text: //===--- Parser.cpp - C Language Family Parser ----------------------------===//
  //
  // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
  // See https://llvm.org/LICENSE.txt for license information.
  // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
  //
  //===----------------------------------------------------------------------===//
  //
  //  This file implements the Parser interfaces.
  //
  //===----------------------------------------------------------------------===//
  
  #include "clang/Parse/Parser.h"
  #include "clang/AST/ASTConsumer.h"
  #include "clang/AST/ASTContext.h"
  #include "clang/AST/DeclTemplate.h"
  #include "clang/Basic/FileManager.h"
  #include "clang/Parse/ParseDiagnostic.h"
  #include "clang/Parse/RAIIObjectsForParser.h"
  #include "clang/Sema/DeclSpec.h"
  #include "clang/Sema/ParsedTemplate.h"
  #include "clang/Sema/Scope.h"
  #include "llvm/Support/Path.h"
  using namespace clang;
  
  
  namespace {
  /// A comment handler that passes comments found by the preprocessor
  /// to the parser action.
  class ActionCommentHandler : public CommentHandler {
    Sema &S;
  
  public:
    explicit ActionCommentHandler(Sema &S) : S(S) { }
  
    bool HandleComment(Preprocessor &PP, SourceRange Comment) override {
      S.ActOnComment(Comment);
      return false;
    }
  };
  } // end anonymous namespace
  
  IdentifierInfo *Parser::getSEHExceptKeyword() {
    // __except is accepted as a (contextual) keyword
    if (!Ident__except && (getLangOpts().MicrosoftExt || getLangOpts().Borland))
      Ident__except = PP.getIdentifierInfo("__except");
  
    return Ident__except;
  }
  
  Parser::Parser(Preprocessor &pp, Sema &actions, bool skipFunctionBodies)
      : PP(pp), PreferredType(pp.isCodeCompletionEnabled()), Actions(actions),
        Diags(PP.getDiagnostics()), GreaterThanIsOperator(true),
        ColonIsSacred(false), InMessageExpression(false),
        TemplateParameterDepth(0), ParsingInObjCContainer(false) {
    SkipFunctionBodies = pp.isCodeCompletionEnabled() || skipFunctionBodies;
    Tok.startToken();
    Tok.setKind(tok::eof);
    Actions.CurScope = nullptr;
    NumCachedScopes = 0;
    CurParsedObjCImpl = nullptr;
  
    // Add #pragma handlers. These are removed and destroyed in the
    // destructor.
    initializePragmaHandlers();
  
    CommentSemaHandler.reset(new ActionCommentHandler(actions));
    PP.addCommentHandler(CommentSemaHandler.get());
  
    PP.setCodeCompletionHandler(*this);
  
    Actions.ParseTypeFromStringCallback =
      [this](StringRef typeStr, StringRef context, SourceLocation includeLoc) {
        return this->parseTypeFromString(typeStr, context, includeLoc);
      };
  }
  
  DiagnosticBuilder Parser::Diag(SourceLocation Loc, unsigned DiagID) {
    return Diags.Report(Loc, DiagID);
  }
  
  DiagnosticBuilder Parser::Diag(const Token &Tok, unsigned DiagID) {
    return Diag(Tok.getLocation(), DiagID);
  }
  
  /// Emits a diagnostic suggesting parentheses surrounding a
  /// given range.
  ///
  /// \param Loc The location where we'll emit the diagnostic.
  /// \param DK The kind of diagnostic to emit.
  /// \param ParenRange Source range enclosing code that should be parenthesized.
  void Parser::SuggestParentheses(SourceLocation Loc, unsigned DK,
                                  SourceRange ParenRange) {
    SourceLocation EndLoc = PP.getLocForEndOfToken(ParenRange.getEnd());
    if (!ParenRange.getEnd().isFileID() || EndLoc.isInvalid()) {
      // We can't display the parentheses, so just dig the
      // warning/error and return.
      Diag(Loc, DK);
      return;
    }
  
    Diag(Loc, DK)
      << FixItHint::CreateInsertion(ParenRange.getBegin(), "(")
      << FixItHint::CreateInsertion(EndLoc, ")");
  }
  
  static bool IsCommonTypo(tok::TokenKind ExpectedTok, const Token &Tok) {
    switch (ExpectedTok) {
    case tok::semi:
      return Tok.is(tok::colon) || Tok.is(tok::comma); // : or , for ;
    default: return false;
    }
  }
  
  bool Parser::ExpectAndConsume(tok::TokenKind ExpectedTok, unsigned DiagID,
                                StringRef Msg) {
    if (Tok.is(ExpectedTok) || Tok.is(tok::code_completion)) {
      ConsumeAnyToken();
      return false;
    }
  
    // Detect common single-character typos and resume.
    if (IsCommonTypo(ExpectedTok, Tok)) {
      SourceLocation Loc = Tok.getLocation();
      {
        DiagnosticBuilder DB = Diag(Loc, DiagID);
        DB << FixItHint::CreateReplacement(
                  SourceRange(Loc), tok::getPunctuatorSpelling(ExpectedTok));
        if (DiagID == diag::err_expected)
          DB << ExpectedTok;
        else if (DiagID == diag::err_expected_after)
          DB << Msg << ExpectedTok;
        else
          DB << Msg;
      }
  
      // Pretend there wasn't a problem.
      ConsumeAnyToken();
      return false;
    }
  
    SourceLocation EndLoc = PP.getLocForEndOfToken(PrevTokLocation);
    const char *Spelling = nullptr;
    if (EndLoc.isValid())
      Spelling = tok::getPunctuatorSpelling(ExpectedTok);
  
    DiagnosticBuilder DB =
        Spelling
            ? Diag(EndLoc, DiagID) << FixItHint::CreateInsertion(EndLoc, Spelling)
            : Diag(Tok, DiagID);
    if (DiagID == diag::err_expected)
      DB << ExpectedTok;
    else if (DiagID == diag::err_expected_after)
      DB << Msg << ExpectedTok;
    else
      DB << Msg;
  
    return true;
  }
  
  bool Parser::ExpectAndConsumeSemi(unsigned DiagID) {
    if (TryConsumeToken(tok::semi))
      return false;
  
    if (Tok.is(tok::code_completion)) {
      handleUnexpectedCodeCompletionToken();
      return false;
    }
  
    if ((Tok.is(tok::r_paren) || Tok.is(tok::r_square)) &&
        NextToken().is(tok::semi)) {
      Diag(Tok, diag::err_extraneous_token_before_semi)
        << PP.getSpelling(Tok)
        << FixItHint::CreateRemoval(Tok.getLocation());
      ConsumeAnyToken(); // The ')' or ']'.
      ConsumeToken(); // The ';'.
      return false;
    }
  
    return ExpectAndConsume(tok::semi, DiagID);
  }
  
  void Parser::ConsumeExtraSemi(ExtraSemiKind Kind, DeclSpec::TST TST) {
    if (!Tok.is(tok::semi)) return;
  
    bool HadMultipleSemis = false;
    SourceLocation StartLoc = Tok.getLocation();
    SourceLocation EndLoc = Tok.getLocation();
    ConsumeToken();
  
    while ((Tok.is(tok::semi) && !Tok.isAtStartOfLine())) {
      HadMultipleSemis = true;
      EndLoc = Tok.getLocation();
      ConsumeToken();
    }
  
    // C++11 allows extra semicolons at namespace scope, but not in any of the
    // other contexts.
    if (Kind == OutsideFunction && getLangOpts().CPlusPlus) {
      if (getLangOpts().CPlusPlus11)
        Diag(StartLoc, diag::warn_cxx98_compat_top_level_semi)
            << FixItHint::CreateRemoval(SourceRange(StartLoc, EndLoc));
      else
        Diag(StartLoc, diag::ext_extra_semi_cxx11)
            << FixItHint::CreateRemoval(SourceRange(StartLoc, EndLoc));
      return;
    }
  
    if (Kind != AfterMemberFunctionDefinition || HadMultipleSemis)
      Diag(StartLoc, diag::ext_extra_semi)
          << Kind << DeclSpec::getSpecifierName(TST,
                                      Actions.getASTContext().getPrintingPolicy())
          << FixItHint::CreateRemoval(SourceRange(StartLoc, EndLoc));
    else
      // A single semicolon is valid after a member function definition.
      Diag(StartLoc, diag::warn_extra_semi_after_mem_fn_def)
        << FixItHint::CreateRemoval(SourceRange(StartLoc, EndLoc));
  }
  
  bool Parser::expectIdentifier() {
    if (Tok.is(tok::identifier))
      return false;
    if (const auto *II = Tok.getIdentifierInfo()) {
      if (II->isCPlusPlusKeyword(getLangOpts())) {
        Diag(Tok, diag::err_expected_token_instead_of_objcxx_keyword)
            << tok::identifier << Tok.getIdentifierInfo();
        // Objective-C++: Recover by treating this keyword as a valid identifier.
        return false;
      }
    }
    Diag(Tok, diag::err_expected) << tok::identifier;
    return true;
  }
  
  void Parser::checkCompoundToken(SourceLocation FirstTokLoc,
                                  tok::TokenKind FirstTokKind, CompoundToken Op) {
    if (FirstTokLoc.isInvalid())
      return;
    SourceLocation SecondTokLoc = Tok.getLocation();
  
    // If either token is in a macro, we expect both tokens to come from the same
    // macro expansion.
    if ((FirstTokLoc.isMacroID() || SecondTokLoc.isMacroID()) &&
        PP.getSourceManager().getFileID(FirstTokLoc) !=
            PP.getSourceManager().getFileID(SecondTokLoc)) {
      Diag(FirstTokLoc, diag::warn_compound_token_split_by_macro)
          << (FirstTokKind == Tok.getKind()) << FirstTokKind << Tok.getKind()
          << static_cast<int>(Op) << SourceRange(FirstTokLoc);
      Diag(SecondTokLoc, diag::note_compound_token_split_second_token_here)
          << (FirstTokKind == Tok.getKind()) << Tok.getKind()
          << SourceRange(SecondTokLoc);
      return;
    }
  
    // We expect the tokens to abut.
    if (Tok.hasLeadingSpace() || Tok.isAtStartOfLine()) {
      SourceLocation SpaceLoc = PP.getLocForEndOfToken(FirstTokLoc);
      if (SpaceLoc.isInvalid())
        SpaceLoc = FirstTokLoc;
      Diag(SpaceLoc, diag::warn_compound_token_split_by_whitespace)
          << (FirstTokKind == Tok.getKind()) << FirstTokKind << Tok.getKind()
          << static_cast<int>(Op) << SourceRange(FirstTokLoc, SecondTokLoc);
      return;
    }
  }
  
  //===----------------------------------------------------------------------===//
  // Error recovery.
  //===----------------------------------------------------------------------===//
  
  static bool HasFlagsSet(Parser::SkipUntilFlags L, Parser::SkipUntilFlags R) {
    return (static_cast<unsigned>(L) & static_cast<unsigned>(R)) != 0;
  }
  
  /// SkipUntil - Read tokens until we get to the specified token, then consume
  /// it (unless no flag StopBeforeMatch).  Because we cannot guarantee that the
  /// token will ever occur, this skips to the next token, or to some likely
  /// good stopping point.  If StopAtSemi is true, skipping will stop at a ';'
  /// character.
  ///
  /// If SkipUntil finds the specified token, it returns true, otherwise it
  /// returns false.
  bool Parser::SkipUntil(ArrayRef<tok::TokenKind> Toks, SkipUntilFlags Flags) {
    // We always want this function to skip at least one token if the first token
    // isn't T and if not at EOF.
    bool isFirstTokenSkipped = true;
    while (true) {
      // If we found one of the tokens, stop and return true.
      for (unsigned i = 0, NumToks = Toks.size(); i != NumToks; ++i) {
        if (Tok.is(Toks[i])) {
          if (HasFlagsSet(Flags, StopBeforeMatch)) {
            // Noop, don't consume the token.
          } else {
            ConsumeAnyToken();
          }
          return true;
        }
      }
  
      // Important special case: The caller has given up and just wants us to
      // skip the rest of the file. Do this without recursing, since we can
      // get here precisely because the caller detected too much recursion.
      if (Toks.size() == 1 && Toks[0] == tok::eof &&
          !HasFlagsSet(Flags, StopAtSemi) &&
          !HasFlagsSet(Flags, StopAtCodeCompletion)) {
        while (Tok.isNot(tok::eof))
          ConsumeAnyToken();
        return true;
      }
  
      switch (Tok.getKind()) {
      case tok::eof:
        // Ran out of tokens.
        return false;
  
      case tok::annot_pragma_openmp:
      case tok::annot_attr_openmp:
      case tok::annot_pragma_openmp_end:
        // Stop before an OpenMP pragma boundary.
        if (OpenMPDirectiveParsing)
          return false;
        ConsumeAnnotationToken();
        break;
      case tok::annot_module_begin:
      case tok::annot_module_end:
      case tok::annot_module_include:
        // Stop before we change submodules. They generally indicate a "good"
        // place to pick up parsing again (except in the special case where
        // we're trying to skip to EOF).
        return false;
  
      case tok::code_completion:
        if (!HasFlagsSet(Flags, StopAtCodeCompletion))
          handleUnexpectedCodeCompletionToken();
        return false;
  
      case tok::l_paren:
        // Recursively skip properly-nested parens.
        ConsumeParen();
        if (HasFlagsSet(Flags, StopAtCodeCompletion))
          SkipUntil(tok::r_paren, StopAtCodeCompletion);
        else
          SkipUntil(tok::r_paren);
        break;
      case tok::l_square:
        // Recursively skip properly-nested square brackets.
        ConsumeBracket();
        if (HasFlagsSet(Flags, StopAtCodeCompletion))
          SkipUntil(tok::r_square, StopAtCodeCompletion);
        else
          SkipUntil(tok::r_square);
        break;
      case tok::l_brace:
        // Recursively skip properly-nested braces.
        ConsumeBrace();
        if (HasFlagsSet(Flags, StopAtCodeCompletion))
          SkipUntil(tok::r_brace, StopAtCodeCompletion);
        else
          SkipUntil(tok::r_brace);
        break;
      case tok::question:
        // Recursively skip ? ... : pairs; these function as brackets. But
        // still stop at a semicolon if requested.
        ConsumeToken();
        SkipUntil(tok::colon,
                  SkipUntilFlags(unsigned(Flags) &
                                 unsigned(StopAtCodeCompletion | StopAtSemi)));
        break;
  
