[flang] Use std::nullopt rather than {}.

Original-commit: flang-compiler/f18@9a740acf8346de10c0dda34ba2706980f9643802
Reviewed-on: https://github.com/flang-compiler/f18/pull/151

diff --git a/flang/lib/common/idioms.h b/flang/lib/common/idioms.h
index 61483b0..675f04c 100644 (file)
--- a/flang/lib/common/idioms.h
+++ b/flang/lib/common/idioms.h
@@ -135,7 +135,7 @@ std::optional<A> GetIf(const VARIANT &u) {
   if (const A * x{std::get_if<A>(&u)}) {
     return {*x};
   }
-  return {};
+  return std::nullopt;
 }
 }  // namespace Fortran::common
 #endif  // FORTRAN_COMMON_IDIOMS_H_