
        rettv->vval.v_string = NULL;
      } else if (opt_type == -1) {      // hidden number option
        rettv->v_type = VAR_NUMBER;
        rettv->vval.v_number = 0;
      } else if (opt_type == 1) {       // number option
        rettv->v_type = VAR_NUMBER;
        rettv->vval.v_number = numval;
      } else {                          // string option
        rettv->v_type = VAR_STRING;
        rettv->vval.v_string = stringval;
      }
    } else if (working && (opt_type == -2 || opt_type == -1))
      ret = FAIL;
  
    *option_end = c;                  // put back for error messages
    *arg = option_end;
  
    return ret;
  }
  
  /*
   * Allocate a variable for a string constant.
   * Return OK or FAIL.
   */
  static int get_string_tv(char_u **arg, typval_T *rettv, int evaluate)
  {
    char_u      *p;
    char_u      *name;
    unsigned int extra = 0;
  
    /*
     * Find the end of the string, skipping backslashed characters.
     */
    for (p = *arg + 1; *p != NUL && *p != '"'; MB_PTR_ADV(p)) {
      if (*p == '\\' && p[1] != NUL) {
        ++p;
        /* A "\<x>" form occupies at least 4 characters, and produces up
         * to 6 characters: reserve space for 2 extra */
        if (*p == '<')
          extra += 2;
      }
    }
  
    if (*p != '"') {
      EMSG2(_("E114: Missing quote: %s"), *arg);
      return FAIL;
    }
  
    // If only parsing, set *arg and return here
    if (!evaluate) {
      *arg = p + 1;
      return OK;
    }
  
    /*
     * Copy the string into allocated memory, handling backslashed
     * characters.
     */
    name = xmalloc(p - *arg + extra);
    rettv->v_type = VAR_STRING;
    rettv->vval.v_string = name;
  
    for (p = *arg + 1; *p != NUL && *p != '"'; ) {
      if (*p == '\\') {
        switch (*++p) {
        case 'b': *name++ = BS; ++p; break;
        case 'e': *name++ = ESC; ++p; break;
        case 'f': *name++ = FF; ++p; break;
        case 'n': *name++ = NL; ++p; break;
        case 'r': *name++ = CAR; ++p; break;
        case 't': *name++ = TAB; ++p; break;
  
        case 'X':           // hex: "\x1", "\x12"
        case 'x':
        case 'u':           // Unicode: "\u0023"
        case 'U':
          if (ascii_isxdigit(p[1])) {
            int n, nr;
            int c = toupper(*p);
  
            if (c == 'X') {
              n = 2;
            } else if (*p == 'u') {
              n = 4;
            } else {
              n = 8;
            }
            nr = 0;
            while (--n >= 0 && ascii_isxdigit(p[1])) {
              ++p;
              nr = (nr << 4) + hex2nr(*p);
            }
            ++p;
            /* For "\u" store the number according to
             * 'encoding'. */
            if (c != 'X') {
              name += utf_char2bytes(nr, name);
            } else {
              *name++ = nr;
            }
          }
          break;
  
        // octal: "\1", "\12", "\123"
        case '0':
        case '1':
        case '2':
        case '3':
        case '4':
        case '5':
        case '6':
        case '7': *name = *p++ - '0';
          if (*p >= '0' && *p <= '7') {
            *name = (*name << 3) + *p++ - '0';
            if (*p >= '0' && *p <= '7')
              *name = (*name << 3) + *p++ - '0';
          }
          ++name;
          break;
  
        // Special key, e.g.: "\<C-W>"
        case '<':
          extra = trans_special((const char_u **)&p, STRLEN(p), name, true, true);
          if (extra != 0) {
            name += extra;
            break;
          }
          FALLTHROUGH;
  
        default:  MB_COPY_CHAR(p, name);
          break;
        }
      } else
        MB_COPY_CHAR(p, name);
  
    }
    *name = NUL;
    if (*p != NUL) {  // just in case
      p++;
    }
    *arg = p;
  
    return OK;
  }
  
  /*
   * Allocate a variable for a 'str''ing' constant.
   * Return OK or FAIL.
   */
  static int get_lit_string_tv(char_u **arg, typval_T *rettv, int evaluate)
  {
    char_u      *p;
    char_u      *str;
    int reduce = 0;
  
    /*
     * Find the end of the string, skipping ''.
     */
    for (p = *arg + 1; *p != NUL; MB_PTR_ADV(p)) {
      if (*p == '\'') {
        if (p[1] != '\'')
          break;
        ++reduce;
        ++p;
      }
    }
  
    if (*p != '\'') {
      EMSG2(_("E115: Missing quote: %s"), *arg);
      return FAIL;
    }
  
    // If only parsing return after setting "*arg"
    if (!evaluate) {
      *arg = p + 1;
      return OK;
    }
  
    /*
     * Copy the string into allocated memory, handling '' to ' reduction.
     */
    str = xmalloc((p - *arg) - reduce);
    rettv->v_type = VAR_STRING;
    rettv->vval.v_string = str;
  
    for (p = *arg + 1; *p != NUL; ) {
      if (*p == '\'') {
        if (p[1] != '\'')
          break;
        ++p;
      }
      MB_COPY_CHAR(p, str);
    }
    *str = NUL;
    *arg = p + 1;
  
    return OK;
  }
  
  /// @return the function name of the partial.
  char_u *partial_name(partial_T *pt)
  {
    if (pt->pt_name != NULL) {
      return pt->pt_name;
    }
    return pt->pt_func->uf_name;
  }
  
  // TODO(ZyX-I): Move to eval/typval.h
  
  static void partial_free(partial_T *pt)
  {
    for (int i = 0; i < pt->pt_argc; i++) {
      tv_clear(&pt->pt_argv[i]);
    }
    xfree(pt->pt_argv);
    tv_dict_unref(pt->pt_dict);
    if (pt->pt_name != NULL) {
      func_unref(pt->pt_name);
      xfree(pt->pt_name);
    } else {
      func_ptr_unref(pt->pt_func);
    }
    xfree(pt);
  }
  
  // TODO(ZyX-I): Move to eval/typval.h
  
  /// Unreference a closure: decrement the reference count and free it when it
  /// becomes zero.
  void partial_unref(partial_T *pt)
  {
    if (pt != NULL && --pt->pt_refcount <= 0) {
      partial_free(pt);
    }
  }
  
  /// Allocate a variable for a List and fill it from "*arg".
  /// Return OK or FAIL.
  static int get_list_tv(char_u **arg, typval_T *rettv, int evaluate)
  {
    list_T      *l = NULL;
  
    if (evaluate) {
      l = tv_list_alloc(kListLenShouldKnow);
    }
  
    *arg = skipwhite(*arg + 1);
    while (**arg != ']' && **arg != NUL) {
      typval_T tv;
      if (eval1(arg, &tv, evaluate) == FAIL) {  // Recursive!
        goto failret;
      }
      if (evaluate) {
        tv.v_lock = VAR_UNLOCKED;
        tv_list_append_owned_tv(l, tv);
      }
  
      if (**arg == ']') {
        break;
      }
      if (**arg != ',') {
        emsgf(_("E696: Missing comma in List: %s"), *arg);
        goto failret;
      }
      *arg = skipwhite(*arg + 1);
    }
  
    if (**arg != ']') {
      emsgf(_("E697: Missing end of List ']': %s"), *arg);
  failret:
      if (evaluate) {
        tv_list_free(l);
      }
      return FAIL;
    }
  
    *arg = skipwhite(*arg + 1);
    if (evaluate) {
      tv_list_set_ret(rettv, l);
    }
  
    return OK;
  }
  
  bool func_equal(
      typval_T *tv1,
      typval_T *tv2,
      bool ic         // ignore case
  ) {
    char_u *s1, *s2;
    dict_T *d1, *d2;
    int a1, a2;
  
    // empty and NULL function name considered the same
    s1 = tv1->v_type == VAR_FUNC ? tv1->vval.v_string
                       : partial_name(tv1->vval.v_partial);
    if (s1 != NULL && *s1 == NUL) {
      s1 = NULL;
    }
    s2 = tv2->v_type == VAR_FUNC ? tv2->vval.v_string
                       : partial_name(tv2->vval.v_partial);
    if (s2 != NULL && *s2 == NUL) {
      s2 = NULL;
    }
    if (s1 == NULL || s2 == NULL) {
      if (s1 != s2) {
        return false;
      }
    } else if (STRCMP(s1, s2) != 0) {
      return false;
    }
  
    // empty dict and NULL dict is different
    d1 = tv1->v_type == VAR_FUNC ? NULL : tv1->vval.v_partial->pt_dict;
    d2 = tv2->v_type == VAR_FUNC ? NULL : tv2->vval.v_partial->pt_dict;
    if (d1 == NULL || d2 == NULL) {
      if (d1 != d2) {
        return false;
      }
    } else if (!tv_dict_equal(d1, d2, ic, true)) {
      return false;
    }
  
    // empty list and no list considered the same
    a1 = tv1->v_type == VAR_FUNC ? 0 : tv1->vval.v_partial->pt_argc;
    a2 = tv2->v_type == VAR_FUNC ? 0 : tv2->vval.v_partial->pt_argc;
    if (a1 != a2) {
      return false;
    }
    for (int i = 0; i < a1; i++) {
      if (!tv_equal(tv1->vval.v_partial->pt_argv + i,
                    tv2->vval.v_partial->pt_argv + i, ic, true)) {
        return false;
      }
    }
    return true;
  }
  
  /// Get next (unique) copy ID
  ///
  /// Used for traversing nested structures e.g. when serializing them or garbage
  /// collecting.
  int get_copyID(void)
    FUNC_ATTR_WARN_UNUSED_RESULT
  {
    // CopyID for recursively traversing lists and dicts
    //
    // This value is needed to avoid endless recursiveness. Last bit is used for
    // previous_funccal and normally ignored when comparing.
    static int current_copyID = 0;
    current_copyID += COPYID_INC;
    return current_copyID;
  }
  
  /*
   * Garbage collection for lists and dictionaries.
   *
   * We use reference counts to be able to free most items right away when they
   * are no longer used.  But for composite items it's possible that it becomes
   * unused while the reference count is > 0: When there is a recursive
   * reference.  Example:
   *	:let l = [1, 2, 3]
   *	:let d = {9: l}
   *	:let l[1] = d
   *
   * Since this is quite unusual we handle this with garbage collection: every
   * once in a while find out which lists and dicts are not referenced from any
   * variable.
   *
   * Here is a good reference text about garbage collection (refers to Python
   * but it applies to all reference-counting mechanisms):
   *	http://python.ca/nas/python/gc/
   */
  
  /// Do garbage collection for lists and dicts.
  ///
  /// @param testing  true if called from test_garbagecollect_now().
  /// @returns        true if some memory was freed.
  bool garbage_collect(bool testing)
  {
    bool abort = false;
  #define ABORTING(func) abort = abort || func
  
    if (!testing) {
      // Only do this once.
      want_garbage_collect = false;
      may_garbage_collect = false;
      garbage_collect_at_exit = false;
    }
  
    // We advance by two (COPYID_INC) because we add one for items referenced
    // through previous_funccal.
    const int copyID = get_copyID();
  
    // 1. Go through all accessible variables and mark all lists and dicts
    // with copyID.
  
    // Don't free variables in the previous_funccal list unless they are only
    // referenced through previous_funccal.  This must be first, because if
    // the item is referenced elsewhere the funccal must not be freed.
    ABORTING(set_ref_in_previous_funccal)(copyID);
  
    // script-local variables
    for (int i = 1; i <= ga_scripts.ga_len; ++i) {
      ABORTING(set_ref_in_ht)(&SCRIPT_VARS(i), copyID, NULL);
    }
  
    FOR_ALL_BUFFERS(buf) {
      // buffer-local variables
      ABORTING(set_ref_in_item)(&buf->b_bufvar.di_tv, copyID, NULL, NULL);
      // buffer marks (ShaDa additional data)
      ABORTING(set_ref_in_fmark)(buf->b_last_cursor, copyID);
      ABORTING(set_ref_in_fmark)(buf->b_last_insert, copyID);
      ABORTING(set_ref_in_fmark)(buf->b_last_change, copyID);
      for (size_t i = 0; i < NMARKS; i++) {
        ABORTING(set_ref_in_fmark)(buf->b_namedm[i], copyID);
      }
      // buffer change list (ShaDa additional data)
      for (int i = 0; i < buf->b_changelistlen; i++) {
        ABORTING(set_ref_in_fmark)(buf->b_changelist[i], copyID);
      }
      // buffer ShaDa additional data
      ABORTING(set_ref_dict)(buf->additional_data, copyID);
  
      // buffer callback functions
      set_ref_in_callback(&buf->b_prompt_callback, copyID, NULL, NULL);
      set_ref_in_callback(&buf->b_prompt_interrupt, copyID, NULL, NULL);
    }
  
    FOR_ALL_TAB_WINDOWS(tp, wp) {
      // window-local variables
      ABORTING(set_ref_in_item)(&wp->w_winvar.di_tv, copyID, NULL, NULL);
      // window jump list (ShaDa additional data)
      for (int i = 0; i < wp->w_jumplistlen; i++) {
        ABORTING(set_ref_in_fmark)(wp->w_jumplist[i].fmark, copyID);
      }
    }
    if (aucmd_win != NULL) {
      ABORTING(set_ref_in_item)(&aucmd_win->w_winvar.di_tv, copyID, NULL, NULL);
    }
  
    // registers (ShaDa additional data)
    {
      const void *reg_iter = NULL;
      do {
        yankreg_T reg;
        char name = NUL;
        bool is_unnamed = false;
        reg_iter = op_global_reg_iter(reg_iter, &name, &reg, &is_unnamed);
        if (name != NUL) {
          ABORTING(set_ref_dict)(reg.additional_data, copyID);
        }
      } while (reg_iter != NULL);
    }
  
    // global marks (ShaDa additional data)
    {
      const void *mark_iter = NULL;
      do {
        xfmark_T fm;
        char name = NUL;
        mark_iter = mark_global_iter(mark_iter, &name, &fm);
        if (name != NUL) {
          ABORTING(set_ref_dict)(fm.fmark.additional_data, copyID);
        }
      } while (mark_iter != NULL);
    }
  
    // tabpage-local variables
    FOR_ALL_TABS(tp) {
      ABORTING(set_ref_in_item)(&tp->tp_winvar.di_tv, copyID, NULL, NULL);
    }
  
    // global variables
    ABORTING(set_ref_in_ht)(&globvarht, copyID, NULL);
  
    // function-local variables
    ABORTING(set_ref_in_call_stack)(copyID);
  
    // named functions (matters for closures)
    ABORTING(set_ref_in_functions)(copyID);
  
    // Channels
    {
      Channel *data;
      map_foreach_value(channels, data, {
        set_ref_in_callback_reader(&data->on_data, copyID, NULL, NULL);
        set_ref_in_callback_reader(&data->on_stderr, copyID, NULL, NULL);
        set_ref_in_callback(&data->on_exit, copyID, NULL, NULL);
      })
    }
  
    // Timers
    {
      timer_T *timer;
      map_foreach_value(timers, timer, {
        set_ref_in_callback(&timer->callback, copyID, NULL, NULL);
      })
    }
  
    // function call arguments, if v:testing is set.
    ABORTING(set_ref_in_func_args)(copyID);
  
    // v: vars
    ABORTING(set_ref_in_ht)(&vimvarht, copyID, NULL);
  
    // history items (ShaDa additional elements)
    if (p_hi) {
      for (uint8_t i = 0; i < HIST_COUNT; i++) {
        const void *iter = NULL;
        do {
          histentry_T hist;
          iter = hist_iter(iter, i, false, &hist);
          if (hist.hisstr != NULL) {
            ABORTING(set_ref_list)(hist.additional_elements, copyID);
          }
        } while (iter != NULL);
      }
    }
  
    // previously used search/substitute patterns (ShaDa additional data)
    {
      SearchPattern pat;
      get_search_pattern(&pat);
      ABORTING(set_ref_dict)(pat.additional_data, copyID);
      get_substitute_pattern(&pat);
      ABORTING(set_ref_dict)(pat.additional_data, copyID);
    }
  
    // previously used replacement string
    {
      SubReplacementString sub;
      sub_get_replacement(&sub);
      ABORTING(set_ref_list)(sub.additional_elements, copyID);
    }
  
    ABORTING(set_ref_in_quickfix)(copyID);
  
    bool did_free = false;
    if (!abort) {
      // 2. Free lists and dictionaries that are not referenced.
      did_free = free_unref_items(copyID);
  
      // 3. Check if any funccal can be freed now.
      //    This may call us back recursively.
      did_free = free_unref_funccal(copyID, testing) || did_free;
    } else if (p_verbose > 0) {
      verb_msg(_(
          "Not enough memory to set references, garbage collection aborted!"));
    }
  #undef ABORTING
    return did_free;
  }
  
  /// Free lists and dictionaries that are no longer referenced.
  ///
  /// @note This function may only be called from garbage_collect().
  ///
  /// @param copyID Free lists/dictionaries that don't have this ID.
  /// @return true, if something was freed.
  static int free_unref_items(int copyID)
  {
    bool did_free = false;
  
    // Let all "free" functions know that we are here. This means no
    // dictionaries, lists, or jobs are to be freed, because we will
    // do that here.
    tv_in_free_unref_items = true;
  
    // PASS 1: free the contents of the items. We don't free the items
    // themselves yet, so that it is possible to decrement refcount counters.
  
    // Go through the list of dicts and free items without the copyID.
    // Don't free dicts that are referenced internally.
    for (dict_T *dd = gc_first_dict; dd != NULL; dd = dd->dv_used_next) {
      if ((dd->dv_copyID & COPYID_MASK) != (copyID & COPYID_MASK)) {
        // Free the Dictionary and ordinary items it contains, but don't
        // recurse into Lists and Dictionaries, they will be in the list
        // of dicts or list of lists.
        tv_dict_free_contents(dd);
        did_free = true;
      }
    }
  
    // Go through the list of lists and free items without the copyID.
    // But don't free a list that has a watcher (used in a for loop), these
    // are not referenced anywhere.
    for (list_T *ll = gc_first_list; ll != NULL; ll = ll->lv_used_next) {
      if ((tv_list_copyid(ll) & COPYID_MASK) != (copyID & COPYID_MASK)
          && !tv_list_has_watchers(ll)) {
        // Free the List and ordinary items it contains, but don't recurse
        // into Lists and Dictionaries, they will be in the list of dicts
        // or list of lists.
        tv_list_free_contents(ll);
        did_free = true;
      }
    }
  
    // PASS 2: free the items themselves.
    dict_T *dd_next;
    for (dict_T *dd = gc_first_dict; dd != NULL; dd = dd_next) {
      dd_next = dd->dv_used_next;
      if ((dd->dv_copyID & COPYID_MASK) != (copyID & COPYID_MASK)) {
        tv_dict_free_dict(dd);
      }
    }
  
    list_T *ll_next;
    for (list_T *ll = gc_first_list; ll != NULL; ll = ll_next) {
      ll_next = ll->lv_used_next;
      if ((ll->lv_copyID & COPYID_MASK) != (copyID & COPYID_MASK)
          && !tv_list_has_watchers(ll)) {
        // Free the List and ordinary items it contains, but don't recurse
        // into Lists and Dictionaries, they will be in the list of dicts
        // or list of lists.
        tv_list_free_list(ll);
      }
    }
    tv_in_free_unref_items = false;
    return did_free;
  }
  
  /// Mark all lists and dicts referenced through hashtab "ht" with "copyID".
  ///
  /// @param ht            Hashtab content will be marked.
  /// @param copyID        New mark for lists and dicts.
  /// @param list_stack    Used to add lists to be marked. Can be NULL.
  ///
  /// @returns             true if setting references failed somehow.
  bool set_ref_in_ht(hashtab_T *ht, int copyID, list_stack_T **list_stack)
    FUNC_ATTR_WARN_UNUSED_RESULT
  {
    bool abort = false;
    ht_stack_T *ht_stack = NULL;
  
    hashtab_T *cur_ht = ht;
    for (;;) {
      if (!abort) {
        // Mark each item in the hashtab.  If the item contains a hashtab
        // it is added to ht_stack, if it contains a list it is added to
        // list_stack.
        HASHTAB_ITER(cur_ht, hi, {
          abort = abort || set_ref_in_item(
              &TV_DICT_HI2DI(hi)->di_tv, copyID, &ht_stack, list_stack);
        });
      }
  
      if (ht_stack == NULL) {
        break;
      }
  
      // take an item from the stack
      cur_ht = ht_stack->ht;
      ht_stack_T *tempitem = ht_stack;
      ht_stack = ht_stack->prev;
      xfree(tempitem);
    }
  
    return abort;
  }
  
  /// Mark all lists and dicts referenced through list "l" with "copyID".
  ///
  /// @param l             List content will be marked.
  /// @param copyID        New mark for lists and dicts.
  /// @param ht_stack      Used to add hashtabs to be marked. Can be NULL.
  ///
  /// @returns             true if setting references failed somehow.
  bool set_ref_in_list(list_T *l, int copyID, ht_stack_T **ht_stack)
    FUNC_ATTR_WARN_UNUSED_RESULT
  {
    bool abort = false;
    list_stack_T *list_stack = NULL;
  
    list_T *cur_l = l;
    for (;;) {
      // Mark each item in the list.  If the item contains a hashtab
      // it is added to ht_stack, if it contains a list it is added to
      // list_stack.
      TV_LIST_ITER(cur_l, li, {
        if (abort) {
          break;
        }
        abort = set_ref_in_item(TV_LIST_ITEM_TV(li), copyID, ht_stack,
                                &list_stack);
      });
  
      if (list_stack == NULL) {
        break;
      }
  
      // take an item from the stack
      cur_l = list_stack->list;
      list_stack_T *tempitem = list_stack;
      list_stack = list_stack->prev;
      xfree(tempitem);
    }
  
    return abort;
  }
  
  /// Mark all lists and dicts referenced through typval "tv" with "copyID".
  ///
  /// @param tv            Typval content will be marked.
  /// @param copyID        New mark for lists and dicts.
  /// @param ht_stack      Used to add hashtabs to be marked. Can be NULL.
  /// @param list_stack    Used to add lists to be marked. Can be NULL.
  ///
  /// @returns             true if setting references failed somehow.
  bool set_ref_in_item(typval_T *tv, int copyID, ht_stack_T **ht_stack,
                       list_stack_T **list_stack)
    FUNC_ATTR_WARN_UNUSED_RESULT
  {
    bool abort = false;
  
    switch (tv->v_type) {
      case VAR_DICT: {
        dict_T *dd = tv->vval.v_dict;
        if (dd != NULL && dd->dv_copyID != copyID) {
          // Didn't see this dict yet.
          dd->dv_copyID = copyID;
          if (ht_stack == NULL) {
            abort = set_ref_in_ht(&dd->dv_hashtab, copyID, list_stack);
          } else {
            ht_stack_T *newitem = try_malloc(sizeof(ht_stack_T));
            if (newitem == NULL) {
              abort = true;
            } else {
              newitem->ht = &dd->dv_hashtab;
              newitem->prev = *ht_stack;
              *ht_stack = newitem;
            }
          }
  
          QUEUE *w = NULL;
          DictWatcher *watcher = NULL;
          QUEUE_FOREACH(w, &dd->watchers) {
            watcher = tv_dict_watcher_node_data(w);
            set_ref_in_callback(&watcher->callback, copyID, ht_stack, list_stack);
          }
        }
        break;
      }
  
      case VAR_LIST: {
        list_T *ll = tv->vval.v_list;
        if (ll != NULL && ll->lv_copyID != copyID) {
          // Didn't see this list yet.
          ll->lv_copyID = copyID;
          if (list_stack == NULL) {
            abort = set_ref_in_list(ll, copyID, ht_stack);
          } else {
            list_stack_T *newitem = try_malloc(sizeof(list_stack_T));
            if (newitem == NULL) {
              abort = true;
            } else {
              newitem->list = ll;
              newitem->prev = *list_stack;
              *list_stack = newitem;
            }
          }
        }
        break;
      }
  
      case VAR_PARTIAL: {
        partial_T *pt = tv->vval.v_partial;
  
        // A partial does not have a copyID, because it cannot contain itself.
        if (pt != NULL) {
          abort = set_ref_in_func(pt->pt_name, pt->pt_func, copyID);
          if (pt->pt_dict != NULL) {
            typval_T dtv;
  
            dtv.v_type = VAR_DICT;
            dtv.vval.v_dict = pt->pt_dict;
            abort = abort || set_ref_in_item(&dtv, copyID, ht_stack, list_stack);
          }
  
          for (int i = 0; i < pt->pt_argc; i++) {
            abort = abort || set_ref_in_item(&pt->pt_argv[i], copyID,
                                             ht_stack, list_stack);
          }
        }
        break;
      }
      case VAR_FUNC:
        abort = set_ref_in_func(tv->vval.v_string, NULL, copyID);
        break;
      case VAR_UNKNOWN:
      case VAR_BOOL:
      case VAR_SPECIAL:
      case VAR_FLOAT:
      case VAR_NUMBER:
      case VAR_STRING: {
        break;
      }
    }
    return abort;
  }
  
