//===- ExprConcepts.h - C++2a Concepts expressions --------------*- 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

/// Defines Expressions and AST nodes for C++2a concepts.

//

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

#ifndef LLVM_CLANG_AST_EXPRCONCEPTS_H

#define LLVM_CLANG_AST_EXPRCONCEPTS_H

#include "clang/AST/ASTContext.h"

#include "clang/AST/ASTConcept.h"

#include "clang/AST/Decl.h"

#include "clang/AST/DeclarationName.h"

#include "clang/AST/DeclTemplate.h"

#include "clang/AST/Expr.h"

#include "clang/AST/NestedNameSpecifier.h"

#include "clang/AST/TemplateBase.h"

#include "clang/AST/Type.h"

#include "clang/Basic/SourceLocation.h"

#include "llvm/Support/TrailingObjects.h"

#include <utility>

#include <string>

namespace clang {

class ASTStmtReader;

class ASTStmtWriter;

/// \brief Represents the specialization of a concept - evaluates to a prvalue

/// of type bool.

///

/// According to C++2a [expr.prim.id]p3 an id-expression that denotes the

/// specialization of a concept results in a prvalue of type bool.

class ConceptSpecializationExpr final : public Expr, public ConceptReference,

      private llvm::TrailingObjects<ConceptSpecializationExpr,

                                    TemplateArgument> {

  friend class ASTStmtReader;

  friend TrailingObjects;

public:

  using SubstitutionDiagnostic = std::pair<SourceLocation, std::string>;

protected:

  /// \brief The number of template arguments in the tail-allocated list of

  /// converted template arguments.

  unsigned NumTemplateArgs;

  /// \brief Information about the satisfaction of the named concept with the

  /// given arguments. If this expression is value dependent, this is to be

  /// ignored.

  ASTConstraintSatisfaction *Satisfaction;

  ConceptSpecializationExpr(const ASTContext &C, NestedNameSpecifierLoc NNS,

                            SourceLocation TemplateKWLoc,

                            DeclarationNameInfo ConceptNameInfo,

                            NamedDecl *FoundDecl, ConceptDecl *NamedConcept,

                            const ASTTemplateArgumentListInfo *ArgsAsWritten,

                            ArrayRef<TemplateArgument> ConvertedArgs,

                            const ConstraintSatisfaction *Satisfaction);

  ConceptSpecializationExpr(const ASTContext &C, ConceptDecl *NamedConcept,

                            ArrayRef<TemplateArgument> ConvertedArgs,

                            const ConstraintSatisfaction *Satisfaction,

                            bool Dependent,

                            bool ContainsUnexpandedParameterPack);

  ConceptSpecializationExpr(EmptyShell Empty, unsigned NumTemplateArgs);

public:

  static ConceptSpecializationExpr *

  Create(const ASTContext &C, NestedNameSpecifierLoc NNS,

         SourceLocation TemplateKWLoc, DeclarationNameInfo ConceptNameInfo,

         NamedDecl *FoundDecl, ConceptDecl *NamedConcept,

         const ASTTemplateArgumentListInfo *ArgsAsWritten,

         ArrayRef<TemplateArgument> ConvertedArgs,

         const ConstraintSatisfaction *Satisfaction);

  static ConceptSpecializationExpr *

  Create(const ASTContext &C, ConceptDecl *NamedConcept,

         ArrayRef<TemplateArgument> ConvertedArgs,

         const ConstraintSatisfaction *Satisfaction,

         bool Dependent,

         bool ContainsUnexpandedParameterPack);

  static ConceptSpecializationExpr *

  Create(ASTContext &C, EmptyShell Empty, unsigned NumTemplateArgs);

  ArrayRef<TemplateArgument> getTemplateArguments() const {

    return ArrayRef<TemplateArgument>(getTrailingObjects<TemplateArgument>(),

                                      NumTemplateArgs);

  }

  /// \brief Set new template arguments for this concept specialization.

  void setTemplateArguments(ArrayRef<TemplateArgument> Converted);

  /// \brief Whether or not the concept with the given arguments was satisfied

  /// when the expression was created.

