Revert 374882 "[Concepts] Concept Specialization Expressions"

This reverts commit ec87b003823d63f3342cf648f55a134c1522e612.
The test fails on Windows, see e.g.
http://lab.llvm.org:8011/builders/clang-x64-windows-msvc/builds/11533/steps/stage%201%20check/logs/stdio

Also revert follow-up r374893.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@374899 91177308-0d34-0410-b5e6-96231b3b80d8

6 files changed, 6 insertions, 179 deletions

diff --git a/include/clang/AST/ExprCXX.h b/include/clang/AST/ExprCXX.h
index 57ccba8b81..61e7a91d9f 100644
--- a/include/clang/AST/ExprCXX.h
+++ b/include/clang/AST/ExprCXX.h
@@ -17,7 +17,6 @@
 #include "clang/AST/Decl.h"
 #include "clang/AST/DeclBase.h"
 #include "clang/AST/DeclCXX.h"
-#include "clang/AST/DeclTemplate.h"
 #include "clang/AST/DeclarationName.h"
 #include "clang/AST/Expr.h"
 #include "clang/AST/NestedNameSpecifier.h"
@@ -57,7 +56,6 @@ class IdentifierInfo;
 class LambdaCapture;
 class NonTypeTemplateParmDecl;
 class TemplateParameterList;
-class Sema;
 
 //===--------------------------------------------------------------------===//
 // C++ Expressions.
@@ -4752,125 +4750,6 @@ public:
   }
 };
 
-/// \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,
-      private llvm::TrailingObjects<ConceptSpecializationExpr,
-                                    TemplateArgument> {
-  friend class ASTStmtReader;
-  friend TrailingObjects;
-
-  // \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 location of the concept name in the expression.
-  SourceLocation ConceptNameLoc;
-
-  /// \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, and whether or not the concept with the given
-  /// arguments was satisfied when the expression was created.
-  /// If any of the template arguments are dependent (this expr would then be
-  /// isValueDependent()), this bit is to be ignored.
-  llvm::PointerIntPair<ConceptDecl *, 1, bool> NamedConcept;
-
-  /// \brief The template argument list source info used to specialize the
-  /// concept.
-  const ASTTemplateArgumentListInfo *ArgsAsWritten = nullptr;
-
-  /// \brief The number of template arguments in the tail-allocated list of
-  /// converted template arguments.
-  unsigned NumTemplateArgs;
-
-  ConceptSpecializationExpr(ASTContext &C, NestedNameSpecifierLoc NNS,
-                            SourceLocation TemplateKWLoc,
-                            SourceLocation ConceptNameLoc, NamedDecl *FoundDecl,
-                            ConceptDecl *NamedConcept,
-                            const ASTTemplateArgumentListInfo *ArgsAsWritten,
-                            ArrayRef<TemplateArgument> ConvertedArgs,
-                            Optional<bool> IsSatisfied);
-
-  ConceptSpecializationExpr(EmptyShell Empty, unsigned NumTemplateArgs);
-
-public:
-
-  static ConceptSpecializationExpr *
-  Create(ASTContext &C, NestedNameSpecifierLoc NNS,
-         SourceLocation TemplateKWLoc, SourceLocation ConceptNameLoc,
-         NamedDecl *FoundDecl, ConceptDecl *NamedConcept,
-         const ASTTemplateArgumentListInfo *ArgsAsWritten,
-         ArrayRef<TemplateArgument> ConvertedArgs, Optional<bool> IsSatisfied);
-
-  static ConceptSpecializationExpr *
-  Create(ASTContext &C, EmptyShell Empty, unsigned NumTemplateArgs);
-
-  const NestedNameSpecifierLoc &getNestedNameSpecifierLoc() const {
-    return NestedNameSpec;
-  }
-
-  NamedDecl *getFoundDecl() const {
-    return FoundDecl;
-  }
-
-  ConceptDecl *getNamedConcept() const {
-    return NamedConcept.getPointer();
-  }
-
-  ArrayRef<TemplateArgument> getTemplateArguments() const {
-    return ArrayRef<TemplateArgument>(getTrailingObjects<TemplateArgument>(),
-                                      NumTemplateArgs);
-  }
-
-  const ASTTemplateArgumentListInfo *getTemplateArgsAsWritten() const {
-    return ArgsAsWritten;
-  }
-
-  /// \brief Set new template arguments for this concept specialization.
-  void setTemplateArguments(const ASTTemplateArgumentListInfo *ArgsAsWritten,
-                            ArrayRef<TemplateArgument> Converted);
-
-  /// \brief Whether or not the concept with the given arguments was satisfied
-  /// when the expression was created. This method assumes that the expression
-  /// is not dependent!
-  bool isSatisfied() const {
-    assert(!isValueDependent()
-           && "isSatisfied called on a dependent ConceptSpecializationExpr");
-    return NamedConcept.getInt();
-  }
-
-  SourceLocation getConceptNameLoc() const { return ConceptNameLoc; }
-
-  SourceLocation getTemplateKWLoc() const { return TemplateKWLoc; }
-
-  static bool classof(const Stmt *T) {
-    return T->getStmtClass() == ConceptSpecializationExprClass;
-  }
-
-  SourceLocation getBeginLoc() const LLVM_READONLY { return ConceptNameLoc; }
-  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
diff --git a/include/clang/AST/RecursiveASTVisitor.h b/include/clang/AST/RecursiveASTVisitor.h
index 998cf9238c..09a6f7840d 100644
--- a/include/clang/AST/RecursiveASTVisitor.h
+++ b/include/clang/AST/RecursiveASTVisitor.h
@@ -2659,12 +2659,6 @@ DEF_TRAVERSE_STMT(CoyieldExpr, {
   }
 })
 