      // Okay, we found a ']' or '}' or ')', which we think should be balanced.
      // Since the user wasn't looking for this token (if they were, it would
      // already be handled), this isn't balanced.  If there is a LHS token at a
      // higher level, we will assume that this matches the unbalanced token
      // and return it.  Otherwise, this is a spurious RHS token, which we skip.
      case tok::r_paren:
        if (ParenCount && !isFirstTokenSkipped)
          return false;  // Matches something.
        ConsumeParen();
        break;
      case tok::r_square:
        if (BracketCount && !isFirstTokenSkipped)
          return false;  // Matches something.
        ConsumeBracket();
        break;
      case tok::r_brace:
        if (BraceCount && !isFirstTokenSkipped)
          return false;  // Matches something.
        ConsumeBrace();
        break;
  
      case tok::semi:
        if (HasFlagsSet(Flags, StopAtSemi))
          return false;
        LLVM_FALLTHROUGH;
      default:
        // Skip this token.
        ConsumeAnyToken();
        break;
      }
      isFirstTokenSkipped = false;
    }
  }
  
  //===----------------------------------------------------------------------===//
  // Scope manipulation
  //===----------------------------------------------------------------------===//
  
  /// EnterScope - Start a new scope.
  void Parser::EnterScope(unsigned ScopeFlags) {
    if (NumCachedScopes) {
      Scope *N = ScopeCache[--NumCachedScopes];
      N->Init(getCurScope(), ScopeFlags);
      Actions.CurScope = N;
    } else {
      Actions.CurScope = new Scope(getCurScope(), ScopeFlags, Diags);
    }
  }
  
  /// ExitScope - Pop a scope off the scope stack.
  void Parser::ExitScope() {
    assert(getCurScope() && "Scope imbalance!");
  
    // Inform the actions module that this scope is going away if there are any
    // decls in it.
    Actions.ActOnPopScope(Tok.getLocation(), getCurScope());
  
    Scope *OldScope = getCurScope();
    Actions.CurScope = OldScope->getParent();
  
    if (NumCachedScopes == ScopeCacheSize)
      delete OldScope;
    else
      ScopeCache[NumCachedScopes++] = OldScope;
  }
  
  /// Set the flags for the current scope to ScopeFlags. If ManageFlags is false,
  /// this object does nothing.
  Parser::ParseScopeFlags::ParseScopeFlags(Parser *Self, unsigned ScopeFlags,
                                   bool ManageFlags)
    : CurScope(ManageFlags ? Self->getCurScope() : nullptr) {
    if (CurScope) {
      OldFlags = CurScope->getFlags();
      CurScope->setFlags(ScopeFlags);
    }
  }
  
  /// Restore the flags for the current scope to what they were before this
  /// object overrode them.
  Parser::ParseScopeFlags::~ParseScopeFlags() {
    if (CurScope)
      CurScope->setFlags(OldFlags);
  }
  
  
  //===----------------------------------------------------------------------===//
  // C99 6.9: External Definitions.
  //===----------------------------------------------------------------------===//
  
  Parser::~Parser() {
    // Clear out the parse-type-from-string callback.
    Actions.ParseTypeFromStringCallback = nullptr;
  
    // If we still have scopes active, delete the scope tree.
    delete getCurScope();
    Actions.CurScope = nullptr;
  
    // Free the scope cache.
    for (unsigned i = 0, e = NumCachedScopes; i != e; ++i)
      delete ScopeCache[i];
  
    resetPragmaHandlers();
  
    PP.removeCommentHandler(CommentSemaHandler.get());
  
    PP.clearCodeCompletionHandler();
  
    DestroyTemplateIds();
  }
  
  /// Initialize - Warm up the parser.
  ///
  void Parser::Initialize() {
    // Create the translation unit scope.  Install it as the current scope.
    assert(getCurScope() == nullptr && "A scope is already active?");
    EnterScope(Scope::DeclScope);
    Actions.ActOnTranslationUnitScope(getCurScope());
  
    // Initialization for Objective-C context sensitive keywords recognition.
    // Referenced in Parser::ParseObjCTypeQualifierList.
    if (getLangOpts().ObjC) {
      ObjCTypeQuals[objc_in] = &PP.getIdentifierTable().get("in");
      ObjCTypeQuals[objc_out] = &PP.getIdentifierTable().get("out");
      ObjCTypeQuals[objc_inout] = &PP.getIdentifierTable().get("inout");
      ObjCTypeQuals[objc_oneway] = &PP.getIdentifierTable().get("oneway");
      ObjCTypeQuals[objc_bycopy] = &PP.getIdentifierTable().get("bycopy");
      ObjCTypeQuals[objc_byref] = &PP.getIdentifierTable().get("byref");
      ObjCTypeQuals[objc_nonnull] = &PP.getIdentifierTable().get("nonnull");
      ObjCTypeQuals[objc_nullable] = &PP.getIdentifierTable().get("nullable");
      ObjCTypeQuals[objc_null_unspecified]
        = &PP.getIdentifierTable().get("null_unspecified");
    }
  
    Ident_instancetype = nullptr;
    Ident_final = nullptr;
    Ident_sealed = nullptr;
    Ident_abstract = nullptr;
    Ident_override = nullptr;
    Ident_GNU_final = nullptr;
    Ident_import = nullptr;
    Ident_module = nullptr;
  
    Ident_super = &PP.getIdentifierTable().get("super");
  
    Ident_vector = nullptr;
    Ident_bool = nullptr;
    Ident_Bool = nullptr;
    Ident_pixel = nullptr;
    if (getLangOpts().AltiVec || getLangOpts().ZVector) {
      Ident_vector = &PP.getIdentifierTable().get("vector");
      Ident_bool = &PP.getIdentifierTable().get("bool");
      Ident_Bool = &PP.getIdentifierTable().get("_Bool");
    }
    if (getLangOpts().AltiVec)
      Ident_pixel = &PP.getIdentifierTable().get("pixel");
  
    Ident_introduced = nullptr;
    Ident_deprecated = nullptr;
    Ident_obsoleted = nullptr;
    Ident_unavailable = nullptr;
    Ident_strict = nullptr;
    Ident_replacement = nullptr;
  
    Ident_language = Ident_defined_in = Ident_generated_declaration = nullptr;
  
    Ident__except = nullptr;
  
    Ident__exception_code = Ident__exception_info = nullptr;
    Ident__abnormal_termination = Ident___exception_code = nullptr;
    Ident___exception_info = Ident___abnormal_termination = nullptr;
    Ident_GetExceptionCode = Ident_GetExceptionInfo = nullptr;
    Ident_AbnormalTermination = nullptr;
  
    if(getLangOpts().Borland) {
      Ident__exception_info        = PP.getIdentifierInfo("_exception_info");
      Ident___exception_info       = PP.getIdentifierInfo("__exception_info");
      Ident_GetExceptionInfo       = PP.getIdentifierInfo("GetExceptionInformation");
      Ident__exception_code        = PP.getIdentifierInfo("_exception_code");
      Ident___exception_code       = PP.getIdentifierInfo("__exception_code");
      Ident_GetExceptionCode       = PP.getIdentifierInfo("GetExceptionCode");
      Ident__abnormal_termination  = PP.getIdentifierInfo("_abnormal_termination");
      Ident___abnormal_termination = PP.getIdentifierInfo("__abnormal_termination");
      Ident_AbnormalTermination    = PP.getIdentifierInfo("AbnormalTermination");
  
      PP.SetPoisonReason(Ident__exception_code,diag::err_seh___except_block);
      PP.SetPoisonReason(Ident___exception_code,diag::err_seh___except_block);
      PP.SetPoisonReason(Ident_GetExceptionCode,diag::err_seh___except_block);
      PP.SetPoisonReason(Ident__exception_info,diag::err_seh___except_filter);
      PP.SetPoisonReason(Ident___exception_info,diag::err_seh___except_filter);
      PP.SetPoisonReason(Ident_GetExceptionInfo,diag::err_seh___except_filter);
      PP.SetPoisonReason(Ident__abnormal_termination,diag::err_seh___finally_block);
      PP.SetPoisonReason(Ident___abnormal_termination,diag::err_seh___finally_block);
      PP.SetPoisonReason(Ident_AbnormalTermination,diag::err_seh___finally_block);
    }
  
    if (getLangOpts().CPlusPlusModules) {
      Ident_import = PP.getIdentifierInfo("import");
      Ident_module = PP.getIdentifierInfo("module");
    }
  
    Actions.Initialize();
  
    // Prime the lexer look-ahead.
    ConsumeToken();
  }
  
  void Parser::DestroyTemplateIds() {
    for (TemplateIdAnnotation *Id : TemplateIds)
      Id->Destroy();
    TemplateIds.clear();
  }
  
  /// Parse the first top-level declaration in a translation unit.
  ///
  ///   translation-unit:
  /// [C]     external-declaration
  /// [C]     translation-unit external-declaration
  /// [C++]   top-level-declaration-seq[opt]
  /// [C++20] global-module-fragment[opt] module-declaration
  ///                 top-level-declaration-seq[opt] private-module-fragment[opt]
  ///
  /// Note that in C, it is an error if there is no first declaration.
  bool Parser::ParseFirstTopLevelDecl(DeclGroupPtrTy &Result,
                                      Sema::ModuleImportState &ImportState) {
    Actions.ActOnStartOfTranslationUnit();
  
    // For C++20 modules, a module decl must be the first in the TU.  We also
    // need to track module imports.
    ImportState = Sema::ModuleImportState::FirstDecl;
    bool NoTopLevelDecls = ParseTopLevelDecl(Result, ImportState);
  
    // C11 6.9p1 says translation units must have at least one top-level
    // declaration. C++ doesn't have this restriction. We also don't want to
    // complain if we have a precompiled header, although technically if the PCH
    // is empty we should still emit the (pedantic) diagnostic.
    // If the main file is a header, we're only pretending it's a TU; don't warn.
    if (NoTopLevelDecls && !Actions.getASTContext().getExternalSource() &&
        !getLangOpts().CPlusPlus && !getLangOpts().IsHeaderFile)
      Diag(diag::ext_empty_translation_unit);
  
    return NoTopLevelDecls;
  }
  
  /// ParseTopLevelDecl - Parse one top-level declaration, return whatever the
  /// action tells us to.  This returns true if the EOF was encountered.
  ///
  ///   top-level-declaration:
  ///           declaration
  /// [C++20]   module-import-declaration
  bool Parser::ParseTopLevelDecl(DeclGroupPtrTy &Result,
                                 Sema::ModuleImportState &ImportState) {
    DestroyTemplateIdAnnotationsRAIIObj CleanupRAII(*this);
  
    // Skip over the EOF token, flagging end of previous input for incremental
    // processing
    if (PP.isIncrementalProcessingEnabled() && Tok.is(tok::eof))
      ConsumeToken();
  
    Result = nullptr;
    switch (Tok.getKind()) {
    case tok::annot_pragma_unused:
      HandlePragmaUnused();
      return false;
  
    case tok::kw_export:
      switch (NextToken().getKind()) {
      case tok::kw_module:
        goto module_decl;
  
      // Note: no need to handle kw_import here. We only form kw_import under
      // the Modules TS, and in that case 'export import' is parsed as an
      // export-declaration containing an import-declaration.
  
