...got overloading, name mangling, type inference, implicit conversions, covariance, etc.

All I can say is...

...it to happen by accident. If such conversions were implicit, you'd get hidden performance...

...I've already given, generally because implicit conversions are often a bad thing. Requiring some...

...larger? Because it doesn't.)

Pan & scan conversions of 16:9 -> 4:3. (Not that...

...with &_dg
}

Note, with proper delegate implicit conversions, you could probably get some better optimization...

I assumed the key type needs to be immutable. If you want to allow instantiation...

...takes advantage of the compiler's implicit conversions, and where necessary we can just add...

[...]

OK, I'll make a branch and give it a try.

[...]

Good idea, IFTI's...

Better:

static if(is(typeof(getConstQual!Key.init.idup):Key) && !is(getConstQual!Key: Key)){

should be

else static if(is(T _ == shared(U),U)) alias shared(const(getConstQual!U...