text: //===- NestedNameSpecifier.h - C++ nested name specifiers -------*- 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
  //
  //===----------------------------------------------------------------------===//
  //
  //  This file defines the NestedNameSpecifier class, which represents
  //  a C++ nested-name-specifier.
  //
  //===----------------------------------------------------------------------===//
  
  #ifndef LLVM_CLANG_AST_NESTEDNAMESPECIFIER_H
  #define LLVM_CLANG_AST_NESTEDNAMESPECIFIER_H
  
  #include "clang/AST/DependenceFlags.h"
  #include "clang/Basic/Diagnostic.h"
  #include "clang/Basic/SourceLocation.h"
  #include "llvm/ADT/DenseMapInfo.h"
  #include "llvm/ADT/FoldingSet.h"
  #include "llvm/ADT/PointerIntPair.h"
  #include "llvm/Support/Compiler.h"
  #include <cstdint>
  #include <cstdlib>
  #include <utility>
  
  namespace clang {
  
  class ASTContext;
  class CXXRecordDecl;
  class IdentifierInfo;
  class LangOptions;
  class NamespaceAliasDecl;
  class NamespaceDecl;
  struct PrintingPolicy;
  class Type;
  class TypeLoc;
  
  /// Represents a C++ nested name specifier, such as
  /// "\::std::vector<int>::".
  ///
  /// C++ nested name specifiers are the prefixes to qualified
  /// names. For example, "foo::" in "foo::x" is a nested name
  /// specifier. Nested name specifiers are made up of a sequence of
  /// specifiers, each of which can be a namespace, type, identifier
  /// (for dependent names), decltype specifier, or the global specifier ('::').
  /// The last two specifiers can only appear at the start of a
  /// nested-namespace-specifier.
  class NestedNameSpecifier : public llvm::FoldingSetNode {
    /// Enumeration describing
    enum StoredSpecifierKind {
      StoredIdentifier = 0,
      StoredDecl = 1,
      StoredTypeSpec = 2,
      StoredTypeSpecWithTemplate = 3
    };
  
    /// The nested name specifier that precedes this nested name
    /// specifier.
    ///
    /// The pointer is the nested-name-specifier that precedes this
    /// one. The integer stores one of the first four values of type
    /// SpecifierKind.
    llvm::PointerIntPair<NestedNameSpecifier *, 2, StoredSpecifierKind> Prefix;
  
    /// The last component in the nested name specifier, which
    /// can be an identifier, a declaration, or a type.
    ///
    /// When the pointer is NULL, this specifier represents the global
    /// specifier '::'. Otherwise, the pointer is one of
    /// IdentifierInfo*, Namespace*, or Type*, depending on the kind of
    /// specifier as encoded within the prefix.
    void* Specifier = nullptr;
  
  public:
    /// The kind of specifier that completes this nested name
    /// specifier.
    enum SpecifierKind {
      /// An identifier, stored as an IdentifierInfo*.
      Identifier,
  
      /// A namespace, stored as a NamespaceDecl*.
      Namespace,
  
      /// A namespace alias, stored as a NamespaceAliasDecl*.
      NamespaceAlias,
  
      /// A type, stored as a Type*.
      TypeSpec,
  
      /// A type that was preceded by the 'template' keyword,
      /// stored as a Type*.
      TypeSpecWithTemplate,
  
      /// The global specifier '::'. There is no stored value.
      Global,
  
      /// Microsoft's '__super' specifier, stored as a CXXRecordDecl* of
      /// the class it appeared in.
      Super
    };
  
  private:
    /// Builds the global specifier.
    NestedNameSpecifier() : Prefix(nullptr, StoredIdentifier) {}
  
    /// Copy constructor used internally to clone nested name
    /// specifiers.
    NestedNameSpecifier(const NestedNameSpecifier &Other) = default;
  
    /// Either find or insert the given nested name specifier
    /// mockup in the given context.
    static NestedNameSpecifier *FindOrInsert(const ASTContext &Context,
                                             const NestedNameSpecifier &Mockup);
  
  public:
    NestedNameSpecifier &operator=(const NestedNameSpecifier &) = delete;
  
