diff --git a/llvm/include/llvm/ADT/PointerUnion.h b/llvm/include/llvm/ADT/PointerUnion.h
--- a/llvm/include/llvm/ADT/PointerUnion.h
+++ b/llvm/include/llvm/ADT/PointerUnion.h
@@ -181,7 +181,7 @@
   explicit operator bool() const { return !isNull(); }
 
   /// Test if the Union currently holds the type matching T.
-  template <typename T> int is() const {
+  template <typename T> bool is() const {
     constexpr int Index = pointer_union_detail::TypeIndex<T, PTs...>::Index;
     static_assert(Index < sizeof...(PTs),
                   "PointerUnion::is<T> given type not in the union");