Don't load ill-formed AmbiguityKind in Sema::Lookup.

This bug was reported by UBSan.

llvm-svn: 216695

1 files changed, 7 insertions, 1 deletions

diff --git a/clang/include/clang/Sema/Lookup.h b/clang/include/clang/Sema/Lookup.h
index 00cc164d964..e050c7ddbf1 100644
--- a/clang/include/clang/Sema/Lookup.h
+++ b/clang/include/clang/Sema/Lookup.h
@@ -424,13 +424,19 @@ public:
         Paths = nullptr;
       }
     } else {
-      AmbiguityKind SavedAK = Ambiguity;
+      AmbiguityKind SavedAK;
+      bool WasAmbiguous = false;
+      if (ResultKind == Ambiguous) {
+        SavedAK = Ambiguity;
+        WasAmbiguous = true;
+      }
       ResultKind = Found;
       resolveKind();
 
       // If we didn't make the lookup unambiguous, restore the old
       // ambiguity kind.
       if (ResultKind == Ambiguous) {
+        assert(WasAmbiguous);
         Ambiguity = SavedAK;
       } else if (Paths) {
         deletePaths(Paths);