    /// Builds a specifier combining a prefix and an identifier.
    ///
    /// The prefix must be dependent, since nested name specifiers
    /// referencing an identifier are only permitted when the identifier
    /// cannot be resolved.
    static NestedNameSpecifier *Create(const ASTContext &Context,
                                       NestedNameSpecifier *Prefix,
                                       IdentifierInfo *II);
  
    /// Builds a nested name specifier that names a namespace.
    static NestedNameSpecifier *Create(const ASTContext &Context,
                                       NestedNameSpecifier *Prefix,
                                       const NamespaceDecl *NS);
  
    /// Builds a nested name specifier that names a namespace alias.
    static NestedNameSpecifier *Create(const ASTContext &Context,
                                       NestedNameSpecifier *Prefix,
                                       NamespaceAliasDecl *Alias);
  
    /// Builds a nested name specifier that names a type.
    static NestedNameSpecifier *Create(const ASTContext &Context,
                                       NestedNameSpecifier *Prefix,
                                       bool Template, const Type *T);
  
    /// Builds a specifier that consists of just an identifier.
    ///
    /// The nested-name-specifier is assumed to be dependent, but has no
    /// prefix because the prefix is implied by something outside of the
    /// nested name specifier, e.g., in "x->Base::f", the "x" has a dependent
    /// type.
    static NestedNameSpecifier *Create(const ASTContext &Context,
                                       IdentifierInfo *II);
  
    /// Returns the nested name specifier representing the global
    /// scope.
    static NestedNameSpecifier *GlobalSpecifier(const ASTContext &Context);
  
    /// Returns the nested name specifier representing the __super scope
    /// for the given CXXRecordDecl.
    static NestedNameSpecifier *SuperSpecifier(const ASTContext &Context,
                                               CXXRecordDecl *RD);
  
    /// Return the prefix of this nested name specifier.
    ///
    /// The prefix contains all of the parts of the nested name
    /// specifier that preced this current specifier. For example, for a
    /// nested name specifier that represents "foo::bar::", the current
    /// specifier will contain "bar::" and the prefix will contain
    /// "foo::".
    NestedNameSpecifier *getPrefix() const { return Prefix.getPointer(); }
  
    /// Determine what kind of nested name specifier is stored.
    SpecifierKind getKind() const;
  
    /// Retrieve the identifier stored in this nested name
    /// specifier.
    IdentifierInfo *getAsIdentifier() const {
      if (Prefix.getInt() == StoredIdentifier)
        return (IdentifierInfo *)Specifier;
  
      return nullptr;
    }
  
    /// Retrieve the namespace stored in this nested name
    /// specifier.
    NamespaceDecl *getAsNamespace() const;
  
    /// Retrieve the namespace alias stored in this nested name
    /// specifier.
    NamespaceAliasDecl *getAsNamespaceAlias() const;
  
    /// Retrieve the record declaration stored in this nested name
    /// specifier.
    CXXRecordDecl *getAsRecordDecl() const;
  
    /// Retrieve the type stored in this nested name specifier.
    const Type *getAsType() const {
      if (Prefix.getInt() == StoredTypeSpec ||
          Prefix.getInt() == StoredTypeSpecWithTemplate)
        return (const Type *)Specifier;
  
      return nullptr;
    }
  
    NestedNameSpecifierDependence getDependence() const;
  
    /// Whether this nested name specifier refers to a dependent
    /// type or not.
    bool isDependent() const;
  
    /// Whether this nested name specifier involves a template
    /// parameter.
    bool isInstantiationDependent() const;
  
    /// Whether this nested-name-specifier contains an unexpanded
    /// parameter pack (for C++11 variadic templates).
    bool containsUnexpandedParameterPack() const;
  
    /// Whether this nested name specifier contains an error.
    bool containsErrors() const;
  
    /// Print this nested name specifier to the given output stream. If
    /// `ResolveTemplateArguments` is true, we'll print actual types, e.g.
    /// `ns::SomeTemplate<int, MyClass>` instead of
    /// `ns::SomeTemplate<Container::value_type, T>`.
    void print(raw_ostream &OS, const PrintingPolicy &Policy,
               bool ResolveTemplateArguments = false) const;
  
    void Profile(llvm::FoldingSetNodeID &ID) const {
      ID.AddPointer(Prefix.getOpaqueValue());
      ID.AddPointer(Specifier);
    }
  