  /// The expression must not be dependent.

  bool isSatisfied() const {

    assert(!isValueDependent()

           && "isSatisfied called on a dependent ConceptSpecializationExpr");

    return Satisfaction->IsSatisfied;

  }

  /// \brief Get elaborated satisfaction info about the template arguments'

  /// satisfaction of the named concept.

  /// The expression must not be dependent.

  const ASTConstraintSatisfaction &getSatisfaction() const {

    assert(!isValueDependent()

           && "getSatisfaction called on dependent ConceptSpecializationExpr");

    return *Satisfaction;

  }

  static bool classof(const Stmt *T) {

    return T->getStmtClass() == ConceptSpecializationExprClass;

  }

  SourceLocation getBeginLoc() const LLVM_READONLY {

    if (auto QualifierLoc = getNestedNameSpecifierLoc())

      return QualifierLoc.getBeginLoc();

    return ConceptName.getBeginLoc();

  }

  SourceLocation getEndLoc() const LLVM_READONLY {

    // If the ConceptSpecializationExpr is the ImmediatelyDeclaredConstraint

    // of a TypeConstraint written syntactically as a constrained-parameter,

    // there may not be a template argument list.

    return ArgsAsWritten->RAngleLoc.isValid() ? 
ArgsAsWritten->RAngleLoc7.44k

                                              : 
ConceptName.getEndLoc()955
;

  }

  // Iterators

  child_range children() {

    return child_range(child_iterator(), child_iterator());

  }

  const_child_range children() const {

    return const_child_range(const_child_iterator(), const_child_iterator());

  }

};

namespace concepts {

/// \brief A static requirement that can be used in a requires-expression to

/// check properties of types and expression.

class Requirement {

public:

  // Note - simple and compound requirements are both represented by the same

  // class (ExprRequirement).

  enum RequirementKind { RK_Type, RK_Simple, RK_Compound, RK_Nested };

private:

  const RequirementKind Kind;

  // FIXME: use RequirementDependence to model dependence?

  bool Dependent : 1;

  bool ContainsUnexpandedParameterPack : 1;

  bool Satisfied : 1;

public:

  struct SubstitutionDiagnostic {

    StringRef SubstitutedEntity;

    // FIXME: Store diagnostics semantically and not as prerendered strings.

    //  Fixing this probably requires serialization of PartialDiagnostic

    //  objects.

    SourceLocation DiagLoc;

    StringRef DiagMessage;

  };

  Requirement(RequirementKind Kind, bool IsDependent,

              bool ContainsUnexpandedParameterPack, bool IsSatisfied = true) :

      Kind(Kind), Dependent(IsDependent),

      ContainsUnexpandedParameterPack(ContainsUnexpandedParameterPack),

      Satisfied(IsSatisfied) {}

  RequirementKind getKind() const { return Kind; }

  bool isSatisfied() const {

    assert(!Dependent &&

           "isSatisfied can only be called on non-dependent requirements.");

    return Satisfied;

  }

  void setSatisfied(bool IsSatisfied) {

    assert(!Dependent &&

           "setSatisfied can only be called on non-dependent requirements.");

    Satisfied = IsSatisfied;

  }

  void setDependent(bool IsDependent) { Dependent = IsDependent; }

  bool isDependent() const { return Dependent; }

  void setContainsUnexpandedParameterPack(bool Contains) {

    ContainsUnexpandedParameterPack = Contains;

  }

  bool containsUnexpandedParameterPack() const {

    return ContainsUnexpandedParameterPack;

  }

};

/// \brief A requires-expression requirement which queries the existence of a

/// type name or type template specialization ('type' requirements).

class TypeRequirement : public Requirement {

public:

  enum SatisfactionStatus {

      SS_Dependent,

      SS_SubstitutionFailure,

      SS_Satisfied

  };

private:

  llvm::PointerUnion<SubstitutionDiagnostic *, TypeSourceInfo *> Value;

  SatisfactionStatus Status;

public:

  friend ASTStmtReader;

  friend ASTStmtWriter;

  /// \brief Construct a type requirement from a type. If the given type is not

  /// dependent, this indicates that the type exists and the requirement will be

  /// satisfied. Otherwise, the SubstitutionDiagnostic constructor is to be

  /// used.

  TypeRequirement(TypeSourceInfo *T);

  /// \brief Construct a type requirement when the nested name specifier is

  /// invalid due to a bad substitution. The requirement is unsatisfied.

