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//===- TemplateName.h - C++ Template Name Representation --------*- 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 TemplateName interface and subclasses.

//

//===----------------------------------------------------------------------===//

#ifndef LLVM_CLANG_AST_TEMPLATENAME_H

#define LLVM_CLANG_AST_TEMPLATENAME_H

#include "clang/AST/DependenceFlags.h"

#include "clang/AST/NestedNameSpecifier.h"

#include "clang/Basic/LLVM.h"

#include "llvm/ADT/FoldingSet.h"

#include "llvm/ADT/PointerIntPair.h"

#include "llvm/ADT/PointerUnion.h"

#include "llvm/Support/PointerLikeTypeTraits.h"

#include <cassert>

#include <optional>

namespace clang {

class ASTContext;

class Decl;

class DependentTemplateName;

class IdentifierInfo;

class NamedDecl;

class NestedNameSpecifier;

enum OverloadedOperatorKind : int;

class OverloadedTemplateStorage;

class AssumedTemplateStorage;

struct PrintingPolicy;

class QualifiedTemplateName;

class SubstTemplateTemplateParmPackStorage;

class SubstTemplateTemplateParmStorage;

class TemplateArgument;

class TemplateDecl;

class TemplateTemplateParmDecl;

class UsingShadowDecl;

/// Implementation class used to describe either a set of overloaded

/// template names or an already-substituted template template parameter pack.

class UncommonTemplateNameStorage {

protected:

  enum Kind {

    Overloaded,

    Assumed, // defined in DeclarationName.h

    SubstTemplateTemplateParm,

    SubstTemplateTemplateParmPack

  };

  struct BitsTag {

    /// A Kind.

    unsigned Kind : 2;

    // The template parameter index.

    unsigned Index : 15;

    /// The pack index, or the number of stored templates

    /// or template arguments, depending on which subclass we have.

    unsigned Data : 15;

  };

  union {

    struct BitsTag Bits;

    void *PointerAlignment;

  };

  UncommonTemplateNameStorage(Kind Kind, unsigned Index, unsigned Data) {

    Bits.Kind = Kind;

    Bits.Index = Index;

    Bits.Data = Data;

  }

public:

  OverloadedTemplateStorage *getAsOverloadedStorage()  {

    return Bits.Kind == Overloaded

             ? reinterpret_cast<OverloadedTemplateStorage *>(this)

             : nullptr;

  }

  AssumedTemplateStorage *getAsAssumedTemplateName()  {

    return Bits.Kind == Assumed

             ? reinterpret_cast<AssumedTemplateStorage *>(this)

             : nullptr;

  }

  SubstTemplateTemplateParmStorage *getAsSubstTemplateTemplateParm() {

    return Bits.Kind == SubstTemplateTemplateParm

             ? reinterpret_cast<SubstTemplateTemplateParmStorage *>(this)

             : nullptr;

  }

  SubstTemplateTemplateParmPackStorage *getAsSubstTemplateTemplateParmPack() {

    return Bits.Kind == SubstTemplateTemplateParmPack

             ? reinterpret_cast<SubstTemplateTemplateParmPackStorage *>(this)

             : nullptr;

  }

};

/// A structure for storing the information associated with an

/// overloaded template name.

class OverloadedTemplateStorage : public UncommonTemplateNameStorage {

  friend class ASTContext;

  OverloadedTemplateStorage(unsigned size)

      : UncommonTemplateNameStorage(Overloaded, 0, size) {}

  NamedDecl **getStorage() {

    return reinterpret_cast<NamedDecl **>(this + 1);

  }

  NamedDecl * const *getStorage() const {

    return reinterpret_cast<NamedDecl *const *>(this + 1);

  }

public:

  unsigned size() const { return Bits.Data; }

  using iterator = NamedDecl *const *;

  iterator begin() const { return getStorage(); }

  iterator end() const { return getStorage() + Bits.Data; }

  llvm::ArrayRef<NamedDecl*> decls() const {

    return llvm::ArrayRef(begin(), end());

  }

};

/// A structure for storing an already-substituted template template

/// parameter pack.

