llvm/clang/include/clang/AST/ASTConcept.h

//===--- 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/NestedNameSpecifier.h"
#include "clang/AST/TemplateBase.h"
#include "clang/Basic/SourceLocation.h"
#include "llvm/ADT/FoldingSet.h"
#include "llvm/ADT/PointerUnion.h"
#include "llvm/ADT/SmallVector.h"
#include <utility>

namespace clang {

class ConceptDecl;
class Expr;
class NamedDecl;
struct PrintingPolicy;

/// The result of a constraint satisfaction check, containing the necessary
/// information to diagnose an unsatisfied constraint.
class ConstraintSatisfaction : public llvm::FoldingSetNode { … };

/// Pairs of unsatisfied atomic constraint expressions along with the
/// substituted constraint expr, if the template arguments could be
/// substituted into them, or a diagnostic if substitution resulted in
/// an invalid expression.
UnsatisfiedConstraintRecord;

/// \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> { … };

/// 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 { … };

/// 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 { … };

} // clang

#endif // LLVM_CLANG_AST_ASTCONCEPT_H