Can't break to a labeled loop from inside a for loop

[catamorphism]

Because for loop bodies are closures, implementing this case is a PITA. I haven't done it yet.

e.g.

loop foo: {
    for whatever() |x| {
         break foo;
    }
}
// ...

[nikomatsakis]

Not critical for 0.6; removing milestone

[catamorphism]

Nominating for milestone 1 (well-defined) so we can discuss whether we actually want to support this.

[nikomatsakis]

I see no reason not to support this. If we can return from the calling function, we can also break to a label. I do see reasons to defer implementing it. :) In particular, I'd like to revisit our label syntax to use lifetime names (which would also give users a way to name the lifetime associated with a block or expression, and resolve the parsing issues we encountered before, since lifetime names are their own kind of token).

[catamorphism]

In that case, nominating for milestone 3 (feature-complete) instead.

[graydon]

accepted for feature-complete milestone

[thestinger]

#6997 is related because this will be trivial when we replace the current for loop

[thestinger]

The old for loop is being removed, foreach has landed as a replacement.