wasm build error in nightly-2018-05-13

[CryZe]

Looks like something broke building wasm in this range: ff2ac35...9fae153

This is the error:

thread 'main' panicked at 'discriminant range is 170141183460469231731687303715884105727...-170141183460469231731687303715884105728', librustc/ty/layout.rs:891:17
note: Run with `RUST_BACKTRACE=1` for a backtrace.
error: internal compiler error: unexpected panic
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
note: rustc 1.27.0-nightly (9fae15374 2018-05-13) running on x86_64-unknown-linux-gnu
note: compiler flags: -C opt-level=3 -C panic=abort --crate-type lib
note: some of the compiler flags provided by cargo are hidden

https://travis-ci.org/LiveSplit/livesplit-core/jobs/378520318#L551

[CryZe]

Considering it is caused in layout.rs, it seems to be a bug introduced by #50622 which was beta backported. So if that's it, the bugfix probably needs to be backported too.

[oli-obk]

cc @eddyb

[eddyb]

Minimal testcase:

enum Void {}
fn foo(_: Result<(Void, u32), (Void, String)>) {}
fn main() {
    let _: fn(_) = foo;
}