Improve diagnostic for the case where a function template candidate is rejected

by overload resolution because deduction succeeds, but the substituted
parameter type for some parameter (with deduced type) doesn't exactly match the
corresponding adjusted argument type.

llvm-svn: 256657

1 files changed, 6 insertions, 2 deletions

diff --git a/clang/lib/Sema/SemaTemplateDeduction.cpp b/clang/lib/Sema/SemaTemplateDeduction.cpp
index 837e0de4038..cd54920b08c 100644
--- a/clang/lib/Sema/SemaTemplateDeduction.cpp
+++ b/clang/lib/Sema/SemaTemplateDeduction.cpp
@@ -2954,8 +2954,12 @@ Sema::FinishTemplateArgumentDeduction(FunctionTemplateDecl *FunctionTemplate,
         continue;
       
       QualType DeducedA = Specialization->getParamDecl(ParamIdx)->getType();
-      if (CheckOriginalCallArgDeduction(*this, OriginalArg, DeducedA))
-        return Sema::TDK_SubstitutionFailure;
+      if (CheckOriginalCallArgDeduction(*this, OriginalArg, DeducedA)) {
+        Info.FirstArg = TemplateArgument(DeducedA);
+        Info.SecondArg = TemplateArgument(OriginalArg.OriginalArgType);
+        Info.CallArgIndex = OriginalArg.ArgIdx;
+        return TDK_DeducedMismatch;
+      }
     }
   }