  
  
  /// Mark all lists and dicts referenced in given mark
  ///
  /// @returns true if setting references failed somehow.
  static inline bool set_ref_in_fmark(fmark_T fm, int copyID)
    FUNC_ATTR_WARN_UNUSED_RESULT
  {
    if (fm.additional_data != NULL
        && fm.additional_data->dv_copyID != copyID) {
      fm.additional_data->dv_copyID = copyID;
      return set_ref_in_ht(&fm.additional_data->dv_hashtab, copyID, NULL);
    }
    return false;
  }
  
  /// Mark all lists and dicts referenced in given list and the list itself
  ///
  /// @returns true if setting references failed somehow.
  static inline bool set_ref_list(list_T *list, int copyID)
    FUNC_ATTR_WARN_UNUSED_RESULT
  {
    if (list != NULL) {
      typval_T tv = (typval_T) {
        .v_type = VAR_LIST,
        .vval = { .v_list = list }
      };
      return set_ref_in_item(&tv, copyID, NULL, NULL);
    }
    return false;
  }
  
  /// Mark all lists and dicts referenced in given dict and the dict itself
  ///
  /// @returns true if setting references failed somehow.
  static inline bool set_ref_dict(dict_T *dict, int copyID)
    FUNC_ATTR_WARN_UNUSED_RESULT
  {
    if (dict != NULL) {
      typval_T tv = (typval_T) {
        .v_type = VAR_DICT,
        .vval = { .v_dict = dict }
      };
      return set_ref_in_item(&tv, copyID, NULL, NULL);
    }
    return false;
  }
  
  /*
   * Allocate a variable for a Dictionary and fill it from "*arg".
   * Return OK or FAIL.  Returns NOTDONE for {expr}.
   */
  static int dict_get_tv(char_u **arg, typval_T *rettv, int evaluate)
  {
    dict_T      *d = NULL;
    typval_T tvkey;
    typval_T tv;
    char_u      *key = NULL;
    dictitem_T  *item;
    char_u      *start = skipwhite(*arg + 1);
    char buf[NUMBUFLEN];
  
    /*
     * First check if it's not a curly-braces thing: {expr}.
     * Must do this without evaluating, otherwise a function may be called
     * twice.  Unfortunately this means we need to call eval1() twice for the
     * first item.
     * But {} is an empty Dictionary.
     */
    if (*start != '}') {
      if (eval1(&start, &tv, false) == FAIL) {    // recursive!
        return FAIL;
      }
      if (*start == '}') {
        return NOTDONE;
      }
    }
  
    if (evaluate) {
      d = tv_dict_alloc();
    }
    tvkey.v_type = VAR_UNKNOWN;
    tv.v_type = VAR_UNKNOWN;
  
    *arg = skipwhite(*arg + 1);
    while (**arg != '}' && **arg != NUL) {
      if (eval1(arg, &tvkey, evaluate) == FAIL) {         // recursive!
        goto failret;
      }
      if (**arg != ':') {
        EMSG2(_("E720: Missing colon in Dictionary: %s"), *arg);
        tv_clear(&tvkey);
        goto failret;
      }
      if (evaluate) {
        key = (char_u *)tv_get_string_buf_chk(&tvkey, buf);
        if (key == NULL) {
          // "key" is NULL when tv_get_string_buf_chk() gave an errmsg
          tv_clear(&tvkey);
          goto failret;
        }
      }
  
      *arg = skipwhite(*arg + 1);
      if (eval1(arg, &tv, evaluate) == FAIL) {  // Recursive!
        if (evaluate) {
          tv_clear(&tvkey);
        }
        goto failret;
      }
      if (evaluate) {
        item = tv_dict_find(d, (const char *)key, -1);
        if (item != NULL) {
          EMSG2(_("E721: Duplicate key in Dictionary: \"%s\""), key);
          tv_clear(&tvkey);
          tv_clear(&tv);
          goto failret;
        }
        item = tv_dict_item_alloc((const char *)key);
        item->di_tv = tv;
        item->di_tv.v_lock = 0;
        if (tv_dict_add(d, item) == FAIL) {
          tv_dict_item_free(item);
        }
      }
      tv_clear(&tvkey);
  
      if (**arg == '}')
        break;
      if (**arg != ',') {
        EMSG2(_("E722: Missing comma in Dictionary: %s"), *arg);
        goto failret;
      }
      *arg = skipwhite(*arg + 1);
    }
  
    if (**arg != '}') {
      EMSG2(_("E723: Missing end of Dictionary '}': %s"), *arg);
  failret:
      if (d != NULL) {
        tv_dict_free(d);
      }
      return FAIL;
    }
  
    *arg = skipwhite(*arg + 1);
    if (evaluate) {
      tv_dict_set_ret(rettv, d);
    }
  
    return OK;
  }
  
  /// Convert the string to a floating point number
  ///
  /// This uses strtod().  setlocale(LC_NUMERIC, "C") has been used earlier to
  /// make sure this always uses a decimal point.
  ///
  /// @param[in]  text  String to convert.
  /// @param[out]  ret_value  Location where conversion result is saved.
  ///
  /// @return Length of the text that was consumed.
  size_t string2float(const char *const text, float_T *const ret_value)
    FUNC_ATTR_NONNULL_ALL
  {
    char *s = NULL;
  
    // MS-Windows does not deal with "inf" and "nan" properly
    if (STRNICMP(text, "inf", 3) == 0) {
      *ret_value = INFINITY;
      return 3;
    }
    if (STRNICMP(text, "-inf", 3) == 0) {
      *ret_value = -INFINITY;
      return 4;
    }
    if (STRNICMP(text, "nan", 3) == 0) {
      *ret_value = NAN;
      return 3;
    }
    *ret_value = strtod(text, &s);
    return (size_t) (s - text);
  }
  
  /// Get the value of an environment variable.
  ///
  /// If the environment variable was not set, silently assume it is empty.
  ///
  /// @param arg Points to the '$'.  It is advanced to after the name.
  /// @return FAIL if the name is invalid.
  ///
  static int get_env_tv(char_u **arg, typval_T *rettv, int evaluate)
  {
    char_u *name;
    char_u *string = NULL;
    int     len;
    int     cc;
  
    ++*arg;
    name = *arg;
    len = get_env_len((const char_u **)arg);
  
    if (evaluate) {
      if (len == 0) {
        return FAIL;  // Invalid empty name.
      }
      cc = name[len];
      name[len] = NUL;
      // First try vim_getenv(), fast for normal environment vars.
      string = (char_u *)vim_getenv((char *)name);
      if (string == NULL || *string == NUL) {
        xfree(string);
  
        // Next try expanding things like $VIM and ${HOME}.
        string = expand_env_save(name - 1);
        if (string != NULL && *string == '$') {
          XFREE_CLEAR(string);
        }
      }
      name[len] = cc;
      rettv->v_type = VAR_STRING;
      rettv->vval.v_string = string;
    }
  
    return OK;
  }
  
  /// Get the argument list for a given window
  void get_arglist_as_rettv(aentry_T *arglist, int argcount,
                            typval_T *rettv)
  {
    tv_list_alloc_ret(rettv, argcount);
    if (arglist != NULL) {
      for (int idx = 0; idx < argcount; idx++) {
        tv_list_append_string(rettv->vval.v_list,
                              (const char *)alist_name(&arglist[idx]), -1);
      }
    }
  }
  
  // Prepare "gap" for an assert error and add the sourcing position.
  void prepare_assert_error(garray_T *gap)
  {
    char buf[NUMBUFLEN];
  
    ga_init(gap, 1, 100);
    if (sourcing_name != NULL) {
      ga_concat(gap, sourcing_name);
      if (sourcing_lnum > 0) {
        ga_concat(gap, (char_u *)" ");
      }
    }
    if (sourcing_lnum > 0) {
      vim_snprintf(buf, ARRAY_SIZE(buf), "line %" PRId64, (int64_t)sourcing_lnum);
      ga_concat(gap, (char_u *)buf);
    }
    if (sourcing_name != NULL || sourcing_lnum > 0) {
      ga_concat(gap, (char_u *)": ");
    }
  }
  
  // Append "str" to "gap", escaping unprintable characters.
  // Changes NL to \n, CR to \r, etc.
  static void ga_concat_esc(garray_T *gap, char_u *str)
  {
    char_u *p;
    char_u buf[NUMBUFLEN];
  
    if (str == NULL) {
      ga_concat(gap, (char_u *)"NULL");
      return;
    }
  
    for (p = str; *p != NUL; p++) {
      switch (*p) {
        case BS: ga_concat(gap, (char_u *)"\\b"); break;
        case ESC: ga_concat(gap, (char_u *)"\\e"); break;
        case FF: ga_concat(gap, (char_u *)"\\f"); break;
        case NL: ga_concat(gap, (char_u *)"\\n"); break;
        case TAB: ga_concat(gap, (char_u *)"\\t"); break;
        case CAR: ga_concat(gap, (char_u *)"\\r"); break;
        case '\\': ga_concat(gap, (char_u *)"\\\\"); break;
        default:
          if (*p < ' ') {
            vim_snprintf((char *)buf, NUMBUFLEN, "\\x%02x", *p);
            ga_concat(gap, buf);
          } else {
            ga_append(gap, *p);
          }
          break;
      }
    }
  }
  
  // Fill "gap" with information about an assert error.
  void fill_assert_error(garray_T *gap, typval_T *opt_msg_tv,
                         char_u *exp_str, typval_T *exp_tv,
                         typval_T *got_tv, assert_type_T atype)
  {
    char_u *tofree;
  
    if (opt_msg_tv->v_type != VAR_UNKNOWN) {
      tofree = (char_u *)encode_tv2echo(opt_msg_tv, NULL);
      ga_concat(gap, tofree);
      xfree(tofree);
      ga_concat(gap, (char_u *)": ");
    }
  
    if (atype == ASSERT_MATCH || atype == ASSERT_NOTMATCH) {
      ga_concat(gap, (char_u *)"Pattern ");
    } else if (atype == ASSERT_NOTEQUAL) {
      ga_concat(gap, (char_u *)"Expected not equal to ");
    } else {
      ga_concat(gap, (char_u *)"Expected ");
    }
  
    if (exp_str == NULL) {
      tofree = (char_u *)encode_tv2string(exp_tv, NULL);
      ga_concat_esc(gap, tofree);
      xfree(tofree);
    } else {
      ga_concat_esc(gap, exp_str);
    }
  
    if (atype != ASSERT_NOTEQUAL) {
      if (atype == ASSERT_MATCH) {
        ga_concat(gap, (char_u *)" does not match ");
      } else if (atype == ASSERT_NOTMATCH) {
        ga_concat(gap, (char_u *)" does match ");
      } else {
        ga_concat(gap, (char_u *)" but got ");
      }
      tofree = (char_u *)encode_tv2string(got_tv, NULL);
      ga_concat_esc(gap, tofree);
      xfree(tofree);
    }
  }
  
  // Add an assert error to v:errors.
  void assert_error(garray_T *gap)
  {
    struct vimvar *vp = &vimvars[VV_ERRORS];
  
    if (vp->vv_type != VAR_LIST || vimvars[VV_ERRORS].vv_list == NULL) {
      // Make sure v:errors is a list.
      set_vim_var_list(VV_ERRORS, tv_list_alloc(1));
    }
    tv_list_append_string(vimvars[VV_ERRORS].vv_list,
                          (const char *)gap->ga_data, (ptrdiff_t)gap->ga_len);
  }
  
  int assert_equal_common(typval_T *argvars, assert_type_T atype)
    FUNC_ATTR_NONNULL_ALL
  {
    garray_T ga;
  
    if (tv_equal(&argvars[0], &argvars[1], false, false)
        != (atype == ASSERT_EQUAL)) {
      prepare_assert_error(&ga);
      fill_assert_error(&ga, &argvars[2], NULL,
                        &argvars[0], &argvars[1], atype);
      assert_error(&ga);
      ga_clear(&ga);
      return 1;
    }
    return 0;
  }
  
  int assert_equalfile(typval_T *argvars)
    FUNC_ATTR_NONNULL_ALL
  {
    char buf1[NUMBUFLEN];
    char buf2[NUMBUFLEN];
    const char *const fname1 = tv_get_string_buf_chk(&argvars[0], buf1);
    const char *const fname2 = tv_get_string_buf_chk(&argvars[1], buf2);
    garray_T ga;
  
    if (fname1 == NULL || fname2 == NULL) {
      return 0;
    }
  
    IObuff[0] = NUL;
    FILE *const fd1 = os_fopen(fname1, READBIN);
    if (fd1 == NULL) {
      snprintf((char *)IObuff, IOSIZE, (char *)e_notread, fname1);
    } else {
      FILE *const fd2 = os_fopen(fname2, READBIN);
      if (fd2 == NULL) {
        fclose(fd1);
        snprintf((char *)IObuff, IOSIZE, (char *)e_notread, fname2);
      } else {
        for (int64_t count = 0; ; count++) {
          const int c1 = fgetc(fd1);
          const int c2 = fgetc(fd2);
          if (c1 == EOF) {
            if (c2 != EOF) {
              STRCPY(IObuff, "first file is shorter");
            }
            break;
          } else if (c2 == EOF) {
            STRCPY(IObuff, "second file is shorter");
            break;
          } else if (c1 != c2) {
            snprintf((char *)IObuff, IOSIZE,
                     "difference at byte %" PRId64, count);
            break;
          }
        }
        fclose(fd1);
        fclose(fd2);
      }
    }
    if (IObuff[0] != NUL) {
      prepare_assert_error(&ga);
      ga_concat(&ga, IObuff);
      assert_error(&ga);
      ga_clear(&ga);
      return 1;
    }
    return 0;
  }
  
  int assert_inrange(typval_T *argvars)
    FUNC_ATTR_NONNULL_ALL
  {
    bool error = false;
    const varnumber_T lower = tv_get_number_chk(&argvars[0], &error);
    const varnumber_T upper = tv_get_number_chk(&argvars[1], &error);
    const varnumber_T actual = tv_get_number_chk(&argvars[2], &error);
  
    if (error) {
      return 0;
    }
    if (actual < lower || actual > upper) {
      garray_T ga;
      prepare_assert_error(&ga);
  
      char msg[55];
      vim_snprintf(msg, sizeof(msg),
                   "range %" PRIdVARNUMBER " - %" PRIdVARNUMBER ",",
                   lower, upper);
      fill_assert_error(&ga, &argvars[3], (char_u *)msg, NULL, &argvars[2],
                        ASSERT_INRANGE);
      assert_error(&ga);
      ga_clear(&ga);
      return 1;
    }
    return 0;
  }
  
  // Common for assert_true() and assert_false().
  int assert_bool(typval_T *argvars, bool is_true)
    FUNC_ATTR_NONNULL_ALL
  {
    bool error = false;
    garray_T ga;
  
    if ((argvars[0].v_type != VAR_NUMBER
         || (tv_get_number_chk(&argvars[0], &error) == 0) == is_true
         || error)
        && (argvars[0].v_type != VAR_BOOL
            || (argvars[0].vval.v_bool
                != (BoolVarValue)(is_true
                                  ? kBoolVarTrue
                                  : kBoolVarFalse)))) {
      prepare_assert_error(&ga);
      fill_assert_error(&ga, &argvars[1],
                        (char_u *)(is_true ? "True" : "False"),
                        NULL, &argvars[0], ASSERT_OTHER);
      assert_error(&ga);
      ga_clear(&ga);
      return 1;
    }
    return 0;
  }
  
  int assert_exception(typval_T *argvars)
    FUNC_ATTR_NONNULL_ALL
  {
    garray_T ga;
  
    const char *const error = tv_get_string_chk(&argvars[0]);
    if (vimvars[VV_EXCEPTION].vv_str == NULL) {
      prepare_assert_error(&ga);
      ga_concat(&ga, (char_u *)"v:exception is not set");
      assert_error(&ga);
      ga_clear(&ga);
      return 1;
    } else if (error != NULL
               && strstr((char *)vimvars[VV_EXCEPTION].vv_str, error) == NULL) {
      prepare_assert_error(&ga);
      fill_assert_error(&ga, &argvars[1], NULL, &argvars[0],
                        &vimvars[VV_EXCEPTION].vv_tv, ASSERT_OTHER);
      assert_error(&ga);
      ga_clear(&ga);
      return 1;
    }
    return 0;
  }
  
  int assert_fails(typval_T *argvars)
    FUNC_ATTR_NONNULL_ALL
  {
    const char *const cmd = tv_get_string_chk(&argvars[0]);
    garray_T    ga;
    int ret = 0;
    int         save_trylevel = trylevel;
  
    // trylevel must be zero for a ":throw" command to be considered failed
    trylevel = 0;
    called_emsg = false;
    suppress_errthrow = true;
    emsg_silent = true;
  
    do_cmdline_cmd(cmd);
    if (!called_emsg) {
      prepare_assert_error(&ga);
      ga_concat(&ga, (const char_u *)"command did not fail: ");
      if (argvars[1].v_type != VAR_UNKNOWN
          && argvars[2].v_type != VAR_UNKNOWN) {
        char *const tofree = encode_tv2echo(&argvars[2], NULL);
        ga_concat(&ga, (char_u *)tofree);
        xfree(tofree);
      } else {
        ga_concat(&ga, (const char_u *)cmd);
      }
      assert_error(&ga);
      ga_clear(&ga);
      ret = 1;
    } else if (argvars[1].v_type != VAR_UNKNOWN) {
      char buf[NUMBUFLEN];
      const char *const error = tv_get_string_buf_chk(&argvars[1], buf);
  
      if (error == NULL
          || strstr((char *)vimvars[VV_ERRMSG].vv_str, error) == NULL) {
        prepare_assert_error(&ga);
        fill_assert_error(&ga, &argvars[2], NULL, &argvars[1],
                          &vimvars[VV_ERRMSG].vv_tv, ASSERT_OTHER);
        assert_error(&ga);
        ga_clear(&ga);
        ret = 1;
      }
    }
  
    trylevel = save_trylevel;
    called_emsg = false;
    suppress_errthrow = false;
    emsg_silent = false;
    emsg_on_display = false;
    set_vim_var_string(VV_ERRMSG, NULL, 0);
    return ret;
  }
  
  int assert_match_common(typval_T *argvars, assert_type_T atype)
    FUNC_ATTR_NONNULL_ALL
  {
    char buf1[NUMBUFLEN];
    char buf2[NUMBUFLEN];
    const char *const pat = tv_get_string_buf_chk(&argvars[0], buf1);
    const char *const text = tv_get_string_buf_chk(&argvars[1], buf2);
  
    if (pat == NULL || text == NULL) {
      EMSG(_(e_invarg));
    } else if (pattern_match((char_u *)pat, (char_u *)text, false)
               != (atype == ASSERT_MATCH)) {
      garray_T ga;
      prepare_assert_error(&ga);
      fill_assert_error(&ga, &argvars[2], NULL, &argvars[0], &argvars[1], atype);
      assert_error(&ga);
      ga_clear(&ga);
      return 1;
    }
    return 0;
  }
  
  /// Find a window: When using a Window ID in any tab page, when using a number
  /// in the current tab page.
  win_T * find_win_by_nr_or_id(typval_T *vp)
  {
    int nr = (int)tv_get_number_chk(vp, NULL);
  
    if (nr >= LOWEST_WIN_ID) {
      return win_id2wp(vp);
    }
  
    return find_win_by_nr(vp, NULL);
  }
  
  /*
   * Implementation of map() and filter().
   */
  void filter_map(typval_T *argvars, typval_T *rettv, int map)
  {
    typval_T    *expr;
    list_T      *l = NULL;
    dictitem_T  *di;
    hashtab_T   *ht;
    hashitem_T  *hi;
    dict_T      *d = NULL;
    typval_T save_val;
    typval_T save_key;
    int rem = false;
    int todo;
    char_u *ermsg = (char_u *)(map ? "map()" : "filter()");
    const char *const arg_errmsg = (map
                                    ? N_("map() argument")
                                    : N_("filter() argument"));
    int save_did_emsg;
    int idx = 0;
  
    if (argvars[0].v_type == VAR_LIST) {
      tv_copy(&argvars[0], rettv);
      if ((l = argvars[0].vval.v_list) == NULL
          || (!map && tv_check_lock(tv_list_locked(l), arg_errmsg,
                                    TV_TRANSLATE))) {
        return;
      }
    } else if (argvars[0].v_type == VAR_DICT) {
      tv_copy(&argvars[0], rettv);
      if ((d = argvars[0].vval.v_dict) == NULL
          || (!map && tv_check_lock(d->dv_lock, arg_errmsg, TV_TRANSLATE))) {
        return;
      }
    } else {
      EMSG2(_(e_listdictarg), ermsg);
      return;
    }
  
    expr = &argvars[1];
    // On type errors, the preceding call has already displayed an error
    // message.  Avoid a misleading error message for an empty string that
    // was not passed as argument.
    if (expr->v_type != VAR_UNKNOWN) {
      prepare_vimvar(VV_VAL, &save_val);
  
      // We reset "did_emsg" to be able to detect whether an error
      // occurred during evaluation of the expression.
      save_did_emsg = did_emsg;
      did_emsg = FALSE;
  
      prepare_vimvar(VV_KEY, &save_key);
      if (argvars[0].v_type == VAR_DICT) {
        vimvars[VV_KEY].vv_type = VAR_STRING;
  
        ht = &d->dv_hashtab;
        hash_lock(ht);
        todo = (int)ht->ht_used;
        for (hi = ht->ht_array; todo > 0; ++hi) {
          if (!HASHITEM_EMPTY(hi)) {
            --todo;
  
            di = TV_DICT_HI2DI(hi);
            if (map
                && (tv_check_lock(di->di_tv.v_lock, arg_errmsg, TV_TRANSLATE)
                    || var_check_ro(di->di_flags, arg_errmsg, TV_TRANSLATE))) {
              break;
            }
  
            vimvars[VV_KEY].vv_str = vim_strsave(di->di_key);
            int r = filter_map_one(&di->di_tv, expr, map, &rem);
            tv_clear(&vimvars[VV_KEY].vv_tv);
            if (r == FAIL || did_emsg) {
              break;
            }
            if (!map && rem) {
              if (var_check_fixed(di->di_flags, arg_errmsg, TV_TRANSLATE)
                  || var_check_ro(di->di_flags, arg_errmsg, TV_TRANSLATE)) {
                break;
              }
              tv_dict_item_remove(d, di);
            }
          }
        }
        hash_unlock(ht);
      } else {
        assert(argvars[0].v_type == VAR_LIST);
        vimvars[VV_KEY].vv_type = VAR_NUMBER;
  
        for (listitem_T *li = tv_list_first(l); li != NULL;) {
          if (map
              && tv_check_lock(TV_LIST_ITEM_TV(li)->v_lock, arg_errmsg,
                               TV_TRANSLATE)) {
            break;
          }
          vimvars[VV_KEY].vv_nr = idx;
          if (filter_map_one(TV_LIST_ITEM_TV(li), expr, map, &rem) == FAIL
              || did_emsg) {
            break;
          }
          if (!map && rem) {
            li = tv_list_item_remove(l, li);
          } else {
            li = TV_LIST_ITEM_NEXT(l, li);
          }
          idx++;
        }
      }
  
      restore_vimvar(VV_KEY, &save_key);
      restore_vimvar(VV_VAL, &save_val);
  
      did_emsg |= save_did_emsg;
    }
  }
  
  static int filter_map_one(typval_T *tv, typval_T *expr, int map, int *remp)
    FUNC_ATTR_NONNULL_ARG(1, 2)
  {
    typval_T rettv;
    typval_T argv[3];
    int retval = FAIL;
  
    tv_copy(tv, &vimvars[VV_VAL].vv_tv);
    argv[0] = vimvars[VV_KEY].vv_tv;
    argv[1] = vimvars[VV_VAL].vv_tv;
    if (eval_expr_typval(expr, argv, 2, &rettv) == FAIL) {
      goto theend;
    }
    if (map) {
      // map(): replace the list item value.
      tv_clear(tv);
      rettv.v_lock = 0;
      *tv = rettv;
    } else {
      bool error = false;
  