  TypeRequirement(SubstitutionDiagnostic *Diagnostic) :

      Requirement(RK_Type, false, false, false), Value(Diagnostic),

      Status(SS_SubstitutionFailure) {}

  SatisfactionStatus getSatisfactionStatus() const { return Status; }

  void setSatisfactionStatus(SatisfactionStatus Status) {

    this->Status = Status;

  }

  bool isSubstitutionFailure() const {

    return Status == SS_SubstitutionFailure;

  }

  SubstitutionDiagnostic *getSubstitutionDiagnostic() const {

    assert(Status == SS_SubstitutionFailure &&

           "Attempted to get substitution diagnostic when there has been no "

           "substitution failure.");

    return Value.get<SubstitutionDiagnostic *>();

  }

  TypeSourceInfo *getType() const {

    assert(!isSubstitutionFailure() &&

           "Attempted to get type when there has been a substitution failure.");

    return Value.get<TypeSourceInfo *>();

  }

  static bool classof(const Requirement *R) {

    return R->getKind() == RK_Type;

  }

};

/// \brief A requires-expression requirement which queries the validity and

/// properties of an expression ('simple' and 'compound' requirements).

class ExprRequirement : public Requirement {

public:

  enum SatisfactionStatus {

      SS_Dependent,

      SS_ExprSubstitutionFailure,

      SS_NoexceptNotMet,

      SS_TypeRequirementSubstitutionFailure,

      SS_ConstraintsNotSatisfied,

      SS_Satisfied

  };

  class ReturnTypeRequirement {

      llvm::PointerIntPair<

          llvm::PointerUnion<TemplateParameterList *, SubstitutionDiagnostic *>,

          1, bool>

          TypeConstraintInfo;

  public:

      friend ASTStmtReader;

      friend ASTStmtWriter;

      /// \brief No return type requirement was specified.

      ReturnTypeRequirement() : TypeConstraintInfo(nullptr, false) {}

      /// \brief A return type requirement was specified but it was a

      /// substitution failure.

      ReturnTypeRequirement(SubstitutionDiagnostic *SubstDiag) :

          TypeConstraintInfo(SubstDiag, false) {}

      /// \brief A 'type constraint' style return type requirement.

      /// \param TPL an invented template parameter list containing a single

      /// type parameter with a type-constraint.

      // TODO: Can we maybe not save the whole template parameter list and just

      //  the type constraint? Saving the whole TPL makes it easier to handle in

      //  serialization but is less elegant.

      ReturnTypeRequirement(TemplateParameterList *TPL);

      bool isDependent() const {

        return TypeConstraintInfo.getInt();

      }

      bool containsUnexpandedParameterPack() const {

        if (!isTypeConstraint())

          return false;

        return getTypeConstraintTemplateParameterList()

                ->containsUnexpandedParameterPack();

      }

      bool isEmpty() const {

        return TypeConstraintInfo.getPointer().isNull();

      }

      bool isSubstitutionFailure() const {

        return !isEmpty() &&

            
TypeConstraintInfo.getPointer().is<SubstitutionDiagnostic *>()3.57k
;

      }

      bool isTypeConstraint() const {

        return !isEmpty() &&

            
TypeConstraintInfo.getPointer().is<TemplateParameterList *>()14.0k
;

      }

      SubstitutionDiagnostic *getSubstitutionDiagnostic() const {

        assert(isSubstitutionFailure());

        return TypeConstraintInfo.getPointer().get<SubstitutionDiagnostic *>();

      }

      const TypeConstraint *getTypeConstraint() const;

      TemplateParameterList *getTypeConstraintTemplateParameterList() const {

        assert(isTypeConstraint());

        return TypeConstraintInfo.getPointer().get<TemplateParameterList *>();

      }

  };

private:

  llvm::PointerUnion<Expr *, SubstitutionDiagnostic *> Value;

  SourceLocation NoexceptLoc; // May be empty if noexcept wasn't specified.

  ReturnTypeRequirement TypeReq;

  ConceptSpecializationExpr *SubstitutedConstraintExpr;

  SatisfactionStatus Status;

public:

  friend ASTStmtReader;

  friend ASTStmtWriter;

  /// \brief Construct a compound requirement.

