lib/Serialization/ModuleFile.h

//===--- ModuleFile.h - Info about a loaded serialized module ---*- C++ -*-===//
//
// This source file is part of the Swift.org open source project
//
// Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
// Licensed under Apache License v2.0 with Runtime Library Exception
//
// See https://swift.org/LICENSE.txt for license information
// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
//
//===----------------------------------------------------------------------===//

#ifndef SWIFT_SERIALIZATION_MODULEFILE_H
#define SWIFT_SERIALIZATION_MODULEFILE_H

#include "ModuleFormat.h"
#include "swift/AST/Identifier.h"
#include "swift/AST/LazyResolver.h"
#include "swift/AST/LinkLibrary.h"
#include "swift/AST/FileUnit.h"
#include "swift/AST/Module.h"
#include "swift/AST/RawComment.h"
#include "swift/AST/TypeLoc.h"
#include "swift/Serialization/Validation.h"
#include "swift/Basic/LLVM.h"
#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/TinyPtrVector.h"
#include "llvm/Bitcode/BitstreamReader.h"
#include "llvm/Support/Error.h"
#include "llvm/Support/MemoryBuffer.h"

namespace llvm {
  class BitstreamCursor;
  class BitstreamReader;
  class MemoryBuffer;
  template <typename Info> class OnDiskIterableChainedHashTable;
}

namespace swift {
class Decl;
class FileUnit;
class ModuleDecl;
class Pattern;
class ProtocolConformance;

/// A serialized module, along with the tools to access it.
class ModuleFile
  : public LazyMemberLoader,
    public LazyConformanceLoader {
  friend class SerializedASTFile;
  friend class DeclDeserializer;
  friend class TypeDeserializer;
  friend class SILDeserializer;
  using Status = serialization::Status;
  using TypeID = serialization::TypeID;

  /// A reference back to the AST representation of the file.
  FileUnit *FileContext = nullptr;

  /// The module that this module is an overlay of, if any.
  ModuleDecl *UnderlyingModule = nullptr;

  /// The module file data.
  std::unique_ptr<llvm::MemoryBuffer> ModuleInputBuffer;
  std::unique_ptr<llvm::MemoryBuffer> ModuleDocInputBuffer;
  std::unique_ptr<llvm::MemoryBuffer> ModuleSourceInfoInputBuffer;

  /// The cursor used to lazily load things from the file.
  llvm::BitstreamCursor DeclTypeCursor;

  llvm::BitstreamCursor SILCursor;
  llvm::BitstreamCursor SILIndexCursor;
  llvm::BitstreamCursor DeclMemberTablesCursor;

  /// The name of the module.
  StringRef Name;
  friend StringRef getNameOfModule(const ModuleFile *);

  /// The target the module was built for.
  StringRef TargetTriple;

  /// The name of the module interface this module was compiled from.
  ///
  /// Empty if this module didn't come from an interface file.
  StringRef ModuleInterfacePath;

  /// The Swift compatibility version in use when this module was built.
  version::Version CompatibilityVersion;

  /// The data blob containing all of the module's identifiers.
  StringRef IdentifierData;

  /// A callback to be invoked every time a type was deserialized.
  std::function<void(Type)> DeserializedTypeCallback;

  /// Is this module file actually a .sib file? .sib files are serialized SIL at
  /// arbitrary granularity and arbitrary stage; unlike serialized Swift
  /// modules, which are assumed to contain canonical SIL for an entire module.
  bool IsSIB = false;

public:
  /// Represents another module that has been imported as a dependency.
  class Dependency {
  public:
    ModuleDecl::ImportedModule Import = {};
    const StringRef RawPath;

  private:
    using ImportFilterKind = ModuleDecl::ImportFilterKind;
    const unsigned RawImportControl : 2;
    const unsigned IsHeader : 1;
    const unsigned IsScoped : 1;

    static unsigned rawControlFromKind(ImportFilterKind importKind) {
      return llvm::countTrailingZeros(static_cast<unsigned>(importKind));
    }
    ImportFilterKind getImportControl() const {
      return static_cast<ImportFilterKind>(1 << RawImportControl);
    }

