text: //===- ASTUnit.h - ASTUnit utility ------------------------------*- C++ -*-===//
  //
  // 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
  //
  //===----------------------------------------------------------------------===//
  //
  // ASTUnit utility class.
  //
  //===----------------------------------------------------------------------===//
  
  #ifndef LLVM_CLANG_FRONTEND_ASTUNIT_H
  #define LLVM_CLANG_FRONTEND_ASTUNIT_H
  
  #include "clang-c/Index.h"
  #include "clang/AST/ASTContext.h"
  #include "clang/Basic/Diagnostic.h"
  #include "clang/Basic/FileSystemOptions.h"
  #include "clang/Basic/LLVM.h"
  #include "clang/Basic/LangOptions.h"
  #include "clang/Basic/SourceLocation.h"
  #include "clang/Basic/SourceManager.h"
  #include "clang/Basic/TargetOptions.h"
  #include "clang/Lex/HeaderSearchOptions.h"
  #include "clang/Lex/ModuleLoader.h"
  #include "clang/Lex/PreprocessingRecord.h"
  #include "clang/Sema/CodeCompleteConsumer.h"
  #include "clang/Serialization/ASTBitCodes.h"
  #include "clang/Frontend/PrecompiledPreamble.h"
  #include "llvm/ADT/ArrayRef.h"
  #include "llvm/ADT/DenseMap.h"
  #include "llvm/ADT/IntrusiveRefCntPtr.h"
  #include "llvm/ADT/None.h"
  #include "llvm/ADT/Optional.h"
  #include "llvm/ADT/STLExtras.h"
  #include "llvm/ADT/SmallVector.h"
  #include "llvm/ADT/StringMap.h"
  #include "llvm/ADT/StringRef.h"
  #include "llvm/ADT/iterator_range.h"
  #include <cassert>
  #include <cstddef>
  #include <cstdint>
  #include <memory>
  #include <string>
  #include <utility>
  #include <vector>
  
  namespace llvm {
  
  class MemoryBuffer;
  
  namespace vfs {
  
  class FileSystem;
  
  } // namespace vfs
  } // namespace llvm
  
  namespace clang {
  
  class ASTContext;
  class ASTDeserializationListener;
  class ASTMutationListener;
  class ASTReader;
  class CompilerInstance;
  class CompilerInvocation;
  class Decl;
  class FileEntry;
  class FileManager;
  class FrontendAction;
  class HeaderSearch;
  class InputKind;
  class InMemoryModuleCache;
  class PCHContainerOperations;
  class PCHContainerReader;
  class Preprocessor;
  class PreprocessorOptions;
  class Sema;
  class TargetInfo;
  
  /// \brief Enumerates the available scopes for skipping function bodies.
  enum class SkipFunctionBodiesScope { None, Preamble, PreambleAndMainFile };
  
  /// Utility class for loading a ASTContext from an AST file.
  class ASTUnit {
  public:
    struct StandaloneFixIt {
      std::pair<unsigned, unsigned> RemoveRange;
      std::pair<unsigned, unsigned> InsertFromRange;
      std::string CodeToInsert;
      bool BeforePreviousInsertions;
    };
  
    struct StandaloneDiagnostic {
      unsigned ID;
      DiagnosticsEngine::Level Level;
      std::string Message;
      std::string Filename;
      unsigned LocOffset;
      std::vector<std::pair<unsigned, unsigned>> Ranges;
      std::vector<StandaloneFixIt> FixIts;
    };
  
  private:
    std::shared_ptr<LangOptions>            LangOpts;
    IntrusiveRefCntPtr<DiagnosticsEngine>   Diagnostics;
    IntrusiveRefCntPtr<FileManager>         FileMgr;
    IntrusiveRefCntPtr<SourceManager>       SourceMgr;
    IntrusiveRefCntPtr<InMemoryModuleCache> ModuleCache;
    std::unique_ptr<HeaderSearch>           HeaderInfo;
    IntrusiveRefCntPtr<TargetInfo>          Target;
    std::shared_ptr<Preprocessor>           PP;
    IntrusiveRefCntPtr<ASTContext>          Ctx;
    std::shared_ptr<TargetOptions>          TargetOpts;
    std::shared_ptr<HeaderSearchOptions>    HSOpts;
    std::shared_ptr<PreprocessorOptions>    PPOpts;
    IntrusiveRefCntPtr<ASTReader> Reader;
    bool HadModuleLoaderFatalFailure = false;
  
    struct ASTWriterData;
    std::unique_ptr<ASTWriterData> WriterData;
  
    FileSystemOptions FileSystemOpts;
  
    /// The AST consumer that received information about the translation
    /// unit as it was parsed or loaded.
    std::unique_ptr<ASTConsumer> Consumer;
  