///

/// This kind of template names occurs when the parameter pack has been

/// provided with a template template argument pack in a context where its

/// enclosing pack expansion could not be fully expanded.

class SubstTemplateTemplateParmPackStorage : public UncommonTemplateNameStorage,

                                             public llvm::FoldingSetNode {

  const TemplateArgument *Arguments;

  llvm::PointerIntPair<Decl *, 1, bool> AssociatedDeclAndFinal;

public:

  SubstTemplateTemplateParmPackStorage(ArrayRef<TemplateArgument> ArgPack,

                                       Decl *AssociatedDecl, unsigned Index,

                                       bool Final);

  /// A template-like entity which owns the whole pattern being substituted.

  /// This will own a set of template parameters.

  Decl *getAssociatedDecl() const;

  /// Returns the index of the replaced parameter in the associated declaration.

  /// This should match the result of `getParameterPack()->getIndex()`.

  unsigned getIndex() const { return Bits.Index; }

  // When true the substitution will be 'Final' (subst node won't be placed).

  bool getFinal() const;

  /// Retrieve the template template parameter pack being substituted.

  TemplateTemplateParmDecl *getParameterPack() const;

  /// Retrieve the template template argument pack with which this

  /// parameter was substituted.

  TemplateArgument getArgumentPack() const;

  void Profile(llvm::FoldingSetNodeID &ID, ASTContext &Context);

  static void Profile(llvm::FoldingSetNodeID &ID, ASTContext &Context,

                      const TemplateArgument &ArgPack, Decl *AssociatedDecl,

                      unsigned Index, bool Final);

};

/// Represents a C++ template name within the type system.

///

/// A C++ template name refers to a template within the C++ type

/// system. In most cases, a template name is simply a reference to a

/// class template, e.g.

///

/// \code

/// template<typename T> class X { };

///

/// X<int> xi;

/// \endcode

///

/// Here, the 'X' in \c X<int> is a template name that refers to the

/// declaration of the class template X, above. Template names can

/// also refer to function templates, C++0x template aliases, etc.

///

/// Some template names are dependent. For example, consider:

///

/// \code

/// template<typename MetaFun, typename T1, typename T2> struct apply2 {

///   typedef typename MetaFun::template apply<T1, T2>::type type;

/// };

/// \endcode

///

/// Here, "apply" is treated as a template name within the typename

/// specifier in the typedef. "apply" is a nested template, and can

/// only be understood in the context of

class TemplateName {

  // NameDecl is either a TemplateDecl or a UsingShadowDecl depending on the

  // NameKind.

  // !! There is no free low bits in 32-bit builds to discriminate more than 4

  // pointer types in PointerUnion.

  using StorageType =

      llvm::PointerUnion<Decl *, UncommonTemplateNameStorage *,

                         QualifiedTemplateName *, DependentTemplateName *>;

  StorageType Storage;

  explicit TemplateName(void *Ptr);

public:

  // Kind of name that is actually stored.

  enum NameKind {

    /// A single template declaration.

    Template,

    /// A set of overloaded template declarations.

    OverloadedTemplate,

    /// An unqualified-id that has been assumed to name a function template

    /// that will be found by ADL.

    AssumedTemplate,

    /// A qualified template name, where the qualification is kept

    /// to describe the source code as written.

    QualifiedTemplate,

    /// A dependent template name that has not been resolved to a

    /// template (or set of templates).

    DependentTemplate,

    /// A template template parameter that has been substituted

    /// for some other template name.

    SubstTemplateTemplateParm,

    /// A template template parameter pack that has been substituted for

    /// a template template argument pack, but has not yet been expanded into

    /// individual arguments.

    SubstTemplateTemplateParmPack,

    /// A template name that refers to a template declaration found through a

    /// specific using shadow declaration.

    UsingTemplate,

  };

  TemplateName() = default;

  explicit TemplateName(TemplateDecl *Template);

  explicit TemplateName(OverloadedTemplateStorage *Storage);

  explicit TemplateName(AssumedTemplateStorage *Storage);

  explicit TemplateName(SubstTemplateTemplateParmStorage *Storage);

  explicit TemplateName(SubstTemplateTemplateParmPackStorage *Storage);

  explicit TemplateName(QualifiedTemplateName *Qual);

  explicit TemplateName(DependentTemplateName *Dep);

  explicit TemplateName(UsingShadowDecl *Using);

  /// Determine whether this template name is NULL.

  bool isNull() const;

  // Get the kind of name that is actually stored.