    /// Dump the nested name specifier to standard output to aid
    /// in debugging.
    void dump(const LangOptions &LO) const;
    void dump() const;
    void dump(llvm::raw_ostream &OS) const;
    void dump(llvm::raw_ostream &OS, const LangOptions &LO) const;
  
    /// \brief Compute the qualification required to get from the current context
    /// (\p CurContext) to the target context (\p TargetContext).
    ///
    /// \param Context the AST context in which the qualification will be used.
    ///
    /// \param CurContext the context where an entity is being named, which is
    /// typically based on the current scope.
    ///
    /// \param TargetContext the context in which the named entity actually
    /// resides.
    ///
    /// \returns a nested name specifier that refers into the target context, or
    /// NULL if no qualification is needed.
    static NestedNameSpecifier *
    getRequiredQualification(ASTContext &Context, const DeclContext *CurContext,
                             const DeclContext *TargetContext);
  };
  
  /// A C++ nested-name-specifier augmented with source location
  /// information.
  class NestedNameSpecifierLoc {
    NestedNameSpecifier *Qualifier = nullptr;
    void *Data = nullptr;
  
    /// Determines the data length for the last component in the
    /// given nested-name-specifier.
    static unsigned getLocalDataLength(NestedNameSpecifier *Qualifier);
  
    /// Determines the data length for the entire
    /// nested-name-specifier.
    static unsigned getDataLength(NestedNameSpecifier *Qualifier);
  
  public:
    /// Construct an empty nested-name-specifier.
    NestedNameSpecifierLoc() = default;
  
    /// Construct a nested-name-specifier with source location information
    /// from
    NestedNameSpecifierLoc(NestedNameSpecifier *Qualifier, void *Data)
        : Qualifier(Qualifier), Data(Data) {}
  
    /// Evaluates true when this nested-name-specifier location is
    /// non-empty.
    explicit operator bool() const { return Qualifier; }
  
    /// Evaluates true when this nested-name-specifier location is
    /// empty.
    bool hasQualifier() const { return Qualifier; }
  
    /// Retrieve the nested-name-specifier to which this instance
    /// refers.
    NestedNameSpecifier *getNestedNameSpecifier() const {
      return Qualifier;
    }
  
    /// Retrieve the opaque pointer that refers to source-location data.
    void *getOpaqueData() const { return Data; }
  
    /// Retrieve the source range covering the entirety of this
    /// nested-name-specifier.
    ///
    /// For example, if this instance refers to a nested-name-specifier
    /// \c \::std::vector<int>::, the returned source range would cover
    /// from the initial '::' to the last '::'.
    SourceRange getSourceRange() const LLVM_READONLY;
  
    /// Retrieve the source range covering just the last part of
    /// this nested-name-specifier, not including the prefix.
    ///
    /// For example, if this instance refers to a nested-name-specifier
    /// \c \::std::vector<int>::, the returned source range would cover
    /// from "vector" to the last '::'.
    SourceRange getLocalSourceRange() const;
  
    /// Retrieve the location of the beginning of this
    /// nested-name-specifier.
    SourceLocation getBeginLoc() const {
      return getSourceRange().getBegin();
    }
  
    /// Retrieve the location of the end of this
    /// nested-name-specifier.
    SourceLocation getEndLoc() const {
      return getSourceRange().getEnd();
    }
  
    /// Retrieve the location of the beginning of this
    /// component of the nested-name-specifier.
    SourceLocation getLocalBeginLoc() const {
      return getLocalSourceRange().getBegin();
    }
  
    /// Retrieve the location of the end of this component of the
    /// nested-name-specifier.
    SourceLocation getLocalEndLoc() const {
      return getLocalSourceRange().getEnd();
    }
  
    /// Return the prefix of this nested-name-specifier.
    ///
    /// For example, if this instance refers to a nested-name-specifier
    /// \c \::std::vector<int>::, the prefix is \c \::std::. Note that the
    /// returned prefix may be empty, if this is the first component of
    /// the nested-name-specifier.
    NestedNameSpecifierLoc getPrefix() const {
      if (!Qualifier)
        return *this;
  
      return NestedNameSpecifierLoc(Qualifier->getPrefix(), Data);
    }
  
    /// For a nested-name-specifier that refers to a type,
    /// retrieve the type with source-location information.
    TypeLoc getTypeLoc() const;
  
