Playground panics when `termination_trait` returns Ok(())

[U007D]

FYI, I tried using the termination_trait feature on Playground but it panics:

Compiling playground v0.0.1 (file:///playground)
thread 'rustc' panicked at 'assertion failed: !substs.has_erasable_regions()', librustc_trans_utils/symbol_names.rs:192:9
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 1.25.0-nightly (27a046e93 2018-02-18) running on x86_64-unknown-linux-gnu

error: Could not compile `playground`.

To learn more, run the command again with --verbose.

This above is code from the run-pass test, which passes, and running the same code running locally on my machine also compiles and runs successfully.

[shepmaster]

I don't believe this to be related to the playground. Notably, I can reproduce this using the nightly on my macOS laptop:

$ rustc --version --verbose
rustc 1.24.0 (4d90ac38c 2018-02-12)
binary: rustc
commit-hash: 4d90ac38c0b61bb69470b61ea2cccea0df48d9e5
commit-date: 2018-02-12
host: x86_64-apple-darwin
release: 1.24.0
LLVM version: 4.0

$ cargo +nightly run
   Compiling term v0.1.0 (file:///private/tmp/term)
thread 'rustc' panicked at 'assertion failed: !substs.has_erasable_regions()', librustc_trans_utils/symbol_names.rs:192:9
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 1.25.0-nightly (27a046e93 2018-02-18) running on x86_64-apple-darwin

error: Could not compile `term`.

To learn more, run the command again with --verbose.

[shepmaster]

Specifically, the latest nightly has a commit hash of rust-lang/rust@4d90ac3, but your commit was rust-lang/rust@e8f03b9. It appears no nightly has been created with your commit yet.

[U007D]

Ah, I was wondering if propagation delay was playing a part in this.

fn main() -> Result<(), failure::Error> used to not compile IIRC. Not sure why it would now if my commit isn't there yet. I'll poke around a bit when I get some free time and will open an issue against the compiler.

Thanks, @shepmaster.