  NameKind getKind() const;

  /// Retrieve the underlying template declaration that

  /// this template name refers to, if known.

  ///

  /// \returns The template declaration that this template name refers

  /// to, if any. If the template name does not refer to a specific

  /// declaration because it is a dependent name, or if it refers to a

  /// set of function templates, returns NULL.

  TemplateDecl *getAsTemplateDecl() const;

  /// Retrieve the underlying, overloaded function template

  /// declarations that this template name refers to, if known.

  ///

  /// \returns The set of overloaded function templates that this template

  /// name refers to, if known. If the template name does not refer to a

  /// specific set of function templates because it is a dependent name or

  /// refers to a single template, returns NULL.

  OverloadedTemplateStorage *getAsOverloadedTemplate() const;

  /// Retrieve information on a name that has been assumed to be a

  /// template-name in order to permit a call via ADL.

  AssumedTemplateStorage *getAsAssumedTemplateName() const;

  /// Retrieve the substituted template template parameter, if

  /// known.

  ///

  /// \returns The storage for the substituted template template parameter,

  /// if known. Otherwise, returns NULL.

  SubstTemplateTemplateParmStorage *getAsSubstTemplateTemplateParm() const;

  /// Retrieve the substituted template template parameter pack, if

  /// known.

  ///

  /// \returns The storage for the substituted template template parameter pack,

  /// if known. Otherwise, returns NULL.

  SubstTemplateTemplateParmPackStorage *

  getAsSubstTemplateTemplateParmPack() const;

  /// Retrieve the underlying qualified template name

  /// structure, if any.

  QualifiedTemplateName *getAsQualifiedTemplateName() const;

  /// Retrieve the underlying dependent template name

  /// structure, if any.

  DependentTemplateName *getAsDependentTemplateName() const;

  /// Retrieve the using shadow declaration through which the underlying

  /// template declaration is introduced, if any.

  UsingShadowDecl *getAsUsingShadowDecl() const;

  TemplateName getUnderlying() const;

  /// Get the template name to substitute when this template name is used as a

  /// template template argument. This refers to the most recent declaration of

  /// the template, including any default template arguments.

  TemplateName getNameToSubstitute() const;

  TemplateNameDependence getDependence() const;

  /// Determines whether this is a dependent template name.

  bool isDependent() const;

  /// Determines whether this is a template name that somehow

  /// depends on a template parameter.

  bool isInstantiationDependent() const;

  /// Determines whether this template name contains an

  /// unexpanded parameter pack (for C++0x variadic templates).

  bool containsUnexpandedParameterPack() const;

  enum class Qualified { None, AsWritten, Fully };

  /// Print the template name.

  ///

  /// \param OS the output stream to which the template name will be

  /// printed.

  ///

  /// \param Qual print the (Qualified::None) simple name,

  /// (Qualified::AsWritten) any written (possibly partial) qualifier, or

  /// (Qualified::Fully) the fully qualified name.

  void print(raw_ostream &OS, const PrintingPolicy &Policy,

             Qualified Qual = Qualified::AsWritten) const;

  /// Debugging aid that dumps the template name.

  void dump(raw_ostream &OS) const;

  /// Debugging aid that dumps the template name to standard

  /// error.

  void dump() const;

  void Profile(llvm::FoldingSetNodeID &ID) {

    ID.AddPointer(Storage.getOpaqueValue());

  }

  /// Retrieve the template name as a void pointer.

  void *getAsVoidPointer() const { return Storage.getOpaqueValue(); }

  /// Build a template name from a void pointer.

  static TemplateName getFromVoidPointer(void *Ptr) {

    return TemplateName(Ptr);

  }

};

/// Insertion operator for diagnostics.  This allows sending TemplateName's

/// into a diagnostic with <<.

const StreamingDiagnostic &operator<<(const StreamingDiagnostic &DB,

                                      TemplateName N);

/// A structure for storing the information associated with a

/// substituted template template parameter.

class SubstTemplateTemplateParmStorage

  : public UncommonTemplateNameStorage, public llvm::FoldingSetNode {

  friend class ASTContext;

  TemplateName Replacement;

  Decl *AssociatedDecl;

  SubstTemplateTemplateParmStorage(TemplateName Replacement,

                                   Decl *AssociatedDecl, unsigned Index,

                                   std::optional<unsigned> PackIndex)

      : UncommonTemplateNameStorage(SubstTemplateTemplateParm, Index,

                                    PackIndex ? *PackIndex + 1 : 0),

        Replacement(Replacement), AssociatedDecl(AssociatedDecl) {

    assert(AssociatedDecl != nullptr);

  }

public:

  /// A template-like entity which owns the whole pattern being substituted.

