Nightly compiler error - Early bound region when generalizing

[andrey-gvrd]

Building xml-rs crate fails with:

error: internal compiler error: ../src/librustc/infer/combine.rs:348: Encountered early bound region when generalizing: ReEarlyBound(TypeSpace, 0, 'a)
note: the compiler unexpectedly panicked. this is a bug.
note: we would appreciate a bug report: https://github.com/rust-lang/rust/blob/master/CONTRIBUTING.md#bug-reports
thread 'rustc' panicked at 'Box<Any>', ../src/librustc_errors/lib.rs:580

Reproduction steps:

git clone https://github.com/netvl/xml-rs
cd xml-rs
rustup toolchain add nightly-2016-07-15
rustup override add nightly-2016-07-15
cargo build

I'm using rust 1.12-nightly (4db1874 2016-07-15).

[TimNN]

This looks like #34839 and should be fixed in the next nightly.

[alexcrichton]

(nightly is out)