ICE: assertion failed: obligations.is_empty()

[Marwes]

Getting an ICE when compiling gluon_vm after upgrading my nightly rustc version.

$ RUST_BACKTRACE=1 cargo build
   Compiling gluon_vm v0.3.0 (file:///C:/Users/Markus/Dropbox/Programming/gluon/vm)
   Compiling lalrpop-snap v0.12.5
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: run with `RUST_BACKTRACE=1` for a backtrace

thread 'rustc' panicked at 'assertion failed: obligations.is_empty()', src\librustc\traits\coherence.rs:64
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.
stack backtrace:
   0: <std::time::SystemTimeError as core::fmt::Display>::fmt
   1: std::panicking::Location::line
   2: std::panicking::Location::line
   3: std::panicking::rust_panic_with_hook
   4: <unknown>
   5: rustc::traits::coherence::overlapping_impls
   6: <rustc_typeck::coherence::inherent_impls_overlap::InherentOverlapChecker<'a, 'tcx> as rustc::hir::itemlikevisit::ItemLikeVisitor<'v>>::visit_item
   7: <rustc_typeck::coherence::inherent_impls::InherentCollect<'a, 'tcx> as rustc::hir::itemlikevisit::ItemLikeVisitor<'v>>::visit_item
   8: rustc::ty::maps::<impl rustc::ty::maps::queries::crate_inherent_impls_overlap_check<'tcx>>::try_get
   9: rustc::ty::maps::<impl rustc::ty::maps::queries::crate_inherent_impls_overlap_check<'tcx>>::get
  10: rustc_typeck::coherence::check_coherence
  11: rustc_typeck::check_crate
  12: rustc_driver::driver::count_nodes
  13: <unknown>
  14: rustc_driver::driver::compile_input
  15: rustc_driver::run_compiler
  16: <unknown>
  17: _rust_maybe_catch_panic
  18: <unknown>
  19: std::sys::imp::thread::Thread::new

error: Could not compile `gluon_vm`.
Build failed, waiting for other jobs to finish...

$ rustc --version --verbose
rustc 1.18.0-nightly (28a742997 2017-04-13)
binary: rustc
commit-hash: 28a74299778cdad4ea999e4ee8f8c1ef793338bd
commit-date: 2017-04-13
host: x86_64-pc-windows-msvc
release: 1.18.0-nightly
LLVM version: 3.9

[Marwes]

Travis built successfully using rustc 1.18.0-nightly (c58c928 2017-04-11) https://travis-ci.org/gluon-lang/gluon/jobs/221228481

[Marwes]

#40570 looks like a likely cause for this regression and @nikomatsakis mentioned being unable to create a test case for #41044. I guess there might be such a test case somewhere in gluon_vm? Not going to have time to attempt a test case extraction at the moment however.

[nikomatsakis]

@Marwes thanks for the bug report. I'll take a look and see what I see!

[nikomatsakis]

triage: P-high

[nikomatsakis]

Minimal reproduction:

struct Function<T, F> { t: T, f: F }

impl<T, R> Function<T, fn() -> R> { fn foo() { } }
impl<T, R> Function<T, fn() -> R> { fn bar() { } }

fn main() { }

[nikomatsakis]

This was fixed by #41377, I believe.

[nikomatsakis]

@Marwes please let me know if you find otherwise :)

[Marwes]

@nikomatsakis It's working again now! Thanks!