    Dependency(StringRef path, bool isHeader, ImportFilterKind importControl,
               bool isScoped)
      : RawPath(path), RawImportControl(rawControlFromKind(importControl)),
        IsHeader(isHeader), IsScoped(isScoped) {
      assert(llvm::countPopulation(static_cast<unsigned>(importControl)) == 1 &&
             "must be a particular filter option, not a bitset");
      assert(getImportControl() == importControl && "not enough bits");
    }

  public:
    Dependency(StringRef path, ImportFilterKind importControl, bool isScoped)
      : Dependency(path, false, importControl, isScoped) {}

    static Dependency forHeader(StringRef headerPath, bool exported) {
      auto importControl = exported ? ImportFilterKind::Public
                                    : ImportFilterKind::Private;
      return Dependency(headerPath, true, importControl, false);
    }

    bool isLoaded() const {
      return Import.second != nullptr;
    }

    bool isExported() const {
      return getImportControl() == ImportFilterKind::Public;
    }
    bool isImplementationOnly() const {
      return getImportControl() == ImportFilterKind::ImplementationOnly;
    }

    bool isHeader() const { return IsHeader; }
    bool isScoped() const { return IsScoped; }

    std::string getPrettyPrintedPath() const;
  };

private:
  /// All modules this module depends on.
  SmallVector<Dependency, 8> Dependencies;

  struct SearchPath {
    StringRef Path;
    bool IsFramework;
    bool IsSystem;
  };
  /// Search paths this module may provide.
  ///
  /// This is not intended for use by frameworks, but may show up in debug
  /// modules.
  std::vector<SearchPath> SearchPaths;

  /// Info for the (lone) imported header for this module.
  struct {
    off_t fileSize;
    time_t fileModTime;
    StringRef contents;
  } importedHeaderInfo = {};

  /// All of this module's link-time dependencies.
  SmallVector<LinkLibrary, 8> LinkLibraries;

public:
  template <typename T>
  class Serialized {
  private:
    using RawBitOffset = uint64_t;

    using ImplTy = PointerUnion<T, serialization::BitOffset>;
    ImplTy Value;

  public:
    /*implicit*/ Serialized(serialization::BitOffset offset) : Value(offset) {}

    bool isComplete() const {
      return Value.template is<T>();
    }

    T get() const {
      return Value.template get<T>();
    }

    /*implicit*/ operator T() const {
      return get();
    }

    /*implicit*/ operator serialization::BitOffset() const {
      return Value.template get<serialization::BitOffset>();
    }

    /*implicit*/ operator RawBitOffset() const {
      return Value.template get<serialization::BitOffset>();
    }

    Serialized &operator=(T deserialized) {
      assert(!isComplete() || ImplTy(deserialized) == Value);
      Value = deserialized;
      return *this;
    }

    void uncheckedOverwrite(T t) {
      Value = t;
    }
  };

  /// A class for holding a value that can be partially deserialized.
  ///
  /// This class assumes that "T()" is not a valid deserialized value.
  template <typename T>
  class PartiallySerialized {
  private:
    using RawBitOffset = decltype(DeclTypeCursor.GetCurrentBitNo());

    /// The deserialized value.
    T Value;

    /// The offset.
    unsigned Offset : 31;

    unsigned IsFullyDeserialized : 1;

  public:
    /*implicit*/ PartiallySerialized(serialization::BitOffset offset)
      : Value(), Offset(offset), IsFullyDeserialized(0) {}

    /*implicit*/ PartiallySerialized(RawBitOffset offset)
      : Value(), Offset(static_cast<unsigned>(offset)), IsFullyDeserialized(0) {
      assert(Offset == offset && "offset is too large");
    }

    bool isDeserialized() const {
      return Value != T();
    }

    bool isFullyDeserialized() const {
      return isDeserialized() && IsFullyDeserialized;
    }

    serialization::BitOffset getOffset() const {
      assert(!isFullyDeserialized());
      return Offset;
    }

    T get() const {
      assert(isDeserialized());
      return Value;
    }

    void reset() {
      IsFullyDeserialized = 0;
      Value = T();
    }

    void set(T value, bool isFullyDeserialized) {
      assert(!isDeserialized() || Value == value);
      Value = value;
      IsFullyDeserialized = isFullyDeserialized;
    }
  };

private:
  /// An allocator for buffers owned by the file.
  llvm::BumpPtrAllocator Allocator;

  /// Allocates a buffer using #Allocator and initializes it with the contents
  /// of the container \p rawData, then stores it in \p buffer.
  ///
  /// \p buffer is passed as an argument rather than returned so that the
  /// element type can be inferred.
  template <typename T, typename RawData>
  void allocateBuffer(MutableArrayRef<T> &buffer, const RawData &rawData);

  /// Allocates a buffer using #Allocator and initializes it with the contents
  /// of the container \p rawData, then stores it in \p buffer.
  ///
  /// \p buffer is passed as an argument rather than returned so that the
  /// element type can be inferred.
  template <typename T, typename RawData>
  void allocateBuffer(ArrayRef<T> &buffer, const RawData &rawData) {
    assert(buffer.empty());
    MutableArrayRef<T> result;
    allocateBuffer(result, rawData);
    buffer = result;
  }