      // Recognize context-sensitive C++20 'export module' and 'export import'
      // declarations.
      case tok::identifier: {
        IdentifierInfo *II = NextToken().getIdentifierInfo();
        if ((II == Ident_module || II == Ident_import) &&
            GetLookAheadToken(2).isNot(tok::coloncolon)) {
          if (II == Ident_module)
            goto module_decl;
          else
            goto import_decl;
        }
        break;
      }
  
      default:
        break;
      }
      break;
  
    case tok::kw_module:
    module_decl:
      Result = ParseModuleDecl(ImportState);
      return false;
  
    case tok::kw_import:
    import_decl: {
      Decl *ImportDecl = ParseModuleImport(SourceLocation(), ImportState);
      Result = Actions.ConvertDeclToDeclGroup(ImportDecl);
      return false;
    }
  
    case tok::annot_module_include:
      Actions.ActOnModuleInclude(Tok.getLocation(),
                                 reinterpret_cast<Module *>(
                                     Tok.getAnnotationValue()));
      ConsumeAnnotationToken();
      return false;
  
    case tok::annot_module_begin:
      Actions.ActOnModuleBegin(Tok.getLocation(), reinterpret_cast<Module *>(
                                                      Tok.getAnnotationValue()));
      ConsumeAnnotationToken();
      ImportState = Sema::ModuleImportState::NotACXX20Module;
      return false;
  
    case tok::annot_module_end:
      Actions.ActOnModuleEnd(Tok.getLocation(), reinterpret_cast<Module *>(
                                                    Tok.getAnnotationValue()));
      ConsumeAnnotationToken();
      ImportState = Sema::ModuleImportState::NotACXX20Module;
      return false;
  
    case tok::eof:
      // Check whether -fmax-tokens= was reached.
      if (PP.getMaxTokens() != 0 && PP.getTokenCount() > PP.getMaxTokens()) {
        PP.Diag(Tok.getLocation(), diag::warn_max_tokens_total)
            << PP.getTokenCount() << PP.getMaxTokens();
        SourceLocation OverrideLoc = PP.getMaxTokensOverrideLoc();
        if (OverrideLoc.isValid()) {
          PP.Diag(OverrideLoc, diag::note_max_tokens_total_override);
        }
      }
  
      // Late template parsing can begin.
      Actions.SetLateTemplateParser(LateTemplateParserCallback, nullptr, this);
      if (!PP.isIncrementalProcessingEnabled())
        Actions.ActOnEndOfTranslationUnit();
      //else don't tell Sema that we ended parsing: more input might come.
      return true;
  
    case tok::identifier:
      // C++2a [basic.link]p3:
      //   A token sequence beginning with 'export[opt] module' or
      //   'export[opt] import' and not immediately followed by '::'
      //   is never interpreted as the declaration of a top-level-declaration.
      if ((Tok.getIdentifierInfo() == Ident_module ||
           Tok.getIdentifierInfo() == Ident_import) &&
          NextToken().isNot(tok::coloncolon)) {
        if (Tok.getIdentifierInfo() == Ident_module)
          goto module_decl;
        else
          goto import_decl;
      }
      break;
  
    default:
      break;
    }
  
    ParsedAttributesWithRange attrs(AttrFactory);
    MaybeParseCXX11Attributes(attrs);
  
    Result = ParseExternalDeclaration(attrs);
    // An empty Result might mean a line with ';' or some parsing error, ignore
    // it.
    if (Result) {
      if (ImportState == Sema::ModuleImportState::FirstDecl)
        // First decl was not modular.
        ImportState = Sema::ModuleImportState::NotACXX20Module;
      else if (ImportState == Sema::ModuleImportState::ImportAllowed)
        // Non-imports disallow further imports.
        ImportState = Sema::ModuleImportState::ImportFinished;
    }
    return false;
  }
  
  /// ParseExternalDeclaration:
  ///
  ///       external-declaration: [C99 6.9], declaration: [C++ dcl.dcl]
  ///         function-definition
  ///         declaration
  /// [GNU]   asm-definition
  /// [GNU]   __extension__ external-declaration
  /// [OBJC]  objc-class-definition
  /// [OBJC]  objc-class-declaration
  /// [OBJC]  objc-alias-declaration
  /// [OBJC]  objc-protocol-definition
  /// [OBJC]  objc-method-definition
  /// [OBJC]  @end
  /// [C++]   linkage-specification
  /// [GNU] asm-definition:
  ///         simple-asm-expr ';'
  /// [C++11] empty-declaration
  /// [C++11] attribute-declaration
  ///
  /// [C++11] empty-declaration:
  ///           ';'
  ///
  /// [C++0x/GNU] 'extern' 'template' declaration
  ///
  /// [Modules-TS] module-import-declaration
  ///
  Parser::DeclGroupPtrTy
  Parser::ParseExternalDeclaration(ParsedAttributesWithRange &attrs,
                                   ParsingDeclSpec *DS) {
    DestroyTemplateIdAnnotationsRAIIObj CleanupRAII(*this);
    ParenBraceBracketBalancer BalancerRAIIObj(*this);
  
    if (PP.isCodeCompletionReached()) {
      cutOffParsing();
      return nullptr;
    }
  
    Decl *SingleDecl = nullptr;
    switch (Tok.getKind()) {
    case tok::annot_pragma_vis:
      HandlePragmaVisibility();
      return nullptr;
    case tok::annot_pragma_pack:
      HandlePragmaPack();
      return nullptr;
    case tok::annot_pragma_msstruct:
      HandlePragmaMSStruct();
      return nullptr;
    case tok::annot_pragma_align:
      HandlePragmaAlign();
      return nullptr;
    case tok::annot_pragma_weak:
      HandlePragmaWeak();
      return nullptr;
    case tok::annot_pragma_weakalias:
      HandlePragmaWeakAlias();
      return nullptr;
    case tok::annot_pragma_redefine_extname:
      HandlePragmaRedefineExtname();
      return nullptr;
    case tok::annot_pragma_fp_contract:
      HandlePragmaFPContract();
      return nullptr;
    case tok::annot_pragma_fenv_access:
    case tok::annot_pragma_fenv_access_ms:
      HandlePragmaFEnvAccess();
      return nullptr;
    case tok::annot_pragma_fenv_round:
      HandlePragmaFEnvRound();
      return nullptr;
    case tok::annot_pragma_float_control:
      HandlePragmaFloatControl();
      return nullptr;
    case tok::annot_pragma_fp:
      HandlePragmaFP();
      break;
    case tok::annot_pragma_opencl_extension:
      HandlePragmaOpenCLExtension();
      return nullptr;
    case tok::annot_attr_openmp:
    case tok::annot_pragma_openmp: {
      AccessSpecifier AS = AS_none;
      return ParseOpenMPDeclarativeDirectiveWithExtDecl(AS, attrs);
    }
    case tok::annot_pragma_ms_pointers_to_members:
      HandlePragmaMSPointersToMembers();
      return nullptr;
    case tok::annot_pragma_ms_vtordisp:
      HandlePragmaMSVtorDisp();
      return nullptr;
    case tok::annot_pragma_ms_pragma:
      HandlePragmaMSPragma();
      return nullptr;
    case tok::annot_pragma_dump:
      HandlePragmaDump();
      return nullptr;
    case tok::annot_pragma_attribute:
      HandlePragmaAttribute();
      return nullptr;
    case tok::semi:
      // Either a C++11 empty-declaration or attribute-declaration.
      SingleDecl =
          Actions.ActOnEmptyDeclaration(getCurScope(), attrs, Tok.getLocation());
      ConsumeExtraSemi(OutsideFunction);
      break;
    case tok::r_brace:
      Diag(Tok, diag::err_extraneous_closing_brace);
      ConsumeBrace();
      return nullptr;
    case tok::eof:
      Diag(Tok, diag::err_expected_external_declaration);
      return nullptr;
    case tok::kw___extension__: {
      // __extension__ silences extension warnings in the subexpression.
      ExtensionRAIIObject O(Diags);  // Use RAII to do this.
      ConsumeToken();
      return ParseExternalDeclaration(attrs);
    }
    case tok::kw_asm: {
      ProhibitAttributes(attrs);
  
      SourceLocation StartLoc = Tok.getLocation();
      SourceLocation EndLoc;
  
      ExprResult Result(ParseSimpleAsm(/*ForAsmLabel*/ false, &EndLoc));
  
      // Check if GNU-style InlineAsm is disabled.
      // Empty asm string is allowed because it will not introduce
      // any assembly code.
      if (!(getLangOpts().GNUAsm || Result.isInvalid())) {
        const auto *SL = cast<StringLiteral>(Result.get());
        if (!SL->getString().trim().empty())
          Diag(StartLoc, diag::err_gnu_inline_asm_disabled);
      }
  
      ExpectAndConsume(tok::semi, diag::err_expected_after,
                       "top-level asm block");
  
      if (Result.isInvalid())
        return nullptr;
      SingleDecl = Actions.ActOnFileScopeAsmDecl(Result.get(), StartLoc, EndLoc);
      break;
    }
    case tok::at:
      return ParseObjCAtDirectives(attrs);
    case tok::minus:
    case tok::plus:
      if (!getLangOpts().ObjC) {
        Diag(Tok, diag::err_expected_external_declaration);
        ConsumeToken();
        return nullptr;
      }
      SingleDecl = ParseObjCMethodDefinition();
      break;
    case tok::code_completion:
      cutOffParsing();
      if (CurParsedObjCImpl) {
        // Code-complete Objective-C methods even without leading '-'/'+' prefix.
        Actions.CodeCompleteObjCMethodDecl(getCurScope(),
                                           /*IsInstanceMethod=*/None,
                                           /*ReturnType=*/nullptr);
      }
      Actions.CodeCompleteOrdinaryName(
          getCurScope(),
          CurParsedObjCImpl ? Sema::PCC_ObjCImplementation : Sema::PCC_Namespace);
      return nullptr;
    case tok::kw_import: {
      Sema::ModuleImportState IS = Sema::ModuleImportState::NotACXX20Module;
      if (getLangOpts().CPlusPlusModules) {
        llvm_unreachable("not expecting a c++20 import here");
        ProhibitAttributes(attrs);
      }
      SingleDecl = ParseModuleImport(SourceLocation(), IS);
    } break;
    case tok::kw_export:
      if (getLangOpts().CPlusPlusModules || getLangOpts().ModulesTS) {
        ProhibitAttributes(attrs);
        SingleDecl = ParseExportDeclaration();
        break;
      }
      // This must be 'export template'. Parse it so we can diagnose our lack
      // of support.
      LLVM_FALLTHROUGH;
    case tok::kw_using:
    case tok::kw_namespace:
    case tok::kw_typedef:
    case tok::kw_template:
    case tok::kw_static_assert:
    case tok::kw__Static_assert:
      // A function definition cannot start with any of these keywords.
      {
        SourceLocation DeclEnd;
        return ParseDeclaration(DeclaratorContext::File, DeclEnd, attrs);
      }
  
    case tok::kw_static:
      // Parse (then ignore) 'static' prior to a template instantiation. This is
      // a GCC extension that we intentionally do not support.
      if (getLangOpts().CPlusPlus && NextToken().is(tok::kw_template)) {
        Diag(ConsumeToken(), diag::warn_static_inline_explicit_inst_ignored)
          << 0;
        SourceLocation DeclEnd;
        return ParseDeclaration(DeclaratorContext::File, DeclEnd, attrs);
      }
      goto dont_know;
  
    case tok::kw_inline:
      if (getLangOpts().CPlusPlus) {
        tok::TokenKind NextKind = NextToken().getKind();
  
        // Inline namespaces. Allowed as an extension even in C++03.
        if (NextKind == tok::kw_namespace) {
          SourceLocation DeclEnd;
          return ParseDeclaration(DeclaratorContext::File, DeclEnd, attrs);
        }
  
        // Parse (then ignore) 'inline' prior to a template instantiation. This is
        // a GCC extension that we intentionally do not support.
        if (NextKind == tok::kw_template) {
          Diag(ConsumeToken(), diag::warn_static_inline_explicit_inst_ignored)
            << 1;
          SourceLocation DeclEnd;
          return ParseDeclaration(DeclaratorContext::File, DeclEnd, attrs);
        }
      }
      goto dont_know;
  
    case tok::kw_extern:
      if (getLangOpts().CPlusPlus && NextToken().is(tok::kw_template)) {
        // Extern templates
        SourceLocation ExternLoc = ConsumeToken();
        SourceLocation TemplateLoc = ConsumeToken();
        Diag(ExternLoc, getLangOpts().CPlusPlus11 ?
               diag::warn_cxx98_compat_extern_template :
               diag::ext_extern_template) << SourceRange(ExternLoc, TemplateLoc);
        SourceLocation DeclEnd;
        return Actions.ConvertDeclToDeclGroup(ParseExplicitInstantiation(
            DeclaratorContext::File, ExternLoc, TemplateLoc, DeclEnd, attrs));
      }
      goto dont_know;
  
    case tok::kw___if_exists:
    case tok::kw___if_not_exists:
      ParseMicrosoftIfExistsExternalDeclaration();
      return nullptr;
  
    case tok::kw_module:
      Diag(Tok, diag::err_unexpected_module_decl);
      SkipUntil(tok::semi);
      return nullptr;
  
    default:
    dont_know:
      if (Tok.isEditorPlaceholder()) {
        ConsumeToken();
        return nullptr;
      }
      // We can't tell whether this is a function-definition or declaration yet.
      return ParseDeclarationOrFunctionDefinition(attrs, DS);
    }
  
    // This routine returns a DeclGroup, if the thing we parsed only contains a
    // single decl, convert it now.
    return Actions.ConvertDeclToDeclGroup(SingleDecl);
  }
  
  /// Determine whether the current token, if it occurs after a
  /// declarator, continues a declaration or declaration list.
  bool Parser::isDeclarationAfterDeclarator() {
    // Check for '= delete' or '= default'
    if (getLangOpts().CPlusPlus && Tok.is(tok::equal)) {
      const Token &KW = NextToken();
      if (KW.is(tok::kw_default) || KW.is(tok::kw_delete))
        return false;
    }
  
    return Tok.is(tok::equal) ||      // int X()=  -> not a function def
      Tok.is(tok::comma) ||           // int X(),  -> not a function def
      Tok.is(tok::semi)  ||           // int X();  -> not a function def
      Tok.is(tok::kw_asm) ||          // int X() __asm__ -> not a function def
      Tok.is(tok::kw___attribute) ||  // int X() __attr__ -> not a function def
      (getLangOpts().CPlusPlus &&
       Tok.is(tok::l_paren));         // int X(0) -> not a function def [C++]
  }
  
  /// Determine whether the current token, if it occurs after a
  /// declarator, indicates the start of a function definition.
  bool Parser::isStartOfFunctionDefinition(const ParsingDeclarator &Declarator) {
    assert(Declarator.isFunctionDeclarator() && "Isn't a function declarator");
    if (Tok.is(tok::l_brace))   // int X() {}
      return true;
  