  /// \param E the expression which is checked by this requirement.

  /// \param IsSimple whether this was a simple requirement in source.

  /// \param NoexceptLoc the location of the noexcept keyword, if it was

  /// specified, otherwise an empty location.

  /// \param Req the requirement for the type of the checked expression.

  /// \param Status the satisfaction status of this requirement.

  ExprRequirement(

      Expr *E, bool IsSimple, SourceLocation NoexceptLoc,

      ReturnTypeRequirement Req, SatisfactionStatus Status,

      ConceptSpecializationExpr *SubstitutedConstraintExpr = nullptr);

  /// \brief Construct a compound requirement whose expression was a

  /// substitution failure. The requirement is not satisfied.

  /// \param E the diagnostic emitted while instantiating the original

  /// expression.

  /// \param IsSimple whether this was a simple requirement in source.

  /// \param NoexceptLoc the location of the noexcept keyword, if it was

  /// specified, otherwise an empty location.

  /// \param Req the requirement for the type of the checked expression (omit

  /// if no requirement was specified).

  ExprRequirement(SubstitutionDiagnostic *E, bool IsSimple,

                  SourceLocation NoexceptLoc, ReturnTypeRequirement Req = {});

  bool isSimple() const { return getKind() == RK_Simple; }

  bool isCompound() const { return getKind() == RK_Compound; }

  bool hasNoexceptRequirement() const { return NoexceptLoc.isValid(); }

  SourceLocation getNoexceptLoc() const { return NoexceptLoc; }

  SatisfactionStatus getSatisfactionStatus() const { return Status; }

  bool isExprSubstitutionFailure() const {

    return Status == SS_ExprSubstitutionFailure;

  }

  const ReturnTypeRequirement &getReturnTypeRequirement() const {

    return TypeReq;

  }

  ConceptSpecializationExpr *

  getReturnTypeRequirementSubstitutedConstraintExpr() const {

    assert(Status >= SS_TypeRequirementSubstitutionFailure);

    return SubstitutedConstraintExpr;

  }

  SubstitutionDiagnostic *getExprSubstitutionDiagnostic() const {

    assert(isExprSubstitutionFailure() &&

           "Attempted to get expression substitution diagnostic when there has "

           "been no expression substitution failure");

    return Value.get<SubstitutionDiagnostic *>();

  }

  Expr *getExpr() const {

    assert(!isExprSubstitutionFailure() &&

           "ExprRequirement has no expression because there has been a "

           "substitution failure.");

    return Value.get<Expr *>();

  }

  static bool classof(const Requirement *R) {

    return R->getKind() == RK_Compound || 
R->getKind() == RK_Simple3.54k
;

  }

};

/// \brief A requires-expression requirement which is satisfied when a general

/// constraint expression is satisfied ('nested' requirements).

class NestedRequirement : public Requirement {

  llvm::PointerUnion<Expr *, SubstitutionDiagnostic *> Value;

  const ASTConstraintSatisfaction *Satisfaction = nullptr;

public:

  friend ASTStmtReader;

  friend ASTStmtWriter;

  NestedRequirement(SubstitutionDiagnostic *SubstDiag) :

      Requirement(RK_Nested, /*IsDependent=*/false,

                  /*ContainsUnexpandedParameterPack*/false,

                  /*IsSatisfied=*/false), Value(SubstDiag) {}

  NestedRequirement(Expr *Constraint) :

      Requirement(RK_Nested, /*IsDependent=*/true,

                  Constraint->containsUnexpandedParameterPack()),

      Value(Constraint) {

    assert(Constraint->isInstantiationDependent() &&

           "Nested requirement with non-dependent constraint must be "

           "constructed with a ConstraintSatisfaction object");

  }

  NestedRequirement(ASTContext &C, Expr *Constraint,

                    const ConstraintSatisfaction &Satisfaction) :

      Requirement(RK_Nested, Constraint->isInstantiationDependent(),

                  Constraint->containsUnexpandedParameterPack(),

                  Satisfaction.IsSatisfied),

      Value(Constraint),

      Satisfaction(ASTConstraintSatisfaction::Create(C, Satisfaction)) {}

  bool isSubstitutionFailure() const {

    return Value.is<SubstitutionDiagnostic *>();

