I've been playing with templates recently and there's something I don't quite get.

template Outer() {
    template Inner(alias param) {
        alias param Inner;
    }
}

void main() {
    long d;
    Outer!().Inner!(d) = 4; // fails
}

Error: template instance cannot use local 'd' as parameter to non-global template Inner(alias param)

Why is it OK to pass aliases to local variables to a normal (global) template, and not OK to a nested one? I'd appreciate a counter-example of sth bad happening in the forbidden case.


Tomek