ICE in typeck: assertion failed in librustc/middle/typeck/check/method/confirm.rs

[msiemens]

Compiling some code (on Linux) resulted in this ICE:

task 'rustc' panicked at 'assertion failed: `(left == right) && (right == left)` (left: `None`, right: `Some(())`)', /home/rustbuild/src/rust-buildbot/slave/nightly-linux/build/src/librustc/middle/typeck/check/method/confirm.rs:152

stack backtrace:
   1:     0x7f256c323b70 - rt::backtrace::imp::write::h990abaacfa2176b6qfy
   2:     0x7f256c326c40 - failure::on_fail::h38b0b794e233abc2QHy
   3:     0x7f256bf79cc0 - unwind::begin_unwind_inner::h2efca3c0591abcbd6Qc
   4:     0x7f256bf798f0 - unwind::begin_unwind_fmt::h1966842b632a71b7hOc
   5:     0x7f256aeba460 - middle::typeck::check::method::confirm::ConfirmContext<'a, 'tcx>::confirm::hcb2ce4cad29797fafyg
   6:     0x7f256aed8610 - middle::typeck::check::method::lookup::hb053a4169f2c1619Dzj
   7:     0x7f256af970b0 - middle::typeck::check::check_expr_with_unifier::check_method_call::h68dfdcfe3a4751a1iop
   8:     0x7f256af8ae90 - middle::typeck::check::check_expr_with_unifier::hb92b2ad3850873267ip
   9:     0x7f256ae6b0f0 - middle::typeck::check::_match::check_match::h5c411f1aa2f77dacezb
  10:     0x7f256af8ae90 - middle::typeck::check::check_expr_with_unifier::hb92b2ad3850873267ip
  11:     0x7f256af3f720 - middle::typeck::check::check_block_with_expected::h3956d795c9aeeb87Kir
  12:     0x7f256af8ae90 - middle::typeck::check::check_expr_with_unifier::hb92b2ad3850873267ip
  13:     0x7f256ae6b0f0 - middle::typeck::check::_match::check_match::h5c411f1aa2f77dacezb
  14:     0x7f256af8ae90 - middle::typeck::check::check_expr_with_unifier::hb92b2ad3850873267ip
  15:     0x7f256af3f720 - middle::typeck::check::check_block_with_expected::h3956d795c9aeeb87Kir
  16:     0x7f256af16690 - middle::typeck::check::check_fn::h1a71f1287e45c3b7xJl
  17:     0x7f256af3cd50 - middle::typeck::check::check_bare_fn::h918284b622e60d7cByl
  18:     0x7f256af435f0 - middle::typeck::check::check_method_body::hd5c696a286263db7D3l
  19:     0x7f256af38bc0 - middle::typeck::check::check_item::h8d5984f625a43c66MSl
  20:     0x7f256af3c680 - visit::walk_mod::h17216003542078371067
  21:     0x7f256af3c9e0 - middle::typeck::check::check_item_types::h4e49e4094b67da4bLxl
  22:     0x7f256b2fbcb0 - util::common::time::h12622327612847767970
  23:     0x7f256b2faef0 - middle::typeck::check_crate::hc4bb4e5d8eba9f8a2hP
  24:     0x7f256c93f500 - driver::driver::phase_3_run_analysis_passes::h3d64e023ddfcea4fLzS
  25:     0x7f256c9345a0 - driver::driver::compile_input::h34658a73b26c5cbfLgS
  26:     0x7f256c9b7740 - driver::run_compiler::hf08ea8f291fae6b9WeU
  27:     0x7f256c9b7630 - driver::run::closure.60675
  28:     0x7f256c7c1080 - task::TaskBuilder::try_future::closure.39831
  29:     0x7f256c2f47d0 - task::TaskBuilder::spawn_internal::closure.30969
  30:     0x7f256bf77a90 - task::Task::spawn::closure.5760
  31:     0x7f256bfd3bd0 - rust_try_inner
  32:     0x7f256bfd3bc0 - rust_try
  33:     0x7f256bf77b70 - unwind::try::haea8bc421c68cd5epFc
  34:     0x7f256bf77930 - task::Task::run::h24525a73fb4c9bb3fOb
  35:     0x7f256bf77520 - task::Task::spawn::closure.5736
  36:     0x7f256bf78f70 - thread::thread_start::ha943fdda31374bc3i6b
  37:     0x7f2566cc7e20 - start_thread
  38:     0x7f256bc3fb59 - clone
  39:                0x0 - <unknown>

