Consider the following code:

// void foo(int) { }
void foo(T : int)(T) { }

void bar(T : string)(T) { }
void baz(T : bool)(T) { }

alias a = foo;
alias a = bar;
alias a = baz;

void test(alias fn)()
{
    fn(0);
    fn(null);
    fn(true);
}

void main() {
    test!a();
}

Result:

onlineapp.d: Error: overload alias `onlineapp.a` forward declaration

If `foo` is a function, as per the comment, I can pass `a` as an overload set to `test()`, even though the other two functions in the set are templated. However, since `foo` is also a template, I get an inexplicable error message.