Fix a -Wreturn-type warning due to this field not explicitly having the
enumeration type.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@139445 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Sema/SemaOverload.cpp b/lib/Sema/SemaOverload.cpp
index a38b7db..c200dae 100644
--- a/lib/Sema/SemaOverload.cpp
+++ b/lib/Sema/SemaOverload.cpp
@@ -7290,7 +7290,7 @@
 
 static unsigned RankDeductionFailure(
     const OverloadCandidate::DeductionFailureInfo &DFI) {
-  switch (DFI.Result) {
+  switch ((Sema::TemplateDeductionResult)DFI.Result) {
   case Sema::TDK_Success:
   case Sema::TDK_Incomplete:
     return 1;