      // filter(): when expr is zero remove the item
      *remp = (tv_get_number_chk(&rettv, &error) == 0);
      tv_clear(&rettv);
      // On type error, nothing has been removed; return FAIL to stop the
      // loop.  The error message was given by tv_get_number_chk().
      if (error) {
        goto theend;
      }
    }
    retval = OK;
  theend:
    tv_clear(&vimvars[VV_VAL].vv_tv);
    return retval;
  }
  
  void common_function(typval_T *argvars, typval_T *rettv,
                       bool is_funcref, FunPtr fptr)
  {
    char_u      *s;
    char_u      *name;
    bool use_string = false;
    partial_T *arg_pt = NULL;
    char_u *trans_name = NULL;
  
    if (argvars[0].v_type == VAR_FUNC) {
      // function(MyFunc, [arg], dict)
      s = argvars[0].vval.v_string;
    } else if (argvars[0].v_type == VAR_PARTIAL
               && argvars[0].vval.v_partial != NULL) {
      // function(dict.MyFunc, [arg])
      arg_pt = argvars[0].vval.v_partial;
      s = partial_name(arg_pt);
    } else {
      // function('MyFunc', [arg], dict)
      s = (char_u *)tv_get_string(&argvars[0]);
      use_string = true;
    }
  
    if ((use_string && vim_strchr(s, AUTOLOAD_CHAR) == NULL) || is_funcref) {
      name = s;
      trans_name = trans_function_name(&name, false,
                                       TFN_INT | TFN_QUIET | TFN_NO_AUTOLOAD
                                       | TFN_NO_DEREF, NULL, NULL);
      if (*name != NUL) {
        s = NULL;
      }
    }
    if (s == NULL || *s == NUL || (use_string && ascii_isdigit(*s))
        || (is_funcref && trans_name == NULL)) {
      emsgf(_(e_invarg2), (use_string
                           ? tv_get_string(&argvars[0])
                           : (const char *)s));
      // Don't check an autoload name for existence here.
    } else if (trans_name != NULL
               && (is_funcref ? find_func(trans_name) == NULL
                   : !translated_function_exists((const char *)trans_name))) {
      emsgf(_("E700: Unknown function: %s"), s);
    } else {
      int dict_idx = 0;
      int arg_idx = 0;
      list_T *list = NULL;
      if (STRNCMP(s, "s:", 2) == 0 || STRNCMP(s, "<SID>", 5) == 0) {
        char sid_buf[25];
        int off = *s == 's' ? 2 : 5;
  
        // Expand s: and <SID> into <SNR>nr_, so that the function can
        // also be called from another script. Using trans_function_name()
        // would also work, but some plugins depend on the name being
        // printable text.
        snprintf(sid_buf, sizeof(sid_buf), "<SNR>%" PRId64 "_",
                 (int64_t)current_sctx.sc_sid);
        name = xmalloc(STRLEN(sid_buf) + STRLEN(s + off) + 1);
        STRCPY(name, sid_buf);
        STRCAT(name, s + off);
      } else {
        name = vim_strsave(s);
      }
  
      if (argvars[1].v_type != VAR_UNKNOWN) {
        if (argvars[2].v_type != VAR_UNKNOWN) {
          // function(name, [args], dict)
          arg_idx = 1;
          dict_idx = 2;
        } else if (argvars[1].v_type == VAR_DICT) {
          // function(name, dict)
          dict_idx = 1;
        } else {
          // function(name, [args])
          arg_idx = 1;
        }
        if (dict_idx > 0) {
          if (argvars[dict_idx].v_type != VAR_DICT) {
            EMSG(_("E922: expected a dict"));
            xfree(name);
            goto theend;
          }
          if (argvars[dict_idx].vval.v_dict == NULL) {
            dict_idx = 0;
          }
        }
        if (arg_idx > 0) {
          if (argvars[arg_idx].v_type != VAR_LIST) {
            EMSG(_("E923: Second argument of function() must be "
                   "a list or a dict"));
            xfree(name);
            goto theend;
          }
          list = argvars[arg_idx].vval.v_list;
          if (tv_list_len(list) == 0) {
            arg_idx = 0;
          } else if (tv_list_len(list) > MAX_FUNC_ARGS) {
            emsg_funcname((char *)e_toomanyarg, s);
            xfree(name);
            goto theend;
          }
        }
      }
      if (dict_idx > 0 || arg_idx > 0 || arg_pt != NULL || is_funcref) {
        partial_T *const pt = xcalloc(1, sizeof(*pt));
  
        // result is a VAR_PARTIAL
        if (arg_idx > 0 || (arg_pt != NULL && arg_pt->pt_argc > 0)) {
          const int arg_len = (arg_pt == NULL ? 0 : arg_pt->pt_argc);
          const int lv_len = tv_list_len(list);
  
          pt->pt_argc = arg_len + lv_len;
          pt->pt_argv = xmalloc(sizeof(pt->pt_argv[0]) * pt->pt_argc);
          int i = 0;
          for (; i < arg_len; i++) {
            tv_copy(&arg_pt->pt_argv[i], &pt->pt_argv[i]);
          }
          if (lv_len > 0) {
            TV_LIST_ITER(list, li, {
              tv_copy(TV_LIST_ITEM_TV(li), &pt->pt_argv[i++]);
            });
          }
        }
  
        // For "function(dict.func, [], dict)" and "func" is a partial
        // use "dict". That is backwards compatible.
        if (dict_idx > 0) {
          // The dict is bound explicitly, pt_auto is false
          pt->pt_dict = argvars[dict_idx].vval.v_dict;
          (pt->pt_dict->dv_refcount)++;
        } else if (arg_pt != NULL) {
          // If the dict was bound automatically the result is also
          // bound automatically.
          pt->pt_dict = arg_pt->pt_dict;
          pt->pt_auto = arg_pt->pt_auto;
          if (pt->pt_dict != NULL) {
            (pt->pt_dict->dv_refcount)++;
          }
        }
  
        pt->pt_refcount = 1;
        if (arg_pt != NULL && arg_pt->pt_func != NULL) {
          pt->pt_func = arg_pt->pt_func;
          func_ptr_ref(pt->pt_func);
          xfree(name);
        } else if (is_funcref) {
          pt->pt_func = find_func(trans_name);
          func_ptr_ref(pt->pt_func);
          xfree(name);
        } else {
          pt->pt_name = name;
          func_ref(name);
        }
  
        rettv->v_type = VAR_PARTIAL;
        rettv->vval.v_partial = pt;
      } else {
        // result is a VAR_FUNC
        rettv->v_type = VAR_FUNC;
        rettv->vval.v_string = name;
        func_ref(name);
      }
    }
  theend:
    xfree(trans_name);
  }
  
  /// Returns buffer options, variables and other attributes in a dictionary.
  dict_T *get_buffer_info(buf_T *buf)
  {
    dict_T *const dict = tv_dict_alloc();
  
    tv_dict_add_nr(dict, S_LEN("bufnr"), buf->b_fnum);
    tv_dict_add_str(dict, S_LEN("name"),
                    buf->b_ffname != NULL ? (const char *)buf->b_ffname : "");
    tv_dict_add_nr(dict, S_LEN("lnum"),
                   buf == curbuf ? curwin->w_cursor.lnum : buflist_findlnum(buf));
    tv_dict_add_nr(dict, S_LEN("linecount"), buf->b_ml.ml_line_count);
    tv_dict_add_nr(dict, S_LEN("loaded"), buf->b_ml.ml_mfp != NULL);
    tv_dict_add_nr(dict, S_LEN("listed"), buf->b_p_bl);
    tv_dict_add_nr(dict, S_LEN("changed"), bufIsChanged(buf));
    tv_dict_add_nr(dict, S_LEN("changedtick"), buf_get_changedtick(buf));
    tv_dict_add_nr(dict, S_LEN("hidden"),
                   buf->b_ml.ml_mfp != NULL && buf->b_nwindows == 0);
  
    // Get a reference to buffer variables
    tv_dict_add_dict(dict, S_LEN("variables"), buf->b_vars);
  
    // List of windows displaying this buffer
    list_T *const windows = tv_list_alloc(kListLenMayKnow);
    FOR_ALL_TAB_WINDOWS(tp, wp) {
      if (wp->w_buffer == buf) {
        tv_list_append_number(windows, (varnumber_T)wp->handle);
      }
    }
    tv_dict_add_list(dict, S_LEN("windows"), windows);
  
    if (buf->b_signlist != NULL) {
      // List of signs placed in this buffer
      tv_dict_add_list(dict, S_LEN("signs"), get_buffer_signs(buf));
    }
  
    tv_dict_add_nr(dict, S_LEN("lastused"), buf->b_last_used);
  
    return dict;
  }
  
  /// Get the line number from VimL object
  ///
  /// @note Unlike tv_get_lnum(), this one supports only "$" special string.
  ///
  /// @param[in]  tv  Object to get value from. Is expected to be a number or
  ///                 a special string "$".
  /// @param[in]  buf  Buffer to take last line number from in case tv is "$". May
  ///                  be NULL, in this case "$" results in zero return.
  ///
  /// @return Line number or 0 in case of error.
  linenr_T tv_get_lnum_buf(const typval_T *const tv,
                           const buf_T *const buf)
    FUNC_ATTR_NONNULL_ARG(1) FUNC_ATTR_WARN_UNUSED_RESULT
  {
    if (tv->v_type == VAR_STRING
        && tv->vval.v_string != NULL
        && tv->vval.v_string[0] == '$'
        && buf != NULL) {
      return buf->b_ml.ml_line_count;
    }
    return tv_get_number_chk(tv, NULL);
  }
  
  void get_qf_loc_list(int is_qf, win_T *wp, typval_T *what_arg,
                       typval_T *rettv)
  {
    if (what_arg->v_type == VAR_UNKNOWN) {
      tv_list_alloc_ret(rettv, kListLenMayKnow);
      if (is_qf || wp != NULL) {
        (void)get_errorlist(NULL, wp, -1, rettv->vval.v_list);
      }
    } else {
      tv_dict_alloc_ret(rettv);
      if (is_qf || wp != NULL) {
        if (what_arg->v_type == VAR_DICT) {
          dict_T *d = what_arg->vval.v_dict;
  
          if (d != NULL) {
            qf_get_properties(wp, d, rettv->vval.v_dict);
          }
        } else {
          EMSG(_(e_dictreq));
        }
      }
    }
  }
  
  /// Returns information (variables, options, etc.) about a tab page
  /// as a dictionary.
  dict_T *get_tabpage_info(tabpage_T *tp, int tp_idx)
  {
    dict_T *const dict = tv_dict_alloc();
  
    tv_dict_add_nr(dict, S_LEN("tabnr"), tp_idx);
  
    list_T *const l = tv_list_alloc(kListLenMayKnow);
    FOR_ALL_WINDOWS_IN_TAB(wp, tp) {
      tv_list_append_number(l, (varnumber_T)wp->handle);
    }
    tv_dict_add_list(dict, S_LEN("windows"), l);
  
    // Make a reference to tabpage variables
    tv_dict_add_dict(dict, S_LEN("variables"), tp->tp_vars);
  
    return dict;
  }
  
  /// Returns information about a window as a dictionary.
  dict_T *get_win_info(win_T *wp, int16_t tpnr, int16_t winnr)
  {
    dict_T *const dict = tv_dict_alloc();
  
    tv_dict_add_nr(dict, S_LEN("tabnr"), tpnr);
    tv_dict_add_nr(dict, S_LEN("winnr"), winnr);
    tv_dict_add_nr(dict, S_LEN("winid"), wp->handle);
    tv_dict_add_nr(dict, S_LEN("height"), wp->w_height);
    tv_dict_add_nr(dict, S_LEN("winrow"), wp->w_winrow + 1);
    tv_dict_add_nr(dict, S_LEN("topline"), wp->w_topline);
    tv_dict_add_nr(dict, S_LEN("botline"), wp->w_botline - 1);
    tv_dict_add_nr(dict, S_LEN("winbar"), wp->w_winbar_height);
    tv_dict_add_nr(dict, S_LEN("width"), wp->w_width);
    tv_dict_add_nr(dict, S_LEN("bufnr"), wp->w_buffer->b_fnum);
    tv_dict_add_nr(dict, S_LEN("wincol"), wp->w_wincol + 1);
  
    tv_dict_add_nr(dict, S_LEN("terminal"), bt_terminal(wp->w_buffer));
    tv_dict_add_nr(dict, S_LEN("quickfix"), bt_quickfix(wp->w_buffer));
    tv_dict_add_nr(dict, S_LEN("loclist"),
                   (bt_quickfix(wp->w_buffer) && wp->w_llist_ref != NULL));
  
    // Add a reference to window variables
    tv_dict_add_dict(dict, S_LEN("variables"), wp->w_vars);
  
    return dict;
  }
  
  // Find window specified by "vp" in tabpage "tp".
  win_T *
  find_win_by_nr(
      typval_T *vp,
      tabpage_T *tp         // NULL for current tab page
  )
  {
    int nr = (int)tv_get_number_chk(vp, NULL);
  
    if (nr < 0) {
      return NULL;
    }
  
    if (nr == 0) {
      return curwin;
    }
  
    // This method accepts NULL as an alias for curtab.
    if (tp == NULL) {
       tp = curtab;
    }
  
    FOR_ALL_WINDOWS_IN_TAB(wp, tp) {
      if (nr >= LOWEST_WIN_ID) {
        if (wp->handle == nr) {
          return wp;
        }
      } else if (--nr <= 0) {
        return wp;
      }
    }
    return NULL;
  }
  
  /// Find window specified by "wvp" in tabpage "tvp".
  win_T *find_tabwin(typval_T *wvp, typval_T *tvp)
  {
    win_T *wp = NULL;
    tabpage_T *tp = NULL;
  
    if (wvp->v_type != VAR_UNKNOWN) {
      if (tvp->v_type != VAR_UNKNOWN) {
        long n = tv_get_number(tvp);
        if (n >= 0) {
          tp = find_tabpage(n);
        }
      } else {
        tp = curtab;
      }
  
      if (tp != NULL) {
        wp = find_win_by_nr(wvp, tp);
      }
    } else {
      wp = curwin;
    }
  
    return wp;
  }
  
  /*
   * getwinvar() and gettabwinvar()
   */
  void
  getwinvar(
      typval_T *argvars,
      typval_T *rettv,
      int off                    // 1 for gettabwinvar()
  )
  {
    win_T *win, *oldcurwin;
    dictitem_T *v;
    tabpage_T *tp = NULL;
    tabpage_T *oldtabpage = NULL;
    bool done = false;
  
    if (off == 1) {
      tp = find_tabpage((int)tv_get_number_chk(&argvars[0], NULL));
    } else {
      tp = curtab;
    }
    win = find_win_by_nr(&argvars[off], tp);
    const char *varname = tv_get_string_chk(&argvars[off + 1]);
  
    rettv->v_type = VAR_STRING;
    rettv->vval.v_string = NULL;
  
    emsg_off++;
    if (win != NULL && varname != NULL) {
      // Set curwin to be our win, temporarily.  Also set the tabpage,
      // otherwise the window is not valid. Only do this when needed,
      // autocommands get blocked.
      bool need_switch_win = tp != curtab || win != curwin;
      if (!need_switch_win
          || switch_win(&oldcurwin, &oldtabpage, win, tp, true) == OK) {
        if (*varname == '&') {
          if (varname[1] == NUL) {
            // get all window-local options in a dict
            dict_T *opts = get_winbuf_options(false);
  
            if (opts != NULL) {
              tv_dict_set_ret(rettv, opts);
              done = true;
            }
          } else if (get_option_tv(&varname, rettv, 1) == OK) {
            // window-local-option
            done = true;
          }
        } else {
          // Look up the variable.
          // Let getwinvar({nr}, "") return the "w:" dictionary.
          v = find_var_in_ht(&win->w_vars->dv_hashtab, 'w', varname,
                             strlen(varname), false);
          if (v != NULL) {
            tv_copy(&v->di_tv, rettv);
            done = true;
          }
        }
      }
  
      if (need_switch_win) {
        // restore previous notion of curwin
        restore_win(oldcurwin, oldtabpage, true);
      }
    }
    emsg_off--;
  
    if (!done && argvars[off + 2].v_type != VAR_UNKNOWN) {
      // use the default return value
      tv_copy(&argvars[off + 2], rettv);
    }
  }
  
  /*
   * This function is used by f_input() and f_inputdialog() functions. The third
   * argument to f_input() specifies the type of completion to use at the
   * prompt. The third argument to f_inputdialog() specifies the value to return
   * when the user cancels the prompt.
   */
  void get_user_input(const typval_T *const argvars,
                      typval_T *const rettv,
                      const bool inputdialog,
                      const bool secret)
    FUNC_ATTR_NONNULL_ALL
  {
    rettv->v_type = VAR_STRING;
    rettv->vval.v_string = NULL;
  
    const char *prompt = "";
    const char *defstr = "";
    const char *cancelreturn = NULL;
    const char *xp_name = NULL;
    Callback input_callback = { .type = kCallbackNone };
    char prompt_buf[NUMBUFLEN];
    char defstr_buf[NUMBUFLEN];
    char cancelreturn_buf[NUMBUFLEN];
    char xp_name_buf[NUMBUFLEN];
    char def[1] = { 0 };
    if (argvars[0].v_type == VAR_DICT) {
      if (argvars[1].v_type != VAR_UNKNOWN) {
        EMSG(_("E5050: {opts} must be the only argument"));
        return;
      }
      dict_T *const dict = argvars[0].vval.v_dict;
      prompt = tv_dict_get_string_buf_chk(dict, S_LEN("prompt"), prompt_buf, "");
      if (prompt == NULL) {
        return;
      }
      defstr = tv_dict_get_string_buf_chk(dict, S_LEN("default"), defstr_buf, "");
      if (defstr == NULL) {
        return;
      }
      cancelreturn = tv_dict_get_string_buf_chk(dict, S_LEN("cancelreturn"),
                                                cancelreturn_buf, def);
      if (cancelreturn == NULL) {  // error
        return;
      }
      if (*cancelreturn == NUL) {
        cancelreturn = NULL;
      }
      xp_name = tv_dict_get_string_buf_chk(dict, S_LEN("completion"),
                                           xp_name_buf, def);
      if (xp_name == NULL) {  // error
        return;
      }
      if (xp_name == def) {  // default to NULL
        xp_name = NULL;
      }
      if (!tv_dict_get_callback(dict, S_LEN("highlight"), &input_callback)) {
        return;
      }
    } else {
      prompt = tv_get_string_buf_chk(&argvars[0], prompt_buf);
      if (prompt == NULL) {
        return;
      }
      if (argvars[1].v_type != VAR_UNKNOWN) {
        defstr = tv_get_string_buf_chk(&argvars[1], defstr_buf);
        if (defstr == NULL) {
          return;
        }
        if (argvars[2].v_type != VAR_UNKNOWN) {
          const char *const arg2 = tv_get_string_buf_chk(&argvars[2],
                                                         cancelreturn_buf);
          if (arg2 == NULL) {
            return;
          }
          if (inputdialog) {
            cancelreturn = arg2;
          } else {
            xp_name = arg2;
          }
        }
      }
    }
  
    int xp_type = EXPAND_NOTHING;
    char *xp_arg = NULL;
    if (xp_name != NULL) {
      // input() with a third argument: completion
      const int xp_namelen = (int)strlen(xp_name);
  
      uint32_t argt;
      if (parse_compl_arg((char_u *)xp_name, xp_namelen, &xp_type,
                          &argt, (char_u **)&xp_arg) == FAIL) {
        return;
      }
    }
  
    const bool cmd_silent_save = cmd_silent;
  
    cmd_silent = false;  // Want to see the prompt.
    // Only the part of the message after the last NL is considered as
    // prompt for the command line, unlsess cmdline is externalized
    const char *p = prompt;
    if (!ui_has(kUICmdline)) {
      const char *lastnl = strrchr(prompt, '\n');
      if (lastnl != NULL) {
        p = lastnl+1;
        msg_start();
        msg_clr_eos();
        msg_puts_attr_len(prompt, p - prompt, echo_attr);
        msg_didout = false;
        msg_starthere();
      }
    }
    cmdline_row = msg_row;
  
    stuffReadbuffSpec(defstr);
  
    const int save_ex_normal_busy = ex_normal_busy;
    ex_normal_busy = 0;
    rettv->vval.v_string =
      (char_u *)getcmdline_prompt(secret ? NUL : '@', p, echo_attr,
                                  xp_type, xp_arg, input_callback);
    ex_normal_busy = save_ex_normal_busy;
    callback_free(&input_callback);
  
    if (rettv->vval.v_string == NULL && cancelreturn != NULL) {
      rettv->vval.v_string = (char_u *)xstrdup(cancelreturn);
    }
  
    xfree(xp_arg);
  
    // Since the user typed this, no need to wait for return.
    need_wait_return = false;
    msg_didout = false;
    cmd_silent = cmd_silent_save;
  }
  
  /// Turn a dictionary into a list
  ///
  /// @param[in]  tv  Dictionary to convert. Is checked for actually being
  ///                 a dictionary, will give an error if not.
  /// @param[out]  rettv  Location where result will be saved.
  /// @param[in]  what  What to save in rettv.
  void dict_list(typval_T *const tv, typval_T *const rettv,
                 const DictListType what)
  {
    if (tv->v_type != VAR_DICT) {
      EMSG(_(e_dictreq));
      return;
    }
    if (tv->vval.v_dict == NULL) {
      return;
    }
  
    tv_list_alloc_ret(rettv, tv_dict_len(tv->vval.v_dict));
  
    TV_DICT_ITER(tv->vval.v_dict, di, {
      typval_T tv_item = { .v_lock = VAR_UNLOCKED };
  
      switch (what) {
        case kDictListKeys: {
          tv_item.v_type = VAR_STRING;
          tv_item.vval.v_string = vim_strsave(di->di_key);
          break;
        }
        case kDictListValues: {
          tv_copy(&di->di_tv, &tv_item);
          break;
        }
        case kDictListItems: {
          // items()
          list_T *const sub_l = tv_list_alloc(2);
          tv_item.v_type = VAR_LIST;
          tv_item.vval.v_list = sub_l;
          tv_list_ref(sub_l);
  
          tv_list_append_owned_tv(sub_l, (typval_T) {
            .v_type = VAR_STRING,
            .v_lock = VAR_UNLOCKED,
            .vval.v_string = (char_u *)xstrdup((const char *)di->di_key),
          });
  
          tv_list_append_tv(sub_l, &di->di_tv);
  
          break;
        }
      }
  
      tv_list_append_owned_tv(rettv->vval.v_list, tv_item);
    });
  }
  
  /// Builds a process argument vector from a VimL object (typval_T).
  ///
  /// @param[in]  cmd_tv      VimL object
  /// @param[out] cmd         Returns the command or executable name.
  /// @param[out] executable  Returns `false` if argv[0] is not executable.
  ///
  /// @returns Result of `shell_build_argv()` if `cmd_tv` is a String.
  ///          Else, string values of `cmd_tv` copied to a (char **) list with
  ///          argv[0] resolved to full path ($PATHEXT-resolved on Windows).
  char **tv_to_argv(typval_T *cmd_tv, const char **cmd, bool *executable)
  {
    if (cmd_tv->v_type == VAR_STRING) {  // String => "shell semantics".
      const char *cmd_str = tv_get_string(cmd_tv);
      if (cmd) {
        *cmd = cmd_str;
      }
      return shell_build_argv(cmd_str, NULL);
    }
  
    if (cmd_tv->v_type != VAR_LIST) {
      EMSG2(_(e_invarg2), "expected String or List");
      return NULL;
    }
  
    list_T *argl = cmd_tv->vval.v_list;
    int argc = tv_list_len(argl);
    if (!argc) {
      EMSG(_(e_invarg));  // List must have at least one item.
      return NULL;
    }
  
    const char *arg0 = tv_get_string_chk(TV_LIST_ITEM_TV(tv_list_first(argl)));
    char *exe_resolved = NULL;
    if (!arg0 || !os_can_exe(arg0, &exe_resolved, true)) {
      if (arg0 && executable) {
        char buf[IOSIZE];
        snprintf(buf, sizeof(buf), "'%s' is not executable", arg0);
        EMSG3(_(e_invargNval), "cmd", buf);
        *executable = false;
      }
      return NULL;
    }
  
    if (cmd) {
      *cmd = exe_resolved;
    }
  
    // Build the argument vector
    int i = 0;
    char **argv = xcalloc(argc + 1, sizeof(char *));
    TV_LIST_ITER_CONST(argl, arg, {
      const char *a = tv_get_string_chk(TV_LIST_ITEM_TV(arg));
      if (!a) {
        // Did emsg in tv_get_string_chk; just deallocate argv.
        shell_free_argv(argv);
        xfree(exe_resolved);
        return NULL;
      }
      argv[i++] = xstrdup(a);
    });
    // Replace argv[0] with absolute path. The only reason for this is to make
    // $PATHEXT work on Windows with jobstart([…]). #9569
    xfree(argv[0]);
    argv[0] = exe_resolved;
  
    return argv;
  }
  
  /// Fill a dictionary with all applicable maparg() like dictionaries
  ///
  /// @param  dict  The dictionary to be filled
  /// @param  mp  The maphash that contains the mapping information
  /// @param  buffer_value  The "buffer" value
  /// @param  compatible  True for compatible with old maparg() dict
  void mapblock_fill_dict(dict_T *const dict,
                          const mapblock_T *const mp,
                          long buffer_value,
                          bool compatible)
    FUNC_ATTR_NONNULL_ALL
  {
    char *const lhs = str2special_save((const char *)mp->m_keys,
                                       compatible, !compatible);
    char *const mapmode = map_mode_to_chars(mp->m_mode);
    varnumber_T noremap_value;
  
    if (compatible) {
      // Keep old compatible behavior
      // This is unable to determine whether a mapping is a <script> mapping
      noremap_value = !!mp->m_noremap;
    } else {
      // Distinguish between <script> mapping
      // If it's not a <script> mapping, check if it's a noremap
      noremap_value = mp->m_noremap == REMAP_SCRIPT ? 2 : !!mp->m_noremap;
    }
  
    if (compatible) {
      tv_dict_add_str(dict, S_LEN("rhs"), (const char *)mp->m_orig_str);
    } else {
      tv_dict_add_allocated_str(dict, S_LEN("rhs"),
                                str2special_save((const char *)mp->m_str, false,
                                                 true));
    }
    tv_dict_add_allocated_str(dict, S_LEN("lhs"), lhs);
    tv_dict_add_nr(dict, S_LEN("noremap"), noremap_value);
    tv_dict_add_nr(dict, S_LEN("script"), mp->m_noremap == REMAP_SCRIPT ? 1 : 0);
    tv_dict_add_nr(dict, S_LEN("expr"),  mp->m_expr ? 1 : 0);
    tv_dict_add_nr(dict, S_LEN("silent"), mp->m_silent ? 1 : 0);
    tv_dict_add_nr(dict, S_LEN("sid"), (varnumber_T)mp->m_script_ctx.sc_sid);
    tv_dict_add_nr(dict, S_LEN("lnum"), (varnumber_T)mp->m_script_ctx.sc_lnum);
    tv_dict_add_nr(dict, S_LEN("buffer"), (varnumber_T)buffer_value);
    tv_dict_add_nr(dict, S_LEN("nowait"), mp->m_nowait ? 1 : 0);
    tv_dict_add_allocated_str(dict, S_LEN("mode"), mapmode);
  }
  
  int matchadd_dict_arg(typval_T *tv, const char **conceal_char,
                        win_T **win)
  {
    dictitem_T *di;
  
    if (tv->v_type != VAR_DICT) {
      EMSG(_(e_dictreq));
      return FAIL;
    }
  
    if ((di = tv_dict_find(tv->vval.v_dict, S_LEN("conceal"))) != NULL) {
      *conceal_char = tv_get_string(&di->di_tv);
    }
  
    if ((di = tv_dict_find(tv->vval.v_dict, S_LEN("window"))) != NULL) {
      *win = find_win_by_nr_or_id(&di->di_tv);
      if (*win == NULL) {
        EMSG(_(e_invalwindow));
        return FAIL;
      }
    }
  
    return OK;
  }
  
  void return_register(int regname, typval_T *rettv)
  {
    char_u buf[2] = { regname, 0 };
  
    rettv->v_type = VAR_STRING;
    rettv->vval.v_string = vim_strsave(buf);
  }
  
  void screenchar_adjust_grid(ScreenGrid **grid, int *row, int *col)
  {
    // TODO(bfredl): this is a hack for legacy tests which use screenchar()
    // to check printed messages on the screen (but not floats etc
    // as these are not legacy features). If the compositor is refactored to
    // have its own buffer, this should just read from it instead.
    msg_scroll_flush();
    if (msg_grid.chars && msg_grid.comp_index > 0 && *row >= msg_grid.comp_row
        && *row < (msg_grid.Rows + msg_grid.comp_row)
        && *col < msg_grid.Columns) {
      *grid = &msg_grid;
      *row -= msg_grid.comp_row;
    }
  }
  