$ rustc --version
rustc 0.13.0-nightly (d9c7c00b9 2014-12-04 21:33:07 +0000)

The same code ICE's with a different stack backtrace when compiling on Windows:

task 'rustc' panicked at 'assertion failed: `(left == right) && (right == left)` (left: `None`, right: `Some(())`)', F:\Dokumente\Coding\rust\rust-lang\src\librustc_typeck\check\method\confirm.rs:153


stack backtrace:
   1: 0x62f30e11 - ZN2rt4init20hfe895a7bc70b7991F2yE
   2:   0x5a5cdc - ZN6unwind18begin_unwind_inner20h76c4802219079ceddocE
   3:   0x5a5a28 - ZN6unwind16begin_unwind_fmt20hb81c38ca2ace2af7olcE
   4:  0x127e312 - ZN5check8regionck51Rcx$LT$$x27a$C$$x20$x27tcx$GT$.Visitor$LT$$x27v$GT$11visit_local20h55dad3e8b86a7683igdE
   5:  0x134628f - ZN5check38TupleArgumentsFlag...std..clone..Clone5clone20he6155115885858c9sgoE
   6:  0x133c709 - ZN5check33LvaluePreference...std..fmt..Show3fmt20h73780114875bfc9eh9mE
   7:  0x123b877
   8:  0x133ce8d - ZN5check33LvaluePreference...std..fmt..Show3fmt20h73780114875bfc9eh9mE
   9:  0x12ff7c3 - ZN5check67GatherLocalsVisitor$LT$$x27a$C$$x20$x27tcx$GT$.Visitor$LT$$x27v$GT$10visit_item20h2343e58ad8be94ecoIkE
  10:  0x133d016 - ZN5check33LvaluePreference...std..fmt..Show3fmt20h73780114875bfc9eh9mE
  11:  0x123b877
  12:  0x133ce8d - ZN5check33LvaluePreference...std..fmt..Show3fmt20h73780114875bfc9eh9mE
  13:  0x12ff750 - ZN5check67GatherLocalsVisitor$LT$$x27a$C$$x20$x27tcx$GT$.Visitor$LT$$x27v$GT$10visit_item20h2343e58ad8be94ecoIkE
  14:  0x12d8c48 - ZN6rscope28UnelidableRscope.RegionScope20default_region_bound20hc1e1f94f25defbdcqxsE
  15:  0x12fcd94 - ZN5check69CheckItemTypesVisitor$LT$$x27a$C$$x20$x27tcx$GT$.Visitor$LT$$x27v$GT$8visit_ty20h6313bfb8cd3ffc01awkE
  16:  0x12fff67 - ZN5check67GatherLocalsVisitor$LT$$x27a$C$$x20$x27tcx$GT$.Visitor$LT$$x27v$GT$10visit_item20h2343e58ad8be94ecoIkE
  17:  0x12f88f1 - ZN5check69CheckItemTypesVisitor$LT$$x27a$C$$x20$x27tcx$GT$.Visitor$LT$$x27v$GT$10visit_item20h720a968a26401682NvkE
  18:  0x12fc92f - ZN5check69CheckItemTypesVisitor$LT$$x27a$C$$x20$x27tcx$GT$.Visitor$LT$$x27v$GT$8visit_ty20h6313bfb8cd3ffc01awkE
  19: 0x615f7461


$ rustc --version
rustc 0.13.0-dev (6f4c11be3 2014-12-05 20:23:10 +0000)

I wasn't able to quickly get a minimal example, but will do so tomorrow.

[msiemens]

Minimal example:

struct Container<'a> {
    s: Struct<'a>
}

struct Struct<'a> {
    parent: &'a Struct<'a>
}

impl<'a> Struct<'a> {
    pub fn new() -> Struct<'a> {
        Struct {
            parent: None
        }
    }

    pub fn get(&self, key: &str) -> Container<'a> {
        match self.parent {
            Some(ref p) => p.get(key),
            None => {/* ... */}
        }
    }
}


fn main() {
    //
}

It still produces different backtraces on Linux and Windows.

[msiemens]

The code doesn't ICE when wrapping Struct::parent in an Option (as used in the impl)