  /// Decls referenced by this module.
  MutableArrayRef<Serialized<Decl*>> Decls;

  /// Local DeclContexts referenced by this module.
  MutableArrayRef<Serialized<DeclContext*>> LocalDeclContexts;

  /// Normal protocol conformances referenced by this module.
  MutableArrayRef<Serialized<NormalProtocolConformance *>> NormalConformances;

  /// SILLayouts referenced by this module.
  MutableArrayRef<Serialized<SILLayout *>> SILLayouts;

  /// Types referenced by this module.
  MutableArrayRef<Serialized<Type>> Types;

  /// Generic signatures referenced by this module.
  MutableArrayRef<Serialized<GenericSignature>> GenericSignatures;

  /// Substitution maps referenced by this module.
  MutableArrayRef<Serialized<SubstitutionMap>> SubstitutionMaps;

  /// Represents an identifier that may or may not have been deserialized yet.
  ///
  /// If \c Ident is empty, the identifier has not been loaded yet.
  class SerializedIdentifier {
  public:
    Identifier Ident;
    unsigned Offset;

    template <typename IntTy>
    /*implicit*/ SerializedIdentifier(IntTy rawOffset)
      : Offset(static_cast<unsigned>(rawOffset)) {
      assert(Offset == rawOffset && "not enough bits");
    }
  };

  /// Identifiers referenced by this module.
  MutableArrayRef<SerializedIdentifier> Identifiers;

  class DeclTableInfo;
  using SerializedDeclTable =
      llvm::OnDiskIterableChainedHashTable<DeclTableInfo>;

  class ExtensionTableInfo;
  using SerializedExtensionTable =
      llvm::OnDiskIterableChainedHashTable<ExtensionTableInfo>;

  class LocalDeclTableInfo;
  using SerializedLocalDeclTable =
      llvm::OnDiskIterableChainedHashTable<LocalDeclTableInfo>;
      
  using OpaqueReturnTypeDeclTableInfo = LocalDeclTableInfo;
  using SerializedOpaqueReturnTypeDeclTable =
      llvm::OnDiskIterableChainedHashTable<OpaqueReturnTypeDeclTableInfo>;

  class NestedTypeDeclsTableInfo;
  using SerializedNestedTypeDeclsTable =
      llvm::OnDiskIterableChainedHashTable<NestedTypeDeclsTableInfo>;

  class DeclMemberNamesTableInfo;
  using SerializedDeclMemberNamesTable =
      llvm::OnDiskIterableChainedHashTable<DeclMemberNamesTableInfo>;

  class DeclMembersTableInfo;
  using SerializedDeclMembersTable =
      llvm::OnDiskIterableChainedHashTable<DeclMembersTableInfo>;

  std::unique_ptr<SerializedDeclTable> TopLevelDecls;
  std::unique_ptr<SerializedDeclTable> OperatorDecls;
  std::unique_ptr<SerializedDeclTable> PrecedenceGroupDecls;
  std::unique_ptr<SerializedDeclTable> ClassMembersForDynamicLookup;
  std::unique_ptr<SerializedDeclTable> OperatorMethodDecls;
  std::unique_ptr<SerializedExtensionTable> ExtensionDecls;
  std::unique_ptr<SerializedLocalDeclTable> LocalTypeDecls;
  std::unique_ptr<SerializedOpaqueReturnTypeDeclTable> OpaqueReturnTypeDecls;
  std::unique_ptr<SerializedNestedTypeDeclsTable> NestedTypeDecls;
  std::unique_ptr<SerializedDeclMemberNamesTable> DeclMemberNames;

  llvm::DenseMap<uint32_t,
           std::unique_ptr<SerializedDeclMembersTable>> DeclMembersTables;

  class ObjCMethodTableInfo;
  using SerializedObjCMethodTable =
    llvm::OnDiskIterableChainedHashTable<ObjCMethodTableInfo>;

  std::unique_ptr<SerializedObjCMethodTable> ObjCMethods;

  llvm::DenseMap<const ValueDecl *, Identifier> PrivateDiscriminatorsByValue;
  llvm::DenseMap<const ValueDecl *, StringRef> FilenamesForPrivateValues;

  TinyPtrVector<Decl *> ImportDecls;