    /// The semantic analysis object used to type-check the translation
    /// unit.
    std::unique_ptr<Sema> TheSema;
  
    /// Optional owned invocation, just used to make the invocation used in
    /// LoadFromCommandLine available.
    std::shared_ptr<CompilerInvocation> Invocation;
  
    /// Fake module loader: the AST unit doesn't need to load any modules.
    TrivialModuleLoader ModuleLoader;
  
    // OnlyLocalDecls - when true, walking this AST should only visit declarations
    // that come from the AST itself, not from included precompiled headers.
    // FIXME: This is temporary; eventually, CIndex will always do this.
    bool OnlyLocalDecls = false;
  
    /// Whether to capture any diagnostics produced.
    bool CaptureDiagnostics = false;
  
    /// Track whether the main file was loaded from an AST or not.
    bool MainFileIsAST;
  
    /// What kind of translation unit this AST represents.
    TranslationUnitKind TUKind = TU_Complete;
  
    /// Whether we should time each operation.
    bool WantTiming;
  
    /// Whether the ASTUnit should delete the remapped buffers.
    bool OwnsRemappedFileBuffers = true;
  
    /// Track the top-level decls which appeared in an ASTUnit which was loaded
    /// from a source file.
    //
    // FIXME: This is just an optimization hack to avoid deserializing large parts
    // of a PCH file when using the Index library on an ASTUnit loaded from
    // source. In the long term we should make the Index library use efficient and
    // more scalable search mechanisms.
    std::vector<Decl*> TopLevelDecls;
  
    /// Sorted (by file offset) vector of pairs of file offset/Decl.
    using LocDeclsTy = SmallVector<std::pair<unsigned, Decl *>, 64>;
    using FileDeclsTy = llvm::DenseMap<FileID, LocDeclsTy *>;
  
    /// Map from FileID to the file-level declarations that it contains.
    /// The files and decls are only local (and non-preamble) ones.
    FileDeclsTy FileDecls;
  
    /// The name of the original source file used to generate this ASTUnit.
    std::string OriginalSourceFile;
  
    /// The set of diagnostics produced when creating the preamble.
    SmallVector<StandaloneDiagnostic, 4> PreambleDiagnostics;
  
    /// The set of diagnostics produced when creating this
    /// translation unit.
    SmallVector<StoredDiagnostic, 4> StoredDiagnostics;
  
    /// The set of diagnostics produced when failing to parse, e.g. due
    /// to failure to load the PCH.
    SmallVector<StoredDiagnostic, 4> FailedParseDiagnostics;
  
    /// The number of stored diagnostics that come from the driver
    /// itself.
    ///
    /// Diagnostics that come from the driver are retained from one parse to
    /// the next.
    unsigned NumStoredDiagnosticsFromDriver = 0;
  
    /// Counter that determines when we want to try building a
    /// precompiled preamble.
    ///
    /// If zero, we will never build a precompiled preamble. Otherwise,
    /// it's treated as a counter that decrements each time we reparse
    /// without the benefit of a precompiled preamble. When it hits 1,
    /// we'll attempt to rebuild the precompiled header. This way, if
    /// building the precompiled preamble fails, we won't try again for
    /// some number of calls.
    unsigned PreambleRebuildCountdown = 0;
  
    /// Counter indicating how often the preamble was build in total.
    unsigned PreambleCounter = 0;
  
    /// Cache pairs "filename - source location"
    ///
    /// Cache contains only source locations from preamble so it is
    /// guaranteed that they stay valid when the SourceManager is recreated.
    /// This cache is used when loading preamble to increase performance
    /// of that loading. It must be cleared when preamble is recreated.
    llvm::StringMap<SourceLocation> PreambleSrcLocCache;
  
    /// The contents of the preamble.
    llvm::Optional<PrecompiledPreamble> Preamble;
  
    /// When non-NULL, this is the buffer used to store the contents of
    /// the main file when it has been padded for use with the precompiled
    /// preamble.
    std::unique_ptr<llvm::MemoryBuffer> SavedMainFileBuffer;
  
    /// The number of warnings that occurred while parsing the preamble.
    ///
    /// This value will be used to restore the state of the \c DiagnosticsEngine
    /// object when re-using the precompiled preamble. Note that only the
    /// number of warnings matters, since we will not save the preamble
    /// when any errors are present.
    unsigned NumWarningsInPreamble = 0;
  
    /// A list of the serialization ID numbers for each of the top-level
    /// declarations parsed within the precompiled preamble.
    std::vector<serialization::DeclID> TopLevelDeclsInPreamble;
  