    /// Determines the data length for the entire
    /// nested-name-specifier.
    unsigned getDataLength() const { return getDataLength(Qualifier); }
  
    friend bool operator==(NestedNameSpecifierLoc X,
                           NestedNameSpecifierLoc Y) {
      return X.Qualifier == Y.Qualifier && X.Data == Y.Data;
    }
  
    friend bool operator!=(NestedNameSpecifierLoc X,
                           NestedNameSpecifierLoc Y) {
      return !(X == Y);
    }
  };
  
  /// Class that aids in the construction of nested-name-specifiers along
  /// with source-location information for all of the components of the
  /// nested-name-specifier.
  class NestedNameSpecifierLocBuilder {
    /// The current representation of the nested-name-specifier we're
    /// building.
    NestedNameSpecifier *Representation = nullptr;
  
    /// Buffer used to store source-location information for the
    /// nested-name-specifier.
    ///
    /// Note that we explicitly manage the buffer (rather than using a
    /// SmallVector) because \c Declarator expects it to be possible to memcpy()
    /// a \c CXXScopeSpec, and CXXScopeSpec uses a NestedNameSpecifierLocBuilder.
    char *Buffer = nullptr;
  
    /// The size of the buffer used to store source-location information
    /// for the nested-name-specifier.
    unsigned BufferSize = 0;
  
    /// The capacity of the buffer used to store source-location
    /// information for the nested-name-specifier.
    unsigned BufferCapacity = 0;
  
  public:
    NestedNameSpecifierLocBuilder() = default;
    NestedNameSpecifierLocBuilder(const NestedNameSpecifierLocBuilder &Other);
  
    NestedNameSpecifierLocBuilder &
    operator=(const NestedNameSpecifierLocBuilder &Other);
  
    ~NestedNameSpecifierLocBuilder() {
      if (BufferCapacity)
        free(Buffer);
    }
  
    /// Retrieve the representation of the nested-name-specifier.
    NestedNameSpecifier *getRepresentation() const { return Representation; }
  
    /// Extend the current nested-name-specifier by another
    /// nested-name-specifier component of the form 'type::'.
    ///
    /// \param Context The AST context in which this nested-name-specifier
    /// resides.
    ///
    /// \param TemplateKWLoc The location of the 'template' keyword, if present.
    ///
    /// \param TL The TypeLoc that describes the type preceding the '::'.
    ///
    /// \param ColonColonLoc The location of the trailing '::'.
    void Extend(ASTContext &Context, SourceLocation TemplateKWLoc, TypeLoc TL,
                SourceLocation ColonColonLoc);
  
    /// Extend the current nested-name-specifier by another
    /// nested-name-specifier component of the form 'identifier::'.
    ///
    /// \param Context The AST context in which this nested-name-specifier
    /// resides.
    ///
    /// \param Identifier The identifier.
    ///
    /// \param IdentifierLoc The location of the identifier.
    ///
    /// \param ColonColonLoc The location of the trailing '::'.
    void Extend(ASTContext &Context, IdentifierInfo *Identifier,
                SourceLocation IdentifierLoc, SourceLocation ColonColonLoc);
  
    /// Extend the current nested-name-specifier by another
    /// nested-name-specifier component of the form 'namespace::'.
    ///
    /// \param Context The AST context in which this nested-name-specifier
    /// resides.
    ///
    /// \param Namespace The namespace.
    ///
    /// \param NamespaceLoc The location of the namespace name.
    ///
    /// \param ColonColonLoc The location of the trailing '::'.
    void Extend(ASTContext &Context, NamespaceDecl *Namespace,
                SourceLocation NamespaceLoc, SourceLocation ColonColonLoc);
  
    /// Extend the current nested-name-specifier by another
    /// nested-name-specifier component of the form 'namespace-alias::'.
    ///
    /// \param Context The AST context in which this nested-name-specifier
    /// resides.
    ///
    /// \param Alias The namespace alias.
    ///
    /// \param AliasLoc The location of the namespace alias
    /// name.
    ///
    /// \param ColonColonLoc The location of the trailing '::'.
    void Extend(ASTContext &Context, NamespaceAliasDecl *Alias,
                SourceLocation AliasLoc, SourceLocation ColonColonLoc);
  
    /// Turn this (empty) nested-name-specifier into the global
    /// nested-name-specifier '::'.
    void MakeGlobal(ASTContext &Context, SourceLocation ColonColonLoc);
  