  ArrayRef<serialization::DeclID> OrderedTopLevelDecls;

  class DeclCommentTableInfo;
  using SerializedDeclCommentTable =
      llvm::OnDiskIterableChainedHashTable<DeclCommentTableInfo>;

  using GroupNameTable = llvm::DenseMap<unsigned, StringRef>;

  std::unique_ptr<GroupNameTable> GroupNamesMap;
  std::unique_ptr<SerializedDeclCommentTable> DeclCommentTable;

  class DeclUSRTableInfo;
  using SerializedDeclUSRTable =
      llvm::OnDiskIterableChainedHashTable<DeclUSRTableInfo>;
  std::unique_ptr<SerializedDeclUSRTable> DeclUSRsTable;

  /// A blob of 0 terminated string segments referenced in \c SourceLocsTextData
  StringRef SourceLocsTextData;

  /// An array of fixed size source location data for each USR appearing in
  /// \c DeclUSRsTable.
  StringRef BasicDeclLocsData;

  struct ModuleBits {
    /// The decl ID of the main class in this module file, if it has one.
    unsigned EntryPointDeclID : 31;

    /// Whether or not this module file comes from a context that had a main
    /// entry point.
    unsigned HasEntryPoint : 1;

    /// Whether this module file comes from a framework.
    unsigned IsFramework : 1;

    /// Whether or not ImportDecls is valid.
    unsigned ComputedImportDecls : 1;

    /// Whether an error has been detected setting up this module file.
    unsigned HasError : 1;

    // Explicitly pad out to the next word boundary.
    unsigned : 0;
  } Bits = {};
  static_assert(sizeof(ModuleBits) <= 8, "The bit set should be small");

  bool hasError() const {
    return Bits.HasError;
  }

  void setEntryPointClassID(serialization::DeclID DID) {
    Bits.HasEntryPoint = true;
    Bits.EntryPointDeclID = DID;
    assert(Bits.EntryPointDeclID == DID && "not enough bits for DeclID");
  }

  /// Creates a new AST node to represent a deserialized decl.
  template <typename T, typename ...Args>
  T *createDecl(Args &&... args);

  /// Constructs a new module and validates it.
  ModuleFile(std::unique_ptr<llvm::MemoryBuffer> moduleInputBuffer,
             std::unique_ptr<llvm::MemoryBuffer> moduleDocInputBuffer,
             std::unique_ptr<llvm::MemoryBuffer> moduleSourceInfoInputBuffer,
             bool isFramework, serialization::ValidationInfo &info,
             serialization::ExtendedValidationInfo *extInfo);

public:
  /// Change the status of the current module.
  Status error(Status issue) {
    assert(issue != Status::Valid);
    assert((issue != Status::Malformed || !FileContext) &&
           "too late to complain about the well-formedness of the module");
    Bits.HasError = true;
    return issue;
  }

  /// Emits one last diagnostic, logs the error, and then aborts for the stack
  /// trace.
  LLVM_ATTRIBUTE_NORETURN void fatal(llvm::Error error);

  LLVM_ATTRIBUTE_NORETURN void fatal() {
    fatal(llvm::make_error<llvm::StringError>(
        "(see \"While...\" info below)", llvm::inconvertibleErrorCode()));
  }

  ASTContext &getContext() const {
    assert(FileContext && "no associated context yet");
    return FileContext->getParentModule()->getASTContext();
  }

  ModuleDecl *getAssociatedModule() const {
    assert(FileContext && "no associated context yet");
    return FileContext->getParentModule();
  }

  FileUnit *getFile() const {
    assert(FileContext && "no associated context yet");
    return FileContext;
  }

private:
  /// Read an on-disk decl hash table stored in index_block::DeclListLayout
  /// format.
  std::unique_ptr<SerializedDeclTable>
  readDeclTable(ArrayRef<uint64_t> fields, StringRef blobData);

  /// Read an on-disk local decl hash table stored in
  /// index_block::DeclListLayout format.
  std::unique_ptr<SerializedLocalDeclTable>
  readLocalDeclTable(ArrayRef<uint64_t> fields, StringRef blobData);

  /// Read an on-disk Objective-C method table stored in
  /// index_block::ObjCMethodTableLayout format.
  std::unique_ptr<ModuleFile::SerializedObjCMethodTable>
  readObjCMethodTable(ArrayRef<uint64_t> fields, StringRef blobData);

  /// Read an on-disk local decl hash table stored in
  /// index_block::ExtensionTableLayout format.
  std::unique_ptr<SerializedExtensionTable>
  readExtensionTable(ArrayRef<uint64_t> fields, StringRef blobData);

  /// Read an on-disk local decl hash table stored in
  /// index_block::NestedTypeDeclsLayout format.
  std::unique_ptr<SerializedNestedTypeDeclsTable>
  readNestedTypeDeclsTable(ArrayRef<uint64_t> fields, StringRef blobData);