    // Handle K&R C argument lists: int X(f) int f; {}
    if (!getLangOpts().CPlusPlus &&
        Declarator.getFunctionTypeInfo().isKNRPrototype())
      return isDeclarationSpecifier();
  
    if (getLangOpts().CPlusPlus && Tok.is(tok::equal)) {
      const Token &KW = NextToken();
      return KW.is(tok::kw_default) || KW.is(tok::kw_delete);
    }
  
    return Tok.is(tok::colon) ||         // X() : Base() {} (used for ctors)
           Tok.is(tok::kw_try);          // X() try { ... }
  }
  
  /// Parse either a function-definition or a declaration.  We can't tell which
  /// we have until we read up to the compound-statement in function-definition.
  /// TemplateParams, if non-NULL, provides the template parameters when we're
  /// parsing a C++ template-declaration.
  ///
  ///       function-definition: [C99 6.9.1]
  ///         decl-specs      declarator declaration-list[opt] compound-statement
  /// [C90] function-definition: [C99 6.7.1] - implicit int result
  /// [C90]   decl-specs[opt] declarator declaration-list[opt] compound-statement
  ///
  ///       declaration: [C99 6.7]
  ///         declaration-specifiers init-declarator-list[opt] ';'
  /// [!C99]  init-declarator-list ';'                   [TODO: warn in c99 mode]
  /// [OMP]   threadprivate-directive
  /// [OMP]   allocate-directive                         [TODO]
  ///
  Parser::DeclGroupPtrTy
  Parser::ParseDeclOrFunctionDefInternal(ParsedAttributesWithRange &attrs,
                                         ParsingDeclSpec &DS,
                                         AccessSpecifier AS) {
    MaybeParseMicrosoftAttributes(DS.getAttributes());
    // Parse the common declaration-specifiers piece.
    ParseDeclarationSpecifiers(DS, ParsedTemplateInfo(), AS,
                               DeclSpecContext::DSC_top_level);
  
    // If we had a free-standing type definition with a missing semicolon, we
    // may get this far before the problem becomes obvious.
    if (DS.hasTagDefinition() && DiagnoseMissingSemiAfterTagDefinition(
                                     DS, AS, DeclSpecContext::DSC_top_level))
      return nullptr;
  
    // C99 6.7.2.3p6: Handle "struct-or-union identifier;", "enum { X };"
    // declaration-specifiers init-declarator-list[opt] ';'
    if (Tok.is(tok::semi)) {
      auto LengthOfTSTToken = [](DeclSpec::TST TKind) {
        assert(DeclSpec::isDeclRep(TKind));
        switch(TKind) {
        case DeclSpec::TST_class:
          return 5;
        case DeclSpec::TST_struct:
          return 6;
        case DeclSpec::TST_union:
          return 5;
        case DeclSpec::TST_enum:
          return 4;
        case DeclSpec::TST_interface:
          return 9;
        default:
          llvm_unreachable("we only expect to get the length of the class/struct/union/enum");
        }
  
      };
      // Suggest correct location to fix '[[attrib]] struct' to 'struct [[attrib]]'
      SourceLocation CorrectLocationForAttributes =
          DeclSpec::isDeclRep(DS.getTypeSpecType())
              ? DS.getTypeSpecTypeLoc().getLocWithOffset(
                    LengthOfTSTToken(DS.getTypeSpecType()))
              : SourceLocation();
      ProhibitAttributes(attrs, CorrectLocationForAttributes);
      ConsumeToken();
      RecordDecl *AnonRecord = nullptr;
      Decl *TheDecl = Actions.ParsedFreeStandingDeclSpec(getCurScope(), AS_none,
                                                         DS, AnonRecord);
      DS.complete(TheDecl);
      if (AnonRecord) {
        Decl* decls[] = {AnonRecord, TheDecl};
        return Actions.BuildDeclaratorGroup(decls);
      }
      return Actions.ConvertDeclToDeclGroup(TheDecl);
    }
  
    DS.takeAttributesFrom(attrs);
  
    // ObjC2 allows prefix attributes on class interfaces and protocols.
    // FIXME: This still needs better diagnostics. We should only accept
    // attributes here, no types, etc.
    if (getLangOpts().ObjC && Tok.is(tok::at)) {
      SourceLocation AtLoc = ConsumeToken(); // the "@"
      if (!Tok.isObjCAtKeyword(tok::objc_interface) &&
          !Tok.isObjCAtKeyword(tok::objc_protocol) &&
          !Tok.isObjCAtKeyword(tok::objc_implementation)) {
        Diag(Tok, diag::err_objc_unexpected_attr);
        SkipUntil(tok::semi);
        return nullptr;
      }
  
      DS.abort();
  
      const char *PrevSpec = nullptr;
      unsigned DiagID;
      if (DS.SetTypeSpecType(DeclSpec::TST_unspecified, AtLoc, PrevSpec, DiagID,
                             Actions.getASTContext().getPrintingPolicy()))
        Diag(AtLoc, DiagID) << PrevSpec;
  
      if (Tok.isObjCAtKeyword(tok::objc_protocol))
        return ParseObjCAtProtocolDeclaration(AtLoc, DS.getAttributes());
  
      if (Tok.isObjCAtKeyword(tok::objc_implementation))
        return ParseObjCAtImplementationDeclaration(AtLoc, DS.getAttributes());
  
      return Actions.ConvertDeclToDeclGroup(
              ParseObjCAtInterfaceDeclaration(AtLoc, DS.getAttributes()));
    }
  
    // If the declspec consisted only of 'extern' and we have a string
    // literal following it, this must be a C++ linkage specifier like
    // 'extern "C"'.
    if (getLangOpts().CPlusPlus && isTokenStringLiteral() &&
        DS.getStorageClassSpec() == DeclSpec::SCS_extern &&
        DS.getParsedSpecifiers() == DeclSpec::PQ_StorageClassSpecifier) {
      Decl *TheDecl = ParseLinkage(DS, DeclaratorContext::File);
      return Actions.ConvertDeclToDeclGroup(TheDecl);
    }
  
    return ParseDeclGroup(DS, DeclaratorContext::File);
  }
  
  Parser::DeclGroupPtrTy
  Parser::ParseDeclarationOrFunctionDefinition(ParsedAttributesWithRange &attrs,
                                               ParsingDeclSpec *DS,
                                               AccessSpecifier AS) {
    if (DS) {
      return ParseDeclOrFunctionDefInternal(attrs, *DS, AS);
    } else {
      ParsingDeclSpec PDS(*this);
      // Must temporarily exit the objective-c container scope for
      // parsing c constructs and re-enter objc container scope
      // afterwards.
      ObjCDeclContextSwitch ObjCDC(*this);
  
      return ParseDeclOrFunctionDefInternal(attrs, PDS, AS);
    }
  }
  
  /// ParseFunctionDefinition - We parsed and verified that the specified
  /// Declarator is well formed.  If this is a K&R-style function, read the
  /// parameters declaration-list, then start the compound-statement.
  ///
  ///       function-definition: [C99 6.9.1]
  ///         decl-specs      declarator declaration-list[opt] compound-statement
  /// [C90] function-definition: [C99 6.7.1] - implicit int result
  /// [C90]   decl-specs[opt] declarator declaration-list[opt] compound-statement
  /// [C++] function-definition: [C++ 8.4]
  ///         decl-specifier-seq[opt] declarator ctor-initializer[opt]
  ///         function-body
  /// [C++] function-definition: [C++ 8.4]
  ///         decl-specifier-seq[opt] declarator function-try-block
  ///
  Decl *Parser::ParseFunctionDefinition(ParsingDeclarator &D,
                                        const ParsedTemplateInfo &TemplateInfo,
                                        LateParsedAttrList *LateParsedAttrs) {
    // Poison SEH identifiers so they are flagged as illegal in function bodies.
    PoisonSEHIdentifiersRAIIObject PoisonSEHIdentifiers(*this, true);
    const DeclaratorChunk::FunctionTypeInfo &FTI = D.getFunctionTypeInfo();
    TemplateParameterDepthRAII CurTemplateDepthTracker(TemplateParameterDepth);
  
    // If this is C90 and the declspecs were completely missing, fudge in an
    // implicit int.  We do this here because this is the only place where
    // declaration-specifiers are completely optional in the grammar.
    if (getLangOpts().ImplicitInt && D.getDeclSpec().isEmpty()) {
      const char *PrevSpec;
      unsigned DiagID;
      const PrintingPolicy &Policy = Actions.getASTContext().getPrintingPolicy();
      D.getMutableDeclSpec().SetTypeSpecType(DeclSpec::TST_int,
                                             D.getIdentifierLoc(),
                                             PrevSpec, DiagID,
                                             Policy);
      D.SetRangeBegin(D.getDeclSpec().getSourceRange().getBegin());
    }
  
    // If this declaration was formed with a K&R-style identifier list for the
    // arguments, parse declarations for all of the args next.
    // int foo(a,b) int a; float b; {}
    if (FTI.isKNRPrototype())
      ParseKNRParamDeclarations(D);
  
    // We should have either an opening brace or, in a C++ constructor,
    // we may have a colon.
    if (Tok.isNot(tok::l_brace) &&
        (!getLangOpts().CPlusPlus ||
         (Tok.isNot(tok::colon) && Tok.isNot(tok::kw_try) &&
          Tok.isNot(tok::equal)))) {
      Diag(Tok, diag::err_expected_fn_body);
  
      // Skip over garbage, until we get to '{'.  Don't eat the '{'.
      SkipUntil(tok::l_brace, StopAtSemi | StopBeforeMatch);
  
      // If we didn't find the '{', bail out.
      if (Tok.isNot(tok::l_brace))
        return nullptr;
    }
  
    // Check to make sure that any normal attributes are allowed to be on
    // a definition.  Late parsed attributes are checked at the end.
    if (Tok.isNot(tok::equal)) {
      for (const ParsedAttr &AL : D.getAttributes())
        if (AL.isKnownToGCC() && !AL.isStandardAttributeSyntax())
          Diag(AL.getLoc(), diag::warn_attribute_on_function_definition) << AL;
    }
  
    // In delayed template parsing mode, for function template we consume the
    // tokens and store them for late parsing at the end of the translation unit.
    if (getLangOpts().DelayedTemplateParsing && Tok.isNot(tok::equal) &&
        TemplateInfo.Kind == ParsedTemplateInfo::Template &&
        Actions.canDelayFunctionBody(D)) {
      MultiTemplateParamsArg TemplateParameterLists(*TemplateInfo.TemplateParams);
  
      ParseScope BodyScope(this, Scope::FnScope | Scope::DeclScope |
                                     Scope::CompoundStmtScope);
      Scope *ParentScope = getCurScope()->getParent();
  
      D.setFunctionDefinitionKind(FunctionDefinitionKind::Definition);
      Decl *DP = Actions.HandleDeclarator(ParentScope, D,
                                          TemplateParameterLists);
      D.complete(DP);
      D.getMutableDeclSpec().abort();
  
      if (SkipFunctionBodies && (!DP || Actions.canSkipFunctionBody(DP)) &&
          trySkippingFunctionBody()) {
        BodyScope.Exit();
        return Actions.ActOnSkippedFunctionBody(DP);
      }
  
      CachedTokens Toks;
      LexTemplateFunctionForLateParsing(Toks);
  
      if (DP) {
        FunctionDecl *FnD = DP->getAsFunction();
        Actions.CheckForFunctionRedefinition(FnD);
        Actions.MarkAsLateParsedTemplate(FnD, DP, Toks);
      }
      return DP;
    }
    else if (CurParsedObjCImpl &&
             !TemplateInfo.TemplateParams &&
             (Tok.is(tok::l_brace) || Tok.is(tok::kw_try) ||
              Tok.is(tok::colon)) &&
        Actions.CurContext->isTranslationUnit()) {
      ParseScope BodyScope(this, Scope::FnScope | Scope::DeclScope |
                                     Scope::CompoundStmtScope);
      Scope *ParentScope = getCurScope()->getParent();
  
      D.setFunctionDefinitionKind(FunctionDefinitionKind::Definition);
      Decl *FuncDecl = Actions.HandleDeclarator(ParentScope, D,
                                                MultiTemplateParamsArg());
      D.complete(FuncDecl);
      D.getMutableDeclSpec().abort();
      if (FuncDecl) {
        // Consume the tokens and store them for later parsing.
        StashAwayMethodOrFunctionBodyTokens(FuncDecl);
        CurParsedObjCImpl->HasCFunction = true;
        return FuncDecl;
      }
      // FIXME: Should we really fall through here?
    }
  
    // Enter a scope for the function body.
    ParseScope BodyScope(this, Scope::FnScope | Scope::DeclScope |
                                   Scope::CompoundStmtScope);
  
    // Tell the actions module that we have entered a function definition with the
    // specified Declarator for the function.
    Sema::SkipBodyInfo SkipBody;
    Decl *Res = Actions.ActOnStartOfFunctionDef(getCurScope(), D,
                                                TemplateInfo.TemplateParams
                                                    ? *TemplateInfo.TemplateParams
                                                    : MultiTemplateParamsArg(),
                                                &SkipBody);
  
    if (SkipBody.ShouldSkip) {
      SkipFunctionBody();
      return Res;
    }
  
    // Break out of the ParsingDeclarator context before we parse the body.
    D.complete(Res);
  
