Returning upvar captured by mutable reference doesn't work

[Zoxc]

This works:

fn main() {
    let a = Box::new(8u8);

    || {
        &a
    };
}

This does not and gives a confusing error:

fn main() {
    let mut a = Box::new(8u8);

    || {
        &mut a
    };
}

The error:

error[E0495]: cannot infer an appropriate lifetime for borrow expression due to conflicting requirements
 --> <anon>:5:9
  |
5 |         &mut a
  |         ^^^^^^
  |
note: first, the lifetime cannot outlive the lifetime  as defined on the body at 4:7...
 --> <anon>:4:8
  |
4 |       || {
  |  ________^ starting here...
5 | |         &mut a
6 | |     };
  | |_____^ ...ending here
note: ...so that closure can access `a`
 --> <anon>:5:9
  |
5 |         &mut a
  |         ^^^^^^
note: but, the lifetime must be valid for the scope of call-site for function at 4:7...
 --> <anon>:4:8
  |
4 |       || {
  |  ________^ starting here...
5 | |         &mut a
6 | |     };
  | |_____^ ...ending here
note: ...so that return value is valid for the call
 --> <anon>:4:5
  |
4 |       || {
  |  _____^ starting here...
5 | |         &mut a
6 | |     };
  | |_____^ ...ending here

[Zoxc]

This also gives a confusing error:

fn main() {
	let mut a = Vec::<bool>::new();

	|| {
		|| {
			a.push(true)
		}
	};
}

rustc 1.16.0 (30cf806ef 2017-03-10)
error: lifetime of `a` is too short to guarantee its contents can be safely reborrowed
 --> <anon>:5:3
  |
5 | 		|| {
  | 		^^
  |
note: `a` would have to be valid for the scope of call-site for function at 4:4...
 --> <anon>:4:5
  |
4 |   	|| {
  |  _____^ starting here...
5 | | 		|| {
6 | | 			a.push(true)
7 | | 		}
8 | | 	};
  | |__^ ...ending here
note: ...but `a` is only valid for the lifetime  as defined on the body at 4:4
 --> <anon>:4:5
  |
4 |   	|| {
  |  _____^ starting here...
5 | | 		|| {
6 | | 			a.push(true)
7 | | 		}
8 | | 	};
  | |__^ ...ending here

error: aborting due to previous error

The following works:

fn main() {
	let a = Vec::<bool>::new();

	|| {
		|| {
			a.len()
		}
	};
}

[Mark-Simulacrum]

None of these examples don't compile today, so I'm presuming this is fixed and marking E-needstest.

[dsprenkels]

Can I take this issue and put this into a run-pass test?

[Mark-Simulacrum]

Sounds good to me, though compile-pass would probably be sufficient - grep for rustc_error.

[dsprenkels]

Ok. Will do. Btw, it looks like this commit was fixed by 9809fe0.