  }

  SubstitutionDiagnostic *getSubstitutionDiagnostic() const {

    assert(isSubstitutionFailure() &&

           "getSubstitutionDiagnostic() may not be called when there was no "

           "substitution failure.");

    return Value.get<SubstitutionDiagnostic *>();

  }

  Expr *getConstraintExpr() const {

    assert(!isSubstitutionFailure() && "getConstraintExpr() may not be called "

                                       "on nested requirements with "

                                       "substitution failures.");

    return Value.get<Expr *>();

  }

  const ASTConstraintSatisfaction &getConstraintSatisfaction() const {

    assert(!isSubstitutionFailure() && "getConstraintSatisfaction() may not be "

                                       "called on nested requirements with "

                                       "substitution failures.");

    return *Satisfaction;

  }

  static bool classof(const Requirement *R) {

    return R->getKind() == RK_Nested;

  }

};

} // namespace concepts

/// C++2a [expr.prim.req]:

///     A requires-expression provides a concise way to express requirements on

///     template arguments. A requirement is one that can be checked by name

///     lookup (6.4) or by checking properties of types and expressions.

///     [...]

///     A requires-expression is a prvalue of type bool [...]

class RequiresExpr final : public Expr,

    llvm::TrailingObjects<RequiresExpr, ParmVarDecl *,

                          concepts::Requirement *> {

  friend TrailingObjects;

  friend class ASTStmtReader;

  unsigned NumLocalParameters;

  unsigned NumRequirements;

  RequiresExprBodyDecl *Body;

  SourceLocation RBraceLoc;

  unsigned numTrailingObjects(OverloadToken<ParmVarDecl *>) const {

    return NumLocalParameters;

  }

  unsigned numTrailingObjects(OverloadToken<concepts::Requirement *>) const {

    return NumRequirements;

  }

  RequiresExpr(ASTContext &C, SourceLocation RequiresKWLoc,

               RequiresExprBodyDecl *Body,

               ArrayRef<ParmVarDecl *> LocalParameters,

               ArrayRef<concepts::Requirement *> Requirements,

               SourceLocation RBraceLoc);

  RequiresExpr(ASTContext &C, EmptyShell Empty, unsigned NumLocalParameters,

               unsigned NumRequirements);

public:

  static RequiresExpr *

  Create(ASTContext &C, SourceLocation RequiresKWLoc,

         RequiresExprBodyDecl *Body, ArrayRef<ParmVarDecl *> LocalParameters,

         ArrayRef<concepts::Requirement *> Requirements,

         SourceLocation RBraceLoc);

  static RequiresExpr *

  Create(ASTContext &C, EmptyShell Empty, unsigned NumLocalParameters,

         unsigned NumRequirements);

  ArrayRef<ParmVarDecl *> getLocalParameters() const {

    return {getTrailingObjects<ParmVarDecl *>(), NumLocalParameters};

  }

  RequiresExprBodyDecl *getBody() const { return Body; }

  ArrayRef<concepts::Requirement *> getRequirements() const {

    return {getTrailingObjects<concepts::Requirement *>(), NumRequirements};

  }

  /// \brief Whether or not the requires clause is satisfied.

  /// The expression must not be dependent.

  bool isSatisfied() const {

    assert(!isValueDependent()

           && "isSatisfied called on a dependent RequiresExpr");

    return RequiresExprBits.IsSatisfied;

  }

  SourceLocation getRequiresKWLoc() const {

    return RequiresExprBits.RequiresKWLoc;

  }

  SourceLocation getRBraceLoc() const { return RBraceLoc; }

  static bool classof(const Stmt *T) {

    return T->getStmtClass() == RequiresExprClass;

  }

  SourceLocation getBeginLoc() const LLVM_READONLY {

    return RequiresExprBits.RequiresKWLoc;

  }

  SourceLocation getEndLoc() const LLVM_READONLY {

    return RBraceLoc;

  }

  // Iterators

  child_range children() {

    return child_range(child_iterator(), child_iterator());

  }

  const_child_range children() const {

    return const_child_range(const_child_iterator(), const_child_iterator());

  }

};

} // namespace clang

#endif // LLVM_CLANG_AST_EXPRCONCEPTS_H