'do' and 'for' cannot instantiate polymorphic functions at requisite closure type

[bblum]

This compiles:

fn not<T>(_x: T) { }

fn main() {
    not(|| { error!("Hello world"); })
}

This does not (or should I say, it does not do not):

fn not<T>(_x: T) { }

fn main() {
    do not { error!("Hello world"); }
}

I am not sure it ever makes sense to have to do this instantiation except in this particular corner case, so feel free to wontfix this.

[pcwalton]

I don't think this is a backwards compatibility issue. Renominating.

[graydon]

closing WONTFIX, do notation doesn't need to work here

[bblum]

but wouldn't it be nice (more consistent) if it could?

It is conceivable that this could be more than the trivial program I posted above:

trait Hello { fn hello(self); }
impl Hello for &fn() {
    fn hello(self) { self(); }
}
fn hello<T: Hello>(x: T) {
    x.hello();
}
fn main() {
    do hello { error!("Hello world"); }
}

I'd say far-future milestone.