    // Break out of the ParsingDeclSpec context, too.  This const_cast is
    // safe because we're always the sole owner.
    D.getMutableDeclSpec().abort();
  
    // With abbreviated function templates - we need to explicitly add depth to
    // account for the implicit template parameter list induced by the template.
    if (auto *Template = dyn_cast_or_null<FunctionTemplateDecl>(Res))
      if (Template->isAbbreviated() &&
          Template->getTemplateParameters()->getParam(0)->isImplicit())
        // First template parameter is implicit - meaning no explicit template
        // parameter list was specified.
        CurTemplateDepthTracker.addDepth(1);
  
    if (TryConsumeToken(tok::equal)) {
      assert(getLangOpts().CPlusPlus && "Only C++ function definitions have '='");
  
      bool Delete = false;
      SourceLocation KWLoc;
      if (TryConsumeToken(tok::kw_delete, KWLoc)) {
        Diag(KWLoc, getLangOpts().CPlusPlus11
                        ? diag::warn_cxx98_compat_defaulted_deleted_function
                        : diag::ext_defaulted_deleted_function)
          << 1 /* deleted */;
        Actions.SetDeclDeleted(Res, KWLoc);
        Delete = true;
      } else if (TryConsumeToken(tok::kw_default, KWLoc)) {
        Diag(KWLoc, getLangOpts().CPlusPlus11
                        ? diag::warn_cxx98_compat_defaulted_deleted_function
                        : diag::ext_defaulted_deleted_function)
          << 0 /* defaulted */;
        Actions.SetDeclDefaulted(Res, KWLoc);
      } else {
        llvm_unreachable("function definition after = not 'delete' or 'default'");
      }
  
      if (Tok.is(tok::comma)) {
        Diag(KWLoc, diag::err_default_delete_in_multiple_declaration)
          << Delete;
        SkipUntil(tok::semi);
      } else if (ExpectAndConsume(tok::semi, diag::err_expected_after,
                                  Delete ? "delete" : "default")) {
        SkipUntil(tok::semi);
      }
  
      Stmt *GeneratedBody = Res ? Res->getBody() : nullptr;
      Actions.ActOnFinishFunctionBody(Res, GeneratedBody, false);
      return Res;
    }
  
    if (SkipFunctionBodies && (!Res || Actions.canSkipFunctionBody(Res)) &&
        trySkippingFunctionBody()) {
      BodyScope.Exit();
      Actions.ActOnSkippedFunctionBody(Res);
      return Actions.ActOnFinishFunctionBody(Res, nullptr, false);
    }
  
    if (Tok.is(tok::kw_try))
      return ParseFunctionTryBlock(Res, BodyScope);
  
    // If we have a colon, then we're probably parsing a C++
    // ctor-initializer.
    if (Tok.is(tok::colon)) {
      ParseConstructorInitializer(Res);
  
      // Recover from error.
      if (!Tok.is(tok::l_brace)) {
        BodyScope.Exit();
        Actions.ActOnFinishFunctionBody(Res, nullptr);
        return Res;
      }
    } else
      Actions.ActOnDefaultCtorInitializers(Res);
  
    // Late attributes are parsed in the same scope as the function body.
    if (LateParsedAttrs)
      ParseLexedAttributeList(*LateParsedAttrs, Res, false, true);
  
    return ParseFunctionStatementBody(Res, BodyScope);
  }
  
  void Parser::SkipFunctionBody() {
    if (Tok.is(tok::equal)) {
      SkipUntil(tok::semi);
      return;
    }
  
    bool IsFunctionTryBlock = Tok.is(tok::kw_try);
    if (IsFunctionTryBlock)
      ConsumeToken();
  
    CachedTokens Skipped;
    if (ConsumeAndStoreFunctionPrologue(Skipped))
      SkipMalformedDecl();
    else {
      SkipUntil(tok::r_brace);
      while (IsFunctionTryBlock && Tok.is(tok::kw_catch)) {
        SkipUntil(tok::l_brace);
        SkipUntil(tok::r_brace);
      }
    }
  }
  
  /// ParseKNRParamDeclarations - Parse 'declaration-list[opt]' which provides
  /// types for a function with a K&R-style identifier list for arguments.
  void Parser::ParseKNRParamDeclarations(Declarator &D) {
    // We know that the top-level of this declarator is a function.
    DeclaratorChunk::FunctionTypeInfo &FTI = D.getFunctionTypeInfo();
  
    // Enter function-declaration scope, limiting any declarators to the
    // function prototype scope, including parameter declarators.
    ParseScope PrototypeScope(this, Scope::FunctionPrototypeScope |
                              Scope::FunctionDeclarationScope | Scope::DeclScope);
  
    // Read all the argument declarations.
    while (isDeclarationSpecifier()) {
      SourceLocation DSStart = Tok.getLocation();
  
      // Parse the common declaration-specifiers piece.
      DeclSpec DS(AttrFactory);
      ParseDeclarationSpecifiers(DS);
  
      // C99 6.9.1p6: 'each declaration in the declaration list shall have at
      // least one declarator'.
      // NOTE: GCC just makes this an ext-warn.  It's not clear what it does with
      // the declarations though.  It's trivial to ignore them, really hard to do
      // anything else with them.
      if (TryConsumeToken(tok::semi)) {
        Diag(DSStart, diag::err_declaration_does_not_declare_param);
        continue;
      }
  
      // C99 6.9.1p6: Declarations shall contain no storage-class specifiers other
      // than register.
      if (DS.getStorageClassSpec() != DeclSpec::SCS_unspecified &&
          DS.getStorageClassSpec() != DeclSpec::SCS_register) {
        Diag(DS.getStorageClassSpecLoc(),
             diag::err_invalid_storage_class_in_func_decl);
        DS.ClearStorageClassSpecs();
      }
      if (DS.getThreadStorageClassSpec() != DeclSpec::TSCS_unspecified) {
        Diag(DS.getThreadStorageClassSpecLoc(),
             diag::err_invalid_storage_class_in_func_decl);
        DS.ClearStorageClassSpecs();
      }
  
      // Parse the first declarator attached to this declspec.
      Declarator ParmDeclarator(DS, DeclaratorContext::KNRTypeList);
      ParseDeclarator(ParmDeclarator);
  
      // Handle the full declarator list.
      while (true) {
        // If attributes are present, parse them.
        MaybeParseGNUAttributes(ParmDeclarator);
  
        // Ask the actions module to compute the type for this declarator.
        Decl *Param =
          Actions.ActOnParamDeclarator(getCurScope(), ParmDeclarator);
  
        if (Param &&
            // A missing identifier has already been diagnosed.
            ParmDeclarator.getIdentifier()) {
  
          // Scan the argument list looking for the correct param to apply this
          // type.
          for (unsigned i = 0; ; ++i) {
            // C99 6.9.1p6: those declarators shall declare only identifiers from
            // the identifier list.
            if (i == FTI.NumParams) {
              Diag(ParmDeclarator.getIdentifierLoc(), diag::err_no_matching_param)
                << ParmDeclarator.getIdentifier();
              break;
            }
  
            if (FTI.Params[i].Ident == ParmDeclarator.getIdentifier()) {
              // Reject redefinitions of parameters.
              if (FTI.Params[i].Param) {
                Diag(ParmDeclarator.getIdentifierLoc(),
                     diag::err_param_redefinition)
                   << ParmDeclarator.getIdentifier();
              } else {
                FTI.Params[i].Param = Param;
              }
              break;
            }
          }
        }
  
        // If we don't have a comma, it is either the end of the list (a ';') or
        // an error, bail out.
        if (Tok.isNot(tok::comma))
          break;
  
        ParmDeclarator.clear();
  
        // Consume the comma.
        ParmDeclarator.setCommaLoc(ConsumeToken());
  
        // Parse the next declarator.
        ParseDeclarator(ParmDeclarator);
      }
  
      // Consume ';' and continue parsing.
      if (!ExpectAndConsumeSemi(diag::err_expected_semi_declaration))
        continue;
  
      // Otherwise recover by skipping to next semi or mandatory function body.
      if (SkipUntil(tok::l_brace, StopAtSemi | StopBeforeMatch))
        break;
      TryConsumeToken(tok::semi);
    }
  
    // The actions module must verify that all arguments were declared.
    Actions.ActOnFinishKNRParamDeclarations(getCurScope(), D, Tok.getLocation());
  }
  
  
  /// ParseAsmStringLiteral - This is just a normal string-literal, but is not
  /// allowed to be a wide string, and is not subject to character translation.
  /// Unlike GCC, we also diagnose an empty string literal when parsing for an
  /// asm label as opposed to an asm statement, because such a construct does not
  /// behave well.
  ///
  /// [GNU] asm-string-literal:
  ///         string-literal
  ///
  ExprResult Parser::ParseAsmStringLiteral(bool ForAsmLabel) {
    if (!isTokenStringLiteral()) {
      Diag(Tok, diag::err_expected_string_literal)
        << /*Source='in...'*/0 << "'asm'";
      return ExprError();
    }
  
    ExprResult AsmString(ParseStringLiteralExpression());
    if (!AsmString.isInvalid()) {
      const auto *SL = cast<StringLiteral>(AsmString.get());
      if (!SL->isAscii()) {
        Diag(Tok, diag::err_asm_operand_wide_string_literal)
          << SL->isWide()
          << SL->getSourceRange();
        return ExprError();
      }
      if (ForAsmLabel && SL->getString().empty()) {
        Diag(Tok, diag::err_asm_operand_wide_string_literal)
            << 2 /* an empty */ << SL->getSourceRange();
        return ExprError();
      }
    }
    return AsmString;
  }
  
  /// ParseSimpleAsm
  ///
  /// [GNU] simple-asm-expr:
  ///         'asm' '(' asm-string-literal ')'
  ///
  ExprResult Parser::ParseSimpleAsm(bool ForAsmLabel, SourceLocation *EndLoc) {
    assert(Tok.is(tok::kw_asm) && "Not an asm!");
    SourceLocation Loc = ConsumeToken();
  
    if (isGNUAsmQualifier(Tok)) {
      // Remove from the end of 'asm' to the end of the asm qualifier.
      SourceRange RemovalRange(PP.getLocForEndOfToken(Loc),
                               PP.getLocForEndOfToken(Tok.getLocation()));
      Diag(Tok, diag::err_global_asm_qualifier_ignored)
          << GNUAsmQualifiers::getQualifierName(getGNUAsmQualifier(Tok))
          << FixItHint::CreateRemoval(RemovalRange);
      ConsumeToken();
    }
  
    BalancedDelimiterTracker T(*this, tok::l_paren);
    if (T.consumeOpen()) {
      Diag(Tok, diag::err_expected_lparen_after) << "asm";
      return ExprError();
    }
  
    ExprResult Result(ParseAsmStringLiteral(ForAsmLabel));
  
    if (!Result.isInvalid()) {
      // Close the paren and get the location of the end bracket
      T.consumeClose();
      if (EndLoc)
        *EndLoc = T.getCloseLocation();
    } else if (SkipUntil(tok::r_paren, StopAtSemi | StopBeforeMatch)) {
      if (EndLoc)
        *EndLoc = Tok.getLocation();
      ConsumeParen();
    }
  
    return Result;
  }
  
  /// Get the TemplateIdAnnotation from the token and put it in the
  /// cleanup pool so that it gets destroyed when parsing the current top level
  /// declaration is finished.
  TemplateIdAnnotation *Parser::takeTemplateIdAnnotation(const Token &tok) {
    assert(tok.is(tok::annot_template_id) && "Expected template-id token");
    TemplateIdAnnotation *
        Id = static_cast<TemplateIdAnnotation *>(tok.getAnnotationValue());
    return Id;
  }
  
  void Parser::AnnotateScopeToken(CXXScopeSpec &SS, bool IsNewAnnotation) {
    // Push the current token back into the token stream (or revert it if it is
    // cached) and use an annotation scope token for current token.
    if (PP.isBacktrackEnabled())
      PP.RevertCachedTokens(1);
    else
      PP.EnterToken(Tok, /*IsReinject=*/true);
    Tok.setKind(tok::annot_cxxscope);
    Tok.setAnnotationValue(Actions.SaveNestedNameSpecifierAnnotation(SS));
    Tok.setAnnotationRange(SS.getRange());
  
    // In case the tokens were cached, have Preprocessor replace them
    // with the annotation token.  We don't need to do this if we've
    // just reverted back to a prior state.
    if (IsNewAnnotation)
      PP.AnnotateCachedTokens(Tok);
  }
  
  /// Attempt to classify the name at the current token position. This may
  /// form a type, scope or primary expression annotation, or replace the token
  /// with a typo-corrected keyword. This is only appropriate when the current
  /// name must refer to an entity which has already been declared.
  ///
  /// \param CCC Indicates how to perform typo-correction for this name. If NULL,
  ///        no typo correction will be performed.
  Parser::AnnotatedNameKind
  Parser::TryAnnotateName(CorrectionCandidateCallback *CCC) {
    assert(Tok.is(tok::identifier) || Tok.is(tok::annot_cxxscope));
  
    const bool EnteringContext = false;
    const bool WasScopeAnnotation = Tok.is(tok::annot_cxxscope);
  
    CXXScopeSpec SS;
    if (getLangOpts().CPlusPlus &&
        ParseOptionalCXXScopeSpecifier(SS, /*ObjectType=*/nullptr,
                                       /*ObjectHasErrors=*/false,
                                       EnteringContext))
      return ANK_Error;
  
    if (Tok.isNot(tok::identifier) || SS.isInvalid()) {
      if (TryAnnotateTypeOrScopeTokenAfterScopeSpec(SS, !WasScopeAnnotation))
        return ANK_Error;
      return ANK_Unresolved;
    }
  
