ASTConcept.h

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//===--- ASTConcept.h - Concepts Related AST Data Structures ----*- 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
//
//===----------------------------------------------------------------------===//
///
/// \file
/// \brief This file provides AST data structures related to concepts.
///
//===----------------------------------------------------------------------===//
 
#ifndef LLVM_CLANG_AST_ASTCONCEPT_H
#define LLVM_CLANG_AST_ASTCONCEPT_H
 
#include "clang/AST/DeclarationName.h"
#include "clang/AST/NestedNameSpecifierBase.h"
#include "clang/AST/TemplateBase.h"
#include "clang/Basic/SourceLocation.h"
#include "clang/Basic/UnsignedOrNone.h"
#include "llvm/ADT/FoldingSet.h"
#include "llvm/ADT/PointerUnion.h"
#include "llvm/ADT/SmallVector.h"
#include <utility>
 
namespace clang {
 
class ConceptDecl;
class TemplateDecl;
class ConceptReference;
class Expr;
class NamedDecl;
struct PrintingPolicy;
 
/// Unsatisfied constraint expressions if the template arguments could be
/// substituted into them, or a diagnostic if substitution resulted in
/// an invalid expression.
///
using ConstraintSubstitutionDiagnostic = std::pair<SourceLocation, StringRef>;
using UnsatisfiedConstraintRecord =
    llvm::PointerUnion<const Expr *, const ConceptReference *,
                       const ConstraintSubstitutionDiagnostic *>;
 
/// The result of a constraint satisfaction check, containing the necessary
/// information to diagnose an unsatisfied constraint.
class ConstraintSatisfaction : public llvm::FoldingSetNode {
  // The template-like entity that 'owns' the constraint checked here (can be a
  // constrained entity or a concept).
  const NamedDecl *ConstraintOwner = nullptr;
  llvm::SmallVector<TemplateArgument, 4> TemplateArgs;
 
public:
 
  ConstraintSatisfaction() = default;
 
  ConstraintSatisfaction(const NamedDecl *ConstraintOwner,
                         ArrayRef<TemplateArgument> TemplateArgs)
      : ConstraintOwner(ConstraintOwner), TemplateArgs(TemplateArgs) {}
 
  bool IsSatisfied = false;
  bool ContainsErrors = false;
 
  /// \brief The substituted constraint expr, if the template arguments could be
  /// substituted into them, or a diagnostic if substitution resulted in an
  /// invalid expression.
  llvm::SmallVector<UnsatisfiedConstraintRecord, 4> Details;
 
  void Profile(llvm::FoldingSetNodeID &ID, const ASTContext &C) {
    Profile(ID, C, ConstraintOwner, TemplateArgs);
  }
 
  static void Profile(llvm::FoldingSetNodeID &ID, const ASTContext &C,
                      const NamedDecl *ConstraintOwner,
                      ArrayRef<TemplateArgument> TemplateArgs);
 
  bool HasSubstitutionFailure() {
    for (const auto &Detail : Details)
      if (Detail.dyn_cast<const ConstraintSubstitutionDiagnostic *>())
        return true;
    return false;
  }
};
 
/// \brief The result of a constraint satisfaction check, containing the
/// necessary information to diagnose an unsatisfied constraint.
///
/// This is safe to store in an AST node, as opposed to ConstraintSatisfaction.
struct ASTConstraintSatisfaction final :
    llvm::TrailingObjects<ASTConstraintSatisfaction,
                          UnsatisfiedConstraintRecord> {
  std::size_t NumRecords;
  bool IsSatisfied : 1;
  bool ContainsErrors : 1;
 
  const UnsatisfiedConstraintRecord *begin() const {
    return getTrailingObjects();
  }
 
  const UnsatisfiedConstraintRecord *end() const {
    return getTrailingObjects() + NumRecords;
  }
 
  ArrayRef<UnsatisfiedConstraintRecord> records() const {
    return {begin(), end()};
  }
 