  /// Set line or list of lines in buffer "buf".
  void set_buffer_lines(buf_T *buf, linenr_T lnum_arg, bool append,
                        const typval_T *lines, typval_T *rettv)
    FUNC_ATTR_NONNULL_ARG(4, 5)
  {
    linenr_T lnum = lnum_arg + (append ? 1 : 0);
    const char *line = NULL;
    list_T      *l = NULL;
    listitem_T  *li = NULL;
    long        added = 0;
    linenr_T append_lnum;
    buf_T       *curbuf_save = NULL;
    win_T       *curwin_save = NULL;
    const bool is_curbuf = buf == curbuf;
  
    // When using the current buffer ml_mfp will be set if needed.  Useful when
    // setline() is used on startup.  For other buffers the buffer must be
    // loaded.
    if (buf == NULL || (!is_curbuf && buf->b_ml.ml_mfp == NULL) || lnum < 1) {
      rettv->vval.v_number = 1;  // FAIL
      return;
    }
  
    if (!is_curbuf) {
      curbuf_save = curbuf;
      curwin_save = curwin;
      curbuf = buf;
      find_win_for_curbuf();
    }
  
    if (append) {
      // appendbufline() uses the line number below which we insert
      append_lnum = lnum - 1;
    } else {
      // setbufline() uses the line number above which we insert, we only
      // append if it's below the last line
      append_lnum = curbuf->b_ml.ml_line_count;
    }
  
    if (lines->v_type == VAR_LIST) {
      l = lines->vval.v_list;
      li = tv_list_first(l);
    } else {
      line = tv_get_string_chk(lines);
    }
  
    // Default result is zero == OK.
    for (;; ) {
      if (lines->v_type == VAR_LIST) {
        // List argument, get next string.
        if (li == NULL) {
          break;
        }
        line = tv_get_string_chk(TV_LIST_ITEM_TV(li));
        li = TV_LIST_ITEM_NEXT(l, li);
      }
  
      rettv->vval.v_number = 1;  // FAIL
      if (line == NULL || lnum > curbuf->b_ml.ml_line_count + 1) {
        break;
      }
  
      // When coming here from Insert mode, sync undo, so that this can be
      // undone separately from what was previously inserted.
      if (u_sync_once == 2) {
        u_sync_once = 1;  // notify that u_sync() was called
        u_sync(true);
      }
  
      if (!append && lnum <= curbuf->b_ml.ml_line_count) {
        // Existing line, replace it.
        if (u_savesub(lnum) == OK
            && ml_replace(lnum, (char_u *)line, true) == OK) {
          changed_bytes(lnum, 0);
          if (is_curbuf && lnum == curwin->w_cursor.lnum) {
            check_cursor_col();
          }
          rettv->vval.v_number = 0;  // OK
        }
      } else if (added > 0 || u_save(lnum - 1, lnum) == OK) {
        // append the line.
        added++;
        if (ml_append(lnum - 1, (char_u *)line, 0, false) == OK) {
          rettv->vval.v_number = 0;  // OK
        }
      }
  
      if (l == NULL) {  // only one string argument
        break;
      }
      lnum++;
    }
  
    if (added > 0) {
      appended_lines_mark(append_lnum, added);
  
      // Only adjust the cursor for buffers other than the current, unless it
      // is the current window. For curbuf and other windows it has been done
      // in mark_adjust_internal().
      FOR_ALL_TAB_WINDOWS(tp, wp) {
        if (wp->w_buffer == buf
            && (wp->w_buffer != curbuf || wp == curwin)
            && wp->w_cursor.lnum > append_lnum) {
          wp->w_cursor.lnum += added;
        }
      }
      check_cursor_col();
      update_topline();
    }
  
    if (!is_curbuf) {
       curbuf = curbuf_save;
       curwin = curwin_save;
    }
  }
  
  /*
   * "setwinvar()" and "settabwinvar()" functions
   */
  
  void setwinvar(typval_T *argvars, typval_T *rettv, int off)
  {
    if (check_secure()) {
      return;
    }
  
    tabpage_T *tp = NULL;
    if (off == 1) {
      tp = find_tabpage((int)tv_get_number_chk(&argvars[0], NULL));
    } else {
      tp = curtab;
    }
    win_T *const win = find_win_by_nr(&argvars[off], tp);
    const char *varname = tv_get_string_chk(&argvars[off + 1]);
    typval_T *varp = &argvars[off + 2];
  
    if (win != NULL && varname != NULL && varp != NULL) {
      win_T       *save_curwin;
      tabpage_T   *save_curtab;
      bool need_switch_win = tp != curtab || win != curwin;
      if (!need_switch_win
          || switch_win(&save_curwin, &save_curtab, win, tp, true) == OK) {
        if (*varname == '&') {
          long numval;
          bool error = false;
  
          varname++;
          numval = tv_get_number_chk(varp, &error);
          char nbuf[NUMBUFLEN];
          const char *const strval = tv_get_string_buf_chk(varp, nbuf);
          if (!error && strval != NULL) {
            set_option_value(varname, numval, strval, OPT_LOCAL);
          }
        } else {
          const size_t varname_len = strlen(varname);
          char *const winvarname = xmalloc(varname_len + 3);
          memcpy(winvarname, "w:", 2);
          memcpy(winvarname + 2, varname, varname_len + 1);
          set_var(winvarname, varname_len + 2, varp, true);
          xfree(winvarname);
        }
      }
      if (need_switch_win) {
        restore_win(save_curwin, save_curtab, true);
      }
    }
  }
  
  /// "stdpath()" helper for list results
  void get_xdg_var_list(const XDGVarType xdg, typval_T *rettv)
    FUNC_ATTR_NONNULL_ALL
  {
    const void *iter = NULL;
    list_T *const list = tv_list_alloc(kListLenShouldKnow);
    rettv->v_type = VAR_LIST;
    rettv->vval.v_list = list;
    tv_list_ref(list);
    char *const dirs = stdpaths_get_xdg_var(xdg);
    if (dirs == NULL) {
      return;
    }
    do {
      size_t dir_len;
      const char *dir;
      iter = vim_env_iter(':', dirs, iter, &dir, &dir_len);
      if (dir != NULL && dir_len > 0) {
        char *dir_with_nvim = xmemdupz(dir, dir_len);
        dir_with_nvim = concat_fnames_realloc(dir_with_nvim, "nvim", true);
        tv_list_append_string(list, dir_with_nvim, strlen(dir_with_nvim));
        xfree(dir_with_nvim);
      }
    } while (iter != NULL);
    xfree(dirs);
  }
  
  static list_T *string_to_list(const char *str, size_t len, const bool keepempty)
  {
    if (!keepempty && str[len - 1] == NL) {
      len--;
    }
    list_T *const list = tv_list_alloc(kListLenMayKnow);
    encode_list_write(list, str, len);
    return list;
  }
  
  // os_system wrapper. Handles 'verbose', :profile, and v:shell_error.
  void get_system_output_as_rettv(typval_T *argvars, typval_T *rettv,
                                  bool retlist)
  {
    proftime_T wait_time;
    bool profiling = do_profiling == PROF_YES;
  
    rettv->v_type = VAR_STRING;
    rettv->vval.v_string = NULL;
  
    if (check_restricted() || check_secure()) {
      return;
    }
  
    // get input to the shell command (if any), and its length
    ptrdiff_t input_len;
    char *input = save_tv_as_string(&argvars[1], &input_len, false);
    if (input_len < 0) {
      assert(input == NULL);
      return;
    }
  
    // get shell command to execute
    bool executable = true;
    char **argv = tv_to_argv(&argvars[0], NULL, &executable);
    if (!argv) {
      if (!executable) {
        set_vim_var_nr(VV_SHELL_ERROR, (long)-1);
      }
      xfree(input);
      return;  // Already did emsg.
    }
  
    if (p_verbose > 3) {
      char *cmdstr = shell_argv_to_str(argv);
      verbose_enter_scroll();
      smsg(_("Executing command: \"%s\""), cmdstr);
      msg_puts("\n\n");
      verbose_leave_scroll();
      xfree(cmdstr);
    }
  
    if (profiling) {
      prof_child_enter(&wait_time);
    }
  
    // execute the command
    size_t nread = 0;
    char *res = NULL;
    int status = os_system(argv, input, input_len, &res, &nread);
  
    if (profiling) {
      prof_child_exit(&wait_time);
    }
  
    xfree(input);
  
    set_vim_var_nr(VV_SHELL_ERROR, (long) status);
  
    if (res == NULL) {
      if (retlist) {
        // return an empty list when there's no output
        tv_list_alloc_ret(rettv, 0);
      } else {
        rettv->vval.v_string = (char_u *) xstrdup("");
      }
      return;
    }
  
    if (retlist) {
      int keepempty = 0;
      if (argvars[1].v_type != VAR_UNKNOWN && argvars[2].v_type != VAR_UNKNOWN) {
        keepempty = tv_get_number(&argvars[2]);
      }
      rettv->vval.v_list = string_to_list(res, nread, (bool)keepempty);
      tv_list_ref(rettv->vval.v_list);
      rettv->v_type = VAR_LIST;
  
      xfree(res);
    } else {
      // res may contain several NULs before the final terminating one.
      // Replace them with SOH (1) like in get_cmd_output() to avoid truncation.
      memchrsub(res, NUL, 1, nread);
  #ifdef USE_CRNL
      // translate <CR><NL> into <NL>
      char *d = res;
      for (char *s = res; *s; ++s) {
        if (s[0] == CAR && s[1] == NL) {
          ++s;
        }
  
        *d++ = *s;
      }
  
      *d = NUL;
  #endif
      rettv->vval.v_string = (char_u *) res;
    }
  }
  
  bool callback_from_typval(Callback *const callback, typval_T *const arg)
    FUNC_ATTR_NONNULL_ALL FUNC_ATTR_WARN_UNUSED_RESULT
  {
    int r = OK;
  
    if (arg->v_type == VAR_PARTIAL && arg->vval.v_partial != NULL) {
      callback->data.partial = arg->vval.v_partial;
      callback->data.partial->pt_refcount++;
      callback->type = kCallbackPartial;
    } else if (arg->v_type == VAR_STRING
               && arg->vval.v_string != NULL
               && ascii_isdigit(*arg->vval.v_string)) {
      r = FAIL;
    } else if (arg->v_type == VAR_FUNC || arg->v_type == VAR_STRING) {
      char_u *name = arg->vval.v_string;
      func_ref(name);
      callback->data.funcref = vim_strsave(name);
      callback->type = kCallbackFuncref;
    } else if (arg->v_type == VAR_NUMBER && arg->vval.v_number == 0) {
      callback->type = kCallbackNone;
    } else {
      r = FAIL;
    }
  
    if (r == FAIL) {
      EMSG(_("E921: Invalid callback argument"));
      return false;
    }
    return true;
  }
  
  bool callback_call(Callback *const callback, const int argcount_in,
                     typval_T *const argvars_in, typval_T *const rettv)
    FUNC_ATTR_NONNULL_ALL
  {
    partial_T *partial;
    char_u *name;
    switch (callback->type) {
      case kCallbackFuncref:
        name = callback->data.funcref;
        partial = NULL;
        break;
  
      case kCallbackPartial:
        partial = callback->data.partial;
        name = partial_name(partial);
        break;
  
      case kCallbackNone:
        return false;
        break;
  
      default:
        abort();
    }
  
    int dummy;
    return call_func(name, (int)STRLEN(name), rettv, argcount_in, argvars_in,
                     NULL, curwin->w_cursor.lnum, curwin->w_cursor.lnum, &dummy,
                     true, partial, NULL);
  }
  
  static bool set_ref_in_callback(Callback *callback, int copyID,
                                  ht_stack_T **ht_stack,
                                  list_stack_T **list_stack)
  {
    typval_T tv;
    switch (callback->type) {
      case kCallbackFuncref:
      case kCallbackNone:
        break;
  
      case kCallbackPartial:
        tv.v_type = VAR_PARTIAL;
        tv.vval.v_partial = callback->data.partial;
        return set_ref_in_item(&tv, copyID, ht_stack, list_stack);
        break;
  
  
      default:
        abort();
    }
    return false;
  }
  
  static bool set_ref_in_callback_reader(CallbackReader *reader, int copyID,
                                         ht_stack_T **ht_stack,
                                         list_stack_T **list_stack)
  {
    if (set_ref_in_callback(&reader->cb, copyID, ht_stack, list_stack)) {
      return true;
    }
  
    if (reader->self) {
      typval_T tv;
      tv.v_type = VAR_DICT;
      tv.vval.v_dict = reader->self;
      return set_ref_in_item(&tv, copyID, ht_stack, list_stack);
    }
    return false;
  }
  
  timer_T *find_timer_by_nr(varnumber_T xx)
  {
      return pmap_get(uint64_t)(timers, xx);
  }
  
  void add_timer_info(typval_T *rettv, timer_T *timer)
  {
    list_T *list = rettv->vval.v_list;
    dict_T *dict = tv_dict_alloc();
  
    tv_list_append_dict(list, dict);
    tv_dict_add_nr(dict, S_LEN("id"), timer->timer_id);
    tv_dict_add_nr(dict, S_LEN("time"), timer->timeout);
    tv_dict_add_nr(dict, S_LEN("paused"), timer->paused);
  
    tv_dict_add_nr(dict, S_LEN("repeat"),
                   (timer->repeat_count < 0 ? -1 : timer->repeat_count));
  
    dictitem_T *di = tv_dict_item_alloc("callback");
    if (tv_dict_add(dict, di) == FAIL) {
      xfree(di);
      return;
    }
  
    if (timer->callback.type == kCallbackPartial) {
      di->di_tv.v_type = VAR_PARTIAL;
      di->di_tv.vval.v_partial = timer->callback.data.partial;
      timer->callback.data.partial->pt_refcount++;
    } else if (timer->callback.type == kCallbackFuncref) {
      di->di_tv.v_type = VAR_FUNC;
      di->di_tv.vval.v_string = vim_strsave(timer->callback.data.funcref);
    }
  }
  
  void add_timer_info_all(typval_T *rettv)
  {
    tv_list_alloc_ret(rettv, timers->table->n_occupied);
    timer_T *timer;
    map_foreach_value(timers, timer, {
      if (!timer->stopped) {
        add_timer_info(rettv, timer);
      }
    })
  }
  
  // invoked on the main loop
  void timer_due_cb(TimeWatcher *tw, void *data)
  {
    timer_T *timer = (timer_T *)data;
    int save_did_emsg = did_emsg;
    int save_called_emsg = called_emsg;
    const bool save_ex_pressedreturn = get_pressedreturn();
  
    if (timer->stopped || timer->paused) {
      return;
    }
  
    timer->refcount++;
    // if repeat was negative repeat forever
    if (timer->repeat_count >= 0 && --timer->repeat_count == 0) {
      timer_stop(timer);
    }
  
    typval_T argv[2] = { TV_INITIAL_VALUE, TV_INITIAL_VALUE };
    argv[0].v_type = VAR_NUMBER;
    argv[0].vval.v_number = timer->timer_id;
    typval_T rettv = TV_INITIAL_VALUE;
    called_emsg = false;
  
    callback_call(&timer->callback, 1, argv, &rettv);
  
    // Handle error message
    if (called_emsg && did_emsg) {
      timer->emsg_count++;
      if (current_exception != NULL) {
        discard_current_exception();
      }
    }
    did_emsg = save_did_emsg;
    called_emsg = save_called_emsg;
    set_pressedreturn(save_ex_pressedreturn);
  
    if (timer->emsg_count >= 3) {
      timer_stop(timer);
    }
  
    tv_clear(&rettv);
  
    if (!timer->stopped && timer->timeout == 0) {
      // special case: timeout=0 means the callback will be
      // invoked again on the next event loop tick.
      // we don't use uv_idle_t to not spin the event loop
      // when the main loop is blocked.
      time_watcher_start(&timer->tw, timer_due_cb, 0, 0);
    }
    timer_decref(timer);
  }
  
  uint64_t timer_start(const long timeout,
                       const int repeat_count,
                       const Callback *const callback)
  {
    timer_T *timer = xmalloc(sizeof *timer);
    timer->refcount = 1;
    timer->stopped = false;
    timer->paused = false;
    timer->emsg_count = 0;
    timer->repeat_count = repeat_count;
    timer->timeout = timeout;
    timer->timer_id = last_timer_id++;
    timer->callback = *callback;
  
    time_watcher_init(&main_loop, &timer->tw, timer);
    timer->tw.events = multiqueue_new_child(main_loop.events);
    // if main loop is blocked, don't queue up multiple events
    timer->tw.blockable = true;
    time_watcher_start(&timer->tw, timer_due_cb, timeout, timeout);
  
    pmap_put(uint64_t)(timers, timer->timer_id, timer);
    return timer->timer_id;
  }
  
  void timer_stop(timer_T *timer)
  {
    if (timer->stopped) {
      // avoid double free
      return;
    }
    timer->stopped = true;
    time_watcher_stop(&timer->tw);
    time_watcher_close(&timer->tw, timer_close_cb);
  }
  
  // This will be run on the main loop after the last timer_due_cb, so at this
  // point it is safe to free the callback.
  static void timer_close_cb(TimeWatcher *tw, void *data)
  {
    timer_T *timer = (timer_T *)data;
    multiqueue_free(timer->tw.events);
    callback_free(&timer->callback);
    pmap_del(uint64_t)(timers, timer->timer_id);
    timer_decref(timer);
  }
  
  static void timer_decref(timer_T *timer)
  {
    if (--timer->refcount == 0) {
      xfree(timer);
    }
  }
  
  void timer_stop_all(void)
  {
    timer_T *timer;
    map_foreach_value(timers, timer, {
      timer_stop(timer);
    })
  }
  
  void timer_teardown(void)
  {
    timer_stop_all();
  }
  
  /// Write "list" of strings to file "fd".
  ///
  /// @param  fp  File to write to.
  /// @param[in]  list  List to write.
  /// @param[in]  binary  Whether to write in binary mode.
  ///
  /// @return true in case of success, false otherwise.
  bool write_list(FileDescriptor *const fp, const list_T *const list,
                  const bool binary)
    FUNC_ATTR_NONNULL_ARG(1)
  {
    int error = 0;
    TV_LIST_ITER_CONST(list, li, {
      const char *const s = tv_get_string_chk(TV_LIST_ITEM_TV(li));
      if (s == NULL) {
        return false;
      }
      const char *hunk_start = s;
      for (const char *p = hunk_start;; p++) {
        if (*p == NUL || *p == NL) {
          if (p != hunk_start) {
            const ptrdiff_t written = file_write(fp, hunk_start,
                                                 (size_t)(p - hunk_start));
            if (written < 0) {
              error = (int)written;
              goto write_list_error;
            }
          }
          if (*p == NUL) {
            break;
          } else {
            hunk_start = p + 1;
            const ptrdiff_t written = file_write(fp, (char[]){ NUL }, 1);
            if (written < 0) {
              error = (int)written;
              break;
            }
          }
        }
      }
      if (!binary || TV_LIST_ITEM_NEXT(list, li) != NULL) {
        const ptrdiff_t written = file_write(fp, "\n", 1);
        if (written < 0) {
          error = (int)written;
          goto write_list_error;
        }
      }
    });
    if ((error = file_flush(fp)) != 0) {
      goto write_list_error;
    }
    return true;
  write_list_error:
    emsgf(_("E80: Error while writing: %s"), os_strerror(error));
    return false;
  }
  
  /// Saves a typval_T as a string.
  ///
  /// For lists or buffers, replaces NLs with NUL and separates items with NLs.
  ///
  /// @param[in]  tv   Value to store as a string.
  /// @param[out] len  Length of the resulting string or -1 on error.
  /// @param[in]  endnl If true, the output will end in a newline (if a list).
  /// @returns an allocated string if `tv` represents a VimL string, list, or
  ///          number; NULL otherwise.
  char *save_tv_as_string(typval_T *tv, ptrdiff_t *const len, bool endnl)
    FUNC_ATTR_MALLOC FUNC_ATTR_NONNULL_ALL
  {
    *len = 0;
    if (tv->v_type == VAR_UNKNOWN) {
      return NULL;
    }
  
    // For other types, let tv_get_string_buf_chk() get the value or
    // print an error.
    if (tv->v_type != VAR_LIST && tv->v_type != VAR_NUMBER) {
      const char *ret = tv_get_string_chk(tv);
      if (ret) {
        *len = strlen(ret);
        return xmemdupz(ret, (size_t)(*len));
      } else {
        *len = -1;
        return NULL;
      }
    }
  
    if (tv->v_type == VAR_NUMBER) {  // Treat number as a buffer-id.
      buf_T *buf = buflist_findnr(tv->vval.v_number);
      if (buf) {
        for (linenr_T lnum = 1; lnum <= buf->b_ml.ml_line_count; lnum++) {
          for (char_u *p = ml_get_buf(buf, lnum, false); *p != NUL; p++) {
            *len += 1;
          }
          *len += 1;
        }
      } else {
        EMSGN(_(e_nobufnr), tv->vval.v_number);
        *len = -1;
        return NULL;
      }
  
      if (*len == 0) {
        return NULL;
      }
  
      char *ret = xmalloc(*len + 1);
      char *end = ret;
      for (linenr_T lnum = 1; lnum <= buf->b_ml.ml_line_count; lnum++) {
        for (char_u *p = ml_get_buf(buf, lnum, false); *p != NUL; p++) {
          *end++ = (*p == '\n') ? NUL : *p;
        }
        *end++ = '\n';
      }
      *end = NUL;
      *len = end - ret;
      return ret;
    }
  
    assert(tv->v_type == VAR_LIST);
    // Pre-calculate the resulting length.
    list_T *list = tv->vval.v_list;
    TV_LIST_ITER_CONST(list, li, {
      *len += strlen(tv_get_string(TV_LIST_ITEM_TV(li))) + 1;
    });
  
    if (*len == 0) {
      return NULL;
    }
  
    char *ret = xmalloc(*len + endnl);
    char *end = ret;
    TV_LIST_ITER_CONST(list, li, {
      for (const char *s = tv_get_string(TV_LIST_ITEM_TV(li)); *s != NUL; s++) {
        *end++ = (*s == '\n') ? NUL : *s;
      }
      if (endnl || TV_LIST_ITEM_NEXT(list, li) != NULL) {
        *end++ = '\n';
      }
    });
    *end = NUL;
    *len = end - ret;
    return ret;
  }
  
