--- test2.d

void act1(T : void)() { }

void act2(T : int)() { }

void call(alias fn, T)()

{

    alias instance = fn!T;

    instance(); // this works

    fn!T(); // this does not!

}

--- test.d

import test2 : act = act1, act = act2, call;

void main()

{

    act!int(); // this works

    act!void(); // this works, so act is an overload set

    call!(act, void); // but not this?

    call!(act, int); // and not this either!

}

​