TemplateName.h

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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;
class DeducedTemplateStorage;
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
    Deduced,
    SubstTemplateTemplateParm,
    SubstTemplateTemplateParmPack
  };
 
  struct BitsTag {
    LLVM_PREFERRED_TYPE(Kind)
    unsigned Kind : 3;
 
    // The template parameter index.
    unsigned Index : 14;
 
    /// 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;
  }
 
  DeducedTemplateStorage *getAsDeducedTemplateName() {
    return Bits.Kind == Deduced
               ? reinterpret_cast<DeducedTemplateStorage *>(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,