We are going to introduce 2 features that basically are 2 hacks
working around the same problem : lifetime.
It may sound like any of these is useful and progress, and
somehow it is, but that is going to create many feature for
underpowered capabilities.
This is this kind of situation where simple and easy collide.
I'd suggest we get a proper lifetime management. For ref return,
we can still make it safe by defining the lifetime of the ref
return as the intersection of the lifetime of the ref parameters
and call it a day. As far as I can tell, this cover the vast
majority of cases.