-DEF_TRAVERSE_STMT(ConceptSpecializationExpr, {
-  TRY_TO(TraverseTemplateArgumentLocsHelper(
-          S->getTemplateArgsAsWritten()->getTemplateArgs(),
-          S->getTemplateArgsAsWritten()->NumTemplateArgs));
-})
-
 // These literals (all of them) do not need any action.
 DEF_TRAVERSE_STMT(IntegerLiteral, {})
 DEF_TRAVERSE_STMT(FixedPointLiteral, {})
diff --git a/include/clang/Basic/DiagnosticSemaKinds.td b/include/clang/Basic/DiagnosticSemaKinds.td
index 968c2dbd56..47a1deef98 100644
--- a/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/include/clang/Basic/DiagnosticSemaKinds.td
@@ -2526,6 +2526,8 @@ def note_private_extern : Note<
   "use __attribute__((visibility(\"hidden\"))) attribute instead">;
 
 // C++ Concepts
+def err_concept_initialized_with_non_bool_type : Error<
+  "constraint expression must be of type 'bool' but is of type %0">;
 def err_concept_decls_may_only_appear_in_global_namespace_scope : Error<
   "concept declarations may only appear in global or namespace scope">;
 def err_concept_no_parameters : Error<
@@ -2537,11 +2539,6 @@ def err_concept_no_associated_constraints : Error<
   "concept cannot have associated constraints">;
 def err_concept_not_implemented : Error<
   "sorry, unimplemented concepts feature %0 used">;
-def err_non_constant_constraint_expression : Error<
-  "substitution into constraint expression resulted in a non-constant "
-  "expression">;
-def err_non_bool_atomic_constraint : Error<
-  "atomic constraint must be of type 'bool' (found %0)">;
 
 def err_template_different_associated_constraints : Error<
   "associated constraints differ in template redeclaration">;
@@ -4499,10 +4496,6 @@ def note_prior_template_arg_substitution : Note<
   " template parameter%1 %2">;
 def note_template_default_arg_checking : Note<
   "while checking a default template argument used here">;
-def note_concept_specialization_here : Note<
-  "while checking the satisfaction of concept '%0' requested here">;
-def note_constraint_substitution_here : Note<
-  "while substituting template arguments into constraint expression here">;
 def note_instantiation_contexts_suppressed : Note<
   "(skipping %0 context%s0 in backtrace; use -ftemplate-backtrace-limit=0 to "
   "see all)">;
diff --git a/include/clang/Basic/StmtNodes.td b/include/clang/Basic/StmtNodes.td
index 6231484e2b..1cef89f371 100644
--- a/include/clang/Basic/StmtNodes.td
+++ b/include/clang/Basic/StmtNodes.td
@@ -163,9 +163,6 @@ def CoawaitExpr : DStmt<CoroutineSuspendExpr>;
 def DependentCoawaitExpr : DStmt<Expr>;
 def CoyieldExpr : DStmt<CoroutineSuspendExpr>;
 
