Fix SimplerObservable build with -Werror=unused-local-typedefs

[folly.git] / folly / String.h

diff --git a/folly/String.h b/folly/String.h
index fc552f11507b2bd7391929bcc37ff6bd90007f77..5d631340fd18ff3569183d583a51f0e5cbd5813a 100644 (file)
--- a/folly/String.h
+++ b/folly/String.h
@@ -491,7 +491,8 @@ struct IsConvertible {
 template <class T>
 struct IsConvertible<
     T,
-    decltype(parseTo(std::declval<folly::StringPiece>(), std::declval<T&>()))> {
+    decltype(static_cast<void>(
+        parseTo(std::declval<folly::StringPiece>(), std::declval<T&>())))> {
   enum { value = true };
 };