  /// Translate a VimL object into a position
  ///
  /// Accepts VAR_LIST and VAR_STRING objects. Does not give an error for invalid
  /// type.
  ///
  /// @param[in]  tv  Object to translate.
  /// @param[in]  dollar_lnum  True when "$" is last line.
  /// @param[out]  ret_fnum  Set to fnum for marks.
  ///
  /// @return Pointer to position or NULL in case of error (e.g. invalid type).
  pos_T *var2fpos(const typval_T *const tv, const int dollar_lnum,
                  int *const ret_fnum)
    FUNC_ATTR_WARN_UNUSED_RESULT FUNC_ATTR_NONNULL_ALL
  {
    static pos_T pos;
    pos_T               *pp;
  
    // Argument can be [lnum, col, coladd].
    if (tv->v_type == VAR_LIST) {
      list_T          *l;
      int len;
      bool error = false;
      listitem_T *li;
  
      l = tv->vval.v_list;
      if (l == NULL) {
        return NULL;
      }
  
      // Get the line number.
      pos.lnum = tv_list_find_nr(l, 0L, &error);
      if (error || pos.lnum <= 0 || pos.lnum > curbuf->b_ml.ml_line_count) {
        // Invalid line number.
        return NULL;
      }
  
      // Get the column number.
      pos.col = tv_list_find_nr(l, 1L, &error);
      if (error) {
        return NULL;
      }
      len = (long)STRLEN(ml_get(pos.lnum));
  
      // We accept "$" for the column number: last column.
      li = tv_list_find(l, 1L);
      if (li != NULL && TV_LIST_ITEM_TV(li)->v_type == VAR_STRING
          && TV_LIST_ITEM_TV(li)->vval.v_string != NULL
          && STRCMP(TV_LIST_ITEM_TV(li)->vval.v_string, "$") == 0) {
        pos.col = len + 1;
      }
  
      // Accept a position up to the NUL after the line.
      if (pos.col == 0 || (int)pos.col > len + 1) {
        // Invalid column number.
        return NULL;
      }
      pos.col--;
  
      // Get the virtual offset.  Defaults to zero.
      pos.coladd = tv_list_find_nr(l, 2L, &error);
      if (error) {
        pos.coladd = 0;
      }
  
      return &pos;
    }
  
    const char *const name = tv_get_string_chk(tv);
    if (name == NULL) {
      return NULL;
    }
    if (name[0] == '.') {  // Cursor.
      return &curwin->w_cursor;
    }
    if (name[0] == 'v' && name[1] == NUL) {  // Visual start.
      if (VIsual_active) {
        return &VIsual;
      }
      return &curwin->w_cursor;
    }
    if (name[0] == '\'') {  // Mark.
      pp = getmark_buf_fnum(curbuf, (uint8_t)name[1], false, ret_fnum);
      if (pp == NULL || pp == (pos_T *)-1 || pp->lnum <= 0) {
        return NULL;
      }
      return pp;
    }
  
    pos.coladd = 0;
  
    if (name[0] == 'w' && dollar_lnum) {
      pos.col = 0;
      if (name[1] == '0') {               // "w0": first visible line
        update_topline();
        // In silent Ex mode topline is zero, but that's not a valid line
        // number; use one instead.
        pos.lnum = curwin->w_topline > 0 ? curwin->w_topline : 1;
        return &pos;
      } else if (name[1] == '$') {      // "w$": last visible line
        validate_botline();
        // In silent Ex mode botline is zero, return zero then.
        pos.lnum = curwin->w_botline > 0 ? curwin->w_botline - 1 : 0;
        return &pos;
      }
    } else if (name[0] == '$') {        // last column or line
      if (dollar_lnum) {
        pos.lnum = curbuf->b_ml.ml_line_count;
        pos.col = 0;
      } else {
        pos.lnum = curwin->w_cursor.lnum;
        pos.col = (colnr_T)STRLEN(get_cursor_line_ptr());
      }
      return &pos;
    }
    return NULL;
  }
  
  /*
   * Convert list in "arg" into a position and optional file number.
   * When "fnump" is NULL there is no file number, only 3 items.
   * Note that the column is passed on as-is, the caller may want to decrement
   * it to use 1 for the first column.
   * Return FAIL when conversion is not possible, doesn't check the position for
   * validity.
   */
  int list2fpos(typval_T *arg, pos_T *posp, int *fnump, colnr_T *curswantp)
  {
    list_T *l;
    long i = 0;
    long n;
  
    // List must be: [fnum, lnum, col, coladd, curswant], where "fnum" is only
    // there when "fnump" isn't NULL; "coladd" and "curswant" are optional.
    if (arg->v_type != VAR_LIST
        || (l = arg->vval.v_list) == NULL
        || tv_list_len(l) < (fnump == NULL ? 2 : 3)
        || tv_list_len(l) > (fnump == NULL ? 4 : 5)) {
      return FAIL;
    }
  
    if (fnump != NULL) {
      n = tv_list_find_nr(l, i++, NULL);  // fnum
      if (n < 0) {
        return FAIL;
      }
      if (n == 0) {
        n = curbuf->b_fnum;  // Current buffer.
      }
      *fnump = n;
    }
  
    n = tv_list_find_nr(l, i++, NULL);  // lnum
    if (n < 0) {
      return FAIL;
    }
    posp->lnum = n;
  
    n = tv_list_find_nr(l, i++, NULL);  // col
    if (n < 0) {
      return FAIL;
    }
    posp->col = n;
  
    n = tv_list_find_nr(l, i, NULL);  // off
    if (n < 0) {
      posp->coladd = 0;
    } else {
      posp->coladd = n;
    }
  
    if (curswantp != NULL) {
      *curswantp = tv_list_find_nr(l, i + 1, NULL);  // curswant
    }
  
    return OK;
  }
  
  /*
   * Get the length of an environment variable name.
   * Advance "arg" to the first character after the name.
   * Return 0 for error.
   */
  static int get_env_len(const char_u **arg)
  {
    int len;
  
    const char_u *p;
    for (p = *arg; vim_isIDc(*p); p++) {
    }
    if (p == *arg) {  // No name found.
      return 0;
    }
  
    len = (int)(p - *arg);
    *arg = p;
    return len;
  }
  
  // Get the length of the name of a function or internal variable.
  // "arg" is advanced to the first non-white character after the name.
  // Return 0 if something is wrong.
  int get_id_len(const char **const arg)
  {
    int len;
  
    // Find the end of the name.
    const char *p;
    for (p = *arg; eval_isnamec(*p); p++) {
      if (*p == ':') {
        // "s:" is start of "s:var", but "n:" is not and can be used in
        // slice "[n:]". Also "xx:" is not a namespace.
        len = (int)(p - *arg);
        if (len > 1
            || (len == 1 && vim_strchr(namespace_char, **arg) == NULL)) {
          break;
        }
      }
    }
    if (p == *arg) {  // no name found
      return 0;
    }
  
    len = (int)(p - *arg);
    *arg = (const char *)skipwhite((const char_u *)p);
  
    return len;
  }
  
  /*
   * Get the length of the name of a variable or function.
   * Only the name is recognized, does not handle ".key" or "[idx]".
   * "arg" is advanced to the first non-white character after the name.
   * Return -1 if curly braces expansion failed.
   * Return 0 if something else is wrong.
   * If the name contains 'magic' {}'s, expand them and return the
   * expanded name in an allocated string via 'alias' - caller must free.
   */
  int get_name_len(const char **const arg,
                   char **alias,
                   int evaluate,
                   int verbose)
  {
    int len;
  
    *alias = NULL;    // default to no alias
  
    if ((*arg)[0] == (char)K_SPECIAL && (*arg)[1] == (char)KS_EXTRA
        && (*arg)[2] == (char)KE_SNR) {
      // Hard coded <SNR>, already translated.
      *arg += 3;
      return get_id_len(arg) + 3;
    }
    len = eval_fname_script(*arg);
    if (len > 0) {
      // literal "<SID>", "s:" or "<SNR>"
      *arg += len;
    }
  
    // Find the end of the name; check for {} construction.
    char_u      *expr_start;
    char_u      *expr_end;
    const char *p = (const char *)find_name_end((char_u *)(*arg),
                                                (const char_u **)&expr_start,
                                                (const char_u **)&expr_end,
                                                len > 0 ? 0 : FNE_CHECK_START);
    if (expr_start != NULL) {
      if (!evaluate) {
        len += (int)(p - *arg);
        *arg = (const char *)skipwhite((const char_u *)p);
        return len;
      }
  
      /*
       * Include any <SID> etc in the expanded string:
       * Thus the -len here.
       */
      char_u *temp_string = make_expanded_name((char_u *)(*arg) - len, expr_start,
                                               expr_end, (char_u *)p);
      if (temp_string == NULL) {
        return -1;
      }
      *alias = (char *)temp_string;
      *arg = (const char *)skipwhite((const char_u *)p);
      return (int)STRLEN(temp_string);
    }
  
    len += get_id_len(arg);
    // Only give an error when there is something, otherwise it will be
    // reported at a higher level.
    if (len == 0 && verbose && **arg != NUL) {
      EMSG2(_(e_invexpr2), *arg);
    }
  
    return len;
  }
  
  // Find the end of a variable or function name, taking care of magic braces.
  // If "expr_start" is not NULL then "expr_start" and "expr_end" are set to the
  // start and end of the first magic braces item.
  // "flags" can have FNE_INCL_BR and FNE_CHECK_START.
  // Return a pointer to just after the name.  Equal to "arg" if there is no
  // valid name.
  const char_u *find_name_end(const char_u *arg, const char_u **expr_start,
                              const char_u **expr_end, int flags)
  {
    int mb_nest = 0;
    int br_nest = 0;
    int len;
  
    if (expr_start != NULL) {
      *expr_start = NULL;
      *expr_end = NULL;
    }
  
    // Quick check for valid starting character.
    if ((flags & FNE_CHECK_START) && !eval_isnamec1(*arg) && *arg != '{') {
      return arg;
    }
  
    const char_u *p;
    for (p = arg; *p != NUL
         && (eval_isnamec(*p)
             || *p == '{'
             || ((flags & FNE_INCL_BR) && (*p == '[' || *p == '.'))
             || mb_nest != 0
             || br_nest != 0); MB_PTR_ADV(p)) {
      if (*p == '\'') {
        // skip over 'string' to avoid counting [ and ] inside it.
        for (p = p + 1; *p != NUL && *p != '\''; MB_PTR_ADV(p)) {
        }
        if (*p == NUL) {
          break;
        }
      } else if (*p == '"') {
        // skip over "str\"ing" to avoid counting [ and ] inside it.
        for (p = p + 1; *p != NUL && *p != '"'; MB_PTR_ADV(p)) {
          if (*p == '\\' && p[1] != NUL) {
            ++p;
          }
        }
        if (*p == NUL) {
          break;
        }
      } else if (br_nest == 0 && mb_nest == 0 && *p == ':') {
        // "s:" is start of "s:var", but "n:" is not and can be used in
        // slice "[n:]".  Also "xx:" is not a namespace. But {ns}: is. */
        len = (int)(p - arg);
        if ((len > 1 && p[-1] != '}')
            || (len == 1 && vim_strchr(namespace_char, *arg) == NULL)) {
          break;
        }
      }
  
      if (mb_nest == 0) {
        if (*p == '[') {
          ++br_nest;
        } else if (*p == ']') {
          --br_nest;
        }
      }
  
      if (br_nest == 0) {
        if (*p == '{') {
          mb_nest++;
          if (expr_start != NULL && *expr_start == NULL) {
            *expr_start = p;
          }
        } else if (*p == '}') {
          mb_nest--;
          if (expr_start != NULL && mb_nest == 0 && *expr_end == NULL) {
            *expr_end = p;
          }
        }
      }
    }
  
    return p;
  }
  
  /*
   * Expands out the 'magic' {}'s in a variable/function name.
   * Note that this can call itself recursively, to deal with
   * constructs like foo{bar}{baz}{bam}
   * The four pointer arguments point to "foo{expre}ss{ion}bar"
   *			"in_start"      ^
   *			"expr_start"	   ^
   *			"expr_end"		 ^
   *			"in_end"			    ^
   *
   * Returns a new allocated string, which the caller must free.
   * Returns NULL for failure.
   */
  static char_u *make_expanded_name(const char_u *in_start, char_u *expr_start,
                                    char_u *expr_end, char_u *in_end)
  {
    char_u c1;
    char_u      *retval = NULL;
    char_u      *temp_result;
    char_u      *nextcmd = NULL;
  
    if (expr_end == NULL || in_end == NULL)
      return NULL;
    *expr_start = NUL;
    *expr_end = NUL;
    c1 = *in_end;
    *in_end = NUL;
  
    temp_result = eval_to_string(expr_start + 1, &nextcmd, FALSE);
    if (temp_result != NULL && nextcmd == NULL) {
      retval = xmalloc(STRLEN(temp_result) + (expr_start - in_start)
                       + (in_end - expr_end) + 1);
      STRCPY(retval, in_start);
      STRCAT(retval, temp_result);
      STRCAT(retval, expr_end + 1);
    }
    xfree(temp_result);
  
    *in_end = c1;                 // put char back for error messages
    *expr_start = '{';
    *expr_end = '}';
  
    if (retval != NULL) {
      temp_result = (char_u *)find_name_end(retval,
                                            (const char_u **)&expr_start,
                                            (const char_u **)&expr_end, 0);
      if (expr_start != NULL) {
        // Further expansion!
        temp_result = make_expanded_name(retval, expr_start,
            expr_end, temp_result);
        xfree(retval);
        retval = temp_result;
      }
    }
  
    return retval;
  }
  
  /*
   * Return TRUE if character "c" can be used in a variable or function name.
   * Does not include '{' or '}' for magic braces.
   */
  int eval_isnamec(int c)
  {
    return ASCII_ISALNUM(c) || c == '_' || c == ':' || c == AUTOLOAD_CHAR;
  }
  
  /*
   * Return TRUE if character "c" can be used as the first character in a
   * variable or function name (excluding '{' and '}').
   */
  int eval_isnamec1(int c)
  {
    return ASCII_ISALPHA(c) || c == '_';
  }
  
  /*
   * Get number v: variable value.
   */
  varnumber_T get_vim_var_nr(int idx) FUNC_ATTR_PURE
  {
    return vimvars[idx].vv_nr;
  }
  
  // Get string v: variable value.  Uses a static buffer, can only be used once.
  // If the String variable has never been set, return an empty string.
  // Never returns NULL;
  char_u *get_vim_var_str(int idx) FUNC_ATTR_PURE FUNC_ATTR_NONNULL_RET
  {
    return (char_u *)tv_get_string(&vimvars[idx].vv_tv);
  }
  
  /*
   * Get List v: variable value.  Caller must take care of reference count when
   * needed.
   */
  list_T *get_vim_var_list(int idx) FUNC_ATTR_PURE
  {
    return vimvars[idx].vv_list;
  }
  
  /// Get Dictionary v: variable value.  Caller must take care of reference count
  /// when needed.
  dict_T *get_vim_var_dict(int idx) FUNC_ATTR_PURE
  {
    return vimvars[idx].vv_dict;
  }
  
  /*
   * Set v:char to character "c".
   */
  void set_vim_var_char(int c)
  {
    char buf[MB_MAXBYTES + 1];
  
    buf[utf_char2bytes(c, (char_u *)buf)] = NUL;
    set_vim_var_string(VV_CHAR, buf, -1);
  }
  
  /*
   * Set v:count to "count" and v:count1 to "count1".
   * When "set_prevcount" is TRUE first set v:prevcount from v:count.
   */
  void set_vcount(long count, long count1, int set_prevcount)
  {
    if (set_prevcount)
      vimvars[VV_PREVCOUNT].vv_nr = vimvars[VV_COUNT].vv_nr;
    vimvars[VV_COUNT].vv_nr = count;
    vimvars[VV_COUNT1].vv_nr = count1;
  }
  
  /// Set number v: variable to the given value
  ///
  /// @param[in]  idx  Index of variable to set.
  /// @param[in]  val  Value to set to.
  void set_vim_var_nr(const VimVarIndex idx, const varnumber_T val)
  {
    tv_clear(&vimvars[idx].vv_tv);
    vimvars[idx].vv_type = VAR_NUMBER;
    vimvars[idx].vv_nr = val;
  }
  
  /// Set boolean v: {true, false} to the given value
  ///
  /// @param[in]  idx  Index of variable to set.
  /// @param[in]  val  Value to set to.
  void set_vim_var_bool(const VimVarIndex idx, const BoolVarValue val)
  {
    tv_clear(&vimvars[idx].vv_tv);
    vimvars[idx].vv_type = VAR_BOOL;
    vimvars[idx].vv_bool = val;
  }
  
  /// Set special v: variable to the given value
  ///
  /// @param[in]  idx  Index of variable to set.
  /// @param[in]  val  Value to set to.
  void set_vim_var_special(const VimVarIndex idx, const SpecialVarValue val)
  {
    tv_clear(&vimvars[idx].vv_tv);
    vimvars[idx].vv_type = VAR_SPECIAL;
    vimvars[idx].vv_special = val;
  }
  
  /// Set string v: variable to the given string
  ///
  /// @param[in]  idx  Index of variable to set.
  /// @param[in]  val  Value to set to. Will be copied.
  /// @param[in]  len  Legth of that value or -1 in which case strlen() will be
  ///                  used.
  void set_vim_var_string(const VimVarIndex idx, const char *const val,
                          const ptrdiff_t len)
  {
    tv_clear(&vimvars[idx].vv_di.di_tv);
    vimvars[idx].vv_type = VAR_STRING;
    if (val == NULL) {
      vimvars[idx].vv_str = NULL;
    } else if (len == -1) {
      vimvars[idx].vv_str = (char_u *) xstrdup(val);
    } else {
      vimvars[idx].vv_str = (char_u *) xstrndup(val, (size_t) len);
    }
  }
  
  /// Set list v: variable to the given list
  ///
  /// @param[in]  idx  Index of variable to set.
  /// @param[in,out]  val  Value to set to. Reference count will be incremented.
  void set_vim_var_list(const VimVarIndex idx, list_T *const val)
  {
    tv_clear(&vimvars[idx].vv_di.di_tv);
    vimvars[idx].vv_type = VAR_LIST;
    vimvars[idx].vv_list = val;
    if (val != NULL) {
      tv_list_ref(val);
    }
  }
  
  /// Set Dictionary v: variable to the given dictionary
  ///
  /// @param[in]  idx  Index of variable to set.
  /// @param[in,out]  val  Value to set to. Reference count will be incremented.
  ///                      Also keys of the dictionary will be made read-only.
  void set_vim_var_dict(const VimVarIndex idx, dict_T *const val)
  {
    tv_clear(&vimvars[idx].vv_di.di_tv);
    vimvars[idx].vv_type = VAR_DICT;
    vimvars[idx].vv_dict = val;
  
    if (val != NULL) {
      val->dv_refcount++;
      // Set readonly
      tv_dict_set_keys_readonly(val);
    }
  }
  
  /// Set the v:argv list.
  void set_argv_var(char **argv, int argc)
  {
    list_T *l = tv_list_alloc(argc);
    int i;
  
    if (l == NULL) {
      getout(1);
    }
    tv_list_set_lock(l, VAR_FIXED);
    for (i = 0; i < argc; i++) {
      tv_list_append_string(l, (const char *const)argv[i], -1);
      TV_LIST_ITEM_TV(tv_list_last(l))->v_lock = VAR_FIXED;
    }
    set_vim_var_list(VV_ARGV, l);
  }
  
  /*
   * Set v:register if needed.
   */
  void set_reg_var(int c)
  {
    char regname;
  
    if (c == 0 || c == ' ') {
      regname = '"';
    } else {
      regname = c;
    }
    // Avoid free/alloc when the value is already right.
    if (vimvars[VV_REG].vv_str == NULL || vimvars[VV_REG].vv_str[0] != c) {
      set_vim_var_string(VV_REG, &regname, 1);
    }
  }
  
  /*
   * Get or set v:exception.  If "oldval" == NULL, return the current value.
   * Otherwise, restore the value to "oldval" and return NULL.
   * Must always be called in pairs to save and restore v:exception!  Does not
   * take care of memory allocations.
   */
  char_u *v_exception(char_u *oldval)
  {
    if (oldval == NULL)
      return vimvars[VV_EXCEPTION].vv_str;
  
    vimvars[VV_EXCEPTION].vv_str = oldval;
    return NULL;
  }
  
  /*
   * Get or set v:throwpoint.  If "oldval" == NULL, return the current value.
   * Otherwise, restore the value to "oldval" and return NULL.
   * Must always be called in pairs to save and restore v:throwpoint!  Does not
   * take care of memory allocations.
   */
  char_u *v_throwpoint(char_u *oldval)
  {
    if (oldval == NULL)
      return vimvars[VV_THROWPOINT].vv_str;
  
    vimvars[VV_THROWPOINT].vv_str = oldval;
    return NULL;
  }
  
  /*
   * Set v:cmdarg.
   * If "eap" != NULL, use "eap" to generate the value and return the old value.
   * If "oldarg" != NULL, restore the value to "oldarg" and return NULL.
   * Must always be called in pairs!
   */
  char_u *set_cmdarg(exarg_T *eap, char_u *oldarg)
  {
    char_u *oldval = vimvars[VV_CMDARG].vv_str;
    if (eap == NULL) {
      xfree(oldval);
      vimvars[VV_CMDARG].vv_str = oldarg;
      return NULL;
    }
  
    size_t len = 0;
    if (eap->force_bin == FORCE_BIN)
      len = 6;
    else if (eap->force_bin == FORCE_NOBIN)
      len = 8;
  
    if (eap->read_edit)
      len += 7;
  
    if (eap->force_ff != 0) {
      len += 10;  // " ++ff=unix"
    }
    if (eap->force_enc != 0) {
      len += STRLEN(eap->cmd + eap->force_enc) + 7;
    }
    if (eap->bad_char != 0) {
      len += 7 + 4;  // " ++bad=" + "keep" or "drop"
    }
  
    const size_t newval_len = len + 1;
    char_u *newval = xmalloc(newval_len);
  
    if (eap->force_bin == FORCE_BIN)
      sprintf((char *)newval, " ++bin");
    else if (eap->force_bin == FORCE_NOBIN)
      sprintf((char *)newval, " ++nobin");
    else
      *newval = NUL;
  
    if (eap->read_edit)
      STRCAT(newval, " ++edit");
  
    if (eap->force_ff != 0) {
      snprintf((char *)newval + STRLEN(newval), newval_len, " ++ff=%s",
               eap->force_ff == 'u' ? "unix" :
               eap->force_ff == 'd' ? "dos" : "mac");
    }
    if (eap->force_enc != 0) {
      snprintf((char *)newval + STRLEN(newval), newval_len, " ++enc=%s",
               eap->cmd + eap->force_enc);
    }
    if (eap->bad_char == BAD_KEEP) {
      STRCPY(newval + STRLEN(newval), " ++bad=keep");
    } else if (eap->bad_char == BAD_DROP) {
      STRCPY(newval + STRLEN(newval), " ++bad=drop");
    } else if (eap->bad_char != 0) {
      snprintf((char *)newval + STRLEN(newval), newval_len, " ++bad=%c",
               eap->bad_char);
    }
    vimvars[VV_CMDARG].vv_str = newval;
    return oldval;
  }
  
  /*
   * Get the value of internal variable "name".
   * Return OK or FAIL.
   */
  int get_var_tv(
      const char *name,
      int len,           // length of "name"
      typval_T *rettv,   // NULL when only checking existence
      dictitem_T **dip,  // non-NULL when typval's dict item is needed
      int verbose,       // may give error message
      int no_autoload    // do not use script autoloading
  )
  {
    int ret = OK;
    typval_T    *tv = NULL;
    dictitem_T  *v;
  
    v = find_var(name, (size_t)len, NULL, no_autoload);
    if (v != NULL) {
      tv = &v->di_tv;
      if (dip != NULL) {
        *dip = v;
      }
    }
  
    if (tv == NULL) {
      if (rettv != NULL && verbose) {
        emsgf(_("E121: Undefined variable: %.*s"), len, name);
      }
      ret = FAIL;
    } else if (rettv != NULL) {
      tv_copy(tv, rettv);
    }
  
    return ret;
  }
  
  /// Check if variable "name[len]" is a local variable or an argument.
  /// If so, "*eval_lavars_used" is set to true.
  static void check_vars(const char *name, size_t len)
  {
    if (eval_lavars_used == NULL) {
      return;
    }
  
    const char *varname;
    hashtab_T *ht = find_var_ht(name, len, &varname);
  
    if (ht == get_funccal_local_ht() || ht == get_funccal_args_ht()) {
      if (find_var(name, len, NULL, true) != NULL) {
        *eval_lavars_used = true;
      }
    }
  }
  
