1! { dg-do compile }
2! { dg-additional-options "-Wall -Wextra -Wno-unused-dummy-argument" }
3! PR fortran/70330 - this used to cause an ICE.
4! Test case by Vladimir Fuka
5function f(o) ! { dg-warning "Return value of function" }
6  optional o
7end function f
8