When diagnosing an ambiguity, only note the candidates that contribute
to the ambiguity, rather than noting all viable candidates.
diff --git a/clang/lib/Sema/SemaCast.cpp b/clang/lib/Sema/SemaCast.cpp
index 0ebb5c6..2ab0a11 100644
--- a/clang/lib/Sema/SemaCast.cpp
+++ b/clang/lib/Sema/SemaCast.cpp
@@ -423,7 +423,7 @@
 
   case OR_Ambiguous:
     msg = diag::err_ovl_ambiguous_conversion_in_cast;
-    howManyCandidates = OCD_ViableCandidates;
+    howManyCandidates = OCD_AmbiguousCandidates;
     break;
 
   case OR_Deleted: