[Concepts] Requires Expressions

Implement support for C++2a requires-expressions.

Re-commit after compilation failure on some platforms due to alignment issues with PointerIntPair.

Differential Revision: https://reviews.llvm.org/D50360

(cherry picked from commit a0f50d7)

clang/include/clang/AST/ASTConcept.h

@@ -22,6 +22,7 @@
 #include <utility>
 namespace clang {
 class ConceptDecl;
+class ConceptSpecializationExpr;
 
 /// \brief The result of a constraint satisfaction check, containing the
 /// necessary information to diagnose an unsatisfied constraint.

clang/include/clang/AST/DeclCXX.h

@@ -1893,6 +1893,37 @@ class CXXDeductionGuideDecl : public FunctionDecl {
   static bool classofKind(Kind K) { return K == CXXDeductionGuide; }
 };
 
+/// \brief Represents the body of a requires-expression.
+///
+/// This decl exists merely to serve as the DeclContext for the local
+/// parameters of the requires expression as well as other declarations inside
+/// it.
+///
+/// \code
+/// template<typename T> requires requires (T t) { {t++} -> regular; }
+/// \endcode
+///
+/// In this example, a RequiresExpr object will be generated for the expression,
+/// and a RequiresExprBodyDecl will be created to hold the parameter t and the
+/// template argument list imposed by the compound requirement.
+class RequiresExprBodyDecl : public Decl, public DeclContext {
+  RequiresExprBodyDecl(ASTContext &C, DeclContext *DC, SourceLocation StartLoc)
+      : Decl(RequiresExprBody, DC, StartLoc), DeclContext(RequiresExprBody) {}
+
+public:
+  friend class ASTDeclReader;
+  friend class ASTDeclWriter;
+
+  static RequiresExprBodyDecl *Create(ASTContext &C, DeclContext *DC,
+                                      SourceLocation StartLoc);
+
+  static RequiresExprBodyDecl *CreateDeserialized(ASTContext &C, unsigned ID);
+
+  // Implement isa/cast/dyncast/etc.
+  static bool classof(const Decl *D) { return classofKind(D->getKind()); }
+  static bool classofKind(Kind K) { return K == RequiresExprBody; }
+};
+
 /// Represents a static or instance method of a struct/union/class.
 ///
 /// In the terminology of the C++ Standard, these are the (static and

clang/include/clang/AST/ExprCXX.h

@@ -14,7 +14,6 @@
 #ifndef LLVM_CLANG_AST_EXPRCXX_H
 #define LLVM_CLANG_AST_EXPRCXX_H
 
-#include "clang/AST/ASTConcept.h"
 #include "clang/AST/Decl.h"
 #include "clang/AST/DeclBase.h"
 #include "clang/AST/DeclCXX.h"
@@ -4836,99 +4835,6 @@ class BuiltinBitCastExpr final
   }
 };
 
-/// \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(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(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 {
-    return ConceptName.getBeginLoc();
-  }
-
-  SourceLocation getEndLoc() const LLVM_READONLY {
-    return ArgsAsWritten->RAngleLoc;
-  }
-
-  // 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_EXPRCXX_H