    /// Whether we should be caching code-completion results.
    bool ShouldCacheCodeCompletionResults : 1;
  
    /// Whether to include brief documentation within the set of code
    /// completions cached.
    bool IncludeBriefCommentsInCodeCompletion : 1;
  
    /// True if non-system source files should be treated as volatile
    /// (likely to change while trying to use them).
    bool UserFilesAreVolatile : 1;
  
    static void ConfigureDiags(IntrusiveRefCntPtr<DiagnosticsEngine> Diags,
                               ASTUnit &AST, bool CaptureDiagnostics);
  
    void TranslateStoredDiagnostics(FileManager &FileMgr,
                                    SourceManager &SrcMan,
                        const SmallVectorImpl<StandaloneDiagnostic> &Diags,
                              SmallVectorImpl<StoredDiagnostic> &Out);
  
    void clearFileLevelDecls();
  
  public:
    /// A cached code-completion result, which may be introduced in one of
    /// many different contexts.
    struct CachedCodeCompletionResult {
      /// The code-completion string corresponding to this completion
      /// result.
      CodeCompletionString *Completion;
  
      /// A bitmask that indicates which code-completion contexts should
      /// contain this completion result.
      ///
      /// The bits in the bitmask correspond to the values of
      /// CodeCompleteContext::Kind. To map from a completion context kind to a
      /// bit, shift 1 by that number of bits. Many completions can occur in
      /// several different contexts.
      uint64_t ShowInContexts;
  
      /// The priority given to this code-completion result.
      unsigned Priority;
  
      /// The libclang cursor kind corresponding to this code-completion
      /// result.
      CXCursorKind Kind;
  
      /// The availability of this code-completion result.
      CXAvailabilityKind Availability;
  
      /// The simplified type class for a non-macro completion result.
      SimplifiedTypeClass TypeClass;
  
      /// The type of a non-macro completion result, stored as a unique
      /// integer used by the string map of cached completion types.
      ///
      /// This value will be zero if the type is not known, or a unique value
      /// determined by the formatted type string. Se \c CachedCompletionTypes
      /// for more information.
      unsigned Type;
    };
  
    /// Retrieve the mapping from formatted type names to unique type
    /// identifiers.
    llvm::StringMap<unsigned> &getCachedCompletionTypes() {
      return CachedCompletionTypes;
    }
  
    /// Retrieve the allocator used to cache global code completions.
    std::shared_ptr<GlobalCodeCompletionAllocator>
    getCachedCompletionAllocator() {
      return CachedCompletionAllocator;
    }
  
    CodeCompletionTUInfo &getCodeCompletionTUInfo() {
      if (!CCTUInfo)
        CCTUInfo = llvm::make_unique<CodeCompletionTUInfo>(
            std::make_shared<GlobalCodeCompletionAllocator>());
      return *CCTUInfo;
    }
  
  private:
    /// Allocator used to store cached code completions.
    std::shared_ptr<GlobalCodeCompletionAllocator> CachedCompletionAllocator;
  
    std::unique_ptr<CodeCompletionTUInfo> CCTUInfo;
  
    /// The set of cached code-completion results.
    std::vector<CachedCodeCompletionResult> CachedCompletionResults;
  
    /// A mapping from the formatted type name to a unique number for that
    /// type, which is used for type equality comparisons.
    llvm::StringMap<unsigned> CachedCompletionTypes;
  
    /// A string hash of the top-level declaration and macro definition
    /// names processed the last time that we reparsed the file.
    ///
    /// This hash value is used to determine when we need to refresh the
    /// global code-completion cache.
    unsigned CompletionCacheTopLevelHashValue = 0;
  
    /// A string hash of the top-level declaration and macro definition
    /// names processed the last time that we reparsed the precompiled preamble.
    ///
    /// This hash value is used to determine when we need to refresh the
    /// global code-completion cache after a rebuild of the precompiled preamble.
    unsigned PreambleTopLevelHashValue = 0;
  
    /// The current hash value for the top-level declaration and macro
    /// definition names
    unsigned CurrentTopLevelHashValue = 0;
  
    /// Bit used by CIndex to mark when a translation unit may be in an
    /// inconsistent state, and is not safe to free.
    unsigned UnsafeToFree : 1;
  
    /// \brief Enumerator specifying the scope for skipping function bodies.
    SkipFunctionBodiesScope SkipFunctionBodies = SkipFunctionBodiesScope::None;
  
    /// Cache any "global" code-completion results, so that we can avoid
    /// recomputing them with each completion.
    void CacheCodeCompletionResults();
  
