[Bug c++/61660] static_assert triggering when it should not

["us15 at os dot inf.tu-dresden.de" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61660

--- Comment #3 from Udo Steinberg <us15 at os dot inf.tu-dresden.de> ---
Created attachment 33035
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=33035&action=edit
Testcase 2

Then, similar to this new test case, I would expect something like the
following:

g++ -std=gnu++11 foo.cc -o foo

foo.cc: In function 'void check_type(unsigned int, unsigned int)':
foo.cc:10:17: error: non-constant condition for static assertion
         case 0: static_assert (s == sizeof (uint16), "must use 16bit type");
break;
                 ^
foo.cc:10:17: error: 's' is not a constant expression

If the compiler does not treat 'x' in the first test case as a constant, it
would be good to issue a warning like it does for 's' in the second test case.