Function signature testing with is expression.

[Alexandru Ermicioi via Digitalmars-d-learn]

Hi,

Have someone tried to test a function against a signature using 
is expression?

Suppose:
--------
struct F {
    static void foo(T)(T i, int o) {}
}

enum bool check(T) = is(F.foo!T == void function(Z, int), Z);

enum correct = check!int;
--------

Upon running it will return false, though, by logic is expression 
could deduce that F.foo is conformat to function signature in 
check test.

It is interesting that it will not work with global functions as 
well:

--------
void foo(int i, double d) {};
enum bool check = is(typeof(foo) == void function(int, double));
--------

It will be as well evaluated to false.

So, the question is, is it I'm doing something wrong, that it 
doesn't work, or is it not implemented?
If not implemented, what simple and short alternatives are 
available?

Thanks.