    /// Clear out and deallocate
    void ClearCachedCompletionResults();
  
    explicit ASTUnit(bool MainFileIsAST);
  
    bool Parse(std::shared_ptr<PCHContainerOperations> PCHContainerOps,
               std::unique_ptr<llvm::MemoryBuffer> OverrideMainBuffer,
               IntrusiveRefCntPtr<llvm::vfs::FileSystem> VFS);
  
    std::unique_ptr<llvm::MemoryBuffer> getMainBufferWithPrecompiledPreamble(
        std::shared_ptr<PCHContainerOperations> PCHContainerOps,
        CompilerInvocation &PreambleInvocationIn,
        IntrusiveRefCntPtr<llvm::vfs::FileSystem> VFS, bool AllowRebuild = true,
        unsigned MaxLines = 0);
    void RealizeTopLevelDeclsFromPreamble();
  
    /// Transfers ownership of the objects (like SourceManager) from
    /// \param CI to this ASTUnit.
    void transferASTDataFromCompilerInstance(CompilerInstance &CI);
  
    /// Allows us to assert that ASTUnit is not being used concurrently,
    /// which is not supported.
    ///
    /// Clients should create instances of the ConcurrencyCheck class whenever
    /// using the ASTUnit in a way that isn't intended to be concurrent, which is
    /// just about any usage.
    /// Becomes a noop in release mode; only useful for debug mode checking.
    class ConcurrencyState {
      void *Mutex; // a llvm::sys::MutexImpl in debug;
  
    public:
      ConcurrencyState();
      ~ConcurrencyState();
  
      void start();
      void finish();
    };
    ConcurrencyState ConcurrencyCheckValue;
  
  public:
    friend class ConcurrencyCheck;
  
    class ConcurrencyCheck {
      ASTUnit &Self;
  
    public:
      explicit ConcurrencyCheck(ASTUnit &Self) : Self(Self) {
        Self.ConcurrencyCheckValue.start();
      }
  
      ~ConcurrencyCheck() {
        Self.ConcurrencyCheckValue.finish();
      }
    };
  
    ASTUnit(const ASTUnit &) = delete;
    ASTUnit &operator=(const ASTUnit &) = delete;
    ~ASTUnit();
  
    bool isMainFileAST() const { return MainFileIsAST; }
  
    bool isUnsafeToFree() const { return UnsafeToFree; }
    void setUnsafeToFree(bool Value) { UnsafeToFree = Value; }
  
    const DiagnosticsEngine &getDiagnostics() const { return *Diagnostics; }
    DiagnosticsEngine &getDiagnostics() { return *Diagnostics; }
  
    const SourceManager &getSourceManager() const { return *SourceMgr; }
    SourceManager &getSourceManager() { return *SourceMgr; }
  
    const Preprocessor &getPreprocessor() const { return *PP; }
    Preprocessor &getPreprocessor() { return *PP; }
    std::shared_ptr<Preprocessor> getPreprocessorPtr() const { return PP; }
  
    const ASTContext &getASTContext() const { return *Ctx; }
    ASTContext &getASTContext() { return *Ctx; }
  
    void setASTContext(ASTContext *ctx) { Ctx = ctx; }
    void setPreprocessor(std::shared_ptr<Preprocessor> pp);
  
    /// Enable source-range based diagnostic messages.
    ///
    /// If diagnostic messages with source-range information are to be expected
    /// and AST comes not from file (e.g. after LoadFromCompilerInvocation) this
    /// function has to be called.
    /// The function is to be called only once and the AST should be associated
    /// with the same source file afterwards.
    void enableSourceFileDiagnostics();
  
    bool hasSema() const { return (bool)TheSema; }
  
    Sema &getSema() const {
      assert(TheSema && "ASTUnit does not have a Sema object!");
      return *TheSema;
    }
  
    const LangOptions &getLangOpts() const {
      assert(LangOpts && "ASTUnit does not have language options");
      return *LangOpts;
    }
  
    const HeaderSearchOptions &getHeaderSearchOpts() const {
      assert(HSOpts && "ASTUnit does not have header search options");
      return *HSOpts;
    }
  
    const PreprocessorOptions &getPreprocessorOpts() const {
      assert(PPOpts && "ASTUnit does not have preprocessor options");
      return *PPOpts;
    }
  
    const FileManager &getFileManager() const { return *FileMgr; }
    FileManager &getFileManager() { return *FileMgr; }
  
    const FileSystemOptions &getFileSystemOpts() const { return FileSystemOpts; }
  
    IntrusiveRefCntPtr<ASTReader> getASTReader() const;
  
    StringRef getOriginalSourceFileName() const {
      return OriginalSourceFile;
    }
  