  /// This will own a set of template parameters.

  Decl *getAssociatedDecl() const { return AssociatedDecl; }

  /// Returns the index of the replaced parameter in the associated declaration.

  /// This should match the result of `getParameter()->getIndex()`.

  unsigned getIndex() const { return Bits.Index; }

  std::optional<unsigned> getPackIndex() const {

    if (Bits.Data == 0)

      return std::nullopt;

    return Bits.Data - 1;

  }

  TemplateTemplateParmDecl *getParameter() const;

  TemplateName getReplacement() const { return Replacement; }

  void Profile(llvm::FoldingSetNodeID &ID);

  static void Profile(llvm::FoldingSetNodeID &ID, TemplateName Replacement,

                      Decl *AssociatedDecl, unsigned Index,

                      std::optional<unsigned> PackIndex);

};

inline TemplateName TemplateName::getUnderlying() const {

  if (SubstTemplateTemplateParmStorage *subst

        = getAsSubstTemplateTemplateParm())

    return subst->getReplacement().getUnderlying();

  return *this;

}

/// Represents a template name that was expressed as a

/// qualified name.

///

/// This kind of template name refers to a template name that was

/// preceded by a nested name specifier, e.g., \c std::vector. Here,

/// the nested name specifier is "std::" and the template name is the

/// declaration for "vector". The QualifiedTemplateName class is only

/// used to provide "sugar" for template names that were expressed

/// with a qualified name, and has no semantic meaning. In this

/// manner, it is to TemplateName what ElaboratedType is to Type,

/// providing extra syntactic sugar for downstream clients.

class QualifiedTemplateName : public llvm::FoldingSetNode {

  friend class ASTContext;

  /// The nested name specifier that qualifies the template name.

  ///

  /// The bit is used to indicate whether the "template" keyword was

  /// present before the template name itself. Note that the

  /// "template" keyword is always redundant in this case (otherwise,

  /// the template name would be a dependent name and we would express

  /// this name with DependentTemplateName).

  llvm::PointerIntPair<NestedNameSpecifier *, 1> Qualifier;

  /// The underlying template name, it is either

  ///  1) a Template -- a template declaration that this qualified name refers

  ///     to.

  ///  2) or a UsingTemplate -- a template declaration introduced by a

  ///     using-shadow declaration.

  TemplateName UnderlyingTemplate;

  QualifiedTemplateName(NestedNameSpecifier *NNS, bool TemplateKeyword,

                        TemplateName Template)

      : Qualifier(NNS, TemplateKeyword ? 1 : 0), UnderlyingTemplate(Template) {

    assert(UnderlyingTemplate.getKind() == TemplateName::Template ||

           UnderlyingTemplate.getKind() == TemplateName::UsingTemplate);

  }

public:

  /// Return the nested name specifier that qualifies this name.

  NestedNameSpecifier *getQualifier() const { return Qualifier.getPointer(); }

  /// Whether the template name was prefixed by the "template"

  /// keyword.

  bool hasTemplateKeyword() const { return Qualifier.getInt(); }

  /// Return the underlying template name.

  TemplateName getUnderlyingTemplate() const { return UnderlyingTemplate; }

  void Profile(llvm::FoldingSetNodeID &ID) {

    Profile(ID, getQualifier(), hasTemplateKeyword(), UnderlyingTemplate);

  }

  static void Profile(llvm::FoldingSetNodeID &ID, NestedNameSpecifier *NNS,

                      bool TemplateKeyword, TemplateName TN) {

    ID.AddPointer(NNS);

    ID.AddBoolean(TemplateKeyword);

    ID.AddPointer(TN.getAsVoidPointer());

  }

};

/// Represents a dependent template name that cannot be

/// resolved prior to template instantiation.

