Nightly regression in borrow checker

[msullivan]

pub type Session = i32;
pub struct StreamParser<'a, T> {
    _tokens: T,
    _session: &'a mut Session,
}

impl<'a, T> StreamParser<'a, T> {
    pub fn thing(&mut self) -> bool { true }
}

pub fn parse_stream<T: Iterator<Item=i32>, U, F>(
        _session: &mut Session, _tokens: T, _f: F) -> U
    where F: Fn(&mut StreamParser<T>) -> U { panic!(); }

pub fn thing(session: &mut Session) {
    let mut stream = vec!(1, 2, 3).into_iter();

    let _b = parse_stream(session,
                          stream.by_ref(),
                          // replacing the above with the following fixes it
                          //&mut stream,
                          |p| p.thing());

}

fn main() {}

compiles on 1.3 stable and 1.4 beta but not on current nightly. It did compile on nightly 6e5a325. Replacing the .by_ref() in the call to parse_stream fixes it.

Potentially related to/a dupe of #28934.

[msullivan]

(Probably want these lables: A-lifetimes T-compiler regression-from-stable-to-nightly)

[alexcrichton]

May be similar or the same as #28853, #28854, or #28934, but seems good to track regardless!

[arielb1]

This looks like a closure inference issue: annotating the closure type fixes it.

[nikomatsakis]

I believe this was fixed by #29006

[arielb1]

This was indeed fixed by #29006.

[nikomatsakis]

triage: P-medium

[nikomatsakis]

triage: P-low