  /// Read an on-disk local decl-name hash table stored in
  /// index_block::DeclMemberNamesLayout format.
  std::unique_ptr<SerializedDeclMemberNamesTable>
  readDeclMemberNamesTable(ArrayRef<uint64_t> fields, StringRef blobData);

  /// Read an on-disk local decl-members hash table stored in
  /// index_block::DeclMembersLayout format.
  std::unique_ptr<SerializedDeclMembersTable>
  readDeclMembersTable(ArrayRef<uint64_t> fields, StringRef blobData);

  /// Reads the index block, which contains global tables.
  ///
  /// Returns false if there was an error.
  bool readIndexBlock(llvm::BitstreamCursor &cursor);

  /// Read an on-disk decl hash table stored in
  /// \c comment_block::DeclCommentListLayout format.
  std::unique_ptr<SerializedDeclCommentTable>
  readDeclCommentTable(ArrayRef<uint64_t> fields, StringRef blobData);

  std::unique_ptr<GroupNameTable>
  readGroupTable(ArrayRef<uint64_t> fields, StringRef blobData);

  /// Reads the comment block, which contains USR to comment mappings.
  ///
  /// Returns false if there was an error.
  bool readCommentBlock(llvm::BitstreamCursor &cursor);

  /// Loads data from #ModuleDocInputBuffer.
  ///
  /// Returns false if there was an error.
  bool readModuleDocIfPresent();

  /// Reads the source loc block, which contains USR to decl location mapping.
  ///
  /// Returns false if there was an error.
  bool readDeclLocsBlock(llvm::BitstreamCursor &cursor);

  /// Loads data from #ModuleSourceInfoInputBuffer.
  ///
  /// Returns false if there was an error.
  bool readModuleSourceInfoIfPresent();

  /// Read an on-disk decl hash table stored in
  /// \c sourceinfo_block::DeclUSRSLayout format.
  std::unique_ptr<SerializedDeclUSRTable>
  readDeclUSRsTable(ArrayRef<uint64_t> fields, StringRef blobData);

  /// Recursively reads a pattern from \c DeclTypeCursor.
  llvm::Expected<Pattern *> readPattern(DeclContext *owningDC);

  ParameterList *readParameterList();
  
  /// Reads a generic param list from \c DeclTypeCursor.
  ///
  /// If the record at the cursor is not a generic param list, returns null
  /// without moving the cursor.
  GenericParamList *maybeReadGenericParams(DeclContext *DC);

  /// Reads a set of requirements from \c DeclTypeCursor.
  void readGenericRequirements(SmallVectorImpl<Requirement> &requirements,
                               llvm::BitstreamCursor &Cursor);

  /// Reads a set of requirements from \c DeclTypeCursor, returns the first
  /// error, if any.
  llvm::Error
  readGenericRequirementsChecked(SmallVectorImpl<Requirement> &requirements,
                                 llvm::BitstreamCursor &Cursor);

  /// Populates the protocol's default witness table.
  ///
  /// Returns true if there is an error.
  ///
  /// Note: this destroys the cursor's position in the stream. Furthermore,
  /// because it reads from the cursor, it is not possible to reset the cursor
  /// after reading. Nothing should ever follow a DEFAULT_WITNESS_TABLE record.
  bool readDefaultWitnessTable(ProtocolDecl *proto);

  /// Resolves a cross-reference, starting from the given module.
  ///
  /// Note: this destroys the cursor's position in the stream. Furthermore,
  /// because it reads from the cursor, it is not possible to reset the cursor
  /// after reading. Nothing should ever follow an XREF record except
  /// XREF_PATH_PIECE records.
  llvm::Expected<Decl *> resolveCrossReference(serialization::ModuleID MID,
                                               uint32_t pathLen);

  /// Populates TopLevelIDs for name lookup.
  void buildTopLevelDeclMap();

  struct AccessorRecord {
    SmallVector<serialization::DeclID, 8> IDs;
  };