  /// check if special v:lua value for calling lua functions
  bool is_luafunc(partial_T *partial)
  {
    return partial == vvlua_partial;
  }
  
  /// check if special v:lua value for calling lua functions
  static bool tv_is_luafunc(typval_T *tv)
  {
    return tv->v_type == VAR_PARTIAL && is_luafunc(tv->vval.v_partial);
  }
  
  /// check the function name after "v:lua."
  int check_luafunc_name(const char *str, bool paren)
  {
    const char *p = str;
    while (ASCII_ISALNUM(*p) || *p == '_' || *p == '.') {
      p++;
    }
    if (*p != (paren ? '(' : NUL)) {
      return 0;
    } else {
      return (int)(p-str);
    }
  }
  
  /// Handle expr[expr], expr[expr:expr] subscript and .name lookup.
  /// Also handle function call with Funcref variable: func(expr)
  /// Can all be combined: dict.func(expr)[idx]['func'](expr)
  int
  handle_subscript(
      const char **const arg,
      typval_T *rettv,
      int evaluate,                   // do more than finding the end
      int verbose                    // give error messages
  )
  {
    int ret = OK;
    dict_T      *selfdict = NULL;
    const char_u *s;
    int len;
    typval_T functv;
    int slen = 0;
    bool lua = false;
  
    if (tv_is_luafunc(rettv)) {
      if (**arg != '.') {
        tv_clear(rettv);
        ret = FAIL;
      } else {
        (*arg)++;
  
        lua = true;
        s = (char_u *)(*arg);
        slen = check_luafunc_name(*arg, true);
        if (slen == 0) {
          tv_clear(rettv);
          ret = FAIL;
        }
        (*arg) += slen;
      }
    }
  
  
    while (ret == OK
           && (**arg == '['
               || (**arg == '.' && rettv->v_type == VAR_DICT)
               || (**arg == '(' && (!evaluate || tv_is_func(*rettv))))
           && !ascii_iswhite(*(*arg - 1))) {
      if (**arg == '(') {
        partial_T *pt = NULL;
        // need to copy the funcref so that we can clear rettv
        if (evaluate) {
          functv = *rettv;
          rettv->v_type = VAR_UNKNOWN;
  
          // Invoke the function.  Recursive!
          if (functv.v_type == VAR_PARTIAL) {
            pt = functv.vval.v_partial;
            if (!lua) {
              s = partial_name(pt);
            }
          } else {
            s = functv.vval.v_string;
          }
        } else {
          s = (char_u *)"";
        }
        ret = get_func_tv(s, lua ? slen : (int)STRLEN(s), rettv, (char_u **)arg,
                          curwin->w_cursor.lnum, curwin->w_cursor.lnum,
                          &len, evaluate, pt, selfdict);
  
        // Clear the funcref afterwards, so that deleting it while
        // evaluating the arguments is possible (see test55).
        if (evaluate) {
          tv_clear(&functv);
        }
  
        /* Stop the expression evaluation when immediately aborting on
         * error, or when an interrupt occurred or an exception was thrown
         * but not caught. */
        if (aborting()) {
          if (ret == OK) {
            tv_clear(rettv);
          }
          ret = FAIL;
        }
        tv_dict_unref(selfdict);
        selfdict = NULL;
      } else {  // **arg == '[' || **arg == '.'
        tv_dict_unref(selfdict);
        if (rettv->v_type == VAR_DICT) {
          selfdict = rettv->vval.v_dict;
          if (selfdict != NULL)
            ++selfdict->dv_refcount;
        } else
          selfdict = NULL;
        if (eval_index((char_u **)arg, rettv, evaluate, verbose) == FAIL) {
          tv_clear(rettv);
          ret = FAIL;
        }
      }
    }
  
    // Turn "dict.Func" into a partial for "Func" bound to "dict".
    if (selfdict != NULL && tv_is_func(*rettv)) {
      set_selfdict(rettv, selfdict);
    }
  
    tv_dict_unref(selfdict);
    return ret;
  }
  
  void set_selfdict(typval_T *const rettv, dict_T *const selfdict)
  {
    // Don't do this when "dict.Func" is already a partial that was bound
    // explicitly (pt_auto is false).
    if (rettv->v_type == VAR_PARTIAL && !rettv->vval.v_partial->pt_auto
        && rettv->vval.v_partial->pt_dict != NULL) {
      return;
    }
    make_partial(selfdict, rettv);
  }
  
  // Turn a typeval into a string.  Similar to tv_get_string_buf() but uses
  // string() on Dict, List, etc.
  static const char *tv_stringify(typval_T *varp, char *buf)
    FUNC_ATTR_NONNULL_ALL
  {
    if (varp->v_type == VAR_LIST
        || varp->v_type == VAR_DICT
        || varp->v_type == VAR_FUNC
        || varp->v_type == VAR_PARTIAL
        || varp->v_type == VAR_FLOAT) {
      typval_T tmp;
  
      f_string(varp, &tmp, NULL);
      const char *const res = tv_get_string_buf(&tmp, buf);
      tv_clear(varp);
      *varp = tmp;
      return res;
    }
    return tv_get_string_buf(varp, buf);
  }
  
  // Find variable "name" in the list of variables.
  // Return a pointer to it if found, NULL if not found.
  // Careful: "a:0" variables don't have a name.
  // When "htp" is not NULL we are writing to the variable, set "htp" to the
  // hashtab_T used.
  dictitem_T *find_var(const char *const name, const size_t name_len,
                       hashtab_T **htp, int no_autoload)
  {
    const char *varname;
    hashtab_T *const ht = find_var_ht(name, name_len, &varname);
    if (htp != NULL) {
      *htp = ht;
    }
    if (ht == NULL) {
      return NULL;
    }
    dictitem_T *const ret = find_var_in_ht(ht, *name,
                                           varname,
                                           name_len - (size_t)(varname - name),
                                           no_autoload || htp != NULL);
    if (ret != NULL) {
      return ret;
    }
  
    // Search in parent scope for lambda
    return find_var_in_scoped_ht(name, name_len, no_autoload || htp != NULL);
  }
  
  /// Find variable in hashtab.
  /// When "varname" is empty returns curwin/curtab/etc vars dictionary.
  ///
  /// @param[in]  ht  Hashtab to find variable in.
  /// @param[in]  htname  Hashtab name (first character).
  /// @param[in]  varname  Variable name.
  /// @param[in]  varname_len  Variable name length.
  /// @param[in]  no_autoload  If true then autoload scripts will not be sourced
  ///                          if autoload variable was not found.
  ///
  /// @return pointer to the dictionary item with the found variable or NULL if it
  ///         was not found.
  dictitem_T *find_var_in_ht(hashtab_T *const ht,
                             int htname,
                             const char *const varname,
                             const size_t varname_len,
                             int no_autoload)
    FUNC_ATTR_WARN_UNUSED_RESULT FUNC_ATTR_NONNULL_ALL
  {
    hashitem_T  *hi;
  
    if (varname_len == 0) {
      // Must be something like "s:", otherwise "ht" would be NULL.
      switch (htname) {
        case 's': return (dictitem_T *)&SCRIPT_SV(current_sctx.sc_sid)->sv_var;
        case 'g': return (dictitem_T *)&globvars_var;
        case 'v': return (dictitem_T *)&vimvars_var;
        case 'b': return (dictitem_T *)&curbuf->b_bufvar;
        case 'w': return (dictitem_T *)&curwin->w_winvar;
        case 't': return (dictitem_T *)&curtab->tp_winvar;
        case 'l': return get_funccal_local_var();
        case 'a': return get_funccal_args_var();
      }
      return NULL;
    }
  
    hi = hash_find_len(ht, varname, varname_len);
    if (HASHITEM_EMPTY(hi)) {
      // For global variables we may try auto-loading the script.  If it
      // worked find the variable again.  Don't auto-load a script if it was
      // loaded already, otherwise it would be loaded every time when
      // checking if a function name is a Funcref variable.
      if (ht == &globvarht && !no_autoload) {
        // Note: script_autoload() may make "hi" invalid. It must either
        // be obtained again or not used.
        if (!script_autoload(varname, varname_len, false) || aborting()) {
          return NULL;
        }
        hi = hash_find_len(ht, varname, varname_len);
      }
      if (HASHITEM_EMPTY(hi)) {
        return NULL;
      }
    }
    return TV_DICT_HI2DI(hi);
  }
  
  /// Finds the dict (g:, l:, s:, …) and hashtable used for a variable.
  ///
  /// @param[in]  name  Variable name, possibly with scope prefix.
  /// @param[in]  name_len  Variable name length.
  /// @param[out]  varname  Will be set to the start of the name without scope
  ///                       prefix.
  /// @param[out]  d  Scope dictionary.
  ///
  /// @return Scope hashtab, NULL if name is not valid.
  static hashtab_T *find_var_ht_dict(const char *name, const size_t name_len,
                                     const char **varname, dict_T **d)
  {
    hashitem_T *hi;
    funccall_T *funccal = get_funccal();
    *d = NULL;
  
    if (name_len == 0) {
      return NULL;
    }
    if (name_len == 1 || name[1] != ':') {
      // name has implicit scope
      if (name[0] == ':' || name[0] == AUTOLOAD_CHAR) {
        // The name must not start with a colon or #.
        return NULL;
      }
      *varname = name;
  
      // "version" is "v:version" in all scopes
      hi = hash_find_len(&compat_hashtab, name, name_len);
      if (!HASHITEM_EMPTY(hi)) {
        return &compat_hashtab;
      }
  
      if (funccal == NULL) {  // global variable
        *d = &globvardict;
      } else {  // l: variable
        *d = &funccal->l_vars;
      }
      goto end;
    }
  
    *varname = name + 2;
    if (*name == 'g') {  // global variable
      *d = &globvardict;
    } else if (name_len > 2
               && (memchr(name + 2, ':', name_len - 2) != NULL
                   || memchr(name + 2, AUTOLOAD_CHAR, name_len - 2) != NULL)) {
      // There must be no ':' or '#' in the rest of the name if g: was not used
      return NULL;
    }
  
    if (*name == 'b') {  // buffer variable
      *d = curbuf->b_vars;
    } else if (*name == 'w') {  // window variable
      *d = curwin->w_vars;
    } else if (*name == 't') {  // tab page variable
      *d = curtab->tp_vars;
    } else if (*name == 'v') {  // v: variable
      *d = &vimvardict;
    } else if (*name == 'a' && funccal != NULL) {  // function argument
      *d = &funccal->l_avars;
    } else if (*name == 'l' && funccal != NULL) {  // local variable
      *d = &funccal->l_vars;
    } else if (*name == 's'  // script variable
               && current_sctx.sc_sid > 0
               && current_sctx.sc_sid <= ga_scripts.ga_len) {
      *d = &SCRIPT_SV(current_sctx.sc_sid)->sv_dict;
    }
  
  end:
    return *d ? &(*d)->dv_hashtab : NULL;
  }
  
  /// Find the hashtable used for a variable
  ///
  /// @param[in]  name  Variable name, possibly with scope prefix.
  /// @param[in]  name_len  Variable name length.
  /// @param[out]  varname  Will be set to the start of the name without scope
  ///                       prefix.
  ///
  /// @return Scope hashtab, NULL if name is not valid.
  hashtab_T *find_var_ht(const char *name, const size_t name_len,
                         const char **varname)
  {
    dict_T *d;
    return find_var_ht_dict(name, name_len, varname, &d);
  }
  
  /*
   * Get the string value of a (global/local) variable.
   * Note: see tv_get_string() for how long the pointer remains valid.
   * Returns NULL when it doesn't exist.
   */
  char_u *get_var_value(const char *const name)
  {
    dictitem_T  *v;
  
    v = find_var(name, strlen(name), NULL, false);
    if (v == NULL) {
      return NULL;
    }
    return (char_u *)tv_get_string(&v->di_tv);
  }
  
  /*
   * Allocate a new hashtab for a sourced script.  It will be used while
   * sourcing this script and when executing functions defined in the script.
   */
  void new_script_vars(scid_T id)
  {
    hashtab_T   *ht;
    scriptvar_T *sv;
  
    ga_grow(&ga_scripts, (int)(id - ga_scripts.ga_len));
    {
      /* Re-allocating ga_data means that an ht_array pointing to
       * ht_smallarray becomes invalid.  We can recognize this: ht_mask is
       * at its init value.  Also reset "v_dict", it's always the same. */
      for (int i = 1; i <= ga_scripts.ga_len; ++i) {
        ht = &SCRIPT_VARS(i);
        if (ht->ht_mask == HT_INIT_SIZE - 1)
          ht->ht_array = ht->ht_smallarray;
        sv = SCRIPT_SV(i);
        sv->sv_var.di_tv.vval.v_dict = &sv->sv_dict;
      }
  
      while (ga_scripts.ga_len < id) {
        sv = SCRIPT_SV(ga_scripts.ga_len + 1) = xcalloc(1, sizeof(scriptvar_T));
        init_var_dict(&sv->sv_dict, &sv->sv_var, VAR_SCOPE);
        ++ga_scripts.ga_len;
      }
    }
  }
  
  /*
   * Initialize dictionary "dict" as a scope and set variable "dict_var" to
   * point to it.
   */
  void init_var_dict(dict_T *dict, ScopeDictDictItem *dict_var, int scope)
  {
    hash_init(&dict->dv_hashtab);
    dict->dv_lock = VAR_UNLOCKED;
    dict->dv_scope = scope;
    dict->dv_refcount = DO_NOT_FREE_CNT;
    dict->dv_copyID = 0;
    dict_var->di_tv.vval.v_dict = dict;
    dict_var->di_tv.v_type = VAR_DICT;
    dict_var->di_tv.v_lock = VAR_FIXED;
    dict_var->di_flags = DI_FLAGS_RO | DI_FLAGS_FIX;
    dict_var->di_key[0] = NUL;
    QUEUE_INIT(&dict->watchers);
  }
  
  /*
   * Unreference a dictionary initialized by init_var_dict().
   */
  void unref_var_dict(dict_T *dict)
  {
    /* Now the dict needs to be freed if no one else is using it, go back to
     * normal reference counting. */
    dict->dv_refcount -= DO_NOT_FREE_CNT - 1;
    tv_dict_unref(dict);
  }
  
  /*
   * Clean up a list of internal variables.
   * Frees all allocated variables and the value they contain.
   * Clears hashtab "ht", does not free it.
   */
  void vars_clear(hashtab_T *ht)
  {
    vars_clear_ext(ht, TRUE);
  }
  
  /*
   * Like vars_clear(), but only free the value if "free_val" is TRUE.
   */
  void vars_clear_ext(hashtab_T *ht, int free_val)
  {
    int todo;
    hashitem_T  *hi;
    dictitem_T  *v;
  
    hash_lock(ht);
    todo = (int)ht->ht_used;
    for (hi = ht->ht_array; todo > 0; ++hi) {
      if (!HASHITEM_EMPTY(hi)) {
        --todo;
  
        // Free the variable.  Don't remove it from the hashtab,
        // ht_array might change then.  hash_clear() takes care of it
        // later.
        v = TV_DICT_HI2DI(hi);
        if (free_val) {
          tv_clear(&v->di_tv);
        }
        if (v->di_flags & DI_FLAGS_ALLOC) {
          xfree(v);
        }
      }
    }
    hash_clear(ht);
    ht->ht_used = 0;
  }
  
  /*
   * Delete a variable from hashtab "ht" at item "hi".
   * Clear the variable value and free the dictitem.
   */
  static void delete_var(hashtab_T *ht, hashitem_T *hi)
  {
    dictitem_T  *di = TV_DICT_HI2DI(hi);
  
    hash_remove(ht, hi);
    tv_clear(&di->di_tv);
    xfree(di);
  }
  
  /*
   * List the value of one internal variable.
   */
  static void list_one_var(dictitem_T *v, const char *prefix, int *first)
  {
    char *const s = encode_tv2echo(&v->di_tv, NULL);
    list_one_var_a(prefix, (const char *)v->di_key, STRLEN(v->di_key),
                   v->di_tv.v_type, (s == NULL ? "" : s), first);
    xfree(s);
  }
  
  /// @param[in]  name_len  Length of the name. May be -1, in this case strlen()
  ///                       will be used.
  /// @param[in,out]  first  When true clear rest of screen and set to false.
  static void list_one_var_a(const char *prefix, const char *name,
                             const ptrdiff_t name_len, const int type,
                             const char *string, int *first)
  {
    // don't use msg() or msg_attr() to avoid overwriting "v:statusmsg"
    msg_start();
    msg_puts(prefix);
    if (name != NULL) {  // "a:" vars don't have a name stored
      msg_puts_attr_len(name, name_len, 0);
    }
    msg_putchar(' ');
    msg_advance(22);
    if (type == VAR_NUMBER) {
      msg_putchar('#');
    } else if (type == VAR_FUNC || type == VAR_PARTIAL) {
      msg_putchar('*');
    } else if (type == VAR_LIST) {
      msg_putchar('[');
      if (*string == '[')
        ++string;
    } else if (type == VAR_DICT) {
      msg_putchar('{');
      if (*string == '{')
        ++string;
    } else
      msg_putchar(' ');
  
    msg_outtrans((char_u *)string);
  
    if (type == VAR_FUNC || type == VAR_PARTIAL) {
      msg_puts("()");
    }
    if (*first) {
      msg_clr_eos();
      *first = FALSE;
    }
  }
  
  /// Set variable to the given value
  ///
  /// If the variable already exists, the value is updated. Otherwise the variable
  /// is created.
  ///
  /// @param[in]  name  Variable name to set.
  /// @param[in]  name_len  Length of the variable name.
  /// @param  tv  Variable value.
  /// @param[in]  copy  True if value in tv is to be copied.
  void set_var(const char *name, const size_t name_len, typval_T *const tv,
               const bool copy)
    FUNC_ATTR_NONNULL_ALL
  {
    set_var_const(name, name_len, tv, copy, false);
  }
  
  /// Set variable to the given value
  ///
  /// If the variable already exists, the value is updated. Otherwise the variable
  /// is created.
  ///
  /// @param[in]  name  Variable name to set.
  /// @param[in]  name_len  Length of the variable name.
  /// @param  tv  Variable value.
  /// @param[in]  copy  True if value in tv is to be copied.
  /// @param[in]  is_const  True if value in tv is to be locked.
  static void set_var_const(const char *name, const size_t name_len,
                            typval_T *const tv, const bool copy,
                            const bool is_const)
    FUNC_ATTR_NONNULL_ALL
  {
    dictitem_T  *v;
    hashtab_T   *ht;
    dict_T *dict;
  
    const char *varname;
    ht = find_var_ht_dict(name, name_len, &varname, &dict);
    const bool watched = tv_dict_is_watched(dict);
  
    if (ht == NULL || *varname == NUL) {
      EMSG2(_(e_illvar), name);
      return;
    }
    v = find_var_in_ht(ht, 0, varname, name_len - (size_t)(varname - name), true);
  
    // Search in parent scope which is possible to reference from lambda
    if (v == NULL) {
      v = find_var_in_scoped_ht((const char *)name, name_len, true);
    }
  
    if (tv_is_func(*tv) && !var_check_func_name(name, v == NULL)) {
      return;
    }
  
    typval_T oldtv = TV_INITIAL_VALUE;
    if (v != NULL) {
      if (is_const) {
        EMSG(_(e_cannot_mod));
        return;
      }
  
      // existing variable, need to clear the value
      if (var_check_ro(v->di_flags, name, name_len)
          || tv_check_lock(v->di_tv.v_lock, name, name_len)) {
        return;
      }
  
      // Handle setting internal v: variables separately where needed to
      // prevent changing the type.
      if (ht == &vimvarht) {
        if (v->di_tv.v_type == VAR_STRING) {
          XFREE_CLEAR(v->di_tv.vval.v_string);
          if (copy || tv->v_type != VAR_STRING) {
            const char *const val = tv_get_string(tv);
  
            // Careful: when assigning to v:errmsg and tv_get_string()
            // causes an error message the variable will alrady be set.
            if (v->di_tv.vval.v_string == NULL) {
              v->di_tv.vval.v_string = (char_u *)xstrdup(val);
            }
          } else {
            // Take over the string to avoid an extra alloc/free.
            v->di_tv.vval.v_string = tv->vval.v_string;
            tv->vval.v_string = NULL;
          }
          return;
        } else if (v->di_tv.v_type == VAR_NUMBER) {
          v->di_tv.vval.v_number = tv_get_number(tv);
          if (strcmp(varname, "searchforward") == 0) {
            set_search_direction(v->di_tv.vval.v_number ? '/' : '?');
          } else if (strcmp(varname, "hlsearch") == 0) {
            no_hlsearch = !v->di_tv.vval.v_number;
            redraw_all_later(SOME_VALID);
          }
          return;
        } else if (v->di_tv.v_type != tv->v_type) {
          EMSG2(_("E963: setting %s to value with wrong type"), name);
          return;
        }
      }
  
      if (watched) {
        tv_copy(&v->di_tv, &oldtv);
      }
      tv_clear(&v->di_tv);
    } else {  // Add a new variable.
      // Can't add "v:" or "a:" variable.
      if (ht == &vimvarht || ht == get_funccal_args_ht()) {
        emsgf(_(e_illvar), name);
        return;
      }
  
      // Make sure the variable name is valid.
      if (!valid_varname(varname)) {
        return;
      }
  
      // Make sure dict is valid
      assert(dict != NULL);
  
      v = xmalloc(sizeof(dictitem_T) + strlen(varname));
      STRCPY(v->di_key, varname);
      if (tv_dict_add(dict, v) == FAIL) {
        xfree(v);
        return;
      }
      v->di_flags = DI_FLAGS_ALLOC;
      if (is_const) {
        v->di_flags |= DI_FLAGS_LOCK;
      }
    }
  
    if (copy || tv->v_type == VAR_NUMBER || tv->v_type == VAR_FLOAT) {
      tv_copy(tv, &v->di_tv);
    } else {
      v->di_tv = *tv;
      v->di_tv.v_lock = 0;
      tv_init(tv);
    }
  
    if (watched) {
      if (oldtv.v_type == VAR_UNKNOWN) {
        tv_dict_watcher_notify(dict, (char *)v->di_key, &v->di_tv, NULL);
      } else {
        tv_dict_watcher_notify(dict, (char *)v->di_key, &v->di_tv, &oldtv);
        tv_clear(&oldtv);
      }
    }
  
    if (is_const) {
      v->di_tv.v_lock |= VAR_LOCKED;
    }
  }
  
  /// Check whether variable is read-only (DI_FLAGS_RO, DI_FLAGS_RO_SBX)
  ///
  /// Also gives an error message.
  ///
  /// @param[in]  flags  di_flags attribute value.
  /// @param[in]  name  Variable name, for use in error message.
  /// @param[in]  name_len  Variable name length. Use #TV_TRANSLATE to translate
  ///                       variable name and compute the length. Use #TV_CSTRING
  ///                       to compute the length with strlen() without
  ///                       translating.
  ///
  ///                       Both #TV_… values are used for optimization purposes:
  ///                       variable name with its length is needed only in case
  ///                       of error, when no error occurs computing them is
  ///                       a waste of CPU resources. This especially applies to
  ///                       gettext.
  ///
  /// @return True if variable is read-only: either always or in sandbox when
  ///         sandbox is enabled, false otherwise.
  bool var_check_ro(const int flags, const char *name,
                    size_t name_len)
    FUNC_ATTR_WARN_UNUSED_RESULT FUNC_ATTR_NONNULL_ALL
  {
    const char *error_message = NULL;
    if (flags & DI_FLAGS_RO) {
      error_message = _(e_readonlyvar);
    } else if ((flags & DI_FLAGS_RO_SBX) && sandbox) {
      error_message = N_("E794: Cannot set variable in the sandbox: \"%.*s\"");
    }
  
    if (error_message == NULL) {
      return false;
    }
    if (name_len == TV_TRANSLATE) {
      name = _(name);
      name_len = strlen(name);
    } else if (name_len == TV_CSTRING) {
      name_len = strlen(name);
    }
  
    emsgf(_(error_message), (int)name_len, name);
  
    return true;
  }
  
  /// Check whether variable is fixed (DI_FLAGS_FIX)
  ///
  /// Also gives an error message.
  ///
  /// @param[in]  flags  di_flags attribute value.
  /// @param[in]  name  Variable name, for use in error message.
  /// @param[in]  name_len  Variable name length. Use #TV_TRANSLATE to translate
  ///                       variable name and compute the length. Use #TV_CSTRING
  ///                       to compute the length with strlen() without
  ///                       translating.
  ///
  ///                       Both #TV_… values are used for optimization purposes:
  ///                       variable name with its length is needed only in case
  ///                       of error, when no error occurs computing them is
  ///                       a waste of CPU resources. This especially applies to
  ///                       gettext.
  ///
  /// @return True if variable is fixed, false otherwise.
  bool var_check_fixed(const int flags, const char *name,
                       size_t name_len)
    FUNC_ATTR_WARN_UNUSED_RESULT FUNC_ATTR_NONNULL_ALL
  {
    if (flags & DI_FLAGS_FIX) {
      if (name_len == TV_TRANSLATE) {
        name = _(name);
        name_len = strlen(name);
      } else if (name_len == TV_CSTRING) {
        name_len = strlen(name);
      }
      EMSG3(_("E795: Cannot delete variable %.*s"), (int)name_len, name);
      return true;
    }
    return false;
  }
  