  ASTConstraintSatisfaction(const ASTContext &C,
                            const ConstraintSatisfaction &Satisfaction);
  ASTConstraintSatisfaction(const ASTContext &C,
                            const ASTConstraintSatisfaction &Satisfaction);
 
  static ASTConstraintSatisfaction *
  Create(const ASTContext &C, const ConstraintSatisfaction &Satisfaction);
  static ASTConstraintSatisfaction *
  Rebuild(const ASTContext &C, const ASTConstraintSatisfaction &Satisfaction);
};
 
/// A reference to a concept and its template args, as it appears in the code.
///
/// Examples:
///   template <int X> requires is_even<X> int half = X/2;
///                             ~~~~~~~~~~ (in ConceptSpecializationExpr)
///
///   std::input_iterator auto I = Container.begin();
///   ~~~~~~~~~~~~~~~~~~~ (in AutoTypeLoc)
///
///   template <std::derives_from<Expr> T> void dump();
///             ~~~~~~~~~~~~~~~~~~~~~~~ (in TemplateTypeParmDecl)
class ConceptReference {
protected:
  // \brief The optional nested name specifier used when naming the concept.
  NestedNameSpecifierLoc NestedNameSpec;
 
  /// \brief The location of the template keyword, if specified when naming the
  /// concept.
  SourceLocation TemplateKWLoc;
 
  /// \brief The concept name used.
  DeclarationNameInfo ConceptName;
 
  /// \brief The declaration found by name lookup when the expression was
  /// created.
  /// Can differ from NamedConcept when, for example, the concept was found
  /// through a UsingShadowDecl.
  NamedDecl *FoundDecl;
 
  /// \brief The concept named.
  TemplateDecl *NamedConcept;
 
  /// \brief The template argument list source info used to specialize the
  /// concept.
  const ASTTemplateArgumentListInfo *ArgsAsWritten;
 
  ConceptReference(NestedNameSpecifierLoc NNS, SourceLocation TemplateKWLoc,
                   DeclarationNameInfo ConceptNameInfo, NamedDecl *FoundDecl,
                   TemplateDecl *NamedConcept,
                   const ASTTemplateArgumentListInfo *ArgsAsWritten)
      : NestedNameSpec(NNS), TemplateKWLoc(TemplateKWLoc),
        ConceptName(ConceptNameInfo), FoundDecl(FoundDecl),
        NamedConcept(NamedConcept), ArgsAsWritten(ArgsAsWritten) {}
 
public:
  static ConceptReference *
  Create(const ASTContext &C, NestedNameSpecifierLoc NNS,
         SourceLocation TemplateKWLoc, DeclarationNameInfo ConceptNameInfo,
         NamedDecl *FoundDecl, TemplateDecl *NamedConcept,
         const ASTTemplateArgumentListInfo *ArgsAsWritten);
 
  const NestedNameSpecifierLoc &getNestedNameSpecifierLoc() const {
    return NestedNameSpec;
  }
 
  const DeclarationNameInfo &getConceptNameInfo() const { return ConceptName; }
 
  SourceLocation getConceptNameLoc() const {
    return getConceptNameInfo().getLoc();
  }
 
  SourceLocation getTemplateKWLoc() const { return TemplateKWLoc; }
 
  SourceLocation getLocation() const { return getConceptNameLoc(); }
 
  SourceLocation getBeginLoc() const LLVM_READONLY;
 
  SourceLocation getEndLoc() const LLVM_READONLY {
    return getTemplateArgsAsWritten() &&
                   getTemplateArgsAsWritten()->getRAngleLoc().isValid()
               ? getTemplateArgsAsWritten()->getRAngleLoc()
               : getConceptNameInfo().getEndLoc();
  }
 
  SourceRange getSourceRange() const LLVM_READONLY {
    return SourceRange(getBeginLoc(), getEndLoc());
  }
 
