2-phase borrow activation ice

[nikomatsakis]

This program ICEs:

#![feature(nll)]

struct Foo {
    
}

impl Foo {
    fn method(&mut self, foo: &mut Foo) {
    }
}

fn main() {
    let mut foo = Foo { };
    foo.method(&mut foo);
}

See also this conversation between @pnkfelix and I on gitter, which I believe to be relevant.

I'm refactoring some of this code, trying to explore the new NLL approach, so I will probably wind up fixing this. But obviously we should have this as a test!

cc @bobtwinkles

[Robbepop]

Is this similar to this ICE?
#49678