Fix a conversion to incomplete type bug -- The error message now specifically states that the type is incomplete and points to the forward declaration of the incomplete type.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@185056 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Sema/SemaInit.cpp b/lib/Sema/SemaInit.cpp
index 9d7fcda..cbca84d 100644
--- a/lib/Sema/SemaInit.cpp
+++ b/lib/Sema/SemaInit.cpp
@@ -6251,9 +6251,15 @@
       break;
 
     case OR_No_Viable_Function:
-      S.Diag(Kind.getLocation(), diag::err_typecheck_nonviable_condition)
-        << Args[0]->getType() << DestType.getNonReferenceType()
-        << Args[0]->getSourceRange();
+      if (!DestType.getNonReferenceType()->isIncompleteType() ||
+          !S.RequireCompleteType(Kind.getLocation(),
+                                 DestType.getNonReferenceType(),
+                          diag::err_typecheck_nonviable_condition_incomplete,
+                               Args[0]->getType(), Args[0]->getSourceRange()))
+        S.Diag(Kind.getLocation(), diag::err_typecheck_nonviable_condition)
+          << Args[0]->getType() << Args[0]->getSourceRange()
+          << DestType.getNonReferenceType();
+
       FailedCandidateSet.NoteCandidates(S, OCD_AllCandidates, Args);
       break;