rustc-beta.5 ICE while printing error

[maurer]

My code has a type error, that's on me, but rustc ICEs while trying to report the error.
This occurs on rustc-beta.5 but not on current Nightly. (Current nightly prints internal compiler error: unprintable span but does not crash, generate a backtrace with RUST_BACKTRACE=1, or exhort me to report the bug.)

Code in question is unmimized, but the input is available here.

maurer@fragarach ~/Sources/holmes $ RUST_BACKTRACE=1 cargo test
   Compiling holmes v0.0.1 (file:///home/maurer/Sources/holmes)
tests/predicate_basic.rs:26:5: 2:42 error: mismatched types:
 expected `()`,
    found `collections::string::String`
(expected (),
    found struct `collections::string::String`) [E0308]
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 'capacity overflow', /home/rustbuild/src/rust-buildbot/slave/beta-dist-rustc-linux/build/src/libcore/option.rs:330

stack backtrace:
   1:     0x7ff852524429 - sys::backtrace::write::h3fdf06e7a8dd7bced4r
   2:     0x7ff85252c136 - panicking::on_panic::hdc3f6d7788894b93jrw
   3:     0x7ff8524ef442 - rt::unwind::begin_unwind_inner::h93ec8cb6029f2822t6v
   4:     0x7ff8524f00ec - rt::unwind::begin_unwind_fmt::h0b4dd831ba99497b74v
   5:     0x7ff85252bd16 - rust_begin_unwind
   6:     0x7ff852578044 - panicking::panic_fmt::h2602585117d51b40wwy
   7:     0x7ff84faa56bf - codemap::CodeMap::span_to_lines::hcb96211657be04b8oiA
   8:     0x7ff84faea607 - diagnostic::emit::h44f1e44ee2adfa9amTB
   9:     0x7ff84fae8454 - diagnostic::EmitterWriter.Emitter::emit::h98c9b52f3bc967504PB
  10:     0x7ff84fae69ab - diagnostic::SpanHandler::span_err_with_code::he869bc155fe9aef6EmB
  11:     0x7ff850382615 - session::Session::span_err_with_code::h9d4c90114cb92befRxq
  12:     0x7ff85057eb19 - middle::infer::error_reporting::InferCtxt<'a, 'tcx>.ErrorReporting<'tcx>::report_type_error::haf794be6c351ab63BRq
  13:     0x7ff850580386 - middle::infer::error_reporting::InferCtxt<'a, 'tcx>.ErrorReporting<'tcx>::report_and_explain_type_error::hedd5208780511c68pTq
  14:     0x7ff8505d8713 - middle::infer::InferCtxt<'a, 'tcx>::report_mismatched_types::hedabf97f021a46449Lz
  15:     0x7ff85133b9b6 - check::demand::coerce::h3c96cf4e187ed1117Hf
  16:     0x7ff8513d349b - check::check_expr_with_unifier::h15794470645070384888
  17:     0x7ff8513a3eec - check::check_block_with_expected::ha385fa00451511c6nUr
  18:     0x7ff8513d3dd8 - check::check_expr_with_unifier::h15794470645070384888
  19:     0x7ff8513a3eec - check::check_block_with_expected::ha385fa00451511c6nUr
  20:     0x7ff8513d3dd8 - check::check_expr_with_unifier::h15794470645070384888
  21:     0x7ff8513a3eec - check::check_block_with_expected::ha385fa00451511c6nUr
  22:     0x7ff8513866d6 - check::check_fn::hbbb50115804bad19UGn
  23:     0x7ff851384c9a - check::closure::check_expr_closure::hd87ca7843a3b19dacsl
  24:     0x7ff8513e57f2 - check::check_expr_with_unifier::h8479634674413911501
  25:     0x7ff8513b2a19 - check::check_expr_with_unifier::h13654519978556571655
  26:     0x7ff85138cb28 - check::check_argument_types::h7a36728b112e36dd6Hp
  27:     0x7ff85138a02b - check::callee::confirm_builtin_call::h98a381787eb801b482l
  28:     0x7ff8513888c1 - check::callee::check_call::hfe6fb95caee17a4bQTl
  29:     0x7ff8513d377b - check::check_expr_with_unifier::h15794470645070384888
  30:     0x7ff8513a3eec - check::check_block_with_expected::ha385fa00451511c6nUr
  31:     0x7ff8513866d6 - check::check_fn::hbbb50115804bad19UGn
  32:     0x7ff85139f5a4 - check::check_bare_fn::he66bf0548da8b8d1twn
  33:     0x7ff85139d702 - check::CheckItemBodiesVisitor<'a, 'tcx>.Visitor<'tcx>::visit_item::h5534b4c58b22cf23wtn
  34:     0x7ff85139d8ef - check::CheckItemBodiesVisitor<'a, 'tcx>.Visitor<'tcx>::visit_item::h5534b4c58b22cf23wtn
  35:     0x7ff8514616aa - check_crate::closure.38021
  36:     0x7ff85145ca40 - check_crate::h44f7d6f01042e613XcC
  37:     0x7ff852a67c88 - driver::phase_3_run_analysis_passes::h071f1f038f4270canGa
  38:     0x7ff852a48d85 - driver::compile_input::hc5c2173550d25b21Qba
  39:     0x7ff852b0a551 - run_compiler::h5fd7a3cba8c0dcd3z4b
  40:     0x7ff852b081a2 - boxed::F.FnBox<A>::call_box::h13268679164253669965
  41:     0x7ff852b076d9 - rt::unwind::try::try_fn::h1333595601538020842
  42:     0x7ff85259eaa8 - rust_try_inner
  43:     0x7ff85259ea95 - rust_try
  44:     0x7ff852b07988 - boxed::F.FnBox<A>::call_box::h18060233810932446010
  45:     0x7ff85252b021 - sys::thread::create::thread_start::h7002e49f5ed4f198aqv
  46:     0x7ff84cddd203 - <unknown>
  47:     0x7ff85218f5bc - clone
  48:                0x0 - <unknown>

Build failed, waiting for other jobs to finish...
Could not compile `holmes`.

To learn more, run the command again with --verbose.
maurer@fragarach ~/Sources/holmes $ 

[steveklabnik]

This occurs on rustc-beta.5 but not on current Nightly

Bummer. At this state in the game, since it is working on nightly, I'm tempted to close as 'won't fix', since the release is basically all put together, but maybe @brson will feel differently, so I'll leave it open for now.

[maurer]

Was going through my open issues, noticed this one - I can't repro on current rust, so I'm closing this.