    /// Turns this (empty) nested-name-specifier into '__super'
    /// nested-name-specifier.
    ///
    /// \param Context The AST context in which this nested-name-specifier
    /// resides.
    ///
    /// \param RD The declaration of the class in which nested-name-specifier
    /// appeared.
    ///
    /// \param SuperLoc The location of the '__super' keyword.
    /// name.
    ///
    /// \param ColonColonLoc The location of the trailing '::'.
    void MakeSuper(ASTContext &Context, CXXRecordDecl *RD,
                   SourceLocation SuperLoc, SourceLocation ColonColonLoc);
  
    /// Make a new nested-name-specifier from incomplete source-location
    /// information.
    ///
    /// This routine should be used very, very rarely, in cases where we
    /// need to synthesize a nested-name-specifier. Most code should instead use
    /// \c Adopt() with a proper \c NestedNameSpecifierLoc.
    void MakeTrivial(ASTContext &Context, NestedNameSpecifier *Qualifier,
                     SourceRange R);
  
    /// Adopt an existing nested-name-specifier (with source-range
    /// information).
    void Adopt(NestedNameSpecifierLoc Other);
  
    /// Retrieve the source range covered by this nested-name-specifier.
    SourceRange getSourceRange() const LLVM_READONLY {
      return NestedNameSpecifierLoc(Representation, Buffer).getSourceRange();
    }
  
    /// Retrieve a nested-name-specifier with location information,
    /// copied into the given AST context.
    ///
    /// \param Context The context into which this nested-name-specifier will be
    /// copied.
    NestedNameSpecifierLoc getWithLocInContext(ASTContext &Context) const;
  
    /// Retrieve a nested-name-specifier with location
    /// information based on the information in this builder.
    ///
    /// This loc will contain references to the builder's internal data and may
    /// be invalidated by any change to the builder.
    NestedNameSpecifierLoc getTemporary() const {
      return NestedNameSpecifierLoc(Representation, Buffer);
    }
  
    /// Clear out this builder, and prepare it to build another
    /// nested-name-specifier with source-location information.
    void Clear() {
      Representation = nullptr;
      BufferSize = 0;
    }
  
    /// Retrieve the underlying buffer.
    ///
    /// \returns A pair containing a pointer to the buffer of source-location
    /// data and the size of the source-location data that resides in that
    /// buffer.
    std::pair<char *, unsigned> getBuffer() const {
      return std::make_pair(Buffer, BufferSize);
    }
  };
  
  /// Insertion operator for diagnostics.  This allows sending
  /// NestedNameSpecifiers into a diagnostic with <<.
  inline const StreamableDiagnosticBase &
  operator<<(const StreamableDiagnosticBase &DB, NestedNameSpecifier *NNS) {
    DB.AddTaggedVal(reinterpret_cast<intptr_t>(NNS),
                    DiagnosticsEngine::ak_nestednamespec);
    return DB;
  }
  
  } // namespace clang
  
  namespace llvm {
  
  template <> struct DenseMapInfo<clang::NestedNameSpecifierLoc> {
    using FirstInfo = DenseMapInfo<clang::NestedNameSpecifier *>;
    using SecondInfo = DenseMapInfo<void *>;
  
    static clang::NestedNameSpecifierLoc getEmptyKey() {
      return clang::NestedNameSpecifierLoc(FirstInfo::getEmptyKey(),
                                           SecondInfo::getEmptyKey());
    }
  
    static clang::NestedNameSpecifierLoc getTombstoneKey() {
      return clang::NestedNameSpecifierLoc(FirstInfo::getTombstoneKey(),
                                           SecondInfo::getTombstoneKey());
    }
  
    static unsigned getHashValue(const clang::NestedNameSpecifierLoc &PairVal) {
      return hash_combine(
          FirstInfo::getHashValue(PairVal.getNestedNameSpecifier()),
          SecondInfo::getHashValue(PairVal.getOpaqueData()));
    }
  
    static bool isEqual(const clang::NestedNameSpecifierLoc &LHS,
                        const clang::NestedNameSpecifierLoc &RHS) {
      return LHS == RHS;
    }
  };
  } // namespace llvm
  
  #endif // LLVM_CLANG_AST_NESTEDNAMESPECIFIER_H
  