    IdentifierInfo *Name = Tok.getIdentifierInfo();
    SourceLocation NameLoc = Tok.getLocation();
  
    // FIXME: Move the tentative declaration logic into ClassifyName so we can
    // typo-correct to tentatively-declared identifiers.
    if (isTentativelyDeclared(Name)) {
      // Identifier has been tentatively declared, and thus cannot be resolved as
      // an expression. Fall back to annotating it as a type.
      if (TryAnnotateTypeOrScopeTokenAfterScopeSpec(SS, !WasScopeAnnotation))
        return ANK_Error;
      return Tok.is(tok::annot_typename) ? ANK_Success : ANK_TentativeDecl;
    }
  
    Token Next = NextToken();
  
    // Look up and classify the identifier. We don't perform any typo-correction
    // after a scope specifier, because in general we can't recover from typos
    // there (eg, after correcting 'A::template B<X>::C' [sic], we would need to
    // jump back into scope specifier parsing).
    Sema::NameClassification Classification = Actions.ClassifyName(
        getCurScope(), SS, Name, NameLoc, Next, SS.isEmpty() ? CCC : nullptr);
  
    // If name lookup found nothing and we guessed that this was a template name,
    // double-check before committing to that interpretation. C++20 requires that
    // we interpret this as a template-id if it can be, but if it can't be, then
    // this is an error recovery case.
    if (Classification.getKind() == Sema::NC_UndeclaredTemplate &&
        isTemplateArgumentList(1) == TPResult::False) {
      // It's not a template-id; re-classify without the '<' as a hint.
      Token FakeNext = Next;
      FakeNext.setKind(tok::unknown);
      Classification =
          Actions.ClassifyName(getCurScope(), SS, Name, NameLoc, FakeNext,
                               SS.isEmpty() ? CCC : nullptr);
    }
  
    switch (Classification.getKind()) {
    case Sema::NC_Error:
      return ANK_Error;
  
    case Sema::NC_Keyword:
      // The identifier was typo-corrected to a keyword.
      Tok.setIdentifierInfo(Name);
      Tok.setKind(Name->getTokenID());
      PP.TypoCorrectToken(Tok);
      if (SS.isNotEmpty())
        AnnotateScopeToken(SS, !WasScopeAnnotation);
      // We've "annotated" this as a keyword.
      return ANK_Success;
  
    case Sema::NC_Unknown:
      // It's not something we know about. Leave it unannotated.
      break;
  
    case Sema::NC_Type: {
      if (TryAltiVecVectorToken())
        // vector has been found as a type id when altivec is enabled but
        // this is followed by a declaration specifier so this is really the
        // altivec vector token.  Leave it unannotated.
        break;
      SourceLocation BeginLoc = NameLoc;
      if (SS.isNotEmpty())
        BeginLoc = SS.getBeginLoc();
  
      /// An Objective-C object type followed by '<' is a specialization of
      /// a parameterized class type or a protocol-qualified type.
      ParsedType Ty = Classification.getType();
      if (getLangOpts().ObjC && NextToken().is(tok::less) &&
          (Ty.get()->isObjCObjectType() ||
           Ty.get()->isObjCObjectPointerType())) {
        // Consume the name.
        SourceLocation IdentifierLoc = ConsumeToken();
        SourceLocation NewEndLoc;
        TypeResult NewType
            = parseObjCTypeArgsAndProtocolQualifiers(IdentifierLoc, Ty,
                                                     /*consumeLastToken=*/false,
                                                     NewEndLoc);
        if (NewType.isUsable())
          Ty = NewType.get();
        else if (Tok.is(tok::eof)) // Nothing to do here, bail out...
          return ANK_Error;
      }
  
      Tok.setKind(tok::annot_typename);
      setTypeAnnotation(Tok, Ty);
      Tok.setAnnotationEndLoc(Tok.getLocation());
      Tok.setLocation(BeginLoc);
      PP.AnnotateCachedTokens(Tok);
      return ANK_Success;
    }
  
    case Sema::NC_OverloadSet:
      Tok.setKind(tok::annot_overload_set);
      setExprAnnotation(Tok, Classification.getExpression());
      Tok.setAnnotationEndLoc(NameLoc);
      if (SS.isNotEmpty())
        Tok.setLocation(SS.getBeginLoc());
      PP.AnnotateCachedTokens(Tok);
      return ANK_Success;
  
    case Sema::NC_NonType:
      if (TryAltiVecVectorToken())
        // vector has been found as a non-type id when altivec is enabled but
        // this is followed by a declaration specifier so this is really the
        // altivec vector token.  Leave it unannotated.
        break;
      Tok.setKind(tok::annot_non_type);
      setNonTypeAnnotation(Tok, Classification.getNonTypeDecl());
      Tok.setLocation(NameLoc);
      Tok.setAnnotationEndLoc(NameLoc);
      PP.AnnotateCachedTokens(Tok);
      if (SS.isNotEmpty())
        AnnotateScopeToken(SS, !WasScopeAnnotation);
      return ANK_Success;
  
    case Sema::NC_UndeclaredNonType:
    case Sema::NC_DependentNonType:
      Tok.setKind(Classification.getKind() == Sema::NC_UndeclaredNonType
                      ? tok::annot_non_type_undeclared
                      : tok::annot_non_type_dependent);
      setIdentifierAnnotation(Tok, Name);
      Tok.setLocation(NameLoc);
      Tok.setAnnotationEndLoc(NameLoc);
      PP.AnnotateCachedTokens(Tok);
      if (SS.isNotEmpty())
        AnnotateScopeToken(SS, !WasScopeAnnotation);
      return ANK_Success;
  
    case Sema::NC_TypeTemplate:
      if (Next.isNot(tok::less)) {
        // This may be a type template being used as a template template argument.
        if (SS.isNotEmpty())
          AnnotateScopeToken(SS, !WasScopeAnnotation);
        return ANK_TemplateName;
      }
      LLVM_FALLTHROUGH;
    case Sema::NC_VarTemplate:
    case Sema::NC_FunctionTemplate:
    case Sema::NC_UndeclaredTemplate: {
      // We have a type, variable or function template followed by '<'.
      ConsumeToken();
      UnqualifiedId Id;
      Id.setIdentifier(Name, NameLoc);
      if (AnnotateTemplateIdToken(
              TemplateTy::make(Classification.getTemplateName()),
              Classification.getTemplateNameKind(), SS, SourceLocation(), Id))
        return ANK_Error;
      return ANK_Success;
    }
    case Sema::NC_Concept: {
      UnqualifiedId Id;
      Id.setIdentifier(Name, NameLoc);
      if (Next.is(tok::less))
        // We have a concept name followed by '<'. Consume the identifier token so
        // we reach the '<' and annotate it.
        ConsumeToken();
      if (AnnotateTemplateIdToken(
              TemplateTy::make(Classification.getTemplateName()),
              Classification.getTemplateNameKind(), SS, SourceLocation(), Id,
              /*AllowTypeAnnotation=*/false, /*TypeConstraint=*/true))
        return ANK_Error;
      return ANK_Success;
    }
    }
  
    // Unable to classify the name, but maybe we can annotate a scope specifier.
    if (SS.isNotEmpty())
      AnnotateScopeToken(SS, !WasScopeAnnotation);
    return ANK_Unresolved;
  }
  
  bool Parser::TryKeywordIdentFallback(bool DisableKeyword) {
    assert(Tok.isNot(tok::identifier));
    Diag(Tok, diag::ext_keyword_as_ident)
      << PP.getSpelling(Tok)
      << DisableKeyword;
    if (DisableKeyword)
      Tok.getIdentifierInfo()->revertTokenIDToIdentifier();
    Tok.setKind(tok::identifier);
    return true;
  }
  
  /// TryAnnotateTypeOrScopeToken - If the current token position is on a
  /// typename (possibly qualified in C++) or a C++ scope specifier not followed
  /// by a typename, TryAnnotateTypeOrScopeToken will replace one or more tokens
  /// with a single annotation token representing the typename or C++ scope
  /// respectively.
  /// This simplifies handling of C++ scope specifiers and allows efficient
  /// backtracking without the need to re-parse and resolve nested-names and
  /// typenames.
  /// It will mainly be called when we expect to treat identifiers as typenames
  /// (if they are typenames). For example, in C we do not expect identifiers
  /// inside expressions to be treated as typenames so it will not be called
  /// for expressions in C.
  /// The benefit for C/ObjC is that a typename will be annotated and
  /// Actions.getTypeName will not be needed to be called again (e.g. getTypeName
  /// will not be called twice, once to check whether we have a declaration
  /// specifier, and another one to get the actual type inside
  /// ParseDeclarationSpecifiers).
  ///
  /// This returns true if an error occurred.
  ///
  /// Note that this routine emits an error if you call it with ::new or ::delete
  /// as the current tokens, so only call it in contexts where these are invalid.
  bool Parser::TryAnnotateTypeOrScopeToken() {
    assert((Tok.is(tok::identifier) || Tok.is(tok::coloncolon) ||
            Tok.is(tok::kw_typename) || Tok.is(tok::annot_cxxscope) ||
            Tok.is(tok::kw_decltype) || Tok.is(tok::annot_template_id) ||
            Tok.is(tok::kw___super)) &&
           "Cannot be a type or scope token!");
  
    if (Tok.is(tok::kw_typename)) {
      // MSVC lets you do stuff like:
      //   typename typedef T_::D D;
      //
      // We will consume the typedef token here and put it back after we have
      // parsed the first identifier, transforming it into something more like:
      //   typename T_::D typedef D;
      if (getLangOpts().MSVCCompat && NextToken().is(tok::kw_typedef)) {
        Token TypedefToken;
        PP.Lex(TypedefToken);
        bool Result = TryAnnotateTypeOrScopeToken();
        PP.EnterToken(Tok, /*IsReinject=*/true);
        Tok = TypedefToken;
        if (!Result)
          Diag(Tok.getLocation(), diag::warn_expected_qualified_after_typename);
        return Result;
      }
  
      // Parse a C++ typename-specifier, e.g., "typename T::type".
      //
      //   typename-specifier:
      //     'typename' '::' [opt] nested-name-specifier identifier
      //     'typename' '::' [opt] nested-name-specifier template [opt]
      //            simple-template-id
      SourceLocation TypenameLoc = ConsumeToken();
      CXXScopeSpec SS;
      if (ParseOptionalCXXScopeSpecifier(SS, /*ObjectType=*/nullptr,
                                         /*ObjectHasErrors=*/false,
                                         /*EnteringContext=*/false, nullptr,
                                         /*IsTypename*/ true))
        return true;
      if (SS.isEmpty()) {
        if (Tok.is(tok::identifier) || Tok.is(tok::annot_template_id) ||
            Tok.is(tok::annot_decltype)) {
          // Attempt to recover by skipping the invalid 'typename'
          if (Tok.is(tok::annot_decltype) ||
              (!TryAnnotateTypeOrScopeToken() && Tok.isAnnotation())) {
            unsigned DiagID = diag::err_expected_qualified_after_typename;
            // MS compatibility: MSVC permits using known types with typename.
            // e.g. "typedef typename T* pointer_type"
            if (getLangOpts().MicrosoftExt)
              DiagID = diag::warn_expected_qualified_after_typename;
            Diag(Tok.getLocation(), DiagID);
            return false;
          }
        }
        if (Tok.isEditorPlaceholder())
          return true;
  
        Diag(Tok.getLocation(), diag::err_expected_qualified_after_typename);
        return true;
      }
  
      TypeResult Ty;
      if (Tok.is(tok::identifier)) {
        // FIXME: check whether the next token is '<', first!
        Ty = Actions.ActOnTypenameType(getCurScope(), TypenameLoc, SS,
                                       *Tok.getIdentifierInfo(),
                                       Tok.getLocation());
      } else if (Tok.is(tok::annot_template_id)) {
        TemplateIdAnnotation *TemplateId = takeTemplateIdAnnotation(Tok);
        if (!TemplateId->mightBeType()) {
          Diag(Tok, diag::err_typename_refers_to_non_type_template)
            << Tok.getAnnotationRange();
          return true;
        }
  
        ASTTemplateArgsPtr TemplateArgsPtr(TemplateId->getTemplateArgs(),
                                           TemplateId->NumArgs);
  
        Ty = TemplateId->isInvalid()
                 ? TypeError()
                 : Actions.ActOnTypenameType(
                       getCurScope(), TypenameLoc, SS, TemplateId->TemplateKWLoc,
                       TemplateId->Template, TemplateId->Name,
                       TemplateId->TemplateNameLoc, TemplateId->LAngleLoc,
                       TemplateArgsPtr, TemplateId->RAngleLoc);
      } else {
        Diag(Tok, diag::err_expected_type_name_after_typename)
          << SS.getRange();
        return true;
      }
  
      SourceLocation EndLoc = Tok.getLastLoc();
      Tok.setKind(tok::annot_typename);
      setTypeAnnotation(Tok, Ty);
      Tok.setAnnotationEndLoc(EndLoc);
      Tok.setLocation(TypenameLoc);
      PP.AnnotateCachedTokens(Tok);
      return false;
    }
  
    // Remembers whether the token was originally a scope annotation.
    bool WasScopeAnnotation = Tok.is(tok::annot_cxxscope);
  
