Video: Generic Programming Galore using D @ Strange Loop 2011

[Andrej Mitrovic]

On 4/11/12, Andrei Alexandrescu <SeeWebsiteForEmail at erdani.org> wrote:
> http://www.infoq.com/presentations/Generic-Programming-Galore-Using-D
>
> Andrei
>

Cool talk! And it just occurred to me that you can actually use a
static assert on a return type in D, e.g.:

import std.traits;
import std.algorithm;

auto min(T1, T2)(T1 t1, T2 t2)
{
    return t1;  // e.g. implementation bug
    static assert(is(typeof(return) == CommonType!(T1, T2)));
}

void main() {
    auto x = min(1, 1.0);
}

I didn't know this until now. It might help in cases where the return
type is a very complicated template instance and you want to enforce
the return expression to be of that type while simultaneously using
auto as the return type in the function declaration.

It does however do this check *after* any implicit conversions to the
return type. So, while my first sample correctly won't compile, the
following will compile:

import std.traits;
import std.algorithm;

CommonType!(T1, T2) min(T1, T2)(T1 t1, T2 t2)
{
    return t1;
    static assert(is(typeof(return) == CommonType!(T1, T2)));
}

void main() {
    auto x = min(1, 1.0);
}

It's interesting to think about.