  /// Sets the accessors for \p storage based on \p rawStorageKind.
  void configureStorage(AbstractStorageDecl *storage,
                        uint8_t rawOpaqueReadOwnership,
                        uint8_t rawReadImpl,
                        uint8_t rawWriteImpl,
                        uint8_t rawReadWriteImpl,
                        AccessorRecord &accessors);

public:
  /// Loads a module from the given memory buffer.
  ///
  /// \param moduleInputBuffer A memory buffer containing the serialized module
  /// data. The created ModuleFile takes ownership of the buffer, even if
  /// there's an error in loading.
  /// \param moduleDocInputBuffer An optional memory buffer containing
  /// documentation data for the module. The created ModuleFile takes ownership
  /// of the buffer, even if there's an error in loading.
  /// \param isFramework If true, this is treated as a framework module for
  /// linking purposes.
  /// \param[out] theModule The loaded module.
  /// \param[out] extInfo Optionally, extra info serialized about the module.
  /// \returns Whether the module was successfully loaded, or what went wrong
  ///          if it was not.
  static serialization::ValidationInfo
  load(std::unique_ptr<llvm::MemoryBuffer> moduleInputBuffer,
       std::unique_ptr<llvm::MemoryBuffer> moduleDocInputBuffer,
       std::unique_ptr<llvm::MemoryBuffer> moduleSourceInfoInputBuffer,
       bool isFramework, std::unique_ptr<ModuleFile> &theModule,
       serialization::ExtendedValidationInfo *extInfo = nullptr) {
    serialization::ValidationInfo info;
    theModule.reset(new ModuleFile(std::move(moduleInputBuffer),
                                   std::move(moduleDocInputBuffer),
                                   std::move(moduleSourceInfoInputBuffer),
                                   isFramework, info, extInfo));
    return info;
  }

  // Out of line to avoid instantiation OnDiskChainedHashTable here.
  ~ModuleFile();

  /// Associates this module file with the AST node representing it.
  ///
  /// Checks that the file is compatible with the AST module it's being loaded
  /// into, loads any dependencies needed to understand the module, and updates
  /// the ASTContext and ClangImporter with search paths and other information
  /// from the module.
  ///
  /// \param file The FileUnit that represents this file's place in the AST.
  /// \param diagLoc A location used for diagnostics that occur during loading.
  /// This does not include diagnostics about \e this file failing to load,
  /// but rather other things that might be imported as part of bringing the
  /// file into the AST.
  /// \param treatAsPartialModule If true, processes implementation-only
  /// information instead of assuming the client won't need it and shouldn't
  /// see it.
  ///
  /// \returns any error that occurred during association, such as being
  /// compiled for a different OS.
  Status associateWithFileContext(FileUnit *file, SourceLoc diagLoc,
                                  bool treatAsPartialModule);

  /// Transfers ownership of a buffer that might contain source code where
  /// other parts of the compiler could have emitted diagnostics, to keep them
  /// alive even if the ModuleFile is destroyed.
  ///
  /// Should only be called when a failure has been reported from
  /// ModuleFile::load or ModuleFile::associateWithFileContext.
  std::unique_ptr<llvm::MemoryBuffer> takeBufferForDiagnostics();

  /// Returns the list of modules this module depends on.
  ArrayRef<Dependency> getDependencies() const {
    return Dependencies;
  }

  /// The module that this module is an overlay for, if any.
  ModuleDecl *getUnderlyingModule() const { return UnderlyingModule; }

  /// Searches the module's top-level decls for the given identifier.
  void lookupValue(DeclName name, SmallVectorImpl<ValueDecl*> &results);

  /// Searches the module's local type decls for the given mangled name.
  TypeDecl *lookupLocalType(StringRef MangledName);
      
  /// Search the module's opaque return type decls for the one corresponding to
  /// the given mangled name.
  OpaqueTypeDecl *lookupOpaqueResultType(StringRef MangledName);

  /// Searches the module's nested type decls table for the given member of
  /// the given type.
  TypeDecl *lookupNestedType(Identifier name, const NominalTypeDecl *parent);

  /// Searches the module's operators for one with the given name and fixity.
  ///
  /// If none is found, returns null.
  OperatorDecl *lookupOperator(Identifier name, DeclKind fixity);

  /// Searches the module's precedence groups for one with the given
  /// name and fixity.
  ///
  /// If none is found, returns null.
  PrecedenceGroupDecl *lookupPrecedenceGroup(Identifier name);

  /// Adds any imported modules to the given vector.
  void getImportedModules(SmallVectorImpl<ModuleDecl::ImportedModule> &results,
                          ModuleDecl::ImportFilter filter);

  void getImportDecls(SmallVectorImpl<Decl *> &Results);

  /// Reports all visible top-level members in this module.
  void lookupVisibleDecls(ModuleDecl::AccessPathTy accessPath,
                          VisibleDeclConsumer &consumer,
                          NLKind lookupKind);

  /// Loads extensions for the given decl.
  ///
  /// Note that this may cause other decls to load as well.
  void loadExtensions(NominalTypeDecl *nominal);

