task 'rustc' failed at 'expect item fn'

[nefigah]

I got an internal compiler error trying to compile my code (which almost certainly isn't well-typed in its current state, but the error message told me to submit a bug report anyway).

rustc 0.12.0-pre-nightly (6b5ec40d4 2014-08-15 00:46:19 +0000)

error: internal compiler error: unexpected failure
note: the compiler hit an unexpected failure path. this is a bug.
note: we would appreciate a bug report: http://doc.rust-lang.org/complement-bugreport.html
note: run with `RUST_BACKTRACE=1` for a backtrace
task 'rustc' failed at 'expect item fn', /Users/rustbuild/src/rust-buildbot/slave/nightly-mac/build/src/libcore/option.rs:243

stack backtrace:
   1:        0x1120a0385 - rt::backtrace::imp::write::h4536a001ce066177jar
   2:        0x1120a3543 - failure::on_fail::hff2f39e7bb3266e3Oqr
   3:        0x1123748c5 - unwind::begin_unwind_inner::h1ddc246b8ab90e50S5d
   4:        0x1123744fb - unwind::begin_unwind_fmt::h01801789b5278947n3d
   5:        0x112374352 - rust_begin_unwind
   6:        0x1123c41ec - failure::begin_unwind::h50eb7cbc3faad06bn5j
   7:        0x10f1c4c9c - middle::typeck::infer::error_reporting::InferCtxt<'a>.ErrorReporting::give_suggestion::h1b40bdaf1b41ca3aEO9
   8:        0x10f1bd16a - middle::typeck::infer::error_reporting::InferCtxt<'a>.ErrorReporting::report_processed_errors::h10993b1a96033985JN9
   9:        0x10f1b8e27 - middle::typeck::infer::error_reporting::InferCtxt<'a>.ErrorReporting::report_region_errors::hc5d7708eec8756aap98
  10:        0x10f0737b5 - middle::typeck::infer::InferCtxt<'a>::resolve_regions_and_report_errors::ha8cdd18d52a67f29BAc
  11:        0x10f0cf87d - middle::typeck::check::check_bare_fn::h54a4c6354dd8f64eJIR
  12:        0x10f0d8cc2 - middle::typeck::check::check_method_body::hef6e38fbadd4af3f8sS
  13:        0x10f0c8af3 - middle::typeck::check::check_item::hf589c8c7d0ccbb41xhS
  14:        0x10f0cf5bd - middle::typeck::check::check_item_types::hc21fce67b5b46b261HR
  15:        0x10eaf7af6 - util::common::time::h3024600184563185324
  16:        0x10f2cd76c - middle::typeck::check_crate::ha430b9795a043407p2i
  17:        0x10f39ae20 - driver::driver::phase_3_run_analysis_passes::h75b0fef474512fa9Vsx
  18:        0x10f395e13 - driver::driver::compile_input::h79ff988559bc8942afx
  19:        0x10f43bf67 - driver::run_compiler::he7d6bb44f05b4ab7vJA
  20:        0x10f43a6e6 - driver::main_args::closure.136974
  21:        0x10f44c63b - task::TaskBuilder<S>::try_future::closure.138135
  22:        0x10f44c545 - task::TaskBuilder<S>::spawn_internal::closure.138112
  23:        0x11168e78c - task::spawn_opts::closure.8425
  24:        0x1123da12c - rust_try_inner
  25:        0x1123da116 - rust_try
  26:        0x112371c9b - unwind::try::h3475e7f0add0adf2nUd
  27:        0x112371a3b - task::Task::run::h445e97db351c9d1fv2c
  28:        0x11168e5ea - task::spawn_opts::closure.8370
  29:        0x112373856 - thread::thread_start::h5ba8f129cf6edff5Fqd
  30:     0x7fff89547899 - _pthread_body
  31:     0x7fff8954772a - _pthread_struct_init

[alexcrichton]

Could you provide the code that causes the ICE as well?

[nefigah]

It seems to happen if I uncomment the following method:

trait Cardlike<'a> {
    fn common_data(&'a self) -> &'a CardData;
    fn query_val(&self, Attribute) -> int;
    /* fn convert_mana_cost(&self) -> int {
        let data = self.common_data();
        let cmc = data.cost.iter().fold(0, |sum, &mana| sum + mana.convert());
        let x = self.query_val(X);
        cmc + x;
    } */
}

[mchesser]

Reduced test case:

trait T<'a> {
    fn a(&'a self) -> &'a bool;
    fn b(&self) {
        self.a();
    }
}

Appears to be a fairly recent regression, (does not occur in 0.11).