    CXXScopeSpec SS;
    if (getLangOpts().CPlusPlus)
      if (ParseOptionalCXXScopeSpecifier(SS, /*ObjectType=*/nullptr,
                                         /*ObjectHasErrors=*/false,
                                         /*EnteringContext*/ false))
        return true;
  
    return TryAnnotateTypeOrScopeTokenAfterScopeSpec(SS, !WasScopeAnnotation);
  }
  
  /// Try to annotate a type or scope token, having already parsed an
  /// optional scope specifier. \p IsNewScope should be \c true unless the scope
  /// specifier was extracted from an existing tok::annot_cxxscope annotation.
  bool Parser::TryAnnotateTypeOrScopeTokenAfterScopeSpec(CXXScopeSpec &SS,
                                                         bool IsNewScope) {
    if (Tok.is(tok::identifier)) {
      // Determine whether the identifier is a type name.
      if (ParsedType Ty = Actions.getTypeName(
              *Tok.getIdentifierInfo(), Tok.getLocation(), getCurScope(), &SS,
              false, NextToken().is(tok::period), nullptr,
              /*IsCtorOrDtorName=*/false,
              /*NonTrivialTypeSourceInfo*/true,
              /*IsClassTemplateDeductionContext*/true)) {
        SourceLocation BeginLoc = Tok.getLocation();
        if (SS.isNotEmpty()) // it was a C++ qualified type name.
          BeginLoc = SS.getBeginLoc();
  
        /// An Objective-C object type followed by '<' is a specialization of
        /// a parameterized class type or a protocol-qualified type.
        if (getLangOpts().ObjC && NextToken().is(tok::less) &&
            (Ty.get()->isObjCObjectType() ||
             Ty.get()->isObjCObjectPointerType())) {
          // Consume the name.
          SourceLocation IdentifierLoc = ConsumeToken();
          SourceLocation NewEndLoc;
          TypeResult NewType
            = parseObjCTypeArgsAndProtocolQualifiers(IdentifierLoc, Ty,
                                                     /*consumeLastToken=*/false,
                                                     NewEndLoc);
          if (NewType.isUsable())
            Ty = NewType.get();
          else if (Tok.is(tok::eof)) // Nothing to do here, bail out...
            return false;
        }
  
        // This is a typename. Replace the current token in-place with an
        // annotation type token.
        Tok.setKind(tok::annot_typename);
        setTypeAnnotation(Tok, Ty);
        Tok.setAnnotationEndLoc(Tok.getLocation());
        Tok.setLocation(BeginLoc);
  
        // In case the tokens were cached, have Preprocessor replace
        // them with the annotation token.
        PP.AnnotateCachedTokens(Tok);
        return false;
      }
  
      if (!getLangOpts().CPlusPlus) {
        // If we're in C, we can't have :: tokens at all (the lexer won't return
        // them).  If the identifier is not a type, then it can't be scope either,
        // just early exit.
        return false;
      }
  
      // If this is a template-id, annotate with a template-id or type token.
      // FIXME: This appears to be dead code. We already have formed template-id
      // tokens when parsing the scope specifier; this can never form a new one.
      if (NextToken().is(tok::less)) {
        TemplateTy Template;
        UnqualifiedId TemplateName;
        TemplateName.setIdentifier(Tok.getIdentifierInfo(), Tok.getLocation());
        bool MemberOfUnknownSpecialization;
        if (TemplateNameKind TNK = Actions.isTemplateName(
                getCurScope(), SS,
                /*hasTemplateKeyword=*/false, TemplateName,
                /*ObjectType=*/nullptr, /*EnteringContext*/false, Template,
                MemberOfUnknownSpecialization)) {
          // Only annotate an undeclared template name as a template-id if the
          // following tokens have the form of a template argument list.
          if (TNK != TNK_Undeclared_template ||
              isTemplateArgumentList(1) != TPResult::False) {
            // Consume the identifier.
            ConsumeToken();
            if (AnnotateTemplateIdToken(Template, TNK, SS, SourceLocation(),
                                        TemplateName)) {
              // If an unrecoverable error occurred, we need to return true here,
              // because the token stream is in a damaged state.  We may not
              // return a valid identifier.
              return true;
            }
          }
        }
      }
  
      // The current token, which is either an identifier or a
      // template-id, is not part of the annotation. Fall through to
      // push that token back into the stream and complete the C++ scope
      // specifier annotation.
    }
  
    if (Tok.is(tok::annot_template_id)) {
      TemplateIdAnnotation *TemplateId = takeTemplateIdAnnotation(Tok);
      if (TemplateId->Kind == TNK_Type_template) {
        // A template-id that refers to a type was parsed into a
        // template-id annotation in a context where we weren't allowed
        // to produce a type annotation token. Update the template-id
        // annotation token to a type annotation token now.
        AnnotateTemplateIdTokenAsType(SS);
        return false;
      }
    }
  
    if (SS.isEmpty())
      return false;
  
    // A C++ scope specifier that isn't followed by a typename.
    AnnotateScopeToken(SS, IsNewScope);
    return false;
  }
  
  /// TryAnnotateScopeToken - Like TryAnnotateTypeOrScopeToken but only
  /// annotates C++ scope specifiers and template-ids.  This returns
  /// true if there was an error that could not be recovered from.
  ///
  /// Note that this routine emits an error if you call it with ::new or ::delete
  /// as the current tokens, so only call it in contexts where these are invalid.
  bool Parser::TryAnnotateCXXScopeToken(bool EnteringContext) {
    assert(getLangOpts().CPlusPlus &&
           "Call sites of this function should be guarded by checking for C++");
    assert(MightBeCXXScopeToken() && "Cannot be a type or scope token!");
  
    CXXScopeSpec SS;
    if (ParseOptionalCXXScopeSpecifier(SS, /*ObjectType=*/nullptr,
                                       /*ObjectHasErrors=*/false,
                                       EnteringContext))
      return true;
    if (SS.isEmpty())
      return false;
  
    AnnotateScopeToken(SS, true);
    return false;
  }
  
  bool Parser::isTokenEqualOrEqualTypo() {
    tok::TokenKind Kind = Tok.getKind();
    switch (Kind) {
    default:
      return false;
    case tok::ampequal:            // &=
    case tok::starequal:           // *=
    case tok::plusequal:           // +=
    case tok::minusequal:          // -=
    case tok::exclaimequal:        // !=
    case tok::slashequal:          // /=
    case tok::percentequal:        // %=
    case tok::lessequal:           // <=
    case tok::lesslessequal:       // <<=
    case tok::greaterequal:        // >=
    case tok::greatergreaterequal: // >>=
    case tok::caretequal:          // ^=
    case tok::pipeequal:           // |=
    case tok::equalequal:          // ==
      Diag(Tok, diag::err_invalid_token_after_declarator_suggest_equal)
          << Kind
          << FixItHint::CreateReplacement(SourceRange(Tok.getLocation()), "=");
      LLVM_FALLTHROUGH;
    case tok::equal:
      return true;
    }
  }
  
  SourceLocation Parser::handleUnexpectedCodeCompletionToken() {
    assert(Tok.is(tok::code_completion));
    PrevTokLocation = Tok.getLocation();
  
    for (Scope *S = getCurScope(); S; S = S->getParent()) {
      if (S->getFlags() & Scope::FnScope) {
        cutOffParsing();
        Actions.CodeCompleteOrdinaryName(getCurScope(),
                                         Sema::PCC_RecoveryInFunction);
        return PrevTokLocation;
      }
  
      if (S->getFlags() & Scope::ClassScope) {
        cutOffParsing();
        Actions.CodeCompleteOrdinaryName(getCurScope(), Sema::PCC_Class);
        return PrevTokLocation;
      }
    }
  
    cutOffParsing();
    Actions.CodeCompleteOrdinaryName(getCurScope(), Sema::PCC_Namespace);
    return PrevTokLocation;
  }
  
  // Code-completion pass-through functions
  
  void Parser::CodeCompleteDirective(bool InConditional) {
    Actions.CodeCompletePreprocessorDirective(InConditional);
  }
  
  void Parser::CodeCompleteInConditionalExclusion() {
    Actions.CodeCompleteInPreprocessorConditionalExclusion(getCurScope());
  }
  
  void Parser::CodeCompleteMacroName(bool IsDefinition) {
    Actions.CodeCompletePreprocessorMacroName(IsDefinition);
  }
  
  void Parser::CodeCompletePreprocessorExpression() {
    Actions.CodeCompletePreprocessorExpression();
  }
  
  void Parser::CodeCompleteMacroArgument(IdentifierInfo *Macro,
                                         MacroInfo *MacroInfo,
                                         unsigned ArgumentIndex) {
    Actions.CodeCompletePreprocessorMacroArgument(getCurScope(), Macro, MacroInfo,
                                                  ArgumentIndex);
  }
  
  void Parser::CodeCompleteIncludedFile(llvm::StringRef Dir, bool IsAngled) {
    Actions.CodeCompleteIncludedFile(Dir, IsAngled);
  }
  
  void Parser::CodeCompleteNaturalLanguage() {
    Actions.CodeCompleteNaturalLanguage();
  }
  
  bool Parser::ParseMicrosoftIfExistsCondition(IfExistsCondition& Result) {
    assert((Tok.is(tok::kw___if_exists) || Tok.is(tok::kw___if_not_exists)) &&
           "Expected '__if_exists' or '__if_not_exists'");
    Result.IsIfExists = Tok.is(tok::kw___if_exists);
    Result.KeywordLoc = ConsumeToken();
  
    BalancedDelimiterTracker T(*this, tok::l_paren);
    if (T.consumeOpen()) {
      Diag(Tok, diag::err_expected_lparen_after)
        << (Result.IsIfExists? "__if_exists" : "__if_not_exists");
      return true;
    }
  
    // Parse nested-name-specifier.
    if (getLangOpts().CPlusPlus)
      ParseOptionalCXXScopeSpecifier(Result.SS, /*ObjectType=*/nullptr,
                                     /*ObjectHasErrors=*/false,
                                     /*EnteringContext=*/false);
  
    // Check nested-name specifier.
    if (Result.SS.isInvalid()) {
      T.skipToEnd();
      return true;
    }
  
    // Parse the unqualified-id.
    SourceLocation TemplateKWLoc; // FIXME: parsed, but unused.
    if (ParseUnqualifiedId(Result.SS, /*ObjectType=*/nullptr,
                           /*ObjectHadErrors=*/false, /*EnteringContext*/ false,
                           /*AllowDestructorName*/ true,
                           /*AllowConstructorName*/ true,
                           /*AllowDeductionGuide*/ false, &TemplateKWLoc,
                           Result.Name)) {
      T.skipToEnd();
      return true;
    }
  
    if (T.consumeClose())
      return true;
  
    // Check if the symbol exists.
    switch (Actions.CheckMicrosoftIfExistsSymbol(getCurScope(), Result.KeywordLoc,
                                                 Result.IsIfExists, Result.SS,
                                                 Result.Name)) {
    case Sema::IER_Exists:
      Result.Behavior = Result.IsIfExists ? IEB_Parse : IEB_Skip;
      break;
  
    case Sema::IER_DoesNotExist:
      Result.Behavior = !Result.IsIfExists ? IEB_Parse : IEB_Skip;
      break;
  
    case Sema::IER_Dependent:
      Result.Behavior = IEB_Dependent;
      break;
  
    case Sema::IER_Error:
      return true;
    }
  
    return false;
  }
  
  void Parser::ParseMicrosoftIfExistsExternalDeclaration() {
    IfExistsCondition Result;
    if (ParseMicrosoftIfExistsCondition(Result))
      return;
  
    BalancedDelimiterTracker Braces(*this, tok::l_brace);
    if (Braces.consumeOpen()) {
      Diag(Tok, diag::err_expected) << tok::l_brace;
      return;
    }
  
    switch (Result.Behavior) {
    case IEB_Parse:
      // Parse declarations below.
      break;
  
    case IEB_Dependent:
      llvm_unreachable("Cannot have a dependent external declaration");
  
    case IEB_Skip:
      Braces.skipToEnd();
      return;
    }
  
    // Parse the declarations.
    // FIXME: Support module import within __if_exists?
    while (Tok.isNot(tok::r_brace) && !isEofOrEom()) {
      ParsedAttributesWithRange attrs(AttrFactory);
      MaybeParseCXX11Attributes(attrs);
      DeclGroupPtrTy Result = ParseExternalDeclaration(attrs);
      if (Result && !getCurScope()->getParent())
        Actions.getASTConsumer().HandleTopLevelDecl(Result.get());
    }
    Braces.consumeClose();
  }
  
  /// Parse a declaration beginning with the 'module' keyword or C++20
  /// context-sensitive keyword (optionally preceded by 'export').
  ///
  ///   module-declaration:   [Modules TS + P0629R0]
  ///     'export'[opt] 'module' module-name attribute-specifier-seq[opt] ';'
  ///
  ///   global-module-fragment:  [C++2a]
  ///     'module' ';' top-level-declaration-seq[opt]
  ///   module-declaration:      [C++2a]
  ///     'export'[opt] 'module' module-name module-partition[opt]
  ///            attribute-specifier-seq[opt] ';'
  ///   private-module-fragment: [C++2a]
  ///     'module' ':' 'private' ';' top-level-declaration-seq[opt]
  Parser::DeclGroupPtrTy
  Parser::ParseModuleDecl(Sema::ModuleImportState &ImportState) {
    SourceLocation StartLoc = Tok.getLocation();
  