///

/// This kind of template name refers to a dependent template name,

/// including its nested name specifier (if any). For example,

/// DependentTemplateName can refer to "MetaFun::template apply",

/// where "MetaFun::" is the nested name specifier and "apply" is the

/// template name referenced. The "template" keyword is implied.

class DependentTemplateName : public llvm::FoldingSetNode {

  friend class ASTContext;

  /// The nested name specifier that qualifies the template

  /// name.

  ///

  /// The bit stored in this qualifier describes whether the \c Name field

  /// is interpreted as an IdentifierInfo pointer (when clear) or as an

  /// overloaded operator kind (when set).

  llvm::PointerIntPair<NestedNameSpecifier *, 1, bool> Qualifier;

  /// The dependent template name.

  union {

    /// The identifier template name.

    ///

    /// Only valid when the bit on \c Qualifier is clear.

    const IdentifierInfo *Identifier;

    /// The overloaded operator name.

    ///

    /// Only valid when the bit on \c Qualifier is set.

    OverloadedOperatorKind Operator;

  };

  /// The canonical template name to which this dependent

  /// template name refers.

  ///

  /// The canonical template name for a dependent template name is

  /// another dependent template name whose nested name specifier is

  /// canonical.

  TemplateName CanonicalTemplateName;

  DependentTemplateName(NestedNameSpecifier *Qualifier,

                        const IdentifierInfo *Identifier)

      : Qualifier(Qualifier, false), Identifier(Identifier),

        CanonicalTemplateName(this) {}

  DependentTemplateName(NestedNameSpecifier *Qualifier,

                        const IdentifierInfo *Identifier,

                        TemplateName Canon)

      : Qualifier(Qualifier, false), Identifier(Identifier),

        CanonicalTemplateName(Canon) {}

  DependentTemplateName(NestedNameSpecifier *Qualifier,

                        OverloadedOperatorKind Operator)

      : Qualifier(Qualifier, true), Operator(Operator),

        CanonicalTemplateName(this) {}

  DependentTemplateName(NestedNameSpecifier *Qualifier,

                        OverloadedOperatorKind Operator,

                        TemplateName Canon)

       : Qualifier(Qualifier, true), Operator(Operator),

         CanonicalTemplateName(Canon) {}

public:

  /// Return the nested name specifier that qualifies this name.

  NestedNameSpecifier *getQualifier() const { return Qualifier.getPointer(); }

  /// Determine whether this template name refers to an identifier.

  bool isIdentifier() const { return !Qualifier.getInt(); }

  /// Returns the identifier to which this template name refers.

  const IdentifierInfo *getIdentifier() const {

    assert(isIdentifier() && "Template name isn't an identifier?");

    return Identifier;

  }

  /// Determine whether this template name refers to an overloaded

  /// operator.

  bool isOverloadedOperator() const { return Qualifier.getInt(); }

  /// Return the overloaded operator to which this template name refers.

  OverloadedOperatorKind getOperator() const {

    assert(isOverloadedOperator() &&

           "Template name isn't an overloaded operator?");

    return Operator;

  }

  void Profile(llvm::FoldingSetNodeID &ID) {

    if (isIdentifier())

      Profile(ID, getQualifier(), getIdentifier());

    else

      Profile(ID, getQualifier(), getOperator());

  }

  static void Profile(llvm::FoldingSetNodeID &ID, NestedNameSpecifier *NNS,

                      const IdentifierInfo *Identifier) {

    ID.AddPointer(NNS);

    ID.AddBoolean(false);

    ID.AddPointer(Identifier);

  }

  static void Profile(llvm::FoldingSetNodeID &ID, NestedNameSpecifier *NNS,

                      OverloadedOperatorKind Operator) {

    ID.AddPointer(NNS);

    ID.AddBoolean(true);

    ID.AddInteger(Operator);

  }

};

} // namespace clang.

namespace llvm {

/// The clang::TemplateName class is effectively a pointer.

template<>

struct PointerLikeTypeTraits<clang::TemplateName> {

  static inline void *getAsVoidPointer(clang::TemplateName TN) {

    return TN.getAsVoidPointer();

  }

  static inline clang::TemplateName getFromVoidPointer(void *Ptr) {

    return clang::TemplateName::getFromVoidPointer(Ptr);

  }

  // No bits are available!

  static constexpr int NumLowBitsAvailable = 0;

};

} // namespace llvm.

#endif // LLVM_CLANG_AST_TEMPLATENAME_H