-// C++2a Concepts expressions
-def ConceptSpecializationExpr : DStmt<Expr>;
-
 // Obj-C Expressions.
 def ObjCStringLiteral : DStmt<Expr>;
 def ObjCBoxedExpr : DStmt<Expr>;
diff --git a/include/clang/Sema/Sema.h b/include/clang/Sema/Sema.h
index 6b2d603206..0403df4ba7 100644
--- a/include/clang/Sema/Sema.h
+++ b/include/clang/Sema/Sema.h
@@ -6047,16 +6047,7 @@ public:
                                            CXXConversionDecl *Conv,
                                            Expr *Src);
 
-  /// Check whether the given expression is a valid constraint expression.
-  /// A diagnostic is emitted if it is not, and false is returned.
-  bool CheckConstraintExpression(Expr *CE);
-
-  bool CalculateConstraintSatisfaction(ConceptDecl *NamedConcept,
-                                       MultiLevelTemplateArgumentList &MLTAL,
-                                       Expr *ConstraintExpr,
-                                       bool &IsSatisfied);
-
-    // ParseObjCStringLiteral - Parse Objective-C string literals.
+  // ParseObjCStringLiteral - Parse Objective-C string literals.
   ExprResult ParseObjCStringLiteral(SourceLocation *AtLocs,
                                     ArrayRef<Expr *> Strings);
 
@@ -6727,9 +6718,9 @@ public:
 
   ExprResult
   CheckConceptTemplateId(const CXXScopeSpec &SS,
-                         SourceLocation TemplateKWLoc,
-                         SourceLocation ConceptNameLoc, NamedDecl *FoundDecl,
-                         ConceptDecl *NamedConcept,
+                         const DeclarationNameInfo &NameInfo,
+                         ConceptDecl *Template,
+                         SourceLocation TemplateLoc,
                          const TemplateArgumentListInfo *TemplateArgs);
 
   void diagnoseMissingTemplateArguments(TemplateName Name, SourceLocation Loc);
@@ -7648,15 +7639,6 @@ public:
       /// member).
       DefiningSynthesizedFunction,
 
-      // We are checking the constraints associated with a constrained entity or
-      // the constraint expression of a concept. This includes the checks that
-      // atomic constraints have the type 'bool' and that they can be constant
-      // evaluated.
-      ConstraintsCheck,
-
-      // We are substituting template arguments into a constraint expression.
-      ConstraintSubstitution,
-
       /// Added for Template instantiation observation.
       /// Memoization means we are _not_ instantiating a template because
       /// it is already instantiated (but we entered a context where we
@@ -7917,23 +7899,6 @@ public:
                           ArrayRef<TemplateArgument> TemplateArgs,
                           SourceRange InstantiationRange);
 
-    struct ConstraintsCheck {};
-    /// \brief Note that we are checking the constraints associated with some
-    /// constrained entity (a concept declaration or a template with associated
-    /// constraints).
-    InstantiatingTemplate(Sema &SemaRef, SourceLocation PointOfInstantiation,
-                          ConstraintsCheck, TemplateDecl *Template,
-                          ArrayRef<TemplateArgument> TemplateArgs,
-                          SourceRange InstantiationRange);
-
-    struct ConstraintSubstitution {};
-    /// \brief Note that we are checking a constraint expression associated
-    /// with a template declaration or as part of the satisfaction check of a
-    /// concept.
-    InstantiatingTemplate(Sema &SemaRef, SourceLocation PointOfInstantiation,
-                          ConstraintSubstitution, TemplateDecl *Template,
-                          sema::TemplateDeductionInfo &DeductionInfo,
-                          SourceRange InstantiationRange);
 
     /// Note that we have finished instantiating this template.
     void Clear();
diff --git a/include/clang/Serialization/ASTBitCodes.h b/include/clang/Serialization/ASTBitCodes.h
index 0d3971dd27..eab1ec86db 100644
--- a/include/clang/Serialization/ASTBitCodes.h
+++ b/include/clang/Serialization/ASTBitCodes.h
@@ -1915,7 +1915,6 @@ namespace serialization {
       EXPR_FUNCTION_PARM_PACK,    // FunctionParmPackExpr
       EXPR_MATERIALIZE_TEMPORARY, // MaterializeTemporaryExpr
       EXPR_CXX_FOLD,              // CXXFoldExpr
-      EXPR_CONCEPT_SPECIALIZATION,// ConceptSpecializationExpr
 
       // CUDA
       EXPR_CUDA_KERNEL_CALL,       // CUDAKernelCallExpr