    Sema::ModuleDeclKind MDK = TryConsumeToken(tok::kw_export)
                                   ? Sema::ModuleDeclKind::Interface
                                   : Sema::ModuleDeclKind::Implementation;
  
    assert(
        (Tok.is(tok::kw_module) ||
         (Tok.is(tok::identifier) && Tok.getIdentifierInfo() == Ident_module)) &&
        "not a module declaration");
    SourceLocation ModuleLoc = ConsumeToken();
  
    // Attributes appear after the module name, not before.
    // FIXME: Suggest moving the attributes later with a fixit.
    DiagnoseAndSkipCXX11Attributes();
  
    // Parse a global-module-fragment, if present.
    if (getLangOpts().CPlusPlusModules && Tok.is(tok::semi)) {
      SourceLocation SemiLoc = ConsumeToken();
      if (ImportState != Sema::ModuleImportState::FirstDecl) {
        Diag(StartLoc, diag::err_global_module_introducer_not_at_start)
          << SourceRange(StartLoc, SemiLoc);
        return nullptr;
      }
      if (MDK == Sema::ModuleDeclKind::Interface) {
        Diag(StartLoc, diag::err_module_fragment_exported)
          << /*global*/0 << FixItHint::CreateRemoval(StartLoc);
      }
      ImportState = Sema::ModuleImportState::GlobalFragment;
      return Actions.ActOnGlobalModuleFragmentDecl(ModuleLoc);
    }
  
    // Parse a private-module-fragment, if present.
    if (getLangOpts().CPlusPlusModules && Tok.is(tok::colon) &&
        NextToken().is(tok::kw_private)) {
      if (MDK == Sema::ModuleDeclKind::Interface) {
        Diag(StartLoc, diag::err_module_fragment_exported)
          << /*private*/1 << FixItHint::CreateRemoval(StartLoc);
      }
      ConsumeToken();
      SourceLocation PrivateLoc = ConsumeToken();
      DiagnoseAndSkipCXX11Attributes();
      ExpectAndConsumeSemi(diag::err_private_module_fragment_expected_semi);
      ImportState = Sema::ModuleImportState::PrivateFragment;
      return Actions.ActOnPrivateModuleFragmentDecl(ModuleLoc, PrivateLoc);
    }
  
    SmallVector<std::pair<IdentifierInfo *, SourceLocation>, 2> Path;
    if (ParseModuleName(ModuleLoc, Path, /*IsImport*/ false))
      return nullptr;
  
    // Parse the optional module-partition.
    SmallVector<std::pair<IdentifierInfo *, SourceLocation>, 2> Partition;
    if (Tok.is(tok::colon)) {
      SourceLocation ColonLoc = ConsumeToken();
      if (!getLangOpts().CPlusPlusModules)
        Diag(ColonLoc, diag::err_unsupported_module_partition)
            << SourceRange(ColonLoc, Partition.back().second);
      // Recover by ignoring the partition name.
      else if (ParseModuleName(ModuleLoc, Partition, /*IsImport*/ false))
        return nullptr;
    }
  
    // We don't support any module attributes yet; just parse them and diagnose.
    ParsedAttributesWithRange Attrs(AttrFactory);
    MaybeParseCXX11Attributes(Attrs);
    ProhibitCXX11Attributes(Attrs, diag::err_attribute_not_module_attr);
  
    ExpectAndConsumeSemi(diag::err_module_expected_semi);
  
    return Actions.ActOnModuleDecl(StartLoc, ModuleLoc, MDK, Path, Partition,
                                   ImportState);
  }
  
  /// Parse a module import declaration. This is essentially the same for
  /// Objective-C and C++20 except for the leading '@' (in ObjC) and the
  /// trailing optional attributes (in C++).
  ///
  /// [ObjC]  @import declaration:
  ///           '@' 'import' module-name ';'
  /// [ModTS] module-import-declaration:
  ///           'import' module-name attribute-specifier-seq[opt] ';'
  /// [C++20] module-import-declaration:
  ///           'export'[opt] 'import' module-name
  ///                   attribute-specifier-seq[opt] ';'
  ///           'export'[opt] 'import' module-partition
  ///                   attribute-specifier-seq[opt] ';'
  ///           'export'[opt] 'import' header-name
  ///                   attribute-specifier-seq[opt] ';'
  Decl *Parser::ParseModuleImport(SourceLocation AtLoc,
                                  Sema::ModuleImportState &ImportState) {
    SourceLocation StartLoc = AtLoc.isInvalid() ? Tok.getLocation() : AtLoc;
  
    SourceLocation ExportLoc;
    TryConsumeToken(tok::kw_export, ExportLoc);
  
    assert((AtLoc.isInvalid() ? Tok.isOneOf(tok::kw_import, tok::identifier)
                              : Tok.isObjCAtKeyword(tok::objc_import)) &&
           "Improper start to module import");
    bool IsObjCAtImport = Tok.isObjCAtKeyword(tok::objc_import);
    SourceLocation ImportLoc = ConsumeToken();
  
    // For C++20 modules, we can have "name" or ":Partition name" as valid input.
    SmallVector<std::pair<IdentifierInfo *, SourceLocation>, 2> Path;
    SmallVector<std::pair<IdentifierInfo *, SourceLocation>, 2> Partition;
    Module *HeaderUnit = nullptr;
    if (Tok.is(tok::header_name)) {
      // This is a header import that the preprocessor decided we should skip
      // because it was malformed in some way. Parse and ignore it; it's already
      // been diagnosed.
      ConsumeToken();
    } else if (Tok.is(tok::annot_header_unit)) {
      // This is a header import that the preprocessor mapped to a module import.
      HeaderUnit = reinterpret_cast<Module *>(Tok.getAnnotationValue());
      ConsumeAnnotationToken();
    } else if (Tok.is(tok::colon)) {
      SourceLocation ColonLoc = ConsumeToken();
      if (!getLangOpts().CPlusPlusModules)
        Diag(ColonLoc, diag::err_unsupported_module_partition)
            << SourceRange(ColonLoc, Partition.back().second);
      // Recover by leaving partition empty.
      else if (ParseModuleName(ColonLoc, Partition, /*IsImport*/ true))
        return nullptr;
    } else {
      if (ParseModuleName(ImportLoc, Path, /*IsImport*/ true))
        return nullptr;
    }
  
    ParsedAttributesWithRange Attrs(AttrFactory);
    MaybeParseCXX11Attributes(Attrs);
    // We don't support any module import attributes yet.
    ProhibitCXX11Attributes(Attrs, diag::err_attribute_not_import_attr);
  
    if (PP.hadModuleLoaderFatalFailure()) {
      // With a fatal failure in the module loader, we abort parsing.
      cutOffParsing();
      return nullptr;
    }
  
    // Diagnose mis-imports.
    bool SeenError = true;
    bool HasPart = !Partition.empty();
    switch (ImportState) {
    case Sema::ModuleImportState::ImportAllowed:
      SeenError = false;
      break;
    case Sema::ModuleImportState::FirstDecl:
    case Sema::ModuleImportState::NotACXX20Module:
      // We can only import a partition within a module purview.
      if (HasPart)
        Diag(ImportLoc, diag::err_partition_import_outside_module);
      else
        SeenError = false;
      break;
    case Sema::ModuleImportState::GlobalFragment:
      // We can only have pre-processor directives in the global module
      // fragment.  We can, however have a header unit import here.
      if (!HeaderUnit)
        Diag(ImportLoc, diag::err_import_in_wrong_fragment) << HasPart << 0;
      else
        SeenError = false;
      break;
    case Sema::ModuleImportState::ImportFinished:
      if (getLangOpts().CPlusPlusModules)
        Diag(ImportLoc, diag::err_import_not_allowed_here);
      else
        SeenError = false;
      break;
    case Sema::ModuleImportState::PrivateFragment:
      Diag(ImportLoc, diag::err_import_in_wrong_fragment) << HasPart << 1;
      break;
    }
    if (SeenError) {
      ExpectAndConsumeSemi(diag::err_module_expected_semi);
      return nullptr;
    }
  
    DeclResult Import;
    if (HeaderUnit)
      Import =
          Actions.ActOnModuleImport(StartLoc, ExportLoc, ImportLoc, HeaderUnit);
    else if (!Path.empty() || !Partition.empty())
      Import = Actions.ActOnModuleImport(StartLoc, ExportLoc, ImportLoc, Path,
                                         Partition);
    ExpectAndConsumeSemi(diag::err_module_expected_semi);
    if (Import.isInvalid())
      return nullptr;
  
    // Using '@import' in framework headers requires modules to be enabled so that
    // the header is parseable. Emit a warning to make the user aware.
    if (IsObjCAtImport && AtLoc.isValid()) {
      auto &SrcMgr = PP.getSourceManager();
      auto *FE = SrcMgr.getFileEntryForID(SrcMgr.getFileID(AtLoc));
      if (FE && llvm::sys::path::parent_path(FE->getDir()->getName())
                    .endswith(".framework"))
        Diags.Report(AtLoc, diag::warn_atimport_in_framework_header);
    }
  
    return Import.get();
  }
  
  /// Parse a C++ Modules TS / Objective-C module name (both forms use the same
  /// grammar).
  ///
  ///         module-name:
  ///           module-name-qualifier[opt] identifier
  ///         module-name-qualifier:
  ///           module-name-qualifier[opt] identifier '.'
  bool Parser::ParseModuleName(
      SourceLocation UseLoc,
      SmallVectorImpl<std::pair<IdentifierInfo *, SourceLocation>> &Path,
      bool IsImport) {
    // Parse the module path.
    while (true) {
      if (!Tok.is(tok::identifier)) {
        if (Tok.is(tok::code_completion)) {
          cutOffParsing();
          Actions.CodeCompleteModuleImport(UseLoc, Path);
          return true;
        }
  
        Diag(Tok, diag::err_module_expected_ident) << IsImport;
        SkipUntil(tok::semi);
        return true;
      }
  
      // Record this part of the module path.
      Path.push_back(std::make_pair(Tok.getIdentifierInfo(), Tok.getLocation()));
      ConsumeToken();
  
      if (Tok.isNot(tok::period))
        return false;
  
      ConsumeToken();
    }
  }
  
  /// Try recover parser when module annotation appears where it must not
  /// be found.
  /// \returns false if the recover was successful and parsing may be continued, or
  /// true if parser must bail out to top level and handle the token there.
  bool Parser::parseMisplacedModuleImport() {
    while (true) {
      switch (Tok.getKind()) {
      case tok::annot_module_end:
        // If we recovered from a misplaced module begin, we expect to hit a
        // misplaced module end too. Stay in the current context when this
        // happens.
        if (MisplacedModuleBeginCount) {
          --MisplacedModuleBeginCount;
          Actions.ActOnModuleEnd(Tok.getLocation(),
                                 reinterpret_cast<Module *>(
                                     Tok.getAnnotationValue()));
          ConsumeAnnotationToken();
          continue;
        }
        // Inform caller that recovery failed, the error must be handled at upper
        // level. This will generate the desired "missing '}' at end of module"
        // diagnostics on the way out.
        return true;
      case tok::annot_module_begin:
        // Recover by entering the module (Sema will diagnose).
        Actions.ActOnModuleBegin(Tok.getLocation(),
                                 reinterpret_cast<Module *>(
                                     Tok.getAnnotationValue()));
        ConsumeAnnotationToken();
        ++MisplacedModuleBeginCount;
        continue;
      case tok::annot_module_include:
        // Module import found where it should not be, for instance, inside a
        // namespace. Recover by importing the module.
        Actions.ActOnModuleInclude(Tok.getLocation(),
                                   reinterpret_cast<Module *>(
                                       Tok.getAnnotationValue()));
        ConsumeAnnotationToken();
        // If there is another module import, process it.
        continue;
      default:
        return false;
      }
    }
    return false;
  }
  
  bool BalancedDelimiterTracker::diagnoseOverflow() {
    P.Diag(P.Tok, diag::err_bracket_depth_exceeded)
      << P.getLangOpts().BracketDepth;
    P.Diag(P.Tok, diag::note_bracket_depth);
    P.cutOffParsing();
    return true;
  }
  
  bool BalancedDelimiterTracker::expectAndConsume(unsigned DiagID,
                                                  const char *Msg,
                                                  tok::TokenKind SkipToTok) {
    LOpen = P.Tok.getLocation();
    if (P.ExpectAndConsume(Kind, DiagID, Msg)) {
      if (SkipToTok != tok::unknown)
        P.SkipUntil(SkipToTok, Parser::StopAtSemi);
      return true;
    }
  
    if (getDepth() < P.getLangOpts().BracketDepth)
      return false;
  
    return diagnoseOverflow();
  }
  
  bool BalancedDelimiterTracker::diagnoseMissingClose() {
    assert(!P.Tok.is(Close) && "Should have consumed closing delimiter");
  
    if (P.Tok.is(tok::annot_module_end))
      P.Diag(P.Tok, diag::err_missing_before_module_end) << Close;
    else
      P.Diag(P.Tok, diag::err_expected) << Close;
    P.Diag(LOpen, diag::note_matching) << Kind;
  
    // If we're not already at some kind of closing bracket, skip to our closing
    // token.
    if (P.Tok.isNot(tok::r_paren) && P.Tok.isNot(tok::r_brace) &&
        P.Tok.isNot(tok::r_square) &&
        P.SkipUntil(Close, FinalToken,
                    Parser::StopAtSemi | Parser::StopBeforeMatch) &&
        P.Tok.is(Close))
      LClose = P.ConsumeAnyToken();
    return true;
  }
  
  void BalancedDelimiterTracker::skipToEnd() {
    P.SkipUntil(Close, Parser::StopBeforeMatch);
    consumeClose();
  }
  