  // TODO(ZyX-I): move to eval/expressions
  
  /// Check if name is a valid name to assign funcref to
  ///
  /// @param[in]  name  Possible function/funcref name.
  /// @param[in]  new_var  True if it is a name for a variable.
  ///
  /// @return false in case of error, true in case of success. Also gives an
  ///         error message if appropriate.
  bool var_check_func_name(const char *const name, const bool new_var)
    FUNC_ATTR_NONNULL_ALL FUNC_ATTR_WARN_UNUSED_RESULT
  {
    // Allow for w: b: s: and t:.
    if (!(vim_strchr((char_u *)"wbst", name[0]) != NULL && name[1] == ':')
        && !ASCII_ISUPPER((name[0] != NUL && name[1] == ':') ? name[2]
                                                             : name[0])) {
      EMSG2(_("E704: Funcref variable name must start with a capital: %s"), name);
      return false;
    }
    // Don't allow hiding a function.  When "v" is not NULL we might be
    // assigning another function to the same var, the type is checked
    // below.
    if (new_var && function_exists((const char *)name, false)) {
      EMSG2(_("E705: Variable name conflicts with existing function: %s"),
            name);
      return false;
    }
    return true;
  }
  
  // TODO(ZyX-I): move to eval/expressions
  
  /// Check if a variable name is valid
  ///
  /// @param[in]  varname  Variable name to check.
  ///
  /// @return false when variable name is not valid, true when it is. Also gives
  ///         an error message if appropriate.
  bool valid_varname(const char *varname)
    FUNC_ATTR_NONNULL_ALL FUNC_ATTR_WARN_UNUSED_RESULT
  {
    for (const char *p = varname; *p != NUL; p++) {
      if (!eval_isnamec1((int)(uint8_t)(*p))
          && (p == varname || !ascii_isdigit(*p))
          && *p != AUTOLOAD_CHAR) {
        emsgf(_(e_illvar), varname);
        return false;
      }
    }
    return true;
  }
  
  /// Make a copy of an item
  ///
  /// Lists and Dictionaries are also copied.
  ///
  /// @param[in]  conv  If not NULL, convert all copied strings.
  /// @param[in]  from  Value to copy.
  /// @param[out]  to  Location where to copy to.
  /// @param[in]  deep  If true, use copy the container and all of the contained
  ///                   containers (nested).
  /// @param[in]  copyID  If non-zero then when container is referenced more then
  ///                     once then copy of it that was already done is used. E.g.
  ///                     when copying list `list = [list2, list2]` (`list[0] is
  ///                     list[1]`) var_item_copy with zero copyID will emit
  ///                     a copy with (`copy[0] isnot copy[1]`), with non-zero it
  ///                     will emit a copy with (`copy[0] is copy[1]`) like in the
  ///                     original list. Not used when deep is false.
  int var_item_copy(const vimconv_T *const conv,
                    typval_T *const from,
                    typval_T *const to,
                    const bool deep,
                    const int copyID)
    FUNC_ATTR_NONNULL_ARG(2, 3)
  {
    static int recurse = 0;
    int ret = OK;
  
    if (recurse >= DICT_MAXNEST) {
      EMSG(_("E698: variable nested too deep for making a copy"));
      return FAIL;
    }
    ++recurse;
  
    switch (from->v_type) {
    case VAR_NUMBER:
    case VAR_FLOAT:
    case VAR_FUNC:
    case VAR_PARTIAL:
    case VAR_BOOL:
    case VAR_SPECIAL:
      tv_copy(from, to);
      break;
    case VAR_STRING:
      if (conv == NULL || conv->vc_type == CONV_NONE
          || from->vval.v_string == NULL) {
        tv_copy(from, to);
      } else {
        to->v_type = VAR_STRING;
        to->v_lock = 0;
        if ((to->vval.v_string = string_convert((vimconv_T *)conv,
                                                from->vval.v_string,
                                                NULL))
            == NULL) {
          to->vval.v_string = (char_u *) xstrdup((char *) from->vval.v_string);
        }
      }
      break;
    case VAR_LIST:
      to->v_type = VAR_LIST;
      to->v_lock = 0;
      if (from->vval.v_list == NULL) {
        to->vval.v_list = NULL;
      } else if (copyID != 0 && tv_list_copyid(from->vval.v_list) == copyID) {
        // Use the copy made earlier.
        to->vval.v_list = tv_list_latest_copy(from->vval.v_list);
        tv_list_ref(to->vval.v_list);
      } else {
        to->vval.v_list = tv_list_copy(conv, from->vval.v_list, deep, copyID);
      }
      if (to->vval.v_list == NULL && from->vval.v_list != NULL) {
        ret = FAIL;
      }
      break;
    case VAR_DICT:
      to->v_type = VAR_DICT;
      to->v_lock = 0;
      if (from->vval.v_dict == NULL) {
        to->vval.v_dict = NULL;
      } else if (copyID != 0 && from->vval.v_dict->dv_copyID == copyID) {
        // use the copy made earlier
        to->vval.v_dict = from->vval.v_dict->dv_copydict;
        ++to->vval.v_dict->dv_refcount;
      } else {
        to->vval.v_dict = tv_dict_copy(conv, from->vval.v_dict, deep, copyID);
      }
      if (to->vval.v_dict == NULL && from->vval.v_dict != NULL) {
        ret = FAIL;
      }
      break;
    case VAR_UNKNOWN:
      internal_error("var_item_copy(UNKNOWN)");
      ret = FAIL;
    }
    --recurse;
    return ret;
  }
  
  /*
   * ":echo expr1 ..."	print each argument separated with a space, add a
   *			newline at the end.
   * ":echon expr1 ..."	print each argument plain.
   */
  void ex_echo(exarg_T *eap)
  {
    char_u      *arg = eap->arg;
    typval_T rettv;
    bool atstart = true;
    bool need_clear = true;
    const int did_emsg_before = did_emsg;
  
    if (eap->skip)
      ++emsg_skip;
    while (*arg != NUL && *arg != '|' && *arg != '\n' && !got_int) {
      // If eval1() causes an error message the text from the command may
      // still need to be cleared. E.g., "echo 22,44".
      need_clr_eos = true;
  
      {
        char_u *p = arg;
        if (eval1(&arg, &rettv, !eap->skip) == FAIL) {
          // Report the invalid expression unless the expression evaluation
          // has been cancelled due to an aborting error, an interrupt, or an
          // exception.
          if (!aborting() && did_emsg == did_emsg_before) {
            EMSG2(_(e_invexpr2), p);
          }
          need_clr_eos = false;
          break;
        }
        need_clr_eos = false;
      }
  
      if (!eap->skip) {
        if (atstart) {
          atstart = false;
          /* Call msg_start() after eval1(), evaluating the expression
           * may cause a message to appear. */
          if (eap->cmdidx == CMD_echo) {
            /* Mark the saved text as finishing the line, so that what
             * follows is displayed on a new line when scrolling back
             * at the more prompt. */
            msg_sb_eol();
            msg_start();
          }
        } else if (eap->cmdidx == CMD_echo) {
          msg_puts_attr(" ", echo_attr);
        }
        char *tofree = encode_tv2echo(&rettv, NULL);
        if (*tofree != NUL) {
          msg_ext_set_kind("echo");
          msg_multiline_attr(tofree, echo_attr, true, &need_clear);
        }
        xfree(tofree);
      }
      tv_clear(&rettv);
      arg = skipwhite(arg);
    }
    eap->nextcmd = check_nextcmd(arg);
  
    if (eap->skip) {
      emsg_skip--;
    } else {
      // remove text that may still be there from the command
      if (need_clear) {
        msg_clr_eos();
      }
      if (eap->cmdidx == CMD_echo) {
        msg_end();
      }
    }
  }
  
  /*
   * ":echohl {name}".
   */
  void ex_echohl(exarg_T *eap)
  {
    echo_attr = syn_name2attr(eap->arg);
  }
  
  /*
   * ":execute expr1 ..."	execute the result of an expression.
   * ":echomsg expr1 ..."	Print a message
   * ":echoerr expr1 ..."	Print an error
   * Each gets spaces around each argument and a newline at the end for
   * echo commands
   */
  void ex_execute(exarg_T *eap)
  {
    char_u *arg = eap->arg;
    typval_T rettv;
    int ret = OK;
    garray_T ga;
    int save_did_emsg;
  
    ga_init(&ga, 1, 80);
  
    if (eap->skip)
      ++emsg_skip;
    while (*arg != NUL && *arg != '|' && *arg != '\n') {
      ret = eval1_emsg(&arg, &rettv, !eap->skip);
      if (ret == FAIL) {
        break;
      }
  
      if (!eap->skip) {
        char buf[NUMBUFLEN];
        const char *const argstr = eap->cmdidx == CMD_execute
          ? tv_get_string_buf(&rettv, buf)
          : tv_stringify(&rettv, buf);
        const size_t len = strlen(argstr);
        ga_grow(&ga, len + 2);
        if (!GA_EMPTY(&ga)) {
          ((char_u *)(ga.ga_data))[ga.ga_len++] = ' ';
        }
        memcpy((char_u *)(ga.ga_data) + ga.ga_len, argstr, len + 1);
        ga.ga_len += len;
      }
  
      tv_clear(&rettv);
      arg = skipwhite(arg);
    }
  
    if (ret != FAIL && ga.ga_data != NULL) {
      if (eap->cmdidx == CMD_echomsg || eap->cmdidx == CMD_echoerr) {
        // Mark the already saved text as finishing the line, so that what
        // follows is displayed on a new line when scrolling back at the
        // more prompt.
        msg_sb_eol();
      }
  
      if (eap->cmdidx == CMD_echomsg) {
        msg_ext_set_kind("echomsg");
        MSG_ATTR(ga.ga_data, echo_attr);
        ui_flush();
      } else if (eap->cmdidx == CMD_echoerr) {
        // We don't want to abort following commands, restore did_emsg.
        save_did_emsg = did_emsg;
        msg_ext_set_kind("echoerr");
        EMSG((char_u *)ga.ga_data);
        if (!force_abort)
          did_emsg = save_did_emsg;
      } else if (eap->cmdidx == CMD_execute)
        do_cmdline((char_u *)ga.ga_data,
            eap->getline, eap->cookie, DOCMD_NOWAIT|DOCMD_VERBOSE);
    }
  
    ga_clear(&ga);
  
    if (eap->skip)
      --emsg_skip;
  
    eap->nextcmd = check_nextcmd(arg);
  }
  
  /*
   * Skip over the name of an option: "&option", "&g:option" or "&l:option".
   * "arg" points to the "&" or '+' when called, to "option" when returning.
   * Returns NULL when no option name found.  Otherwise pointer to the char
   * after the option name.
   */
  static const char *find_option_end(const char **const arg, int *const opt_flags)
  {
    const char *p = *arg;
  
    ++p;
    if (*p == 'g' && p[1] == ':') {
      *opt_flags = OPT_GLOBAL;
      p += 2;
    } else if (*p == 'l' && p[1] == ':') {
      *opt_flags = OPT_LOCAL;
      p += 2;
    } else {
      *opt_flags = 0;
    }
  
    if (!ASCII_ISALPHA(*p)) {
      return NULL;
    }
    *arg = p;
  
    if (p[0] == 't' && p[1] == '_' && p[2] != NUL && p[3] != NUL) {
      p += 4;  // t_xx/termcap option
    } else {
      while (ASCII_ISALPHA(*p)) {
        p++;
      }
    }
    return p;
  }
  
  /// Start profiling function "fp".
  void func_do_profile(ufunc_T *fp)
  {
    int len = fp->uf_lines.ga_len;
  
    if (!fp->uf_prof_initialized) {
      if (len == 0) {
        len = 1;  // avoid getting error for allocating zero bytes
      }
      fp->uf_tm_count = 0;
      fp->uf_tm_self = profile_zero();
      fp->uf_tm_total = profile_zero();
  
      if (fp->uf_tml_count == NULL) {
        fp->uf_tml_count = xcalloc(len, sizeof(int));
      }
  
      if (fp->uf_tml_total == NULL) {
        fp->uf_tml_total = xcalloc(len, sizeof(proftime_T));
      }
  
      if (fp->uf_tml_self == NULL) {
        fp->uf_tml_self = xcalloc(len, sizeof(proftime_T));
      }
  
      fp->uf_tml_idx = -1;
      fp->uf_prof_initialized = true;
    }
  
    fp->uf_profiling = TRUE;
  }
  
  /*
   * Dump the profiling results for all functions in file "fd".
   */
  void func_dump_profile(FILE *fd)
  {
    hashitem_T  *hi;
    int todo;
    ufunc_T     *fp;
    ufunc_T     **sorttab;
    int st_len = 0;
  
    todo = (int)func_hashtab.ht_used;
    if (todo == 0) {
      return;         // nothing to dump
    }
  
    sorttab = xmalloc(sizeof(ufunc_T *) * todo);
  
    for (hi = func_hashtab.ht_array; todo > 0; ++hi) {
      if (!HASHITEM_EMPTY(hi)) {
        --todo;
        fp = HI2UF(hi);
        if (fp->uf_prof_initialized) {
          sorttab[st_len++] = fp;
  
          if (fp->uf_name[0] == K_SPECIAL) {
            fprintf(fd, "FUNCTION  <SNR>%s()\n", fp->uf_name + 3);
          } else {
            fprintf(fd, "FUNCTION  %s()\n", fp->uf_name);
          }
          if (fp->uf_script_ctx.sc_sid != 0) {
            bool should_free;
            const LastSet last_set = (LastSet){
              .script_ctx = fp->uf_script_ctx,
                .channel_id = 0,
            };
            char_u *p = get_scriptname(last_set, &should_free);
            fprintf(fd, "    Defined: %s:%" PRIdLINENR "\n",
                    p, fp->uf_script_ctx.sc_lnum);
            if (should_free) {
              xfree(p);
            }
          }
          if (fp->uf_tm_count == 1) {
            fprintf(fd, "Called 1 time\n");
          } else {
            fprintf(fd, "Called %d times\n", fp->uf_tm_count);
          }
          fprintf(fd, "Total time: %s\n", profile_msg(fp->uf_tm_total));
          fprintf(fd, " Self time: %s\n", profile_msg(fp->uf_tm_self));
          fprintf(fd, "\n");
          fprintf(fd, "count  total (s)   self (s)\n");
  
          for (int i = 0; i < fp->uf_lines.ga_len; ++i) {
            if (FUNCLINE(fp, i) == NULL)
              continue;
            prof_func_line(fd, fp->uf_tml_count[i],
                &fp->uf_tml_total[i], &fp->uf_tml_self[i], TRUE);
            fprintf(fd, "%s\n", FUNCLINE(fp, i));
          }
          fprintf(fd, "\n");
        }
      }
    }
  
    if (st_len > 0) {
      qsort((void *)sorttab, (size_t)st_len, sizeof(ufunc_T *),
          prof_total_cmp);
      prof_sort_list(fd, sorttab, st_len, "TOTAL", FALSE);
      qsort((void *)sorttab, (size_t)st_len, sizeof(ufunc_T *),
          prof_self_cmp);
      prof_sort_list(fd, sorttab, st_len, "SELF", TRUE);
    }
  
    xfree(sorttab);
  }
  
  static void
  prof_sort_list(
      FILE *fd,
      ufunc_T **sorttab,
      int st_len,
      char *title,
      int prefer_self                // when equal print only self time
  )
  {
    int i;
    ufunc_T     *fp;
  
    fprintf(fd, "FUNCTIONS SORTED ON %s TIME\n", title);
    fprintf(fd, "count  total (s)   self (s)  function\n");
    for (i = 0; i < 20 && i < st_len; ++i) {
      fp = sorttab[i];
      prof_func_line(fd, fp->uf_tm_count, &fp->uf_tm_total, &fp->uf_tm_self,
          prefer_self);
      if (fp->uf_name[0] == K_SPECIAL)
        fprintf(fd, " <SNR>%s()\n", fp->uf_name + 3);
      else
        fprintf(fd, " %s()\n", fp->uf_name);
    }
    fprintf(fd, "\n");
  }
  
  /*
   * Print the count and times for one function or function line.
   */
  static void prof_func_line(
      FILE        *fd,
      int count,
      proftime_T  *total,
      proftime_T  *self,
      int prefer_self                 // when equal print only self time
  )
  {
    if (count > 0) {
      fprintf(fd, "%5d ", count);
      if (prefer_self && profile_equal(*total, *self))
        fprintf(fd, "           ");
      else
        fprintf(fd, "%s ", profile_msg(*total));
      if (!prefer_self && profile_equal(*total, *self))
        fprintf(fd, "           ");
      else
        fprintf(fd, "%s ", profile_msg(*self));
    } else
      fprintf(fd, "                            ");
  }
  
  /*
   * Compare function for total time sorting.
   */
  static int prof_total_cmp(const void *s1, const void *s2)
  {
    ufunc_T *p1 = *(ufunc_T **)s1;
    ufunc_T *p2 = *(ufunc_T **)s2;
    return profile_cmp(p1->uf_tm_total, p2->uf_tm_total);
  }
  
  /*
   * Compare function for self time sorting.
   */
  static int prof_self_cmp(const void *s1, const void *s2)
  {
    ufunc_T *p1 = *(ufunc_T **)s1;
    ufunc_T *p2 = *(ufunc_T **)s2;
    return profile_cmp(p1->uf_tm_self, p2->uf_tm_self);
  }
  
  /// Return the autoload script name for a function or variable name
  /// Caller must make sure that "name" contains AUTOLOAD_CHAR.
  ///
  /// @param[in]  name  Variable/function name.
  /// @param[in]  name_len  Name length.
  ///
  /// @return [allocated] autoload script name.
  char *autoload_name(const char *const name, const size_t name_len)
    FUNC_ATTR_MALLOC FUNC_ATTR_WARN_UNUSED_RESULT
  {
    // Get the script file name: replace '#' with '/', append ".vim".
    char *const scriptname = xmalloc(name_len + sizeof("autoload/.vim"));
    memcpy(scriptname, "autoload/", sizeof("autoload/") - 1);
    memcpy(scriptname + sizeof("autoload/") - 1, name, name_len);
    size_t auchar_idx = 0;
    for (size_t i = sizeof("autoload/") - 1;
         i - sizeof("autoload/") + 1 < name_len;
         i++) {
      if (scriptname[i] == AUTOLOAD_CHAR) {
        scriptname[i] = '/';
        auchar_idx = i;
      }
    }
    memcpy(scriptname + auchar_idx, ".vim", sizeof(".vim"));
  
    return scriptname;
  }
  
  /// If name has a package name try autoloading the script for it
  ///
  /// @param[in]  name  Variable/function name.
  /// @param[in]  name_len  Name length.
  /// @param[in]  reload  If true, load script again when already loaded.
  ///
  /// @return true if a package was loaded.
  bool script_autoload(const char *const name, const size_t name_len,
                       const bool reload)
  {
    // If there is no '#' after name[0] there is no package name.
    const char *p = memchr(name, AUTOLOAD_CHAR, name_len);
    if (p == NULL || p == name) {
      return false;
    }
  
    bool ret = false;
    char *tofree = autoload_name(name, name_len);
    char *scriptname = tofree;
  
    // Find the name in the list of previously loaded package names.  Skip
    // "autoload/", it's always the same.
    int i = 0;
    for (; i < ga_loaded.ga_len; i++) {
      if (STRCMP(((char **)ga_loaded.ga_data)[i] + 9, scriptname + 9) == 0) {
        break;
      }
    }
    if (!reload && i < ga_loaded.ga_len) {
      ret = false;  // Was loaded already.
    } else {
      // Remember the name if it wasn't loaded already.
      if (i == ga_loaded.ga_len) {
        GA_APPEND(char *, &ga_loaded, scriptname);
        tofree = NULL;
      }
  
      // Try loading the package from $VIMRUNTIME/autoload/<name>.vim
      if (source_runtime((char_u *)scriptname, 0) == OK) {
        ret = true;
      }
    }
  
    xfree(tofree);
    return ret;
  }
  
  /*
   * Called when starting to read a function line.
   * "sourcing_lnum" must be correct!
   * When skipping lines it may not actually be executed, but we won't find out
   * until later and we need to store the time now.
   */
  void func_line_start(void *cookie)
  {
    funccall_T  *fcp = (funccall_T *)cookie;
    ufunc_T     *fp = fcp->func;
  
    if (fp->uf_profiling && sourcing_lnum >= 1
        && sourcing_lnum <= fp->uf_lines.ga_len) {
      fp->uf_tml_idx = sourcing_lnum - 1;
      // Skip continuation lines.
      while (fp->uf_tml_idx > 0 && FUNCLINE(fp, fp->uf_tml_idx) == NULL) {
        fp->uf_tml_idx--;
      }
      fp->uf_tml_execed = false;
      fp->uf_tml_start = profile_start();
      fp->uf_tml_children = profile_zero();
      fp->uf_tml_wait = profile_get_wait();
    }
  }
  
  /*
   * Called when actually executing a function line.
   */
  void func_line_exec(void *cookie)
  {
    funccall_T  *fcp = (funccall_T *)cookie;
    ufunc_T     *fp = fcp->func;
  
    if (fp->uf_profiling && fp->uf_tml_idx >= 0)
      fp->uf_tml_execed = TRUE;
  }
  
  /*
   * Called when done with a function line.
   */
  void func_line_end(void *cookie)
  {
    funccall_T  *fcp = (funccall_T *)cookie;
    ufunc_T     *fp = fcp->func;
  
    if (fp->uf_profiling && fp->uf_tml_idx >= 0) {
      if (fp->uf_tml_execed) {
        ++fp->uf_tml_count[fp->uf_tml_idx];
        fp->uf_tml_start = profile_end(fp->uf_tml_start);
        fp->uf_tml_start = profile_sub_wait(fp->uf_tml_wait, fp->uf_tml_start);
        fp->uf_tml_total[fp->uf_tml_idx] =
          profile_add(fp->uf_tml_total[fp->uf_tml_idx], fp->uf_tml_start);
        fp->uf_tml_self[fp->uf_tml_idx] =
          profile_self(fp->uf_tml_self[fp->uf_tml_idx], fp->uf_tml_start,
            fp->uf_tml_children);
      }
      fp->uf_tml_idx = -1;
    }
  }
  
  static var_flavour_T var_flavour(char_u *varname)
  {
    char_u *p = varname;
  
    if (ASCII_ISUPPER(*p)) {
      while (*(++p))
        if (ASCII_ISLOWER(*p)) {
          return VAR_FLAVOUR_SESSION;
        }
      return VAR_FLAVOUR_SHADA;
    } else {
      return VAR_FLAVOUR_DEFAULT;
    }
  }
  