  /// Load the methods within the given class that produce
  /// Objective-C class or instance methods with the given selector.
  ///
  /// \param classDecl The class in which we are searching for @objc methods.
  /// The search only considers this class and its extensions; not any
  /// superclasses.
  ///
  /// \param selector The selector to search for.
  ///
  /// \param isInstanceMethod Whether we are looking for an instance method
  /// (vs. a class method).
  ///
  /// \param methods The list of @objc methods in this class that have this
  /// selector and are instance/class methods as requested.
  void loadObjCMethods(ClassDecl *classDecl,
                       ObjCSelector selector,
                       bool isInstanceMethod,
                       llvm::TinyPtrVector<AbstractFunctionDecl *> &methods);

  /// Reports all class members in the module to the given consumer.
  ///
  /// This is intended for use with id-style lookup and code completion.
  void lookupClassMembers(ModuleDecl::AccessPathTy accessPath,
                          VisibleDeclConsumer &consumer);

  /// Adds class members in the module with the given name to the given vector.
  ///
  /// This is intended for use with id-style lookup.
  void lookupClassMember(ModuleDecl::AccessPathTy accessPath,
                         DeclName name,
                         SmallVectorImpl<ValueDecl*> &results);

  /// Find all Objective-C methods with the given selector.
  void lookupObjCMethods(
         ObjCSelector selector,
         SmallVectorImpl<AbstractFunctionDecl *> &results);

  /// Reports all link-time dependencies.
  void collectLinkLibraries(ModuleDecl::LinkLibraryCallback callback) const;

  /// Adds all top-level decls to the given vector.
  void getTopLevelDecls(SmallVectorImpl<Decl*> &Results);

  /// Adds all precedence groups to the given vector.
  void getPrecedenceGroups(SmallVectorImpl<PrecedenceGroupDecl*> &Results);

  /// Adds all local type decls to the given vector.
  void getLocalTypeDecls(SmallVectorImpl<TypeDecl*> &Results);
      
  /// Add all opaque return type decls in the module to the given vector.
  void getOpaqueReturnTypeDecls(SmallVectorImpl<OpaqueTypeDecl*> &Results);

  /// Adds all top-level decls to the given vector.
  ///
  /// This includes all decls that should be displayed to clients of the module.
  /// This can differ from \c getTopLevelDecls, e.g. it returns decls from a
  /// shadowed clang module.
  void getDisplayDecls(SmallVectorImpl<Decl*> &results);

  StringRef getModuleFilename() const {
    if (!ModuleInterfacePath.empty())
      return ModuleInterfacePath;
    // FIXME: This seems fragile, maybe store the filename separately ?
    return ModuleInputBuffer->getBufferIdentifier();
  }

  /// AST-verify imported decls.
  ///
  /// Has no effect in NDEBUG builds.
  void verify() const;

  virtual void loadAllMembers(Decl *D,
                              uint64_t contextData) override;

  virtual
  Optional<TinyPtrVector<ValueDecl *>>
  loadNamedMembers(const IterableDeclContext *IDC, DeclBaseName N,
                   uint64_t contextData) override;

  virtual void
  loadAllConformances(const Decl *D, uint64_t contextData,
                    SmallVectorImpl<ProtocolConformance*> &Conforms) override;

  virtual Type loadAssociatedTypeDefault(const AssociatedTypeDecl *ATD,
                                         uint64_t contextData) override;

  virtual void finishNormalConformance(NormalProtocolConformance *conformance,
                                       uint64_t contextData) override;

  void
  loadRequirementSignature(const ProtocolDecl *proto, uint64_t contextData,
                           SmallVectorImpl<Requirement> &requirements) override;

  Optional<StringRef> getGroupNameById(unsigned Id) const;
  Optional<StringRef> getSourceFileNameById(unsigned Id) const;
  Optional<StringRef> getGroupNameForDecl(const Decl *D) const;
  Optional<StringRef> getSourceFileNameForDecl(const Decl *D) const;
  Optional<unsigned> getSourceOrderForDecl(const Decl *D) const;
  void collectAllGroups(std::vector<StringRef> &Names) const;
  Optional<CommentInfo> getCommentForDecl(const Decl *D) const;
  Optional<CommentInfo> getCommentForDeclByUSR(StringRef USR) const;
  Optional<StringRef> getGroupNameByUSR(StringRef USR) const;
  Optional<BasicDeclLocs> getBasicDeclLocsForDecl(const Decl *D) const;
  Identifier getDiscriminatorForPrivateValue(const ValueDecl *D);

