Going from CTFE-land to Template-land

[Bill Baxter]

Currently this doesn't work, because the CTFE function doesn't "know"
that it's running compile-time:

int templ_incr(int x)() {
    return x+1;
}

int ctfe_incr(int x) {
    return templ_incr!(x);
}

Seems common to write a function that you know is only intended to be
used compile-time.
But it can't compile because the compiler doesn't know you only plan
to call it at compile-time.

Is something version(__ctfe) might help with?  E.g.
version(__ctfe) {
    // only allow cfte_incr to be called at compile-time so it can use templates
    int ctfe_incr(int x) {
        return templ_incr!(x);
    }
}

Or is there something more fundamental preventing CTFE funcs from
instantiating templates?

--bb