  NamedDecl *getFoundDecl() const {
    return FoundDecl;
  }
 
  TemplateDecl *getNamedConcept() const { return NamedConcept; }
 
  const ASTTemplateArgumentListInfo *getTemplateArgsAsWritten() const {
    return ArgsAsWritten;
  }
 
  /// \brief Whether or not template arguments were explicitly specified in the
  /// concept reference (they might not be in type constraints, for example)
  bool hasExplicitTemplateArgs() const {
    return ArgsAsWritten != nullptr;
  }
 
  void print(llvm::raw_ostream &OS, const PrintingPolicy &Policy) const;
  void dump() const;
  void dump(llvm::raw_ostream &) const;
};
 
/// Models the abbreviated syntax to constrain a template type parameter:
///   template <convertible_to<string> T> void print(T object);
///             ~~~~~~~~~~~~~~~~~~~~~~
/// Semantically, this adds an "immediately-declared constraint" with extra arg:
///    requires convertible_to<T, string>
///
/// In the C++ grammar, a type-constraint is also used for auto types:
///    convertible_to<string> auto X = ...;
/// We do *not* model these as TypeConstraints, but AutoType(Loc) directly.
class TypeConstraint {
  /// \brief The immediately-declared constraint expression introduced by this
  /// type-constraint.
  Expr *ImmediatelyDeclaredConstraint = nullptr;
  ConceptReference *ConceptRef;
  UnsignedOrNone ArgPackSubstIndex;
 
public:
  TypeConstraint(ConceptReference *ConceptRef,
                 Expr *ImmediatelyDeclaredConstraint,
                 UnsignedOrNone ArgPackSubstIndex)
      : ImmediatelyDeclaredConstraint(ImmediatelyDeclaredConstraint),
        ConceptRef(ConceptRef), ArgPackSubstIndex(ArgPackSubstIndex) {}
 
  /// \brief Get the immediately-declared constraint expression introduced by
  /// this type-constraint, that is - the constraint expression that is added to
  /// the associated constraints of the enclosing declaration in practice.
  Expr *getImmediatelyDeclaredConstraint() const {
    return ImmediatelyDeclaredConstraint;
  }
 
  ConceptReference *getConceptReference() const { return ConceptRef; }
 
  UnsignedOrNone getArgPackSubstIndex() const { return ArgPackSubstIndex; }
 
  // FIXME: Instead of using these concept related functions the callers should
  // directly work with the corresponding ConceptReference.
  TemplateDecl *getNamedConcept() const {
    return ConceptRef->getNamedConcept();
  }
 
  SourceLocation getConceptNameLoc() const {
    return ConceptRef->getConceptNameLoc();
  }
 
  bool hasExplicitTemplateArgs() const {
    return ConceptRef->hasExplicitTemplateArgs();
  }
 
  const ASTTemplateArgumentListInfo *getTemplateArgsAsWritten() const {
    return ConceptRef->getTemplateArgsAsWritten();
  }
 
  SourceLocation getTemplateKWLoc() const {
    return ConceptRef->getTemplateKWLoc();
  }
 
  NamedDecl *getFoundDecl() const { return ConceptRef->getFoundDecl(); }
 
  const NestedNameSpecifierLoc &getNestedNameSpecifierLoc() const {
    return ConceptRef->getNestedNameSpecifierLoc();
  }
 
  const DeclarationNameInfo &getConceptNameInfo() const {
    return ConceptRef->getConceptNameInfo();
  }
 
  void print(llvm::raw_ostream &OS, const PrintingPolicy &Policy) const {
    ConceptRef->print(OS, Policy);
  }
};
 
/// Insertion operator for diagnostics.  This allows sending ConceptReferences's
/// into a diagnostic with <<.
const StreamingDiagnostic &operator<<(const StreamingDiagnostic &DB,
                                      const ConceptReference *C);
 
} // clang
 
#endif // LLVM_CLANG_AST_ASTCONCEPT_H