  // MARK: Deserialization interface

  llvm::BitstreamCursor getSILCursor() const {
    return SILCursor;
  }
  llvm::BitstreamCursor getSILIndexCursor() const {
    return SILIndexCursor;
  }

  /// Returns the type with the given ID, deserializing it if needed.
  ///
  /// \sa getTypeChecked
  Type getType(serialization::TypeID TID);

  /// Returns the type with the given ID, deserializing it if needed.
  llvm::Expected<Type> getTypeChecked(serialization::TypeID TID);

  /// Returns the base name with the given ID, deserializing it if needed.
  DeclBaseName getDeclBaseName(serialization::IdentifierID IID);

  /// Convenience method to retrieve the identifier backing the name with
  /// given ID. Asserts that the name with this ID is not special.
  Identifier getIdentifier(serialization::IdentifierID IID);

  /// Convenience method to retrieve the text of the name with the given ID.
  /// This can be used if the result doesn't need to be uniqued in the
  /// ASTContext. Asserts that the name with this ID is not special.
  StringRef getIdentifierText(serialization::IdentifierID IID);

  /// Returns the decl with the given ID, deserializing it if needed.
  ///
  /// \param DID The ID for the decl within this module.
  /// \sa getDeclChecked
  Decl *getDecl(serialization::DeclID DID);

  /// Returns the decl with the given ID, deserializing it if needed.
  ///
  /// \param DID The ID for the decl within this module.
  llvm::Expected<Decl *>
  getDeclChecked(serialization::DeclID DID);

  /// Returns the decl context with the given ID, deserializing it if needed.
  DeclContext *getDeclContext(serialization::DeclContextID DID);

  /// Returns the local decl context with the given ID, deserializing it if needed.
  DeclContext *getLocalDeclContext(serialization::LocalDeclContextID DID);

  /// Returns the appropriate module for the given ID.
  ModuleDecl *getModule(serialization::ModuleID MID);

  /// Returns the appropriate module for the given name.
  ///
  /// If the name matches the name of the current module, a shadowed module
  /// is loaded instead.
  ModuleDecl *getModule(ArrayRef<Identifier> name, bool allowLoading = false);

  /// Returns the generic signature for the given ID.
  GenericSignature getGenericSignature(serialization::GenericSignatureID ID);

  /// Returns the generic signature for the given ID or the first error.
  llvm::Expected<GenericSignature>
  getGenericSignatureChecked(serialization::GenericSignatureID ID);

  /// Returns the substitution map for the given ID, deserializing it if
  /// needed.
  SubstitutionMap getSubstitutionMap(serialization::SubstitutionMapID id);

  /// Returns the substitution map for the given ID, deserializing it if
  /// needed, or the first error.
  llvm::Expected<SubstitutionMap>
  getSubstitutionMapChecked(serialization::SubstitutionMapID id);

  /// Recursively reads a protocol conformance from the given cursor.
  ProtocolConformanceRef readConformance(llvm::BitstreamCursor &Cursor,
                                         GenericEnvironment *genericEnv =
                                           nullptr);

  /// Recursively reads a protocol conformance from the given cursor,
  /// returns the conformance or the first error.
  llvm::Expected<ProtocolConformanceRef>
  readConformanceChecked(llvm::BitstreamCursor &Cursor,
                         GenericEnvironment *genericEnv = nullptr);
  
  /// Read a SILLayout from the given cursor.
  SILLayout *readSILLayout(llvm::BitstreamCursor &Cursor);

  /// Read the given normal conformance from the current module file.
  NormalProtocolConformance *
  readNormalConformance(serialization::NormalConformanceID id);

  /// Reads a foreign error conformance from \c DeclTypeCursor, if present.
  Optional<ForeignErrorConvention> maybeReadForeignErrorConvention();

  /// Reads inlinable body text from \c DeclTypeCursor, if present.
  Optional<StringRef> maybeReadInlinableBodyText();

  /// Reads pattern initializer text from \c DeclTypeCursor, if present.
  Optional<StringRef> maybeReadPatternInitializerText();
};

template <typename T, typename RawData>
void ModuleFile::allocateBuffer(MutableArrayRef<T> &buffer,
                                const RawData &rawData) {
  assert(buffer.empty() && "reallocating deserialized buffer");
  if (rawData.empty())
    return;

  void *rawBuffer = Allocator.Allocate(sizeof(T) * rawData.size(), alignof(T));
  buffer = llvm::makeMutableArrayRef(static_cast<T *>(rawBuffer),
                                     rawData.size());
  std::uninitialized_copy(rawData.begin(), rawData.end(), buffer.begin());
}

} // end namespace swift

#endif