commit fdf80e86a52849813d05da4b6c25884c06ba9e98
author Saar Raz <saar@raz.email> Fri Dec 06 01:30:21 2019 +0200
committer Saar Raz <saar@raz.email> Fri Dec 06 01:34:20 2019 +0200
tree f08ca57be85567d41a118bedb588a8152763c360
parent 7faa8440440f280912c33a27c14c0dc4031532de

[Concepts] Constraint Enforcement & Diagnostics

Part of the C++20 concepts implementation effort.
- Associated constraints (requires clauses, currently) are now enforced when instantiating/specializing templates and when considering partial specializations and function overloads.
- Elaborated diagnostics give helpful insight as to why the constraints were not satisfied.
Phabricator: D41569

Re-commit, after fixing some memory bugs.

clang/lib/AST/ExprCXX.cpp

diff --git a/clang/lib/AST/ExprCXX.cpp b/clang/lib/AST/ExprCXX.cpp
index 0fb132d..bef181e 100644
--- a/clang/lib/AST/ExprCXX.cpp
+++ b/clang/lib/AST/ExprCXX.cpp
@@ -1769,18 +1769,19 @@
     NestedNameSpecifierLoc NNS, SourceLocation TemplateKWLoc,
     SourceLocation ConceptNameLoc, NamedDecl *FoundDecl,
     ConceptDecl *NamedConcept, const ASTTemplateArgumentListInfo *ArgsAsWritten,
-    ArrayRef<TemplateArgument> ConvertedArgs, Optional<bool> IsSatisfied)
+    ArrayRef<TemplateArgument> ConvertedArgs,
+    const ConstraintSatisfaction *Satisfaction)
     : Expr(ConceptSpecializationExprClass, C.BoolTy, VK_RValue, OK_Ordinary,
            /*TypeDependent=*/false,
            // All the flags below are set in setTemplateArguments.
-           /*ValueDependent=*/!IsSatisfied.hasValue(),
-           /*InstantiationDependent=*/false,
+           /*ValueDependent=*/!Satisfaction, /*InstantiationDependent=*/false,
            /*ContainsUnexpandedParameterPacks=*/false),
       NestedNameSpec(NNS), TemplateKWLoc(TemplateKWLoc),
       ConceptNameLoc(ConceptNameLoc), FoundDecl(FoundDecl),
-      NamedConcept(NamedConcept, IsSatisfied ? *IsSatisfied : true),
-      NumTemplateArgs(ConvertedArgs.size()) {
-
+      NamedConcept(NamedConcept), NumTemplateArgs(ConvertedArgs.size()),
+      Satisfaction(Satisfaction ?
+                   ASTConstraintSatisfaction::Create(C, *Satisfaction) :
+                   nullptr) {
   setTemplateArguments(ArgsAsWritten, ConvertedArgs);
 }
 
@@ -1827,13 +1828,13 @@
                                   ConceptDecl *NamedConcept,
                                const ASTTemplateArgumentListInfo *ArgsAsWritten,
                                   ArrayRef<TemplateArgument> ConvertedArgs,
-                                  Optional<bool> IsSatisfied) {
+                                  const ConstraintSatisfaction *Satisfaction) {
   void *Buffer = C.Allocate(totalSizeToAlloc<TemplateArgument>(
                                 ConvertedArgs.size()));
   return new (Buffer) ConceptSpecializationExpr(C, NNS, TemplateKWLoc,
                                                 ConceptNameLoc, FoundDecl,
                                                 NamedConcept, ArgsAsWritten,
-                                                ConvertedArgs, IsSatisfied);
+                                                ConvertedArgs, Satisfaction);
 }
 
 ConceptSpecializationExpr *