Teach the evaluation of the __is_convertible_to trait to translate

access control errors into SFINAE errors, so that the trait provides
enough support to implement the C++0x std::is_convertible type trait.

To get there, the SFINAETrap now knows how to set up a SFINAE context
independent of any template instantiations or template argument
deduction steps, and (separately) can set a Sema flag to translate
access control errors into SFINAE errors. The latter can also be
useful if we decide that access control errors during template argument
deduction should cause substitution failure (rather than a hard error)
as has been proposed for C++0x.

llvm-svn: 124446

1 files changed, 11 insertions, 5 deletions

diff --git a/clang/lib/Sema/Sema.cpp b/clang/lib/Sema/Sema.cpp
index e37f6175496..44bb71e57b3 100644
--- a/clang/lib/Sema/Sema.cpp
+++ b/clang/lib/Sema/Sema.cpp
@@ -139,7 +139,8 @@ Sema::Sema(Preprocessor &pp, ASTContext &ctxt, ASTConsumer &consumer,
     IdResolver(pp.getLangOptions()), CXXTypeInfoDecl(0), MSVCGuidDecl(0),
     GlobalNewDeleteDeclared(false), 
     CompleteTranslationUnit(CompleteTranslationUnit),
-    NumSFINAEErrors(0), SuppressAccessChecking(false),
+    NumSFINAEErrors(0), SuppressAccessChecking(false), 
+    AccessCheckingSFINAE(false), InNonInstantiationSFINAEContext(false),
     NonInstantiationEntries(0), ArgumentPackSubstitutionIndex(-1),
     CurrentInstantiationScope(0), TyposCorrected(0),
     AnalysisWarnings(*this)
@@ -450,14 +451,18 @@ Sema::SemaDiagnosticBuilder::~SemaDiagnosticBuilder() {
   if (!isActive())
     return;
   
-  if (TemplateDeductionInfo *Info = SemaRef.isSFINAEContext()) {
+  if (llvm::Optional<TemplateDeductionInfo*> Info = SemaRef.isSFINAEContext()) {
     switch (DiagnosticIDs::getDiagnosticSFINAEResponse(getDiagID())) {
-    case DiagnosticIDs::SFINAE_AccessControl:
     case DiagnosticIDs::SFINAE_Report:
       // Fall through; we'll report the diagnostic below.
       break;
       
-          
+    case DiagnosticIDs::SFINAE_AccessControl:
+      // Unless access checking is specifically called out as a SFINAE
+      // error, report this diagnostic.
+      if (!SemaRef.AccessCheckingSFINAE)
+        break;
+        
     case DiagnosticIDs::SFINAE_SubstitutionFailure:
       // Count this failure so that we know that template argument deduction
       // has failed.
@@ -473,7 +478,8 @@ Sema::SemaDiagnosticBuilder::~SemaDiagnosticBuilder() {
       FlushCounts();
       DiagnosticInfo DiagInfo(&SemaRef.Diags);
         
-      Info->addSuppressedDiagnostic(DiagInfo.getLocation(),
+      if (*Info)
+        (*Info)->addSuppressedDiagnostic(DiagInfo.getLocation(),
                         PartialDiagnostic(DiagInfo,
                                           SemaRef.Context.getDiagAllocator()));