    ASTMutationListener *getASTMutationListener();
    ASTDeserializationListener *getDeserializationListener();
  
    bool getOnlyLocalDecls() const { return OnlyLocalDecls; }
  
    bool getOwnsRemappedFileBuffers() const { return OwnsRemappedFileBuffers; }
    void setOwnsRemappedFileBuffers(bool val) { OwnsRemappedFileBuffers = val; }
  
    StringRef getMainFileName() const;
  
    /// If this ASTUnit came from an AST file, returns the filename for it.
    StringRef getASTFileName() const;
  
    using top_level_iterator = std::vector<Decl *>::iterator;
  
    top_level_iterator top_level_begin() {
      assert(!isMainFileAST() && "Invalid call for AST based ASTUnit!");
      if (!TopLevelDeclsInPreamble.empty())
        RealizeTopLevelDeclsFromPreamble();
      return TopLevelDecls.begin();
    }
  
    top_level_iterator top_level_end() {
      assert(!isMainFileAST() && "Invalid call for AST based ASTUnit!");
      if (!TopLevelDeclsInPreamble.empty())
        RealizeTopLevelDeclsFromPreamble();
      return TopLevelDecls.end();
    }
  
    std::size_t top_level_size() const {
      assert(!isMainFileAST() && "Invalid call for AST based ASTUnit!");
      return TopLevelDeclsInPreamble.size() + TopLevelDecls.size();
    }
  
    bool top_level_empty() const {
      assert(!isMainFileAST() && "Invalid call for AST based ASTUnit!");
      return TopLevelDeclsInPreamble.empty() && TopLevelDecls.empty();
    }
  
    /// Add a new top-level declaration.
    void addTopLevelDecl(Decl *D) {
      TopLevelDecls.push_back(D);
    }
  
    /// Add a new local file-level declaration.
    void addFileLevelDecl(Decl *D);
  
    /// Get the decls that are contained in a file in the Offset/Length
    /// range. \p Length can be 0 to indicate a point at \p Offset instead of
    /// a range.
    void findFileRegionDecls(FileID File, unsigned Offset, unsigned Length,
                             SmallVectorImpl<Decl *> &Decls);
  
    /// Retrieve a reference to the current top-level name hash value.
    ///
    /// Note: This is used internally by the top-level tracking action
    unsigned &getCurrentTopLevelHashValue() { return CurrentTopLevelHashValue; }
  
    /// Get the source location for the given file:line:col triplet.
    ///
    /// The difference with SourceManager::getLocation is that this method checks
    /// whether the requested location points inside the precompiled preamble
    /// in which case the returned source location will be a "loaded" one.
    SourceLocation getLocation(const FileEntry *File,
                               unsigned Line, unsigned Col) const;
  
    /// Get the source location for the given file:offset pair.
    SourceLocation getLocation(const FileEntry *File, unsigned Offset) const;
  
    /// If \p Loc is a loaded location from the preamble, returns
    /// the corresponding local location of the main file, otherwise it returns
    /// \p Loc.
    SourceLocation mapLocationFromPreamble(SourceLocation Loc) const;
  
    /// If \p Loc is a local location of the main file but inside the
    /// preamble chunk, returns the corresponding loaded location from the
    /// preamble, otherwise it returns \p Loc.
    SourceLocation mapLocationToPreamble(SourceLocation Loc) const;
  
    bool isInPreambleFileID(SourceLocation Loc) const;
    bool isInMainFileID(SourceLocation Loc) const;
    SourceLocation getStartOfMainFileID() const;
    SourceLocation getEndOfPreambleFileID() const;
  
    /// \see mapLocationFromPreamble.
    SourceRange mapRangeFromPreamble(SourceRange R) const {
      return SourceRange(mapLocationFromPreamble(R.getBegin()),
                         mapLocationFromPreamble(R.getEnd()));
    }
  
    /// \see mapLocationToPreamble.
    SourceRange mapRangeToPreamble(SourceRange R) const {
      return SourceRange(mapLocationToPreamble(R.getBegin()),
                         mapLocationToPreamble(R.getEnd()));
    }
  
    unsigned getPreambleCounterForTests() const { return PreambleCounter; }
  
    // Retrieve the diagnostics associated with this AST
    using stored_diag_iterator = StoredDiagnostic *;
    using stored_diag_const_iterator = const StoredDiagnostic *;
  
    stored_diag_const_iterator stored_diag_begin() const {
      return StoredDiagnostics.begin();
    }
  
    stored_diag_iterator stored_diag_begin() {
      return StoredDiagnostics.begin();
    }
  
    stored_diag_const_iterator stored_diag_end() const {
      return StoredDiagnostics.end();
    }
  
    stored_diag_iterator stored_diag_end() {
      return StoredDiagnostics.end();
    }
  
