All 4 forms below should error:
void main()
{
enum e = is(int Int);
assert(is(int Int1 == const));
if (is(int Int2)) {} // only this is caught
auto x = is(int Int3 : float);
}
isexpident.d(14): Error: can only declare type aliases within `static if` conditionals or `static assert`s
PR incoming.