3 files changed, 48 insertions, 1 deletions
diff --git a/lib/Sema/Sema.cpp b/lib/Sema/Sema.cpp
index e3cea5be42..4dc5222072 100644
--- a/lib/Sema/Sema.cpp
+++ b/lib/Sema/Sema.cpp
@@ -316,7 +316,8 @@ NamedDecl *Sema::getCurFunctionOrMethodDecl() {
 }
 
 Sema::SemaDiagnosticBuilder::~SemaDiagnosticBuilder() {
-  this->Emit();
+  if (!this->Emit())
+    return;
   
   // If this is not a note, and we're in a template instantiation
   // that is different from the last template instantiation where
diff --git a/lib/Sema/Sema.h b/lib/Sema/Sema.h
index 169ce8216c..b310568740 100644
--- a/lib/Sema/Sema.h
+++ b/lib/Sema/Sema.h
@@ -297,11 +297,21 @@ public:
     SemaDiagnosticBuilder(DiagnosticBuilder &DB, Sema &SemaRef, unsigned DiagID)
       : DiagnosticBuilder(DB), SemaRef(SemaRef), DiagID(DiagID) { }
 
+    explicit SemaDiagnosticBuilder(Sema &SemaRef) 
+      : DiagnosticBuilder(DiagnosticBuilder::Suppress), SemaRef(SemaRef) { }
+
     ~SemaDiagnosticBuilder();
   };
 
   /// \brief Emit a diagnostic.
   SemaDiagnosticBuilder Diag(SourceLocation Loc, unsigned DiagID) {
+    if (isSFINAEContext() && Diagnostic::isBuiltinSFINAEDiag(DiagID)) {
+      // If we encountered an error during template argument
+      // deduction, and that error is one of the SFINAE errors,
+      // supress the diagnostic.
+      return SemaDiagnosticBuilder(*this);
+    }
+
     DiagnosticBuilder DB = Diags.Report(FullSourceLoc(Loc, SourceMgr), DiagID);
     return SemaDiagnosticBuilder(DB, *this, DiagID);
   }
@@ -2322,6 +2332,14 @@ public:
 
   void PrintInstantiationStack();
 
+  /// \brief Determines whether we are currently in a context where
+  /// template argument substitution failures are not considered
+  /// errors.
+  ///
+  /// When this routine returns true, the emission of most diagnostics
+  /// will be suppressed and there will be no local error recovery.
+  bool isSFINAEContext() const;
+
   /// \brief A stack-allocated class that identifies which local
   /// variable declaration instantiations are present in this scope.
   ///
diff --git a/lib/Sema/SemaTemplateInstantiate.cpp b/lib/Sema/SemaTemplateInstantiate.cpp
index 4d03e79c65..18b2d75acc 100644
--- a/lib/Sema/SemaTemplateInstantiate.cpp
+++ b/lib/Sema/SemaTemplateInstantiate.cpp
@@ -199,6 +199,34 @@ void Sema::PrintInstantiationStack() {
   }
 }
 
+bool Sema::isSFINAEContext() const {
+  using llvm::SmallVector;
+  for (SmallVector<ActiveTemplateInstantiation, 16>::const_reverse_iterator
+         Active = ActiveTemplateInstantiations.rbegin(),
+         ActiveEnd = ActiveTemplateInstantiations.rend();
+       Active != ActiveEnd;
+       ++Active) {
+
+    switch(Active->Kind) {
+    case ActiveTemplateInstantiation::PartialSpecDeductionInstantiation:
+      // We're in a template argument deduction context, so SFINAE
+      // applies.
+      return true;
+
+    case ActiveTemplateInstantiation::DefaultTemplateArgumentInstantiation:
+      // A default template argument instantiation may or may not be a
+      // SFINAE context; look further up the stack.
+      break;
+
+    case ActiveTemplateInstantiation::TemplateInstantiation:
+      // This is a template instantiation, so there is no SFINAE.
+      return false;
+    }
+  }
+
+  return false;
+}
+
 //===----------------------------------------------------------------------===/
 // Template Instantiation for Types
 //===----------------------------------------------------------------------===/