    unsigned stored_diag_size() const { return StoredDiagnostics.size(); }
  
    stored_diag_iterator stored_diag_afterDriver_begin() {
      if (NumStoredDiagnosticsFromDriver > StoredDiagnostics.size())
        NumStoredDiagnosticsFromDriver = 0;
      return StoredDiagnostics.begin() + NumStoredDiagnosticsFromDriver;
    }
  
    using cached_completion_iterator =
        std::vector<CachedCodeCompletionResult>::iterator;
  
    cached_completion_iterator cached_completion_begin() {
      return CachedCompletionResults.begin();
    }
  
    cached_completion_iterator cached_completion_end() {
      return CachedCompletionResults.end();
    }
  
    unsigned cached_completion_size() const {
      return CachedCompletionResults.size();
    }
  
    /// Returns an iterator range for the local preprocessing entities
    /// of the local Preprocessor, if this is a parsed source file, or the loaded
    /// preprocessing entities of the primary module if this is an AST file.
    llvm::iterator_range<PreprocessingRecord::iterator>
    getLocalPreprocessingEntities() const;
  
    /// Type for a function iterating over a number of declarations.
    /// \returns true to continue iteration and false to abort.
    using DeclVisitorFn = bool (*)(void *context, const Decl *D);
  
    /// Iterate over local declarations (locally parsed if this is a parsed
    /// source file or the loaded declarations of the primary module if this is an
    /// AST file).
    /// \returns true if the iteration was complete or false if it was aborted.
    bool visitLocalTopLevelDecls(void *context, DeclVisitorFn Fn);
  
    /// Get the PCH file if one was included.
    const FileEntry *getPCHFile();
  
    /// Returns true if the ASTUnit was constructed from a serialized
    /// module file.
    bool isModuleFile() const;
  
    std::unique_ptr<llvm::MemoryBuffer>
    getBufferForFile(StringRef Filename, std::string *ErrorStr = nullptr);
  
    /// Determine what kind of translation unit this AST represents.
    TranslationUnitKind getTranslationUnitKind() const { return TUKind; }
  
    /// Determine the input kind this AST unit represents.
    InputKind getInputKind() const;
  
    /// A mapping from a file name to the memory buffer that stores the
    /// remapped contents of that file.
    using RemappedFile = std::pair<std::string, llvm::MemoryBuffer *>;
  
    /// Create a ASTUnit. Gets ownership of the passed CompilerInvocation.
    static std::unique_ptr<ASTUnit>
    create(std::shared_ptr<CompilerInvocation> CI,
           IntrusiveRefCntPtr<DiagnosticsEngine> Diags, bool CaptureDiagnostics,
           bool UserFilesAreVolatile);
  
    enum WhatToLoad {
      /// Load options and the preprocessor state.
      LoadPreprocessorOnly,
  
      /// Load the AST, but do not restore Sema state.
      LoadASTOnly,
  
      /// Load everything, including Sema.
      LoadEverything
    };
  
    /// Create a ASTUnit from an AST file.
    ///
    /// \param Filename - The AST file to load.
    ///
    /// \param PCHContainerRdr - The PCHContainerOperations to use for loading and
    /// creating modules.
    /// \param Diags - The diagnostics engine to use for reporting errors; its
    /// lifetime is expected to extend past that of the returned ASTUnit.
    ///
    /// \returns - The initialized ASTUnit or null if the AST failed to load.
    static std::unique_ptr<ASTUnit> LoadFromASTFile(
        const std::string &Filename, const PCHContainerReader &PCHContainerRdr,
        WhatToLoad ToLoad, IntrusiveRefCntPtr<DiagnosticsEngine> Diags,
        const FileSystemOptions &FileSystemOpts, bool UseDebugInfo = false,
        bool OnlyLocalDecls = false, ArrayRef<RemappedFile> RemappedFiles = None,
        bool CaptureDiagnostics = false, bool AllowPCHWithCompilerErrors = false,
        bool UserFilesAreVolatile = false);
  
  private:
    /// Helper function for \c LoadFromCompilerInvocation() and
    /// \c LoadFromCommandLine(), which loads an AST from a compiler invocation.
    ///
    /// \param PrecompilePreambleAfterNParses After how many parses the preamble
    /// of this translation unit should be precompiled, to improve the performance
    /// of reparsing. Set to zero to disable preambles.
    ///
    /// \param VFS - A llvm::vfs::FileSystem to be used for all file accesses.
    /// Note that preamble is saved to a temporary directory on a RealFileSystem,
    /// so in order for it to be loaded correctly, VFS should have access to
    /// it(i.e., be an overlay over RealFileSystem).
    ///
    /// \returns \c true if a catastrophic failure occurred (which means that the
    /// \c ASTUnit itself is invalid), or \c false otherwise.
    bool LoadFromCompilerInvocation(
        std::shared_ptr<PCHContainerOperations> PCHContainerOps,
        unsigned PrecompilePreambleAfterNParses,
        IntrusiveRefCntPtr<llvm::vfs::FileSystem> VFS);
  