  /// Iterate over global variables
  ///
  /// @warning No modifications to global variable dictionary must be performed
  ///          while iteration is in progress.
  ///
  /// @param[in]   iter   Iterator. Pass NULL to start iteration.
  /// @param[out]  name   Variable name.
  /// @param[out]  rettv  Variable value.
  ///
  /// @return Pointer that needs to be passed to next `var_shada_iter` invocation
  ///         or NULL to indicate that iteration is over.
  const void *var_shada_iter(const void *const iter, const char **const name,
                             typval_T *rettv, var_flavour_T flavour)
    FUNC_ATTR_WARN_UNUSED_RESULT FUNC_ATTR_NONNULL_ARG(2, 3)
  {
    const hashitem_T *hi;
    const hashitem_T *hifirst = globvarht.ht_array;
    const size_t hinum = (size_t) globvarht.ht_mask + 1;
    *name = NULL;
    if (iter == NULL) {
      hi = globvarht.ht_array;
      while ((size_t) (hi - hifirst) < hinum
             && (HASHITEM_EMPTY(hi)
                 || !(var_flavour(hi->hi_key) & flavour))) {
        hi++;
      }
      if ((size_t) (hi - hifirst) == hinum) {
        return NULL;
      }
    } else {
      hi = (const hashitem_T *) iter;
    }
    *name = (char *)TV_DICT_HI2DI(hi)->di_key;
    tv_copy(&TV_DICT_HI2DI(hi)->di_tv, rettv);
    while ((size_t)(++hi - hifirst) < hinum) {
      if (!HASHITEM_EMPTY(hi) && (var_flavour(hi->hi_key) & flavour)) {
        return hi;
      }
    }
    return NULL;
  }
  
  void var_set_global(const char *const name, typval_T vartv)
  {
    funccal_entry_T funccall_entry;
  
    save_funccal(&funccall_entry);
    set_var(name, strlen(name), &vartv, false);
    restore_funccal();
  }
  
  int store_session_globals(FILE *fd)
  {
    TV_DICT_ITER(&globvardict, this_var, {
      if ((this_var->di_tv.v_type == VAR_NUMBER
           || this_var->di_tv.v_type == VAR_STRING)
          && var_flavour(this_var->di_key) == VAR_FLAVOUR_SESSION) {
        // Escape special characters with a backslash.  Turn a LF and
        // CR into \n and \r.
        char_u *const p = vim_strsave_escaped(
            (const char_u *)tv_get_string(&this_var->di_tv),
            (const char_u *)"\\\"\n\r");
        for (char_u *t = p; *t != NUL; t++) {
          if (*t == '\n') {
            *t = 'n';
          } else if (*t == '\r') {
            *t = 'r';
          }
        }
        if ((fprintf(fd, "let %s = %c%s%c",
                     this_var->di_key,
                     ((this_var->di_tv.v_type == VAR_STRING) ? '"'
                      : ' '),
                     p,
                     ((this_var->di_tv.v_type == VAR_STRING) ? '"'
                      : ' ')) < 0)
            || put_eol(fd) == FAIL) {
          xfree(p);
          return FAIL;
        }
        xfree(p);
      } else if (this_var->di_tv.v_type == VAR_FLOAT
                 && var_flavour(this_var->di_key) == VAR_FLAVOUR_SESSION) {
        float_T f = this_var->di_tv.vval.v_float;
        int sign = ' ';
  
        if (f < 0) {
          f = -f;
          sign = '-';
        }
        if ((fprintf(fd, "let %s = %c%f", this_var->di_key, sign, f) < 0)
            || put_eol(fd) == FAIL) {
          return FAIL;
        }
      }
    });
    return OK;
  }
  
  /*
   * Display script name where an item was last set.
   * Should only be invoked when 'verbose' is non-zero.
   */
  void last_set_msg(sctx_T script_ctx)
  {
    const LastSet last_set = (LastSet){
      .script_ctx = script_ctx,
      .channel_id = 0,
    };
    option_last_set_msg(last_set);
  }
  
  /// Displays where an option was last set.
  ///
  /// Should only be invoked when 'verbose' is non-zero.
  void option_last_set_msg(LastSet last_set)
  {
    if (last_set.script_ctx.sc_sid != 0) {
      bool should_free;
      char_u *p = get_scriptname(last_set, &should_free);
      verbose_enter();
      MSG_PUTS(_("\n\tLast set from "));
      MSG_PUTS(p);
      if (last_set.script_ctx.sc_lnum > 0) {
        MSG_PUTS(_(line_msg));
        msg_outnum((long)last_set.script_ctx.sc_lnum);
      }
      if (should_free) {
        xfree(p);
      }
      verbose_leave();
    }
  }
  
  // reset v:option_new, v:option_old and v:option_type
  void reset_v_option_vars(void)
  {
    set_vim_var_string(VV_OPTION_NEW,  NULL, -1);
    set_vim_var_string(VV_OPTION_OLD,  NULL, -1);
    set_vim_var_string(VV_OPTION_TYPE, NULL, -1);
  }
  
  /*
   * Adjust a filename, according to a string of modifiers.
   * *fnamep must be NUL terminated when called.  When returning, the length is
   * determined by *fnamelen.
   * Returns VALID_ flags or -1 for failure.
   * When there is an error, *fnamep is set to NULL.
   */
  int
  modify_fname(
      char_u *src,              // string with modifiers
      bool tilde_file,          // "~" is a file name, not $HOME
      size_t *usedlen,          // characters after src that are used
      char_u **fnamep,          // file name so far
      char_u **bufp,            // buffer for allocated file name or NULL
      size_t *fnamelen          // length of fnamep
  )
  {
    int valid = 0;
    char_u      *tail;
    char_u      *s, *p, *pbuf;
    char_u dirname[MAXPATHL];
    int c;
    int has_fullname = 0;
  
  repeat:
    // ":p" - full path/file_name
    if (src[*usedlen] == ':' && src[*usedlen + 1] == 'p') {
      has_fullname = 1;
  
      valid |= VALID_PATH;
      *usedlen += 2;
  
      // Expand "~/path" for all systems and "~user/path" for Unix
      if ((*fnamep)[0] == '~'
  #if !defined(UNIX)
          && ((*fnamep)[1] == '/'
  # ifdef BACKSLASH_IN_FILENAME
              || (*fnamep)[1] == '\\'
  # endif
              || (*fnamep)[1] == NUL)
  #endif
          && !(tilde_file && (*fnamep)[1] == NUL)
          ) {
        *fnamep = expand_env_save(*fnamep);
        xfree(*bufp);          // free any allocated file name
        *bufp = *fnamep;
        if (*fnamep == NULL)
          return -1;
      }
  
      // When "/." or "/.." is used: force expansion to get rid of it.
      for (p = *fnamep; *p != NUL; MB_PTR_ADV(p)) {
        if (vim_ispathsep(*p)
            && p[1] == '.'
            && (p[2] == NUL
                || vim_ispathsep(p[2])
                || (p[2] == '.'
                    && (p[3] == NUL || vim_ispathsep(p[3]))))) {
          break;
        }
      }
  
      // FullName_save() is slow, don't use it when not needed.
      if (*p != NUL || !vim_isAbsName(*fnamep)) {
        *fnamep = (char_u *)FullName_save((char *)(*fnamep), *p != NUL);
        xfree(*bufp);          // free any allocated file name
        *bufp = *fnamep;
        if (*fnamep == NULL)
          return -1;
      }
  
      // Append a path separator to a directory.
      if (os_isdir(*fnamep)) {
        // Make room for one or two extra characters.
        *fnamep = vim_strnsave(*fnamep, STRLEN(*fnamep) + 2);
        xfree(*bufp);          // free any allocated file name
        *bufp = *fnamep;
        if (*fnamep == NULL)
          return -1;
        add_pathsep((char *)*fnamep);
      }
    }
  
    // ":." - path relative to the current directory
    // ":~" - path relative to the home directory
    // ":8" - shortname path - postponed till after
    while (src[*usedlen] == ':'
           && ((c = src[*usedlen + 1]) == '.' || c == '~' || c == '8')) {
      *usedlen += 2;
      if (c == '8') {
        continue;
      }
      pbuf = NULL;
      // Need full path first (use expand_env() to remove a "~/")
      if (!has_fullname) {
        if (c == '.' && **fnamep == '~')
          p = pbuf = expand_env_save(*fnamep);
        else
          p = pbuf = (char_u *)FullName_save((char *)*fnamep, FALSE);
      } else
        p = *fnamep;
  
      has_fullname = 0;
  
      if (p != NULL) {
        if (c == '.') {
          os_dirname(dirname, MAXPATHL);
          s = path_shorten_fname(p, dirname);
          if (s != NULL) {
            *fnamep = s;
            if (pbuf != NULL) {
              xfree(*bufp);               // free any allocated file name
              *bufp = pbuf;
              pbuf = NULL;
            }
          }
        } else {
          home_replace(NULL, p, dirname, MAXPATHL, true);
          // Only replace it when it starts with '~'
          if (*dirname == '~') {
            s = vim_strsave(dirname);
            *fnamep = s;
            xfree(*bufp);
            *bufp = s;
          }
        }
        xfree(pbuf);
      }
    }
  
    tail = path_tail(*fnamep);
    *fnamelen = STRLEN(*fnamep);
  
    // ":h" - head, remove "/file_name", can be repeated
    // Don't remove the first "/" or "c:\"
    while (src[*usedlen] == ':' && src[*usedlen + 1] == 'h') {
      valid |= VALID_HEAD;
      *usedlen += 2;
      s = get_past_head(*fnamep);
      while (tail > s && after_pathsep((char *)s, (char *)tail)) {
        MB_PTR_BACK(*fnamep, tail);
      }
      *fnamelen = (size_t)(tail - *fnamep);
      if (*fnamelen == 0) {
        // Result is empty.  Turn it into "." to make ":cd %:h" work.
        xfree(*bufp);
        *bufp = *fnamep = tail = vim_strsave((char_u *)".");
        *fnamelen = 1;
      } else {
        while (tail > s && !after_pathsep((char *)s, (char *)tail)) {
          MB_PTR_BACK(*fnamep, tail);
        }
      }
    }
  
    // ":8" - shortname
    if (src[*usedlen] == ':' && src[*usedlen + 1] == '8') {
      *usedlen += 2;
    }
  
  
    // ":t" - tail, just the basename
    if (src[*usedlen] == ':' && src[*usedlen + 1] == 't') {
      *usedlen += 2;
      *fnamelen -= (size_t)(tail - *fnamep);
      *fnamep = tail;
    }
  
    // ":e" - extension, can be repeated
    // ":r" - root, without extension, can be repeated
    while (src[*usedlen] == ':'
           && (src[*usedlen + 1] == 'e' || src[*usedlen + 1] == 'r')) {
      /* find a '.' in the tail:
       * - for second :e: before the current fname
       * - otherwise: The last '.'
       */
      const bool is_second_e = *fnamep > tail;
      if (src[*usedlen + 1] == 'e' && is_second_e) {
        s = *fnamep - 2;
      } else {
        s = *fnamep + *fnamelen - 1;
      }
  
      for (; s > tail; s--) {
        if (s[0] == '.') {
          break;
        }
      }
      if (src[*usedlen + 1] == 'e') {
        if (s > tail || (0 && is_second_e && s == tail)) {
          // we stopped at a '.' (so anchor to &'.' + 1)
          char_u *newstart = s + 1;
          size_t distance_stepped_back = *fnamep - newstart;
          *fnamelen += distance_stepped_back;
          *fnamep = newstart;
        } else if (*fnamep <= tail) {
          *fnamelen = 0;
        }
      } else {
        // :r - Remove one extension
        //
        // Ensure that `s` doesn't go before `*fnamep`,
        // since then we're taking too many roots:
        //
        // "path/to/this.file.ext" :e:e:r:r
        //          ^    ^-------- *fnamep
        //          +------------- tail
        //
        // Also ensure `s` doesn't go before `tail`,
        // since then we're taking too many roots again:
        //
        // "path/to/this.file.ext" :r:r:r
        //  ^       ^------------- tail
        //  +--------------------- *fnamep
        if (s > MAX(tail, *fnamep)) {
          *fnamelen = (size_t)(s - *fnamep);
        }
      }
      *usedlen += 2;
    }
  
    // ":s?pat?foo?" - substitute
    // ":gs?pat?foo?" - global substitute
    if (src[*usedlen] == ':'
        && (src[*usedlen + 1] == 's'
            || (src[*usedlen + 1] == 'g' && src[*usedlen + 2] == 's'))) {
      char_u      *str;
      char_u      *pat;
      char_u      *sub;
      int sep;
      char_u      *flags;
      int didit = FALSE;
  
      flags = (char_u *)"";
      s = src + *usedlen + 2;
      if (src[*usedlen + 1] == 'g') {
        flags = (char_u *)"g";
        ++s;
      }
  
      sep = *s++;
      if (sep) {
        // find end of pattern
        p = vim_strchr(s, sep);
        if (p != NULL) {
          pat = vim_strnsave(s, (int)(p - s));
          s = p + 1;
          // find end of substitution
          p = vim_strchr(s, sep);
          if (p != NULL) {
            sub = vim_strnsave(s, (int)(p - s));
            str = vim_strnsave(*fnamep, *fnamelen);
            *usedlen = (size_t)(p + 1 - src);
            s = do_string_sub(str, pat, sub, NULL, flags);
            *fnamep = s;
            *fnamelen = STRLEN(s);
            xfree(*bufp);
            *bufp = s;
            didit = TRUE;
            xfree(sub);
            xfree(str);
          }
          xfree(pat);
        }
        // after using ":s", repeat all the modifiers
        if (didit) {
          goto repeat;
        }
      }
    }
  
    if (src[*usedlen] == ':' && src[*usedlen + 1] == 'S') {
      // vim_strsave_shellescape() needs a NUL terminated string.
      c = (*fnamep)[*fnamelen];
      if (c != NUL) {
        (*fnamep)[*fnamelen] = NUL;
      }
      p = vim_strsave_shellescape(*fnamep, false, false);
      if (c != NUL) {
        (*fnamep)[*fnamelen] = c;
      }
      xfree(*bufp);
      *bufp = *fnamep = p;
      *fnamelen = STRLEN(p);
      *usedlen += 2;
    }
  
    return valid;
  }
  
  /// Perform a substitution on "str" with pattern "pat" and substitute "sub".
  /// When "sub" is NULL "expr" is used, must be a VAR_FUNC or VAR_PARTIAL.
  /// "flags" can be "g" to do a global substitute.
  /// Returns an allocated string, NULL for error.
  char_u *do_string_sub(char_u *str, char_u *pat, char_u *sub,
                        typval_T *expr, char_u *flags)
  {
    int sublen;
    regmatch_T regmatch;
    int do_all;
    char_u      *tail;
    char_u      *end;
    garray_T ga;
    char_u      *save_cpo;
    char_u      *zero_width = NULL;
  
    // Make 'cpoptions' empty, so that the 'l' flag doesn't work here
    save_cpo = p_cpo;
    p_cpo = empty_option;
  
    ga_init(&ga, 1, 200);
  
    do_all = (flags[0] == 'g');
  
    regmatch.rm_ic = p_ic;
    regmatch.regprog = vim_regcomp(pat, RE_MAGIC + RE_STRING);
    if (regmatch.regprog != NULL) {
      tail = str;
      end = str + STRLEN(str);
      while (vim_regexec_nl(&regmatch, str, (colnr_T)(tail - str))) {
        // Skip empty match except for first match.
        if (regmatch.startp[0] == regmatch.endp[0]) {
          if (zero_width == regmatch.startp[0]) {
            // avoid getting stuck on a match with an empty string
            int i = utfc_ptr2len(tail);
            memmove((char_u *)ga.ga_data + ga.ga_len, tail, (size_t)i);
            ga.ga_len += i;
            tail += i;
            continue;
          }
          zero_width = regmatch.startp[0];
        }
  
        // Get some space for a temporary buffer to do the substitution
        // into.  It will contain:
        // - The text up to where the match is.
        // - The substituted text.
        // - The text after the match.
        sublen = vim_regsub(&regmatch, sub, expr, tail, false, true, false);
        ga_grow(&ga, (int)((end - tail) + sublen -
                       (regmatch.endp[0] - regmatch.startp[0])));
  
        // copy the text up to where the match is
        int i = (int)(regmatch.startp[0] - tail);
        memmove((char_u *)ga.ga_data + ga.ga_len, tail, (size_t)i);
        // add the substituted text
        (void)vim_regsub(&regmatch, sub, expr, (char_u *)ga.ga_data
                         + ga.ga_len + i, true, true, false);
        ga.ga_len += i + sublen - 1;
        tail = regmatch.endp[0];
        if (*tail == NUL)
          break;
        if (!do_all)
          break;
      }
  
      if (ga.ga_data != NULL)
        STRCPY((char *)ga.ga_data + ga.ga_len, tail);
  
      vim_regfree(regmatch.regprog);
    }
  
    char_u *ret = vim_strsave(ga.ga_data == NULL ? str : (char_u *)ga.ga_data);
    ga_clear(&ga);
    if (p_cpo == empty_option) {
      p_cpo = save_cpo;
    } else {
      // Darn, evaluating {sub} expression or {expr} changed the value.
      free_string_option(save_cpo);
    }
  
    return ret;
  }
  
  /// common code for getting job callbacks for jobstart, termopen and rpcstart
  ///
  /// @return true/false on success/failure.
  bool common_job_callbacks(dict_T *vopts,
                            CallbackReader *on_stdout,
                            CallbackReader *on_stderr,
                            Callback *on_exit)
  {
    if (tv_dict_get_callback(vopts, S_LEN("on_stdout"), &on_stdout->cb)
        &&tv_dict_get_callback(vopts, S_LEN("on_stderr"), &on_stderr->cb)
        && tv_dict_get_callback(vopts, S_LEN("on_exit"), on_exit)) {
      on_stdout->buffered = tv_dict_get_number(vopts, "stdout_buffered");
      on_stderr->buffered = tv_dict_get_number(vopts, "stderr_buffered");
      if (on_stdout->buffered && on_stdout->cb.type == kCallbackNone) {
        on_stdout->self = vopts;
      }
      if (on_stderr->buffered && on_stderr->cb.type == kCallbackNone) {
        on_stderr->self = vopts;
      }
      vopts->dv_refcount++;
      return true;
    }
  
    callback_reader_free(on_stdout);
    callback_reader_free(on_stderr);
    callback_free(on_exit);
    return false;
  }
  
  
  Channel *find_job(uint64_t id, bool show_error)
  {
    Channel *data = find_channel(id);
    if (!data || data->streamtype != kChannelStreamProc
        || process_is_stopped(&data->stream.proc)) {
      if (show_error) {
        if (data && data->streamtype != kChannelStreamProc) {
          EMSG(_(e_invchanjob));
        } else {
          EMSG(_(e_invchan));
        }
      }
      return NULL;
    }
    return data;
  }
  
  
  void script_host_eval(char *name, typval_T *argvars, typval_T *rettv)
  {
    if (check_restricted() || check_secure()) {
      return;
    }
  
    if (argvars[0].v_type != VAR_STRING) {
      EMSG(_(e_invarg));
      return;
    }
  
    list_T *args = tv_list_alloc(1);
    tv_list_append_string(args, (const char *)argvars[0].vval.v_string, -1);
    *rettv = eval_call_provider(name, "eval", args);
  }
  
  typval_T eval_call_provider(char *provider, char *method, list_T *arguments)
  {
    if (!eval_has_provider(provider)) {
      emsgf("E319: No \"%s\" provider found. Run \":checkhealth provider\"",
            provider);
      return (typval_T){
        .v_type = VAR_NUMBER,
        .v_lock = VAR_UNLOCKED,
        .vval.v_number = (varnumber_T)0
      };
    }
  
    char func[256];
    int name_len = snprintf(func, sizeof(func), "provider#%s#Call", provider);
  
    // Save caller scope information
    struct caller_scope saved_provider_caller_scope = provider_caller_scope;
    provider_caller_scope = (struct caller_scope) {
      .script_ctx = current_sctx,
      .sourcing_name = sourcing_name,
      .sourcing_lnum = sourcing_lnum,
      .autocmd_fname = autocmd_fname,
      .autocmd_match = autocmd_match,
      .autocmd_bufnr = autocmd_bufnr,
      .funccalp = (void *)get_current_funccal()
    };
    funccal_entry_T funccal_entry;
    save_funccal(&funccal_entry);
    provider_call_nesting++;
  
    typval_T argvars[3] = {
      {.v_type = VAR_STRING, .vval.v_string = (uint8_t *)method, .v_lock = 0},
      {.v_type = VAR_LIST, .vval.v_list = arguments, .v_lock = 0},
      {.v_type = VAR_UNKNOWN}
    };
    typval_T rettv = { .v_type = VAR_UNKNOWN, .v_lock = VAR_UNLOCKED };
    tv_list_ref(arguments);
  
    int dummy;
    (void)call_func((const char_u *)func,
                    name_len,
                    &rettv,
                    2,
                    argvars,
                    NULL,
                    curwin->w_cursor.lnum,
                    curwin->w_cursor.lnum,
                    &dummy,
                    true,
                    NULL,
                    NULL);
  
    tv_list_unref(arguments);
    // Restore caller scope information
    restore_funccal();
    provider_caller_scope = saved_provider_caller_scope;
    provider_call_nesting--;
    assert(provider_call_nesting >= 0);
  
    return rettv;
  }
  
  /// Checks if provider for feature `feat` is enabled.
  bool eval_has_provider(const char *feat)
  {
    if (!strequal(feat, "clipboard")
        && !strequal(feat, "python")
        && !strequal(feat, "python3")
        && !strequal(feat, "python_compiled")
        && !strequal(feat, "python_dynamic")
        && !strequal(feat, "python3_compiled")
        && !strequal(feat, "python3_dynamic")
        && !strequal(feat, "perl")
        && !strequal(feat, "ruby")
        && !strequal(feat, "node")) {
      // Avoid autoload for non-provider has() features.
      return false;
    }
  
    char name[32];  // Normalized: "python_compiled" => "python".
    snprintf(name, sizeof(name), "%s", feat);
    strchrsub(name, '_', '\0');  // Chop any "_xx" suffix.
  
    char buf[256];
    typval_T tv;
    // Get the g:loaded_xx_provider variable.
    int len = snprintf(buf, sizeof(buf), "g:loaded_%s_provider", name);
    if (get_var_tv(buf, len, &tv, NULL, false, true) == FAIL) {
      // Trigger autoload once.
      len = snprintf(buf, sizeof(buf), "provider#%s#bogus", name);
      script_autoload(buf, len, false);
  
      // Retry the (non-autoload-style) variable.
      len = snprintf(buf, sizeof(buf), "g:loaded_%s_provider", name);
      if (get_var_tv(buf, len, &tv, NULL, false, true) == FAIL) {
        // Show a hint if Call() is defined but g:loaded_xx_provider is missing.
        snprintf(buf, sizeof(buf), "provider#%s#Call", name);
        if (!!find_func((char_u *)buf) && p_lpl) {
          emsgf("provider: %s: missing required variable g:loaded_%s_provider",
                name, name);
        }
        return false;
      }
    }
  
    bool ok = (tv.v_type == VAR_NUMBER)
      ? 2 == tv.vval.v_number  // Value of 2 means "loaded and working".
      : false;
  
    if (ok) {
      // Call() must be defined if provider claims to be working.
      snprintf(buf, sizeof(buf), "provider#%s#Call", name);
      if (!find_func((char_u *)buf)) {
        emsgf("provider: %s: g:loaded_%s_provider=2 but %s is not defined",
              name, name, buf);
        ok = false;
      }
    }
  
    return ok;
  }
  
  /// Writes "<sourcing_name>:<sourcing_lnum>" to `buf[bufsize]`.
  void eval_fmt_source_name_line(char *buf, size_t bufsize)
  {
    if (sourcing_name) {
      snprintf(buf, bufsize, "%s:%" PRIdLINENR, sourcing_name, sourcing_lnum);
    } else {
      snprintf(buf, bufsize, "?");
    }
  }
  
  /// ":checkhealth [plugins]"
  void ex_checkhealth(exarg_T *eap)
  {
    bool found = !!find_func((char_u *)"health#check");
    if (!found
        && script_autoload("health#check", sizeof("health#check") - 1, false)) {
      found = !!find_func((char_u *)"health#check");
    }
    if (!found) {
      const char *vimruntime_env = os_getenv("VIMRUNTIME");
      if (vimruntime_env == NULL) {
        EMSG(_("E5009: $VIMRUNTIME is empty or unset"));
      } else {
        bool rtp_ok = NULL != strstr((char *)p_rtp, vimruntime_env);
        if (rtp_ok) {
          EMSG2(_("E5009: Invalid $VIMRUNTIME: %s"), vimruntime_env);
        } else {
          EMSG(_("E5009: Invalid 'runtimepath'"));
        }
      }
      return;
    }
  
    size_t bufsize = STRLEN(eap->arg) + sizeof("call health#check('')");
    char *buf = xmalloc(bufsize);
    snprintf(buf, bufsize, "call health#check('%s')", eap->arg);
  
    do_cmdline_cmd(buf);
  
    xfree(buf);
  }
  
  void invoke_prompt_callback(void)
  {
      typval_T rettv;
      typval_T argv[2];
      char_u *text;
      char_u *prompt;
      linenr_T lnum = curbuf->b_ml.ml_line_count;
  
      // Add a new line for the prompt before invoking the callback, so that
      // text can always be inserted above the last line.
      ml_append(lnum, (char_u  *)"", 0, false);
      curwin->w_cursor.lnum = lnum + 1;
      curwin->w_cursor.col = 0;
  
      if (curbuf->b_prompt_callback.type == kCallbackNone) {
        return;
      }
      text = ml_get(lnum);
      prompt = prompt_text();
      if (STRLEN(text) >= STRLEN(prompt)) {
        text += STRLEN(prompt);
      }
      argv[0].v_type = VAR_STRING;
      argv[0].vval.v_string = vim_strsave(text);
      argv[1].v_type = VAR_UNKNOWN;
  
      callback_call(&curbuf->b_prompt_callback, 1, argv, &rettv);
      tv_clear(&argv[0]);
      tv_clear(&rettv);
  }
  
  // Return true When the interrupt callback was invoked.
  bool invoke_prompt_interrupt(void)
  {
      typval_T rettv;
      typval_T argv[1];
  
      if (curbuf->b_prompt_interrupt.type == kCallbackNone) {
        return false;
      }
      argv[0].v_type = VAR_UNKNOWN;
  
      got_int = false;  // don't skip executing commands
      callback_call(&curbuf->b_prompt_interrupt, 0, argv, &rettv);
      tv_clear(&rettv);
      return true;
  }
  