  public:
    /// Create an ASTUnit from a source file, via a CompilerInvocation
    /// object, by invoking the optionally provided ASTFrontendAction.
    ///
    /// \param CI - The compiler invocation to use; it must have exactly one input
    /// source file. The ASTUnit takes ownership of the CompilerInvocation object.
    ///
    /// \param PCHContainerOps - The PCHContainerOperations to use for loading and
    /// creating modules.
    ///
    /// \param Diags - The diagnostics engine to use for reporting errors; its
    /// lifetime is expected to extend past that of the returned ASTUnit.
    ///
    /// \param Action - The ASTFrontendAction to invoke. Its ownership is not
    /// transferred.
    ///
    /// \param Unit - optionally an already created ASTUnit. Its ownership is not
    /// transferred.
    ///
    /// \param Persistent - if true the returned ASTUnit will be complete.
    /// false means the caller is only interested in getting info through the
    /// provided \see Action.
    ///
    /// \param ErrAST - If non-null and parsing failed without any AST to return
    /// (e.g. because the PCH could not be loaded), this accepts the ASTUnit
    /// mainly to allow the caller to see the diagnostics.
    /// This will only receive an ASTUnit if a new one was created. If an already
    /// created ASTUnit was passed in \p Unit then the caller can check that.
    ///
    static ASTUnit *LoadFromCompilerInvocationAction(
        std::shared_ptr<CompilerInvocation> CI,
        std::shared_ptr<PCHContainerOperations> PCHContainerOps,
        IntrusiveRefCntPtr<DiagnosticsEngine> Diags,
        FrontendAction *Action = nullptr, ASTUnit *Unit = nullptr,
        bool Persistent = true, StringRef ResourceFilesPath = StringRef(),
        bool OnlyLocalDecls = false, bool CaptureDiagnostics = false,
        unsigned PrecompilePreambleAfterNParses = 0,
        bool CacheCodeCompletionResults = false,
        bool IncludeBriefCommentsInCodeCompletion = false,
        bool UserFilesAreVolatile = false,
        std::unique_ptr<ASTUnit> *ErrAST = nullptr);
  
    /// LoadFromCompilerInvocation - Create an ASTUnit from a source file, via a
    /// CompilerInvocation object.
    ///
    /// \param CI - The compiler invocation to use; it must have exactly one input
    /// source file. The ASTUnit takes ownership of the CompilerInvocation object.
    ///
    /// \param PCHContainerOps - The PCHContainerOperations to use for loading and
    /// creating modules.
    ///
    /// \param Diags - The diagnostics engine to use for reporting errors; its
    /// lifetime is expected to extend past that of the returned ASTUnit.
    //
    // FIXME: Move OnlyLocalDecls, UseBumpAllocator to setters on the ASTUnit, we
    // shouldn't need to specify them at construction time.
    static std::unique_ptr<ASTUnit> LoadFromCompilerInvocation(
        std::shared_ptr<CompilerInvocation> CI,
        std::shared_ptr<PCHContainerOperations> PCHContainerOps,
        IntrusiveRefCntPtr<DiagnosticsEngine> Diags, FileManager *FileMgr,
        bool OnlyLocalDecls = false, bool CaptureDiagnostics = false,
        unsigned PrecompilePreambleAfterNParses = 0,
        TranslationUnitKind TUKind = TU_Complete,
        bool CacheCodeCompletionResults = false,
        bool IncludeBriefCommentsInCodeCompletion = false,
        bool UserFilesAreVolatile = false);
  
    /// LoadFromCommandLine - Create an ASTUnit from a vector of command line
    /// arguments, which must specify exactly one source file.
    ///
    /// \param ArgBegin - The beginning of the argument vector.
    ///
    /// \param ArgEnd - The end of the argument vector.
    ///
    /// \param PCHContainerOps - The PCHContainerOperations to use for loading and
    /// creating modules.
    ///
    /// \param Diags - The diagnostics engine to use for reporting errors; its
    /// lifetime is expected to extend past that of the returned ASTUnit.
    ///
    /// \param ResourceFilesPath - The path to the compiler resource files.
    ///
    /// \param ModuleFormat - If provided, uses the specific module format.
    ///
    /// \param ErrAST - If non-null and parsing failed without any AST to return
    /// (e.g. because the PCH could not be loaded), this accepts the ASTUnit
    /// mainly to allow the caller to see the diagnostics.
    ///
    /// \param VFS - A llvm::vfs::FileSystem to be used for all file accesses.
    /// Note that preamble is saved to a temporary directory on a RealFileSystem,
    /// so in order for it to be loaded correctly, VFS should have access to
    /// it(i.e., be an overlay over RealFileSystem). RealFileSystem will be used
    /// if \p VFS is nullptr.
    ///
    // FIXME: Move OnlyLocalDecls, UseBumpAllocator to setters on the ASTUnit, we
    // shouldn't need to specify them at construction time.
    static ASTUnit *LoadFromCommandLine(
        const char **ArgBegin, const char **ArgEnd,
        std::shared_ptr<PCHContainerOperations> PCHContainerOps,
        IntrusiveRefCntPtr<DiagnosticsEngine> Diags, StringRef ResourceFilesPath,
        bool OnlyLocalDecls = false, bool CaptureDiagnostics = false,
        ArrayRef<RemappedFile> RemappedFiles = None,
        bool RemappedFilesKeepOriginalName = true,
        unsigned PrecompilePreambleAfterNParses = 0,
        TranslationUnitKind TUKind = TU_Complete,
        bool CacheCodeCompletionResults = false,
        bool IncludeBriefCommentsInCodeCompletion = false,
        bool AllowPCHWithCompilerErrors = false,
        SkipFunctionBodiesScope SkipFunctionBodies =
            SkipFunctionBodiesScope::None,
        bool SingleFileParse = false, bool UserFilesAreVolatile = false,
        bool ForSerialization = false,
        llvm::Optional<StringRef> ModuleFormat = llvm::None,
        std::unique_ptr<ASTUnit> *ErrAST = nullptr,
        IntrusiveRefCntPtr<llvm::vfs::FileSystem> VFS = nullptr);
  
    /// Reparse the source files using the same command-line options that
    /// were originally used to produce this translation unit.
    ///
    /// \param VFS - A llvm::vfs::FileSystem to be used for all file accesses.
    /// Note that preamble is saved to a temporary directory on a RealFileSystem,
    /// so in order for it to be loaded correctly, VFS should give an access to
    /// this(i.e. be an overlay over RealFileSystem).
    /// FileMgr->getVirtualFileSystem() will be used if \p VFS is nullptr.
    ///
    /// \returns True if a failure occurred that causes the ASTUnit not to
    /// contain any translation-unit information, false otherwise.
    bool Reparse(std::shared_ptr<PCHContainerOperations> PCHContainerOps,
                 ArrayRef<RemappedFile> RemappedFiles = None,
                 IntrusiveRefCntPtr<llvm::vfs::FileSystem> VFS = nullptr);
  
    /// Free data that will be re-generated on the next parse.
    ///
    /// Preamble-related data is not affected.
    void ResetForParse();
  
    /// Perform code completion at the given file, line, and
    /// column within this translation unit.
    ///
    /// \param File The file in which code completion will occur.
    ///
    /// \param Line The line at which code completion will occur.
    ///
    /// \param Column The column at which code completion will occur.
    ///
    /// \param IncludeMacros Whether to include macros in the code-completion
    /// results.
    ///
    /// \param IncludeCodePatterns Whether to include code patterns (such as a
    /// for loop) in the code-completion results.
    ///
    /// \param IncludeBriefComments Whether to include brief documentation within
    /// the set of code completions returned.
    ///
    /// FIXME: The Diag, LangOpts, SourceMgr, FileMgr, StoredDiagnostics, and
    /// OwnedBuffers parameters are all disgusting hacks. They will go away.
    void CodeComplete(StringRef File, unsigned Line, unsigned Column,
                      ArrayRef<RemappedFile> RemappedFiles, bool IncludeMacros,
                      bool IncludeCodePatterns, bool IncludeBriefComments,
                      CodeCompleteConsumer &Consumer,
                      std::shared_ptr<PCHContainerOperations> PCHContainerOps,
                      DiagnosticsEngine &Diag, LangOptions &LangOpts,
                      SourceManager &SourceMgr, FileManager &FileMgr,
                      SmallVectorImpl<StoredDiagnostic> &StoredDiagnostics,
                      SmallVectorImpl<const llvm::MemoryBuffer *> &OwnedBuffers);
  
    /// Save this translation unit to a file with the given name.
    ///
    /// \returns true if there was a file error or false if the save was
    /// successful.
    bool Save(StringRef File);
  
    /// Serialize this translation unit with the given output stream.
    ///
    /// \returns True if an error occurred, false otherwise.
    bool serialize(raw_ostream &OS);
  };
  
  } // namespace clang
  
  #endif // LLVM_CLANG_FRONTEND_ASTUNIT_H
  