<p dir="auto">Here's the backtrace. Let me know if the code I was compiling would be helpful, I tagged the rev locally.</p>
<p dir="auto"><code class="notranslate">rustc 1.1.0-nightly (7bd71637c 2015-05-06) (built 2015-05-06)</code></p>
<div class="snippet-clipboard-content notranslate position-relative overflow-auto" data-snippet-clipboard-copy-content="$ RUST_BACKTRACE=1 cargo test   
Compiling dumbmath v0.1.6 (file:///home/nicholasbishop/dumbmath)
error: internal compiler error: Impl DefId { krate: 2, node: 26942 } was matchable against Obligation(predicate=Binder(TraitPredicate(&lt;f32 as core::ops::Div&lt;_&gt;&gt;)),depth=1) but now is not
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 'Box&lt;Any&gt;', /home/rustbuild/src/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/libsyntax/diagnostic.rs:230

stack backtrace:
   1:     0x7fbee3ae6f89 - sys::backtrace::write::h89d94970ae1bc478fhs
   2:     0x7fbee3aeef09 - panicking::on_panic::h314cddb0409059cbkXw
   3:     0x7fbee3aaf0f2 - rt::unwind::begin_unwind_inner::hd6748515f1d9c0b2uCw
   4:     0x7fbee0e85fbd - rt::unwind::begin_unwind::h9184602946677297306
   5:     0x7fbee0e8667b - diagnostic::Handler::bug::h6d48c8060c15a3b4a2B
   6:     0x7fbee1c36304 - middle::traits::select::SelectionContext&lt;'cx, 'tcx&gt;::rematch_impl::h10b0cc0f4e83f0c3EuT
   7:     0x7fbee1c35c2f - middle::infer::InferCtxt&lt;'a, 'tcx&gt;::commit_if_ok::h17325861492725920879
   8:     0x7fbee1c1c8a5 - middle::traits::select::SelectionContext&lt;'cx, 'tcx&gt;::confirm_candidate::hca3234a85605343cUMS
   9:     0x7fbee1afacc5 - middle::traits::select::SelectionContext&lt;'cx, 'tcx&gt;::select::hec5ba022f7c648beiPQ
  10:     0x7fbee1c09d35 - middle::traits::project::project_type::h74992cfacc671364CwP
  11:     0x7fbee1c0896b - middle::traits::project::opt_normalize_projection_type::ha8866d0a50189fbcepP
  12:     0x7fbee1c0599f - middle::traits::project::project_and_unify_type::h1300a4d0fa05187d87O
  13:     0x7fbee1c03970 - middle::infer::InferCtxt&lt;'a, 'tcx&gt;::commit_if_ok::h107823834106425565
  14:     0x7fbee1bfb888 - middle::traits::fulfill::FulfillmentContext&lt;'tcx&gt;::select::hec0877a5f2e11ad0HHO
  15:     0x7fbee1bfb29b - middle::traits::fulfill::FulfillmentContext&lt;'tcx&gt;::select_where_possible::h301bc31d4e510c07VGO
  16:     0x7fbee323d048 - check::vtable::select_fcx_obligations_where_possible::h72b84a124c3a5b40I6b
  17:     0x7fbee325914a - check::FnCtxt&lt;'a, 'tcx&gt;::resolve_type_vars_if_possible::h74b2cbbcdf641686cPo
  18:     0x7fbee32b674e - check::op::check_binop::hba99f04615a48d79oYm
  19:     0x7fbee32ec9cd - check::check_expr_with_unifier::h12689752184703274217
  20:     0x7fbee3312c4b - check::check_decl_local::h28a2e7870f672b04j7r
  21:     0x7fbee32c23f1 - check::check_block_with_expected::h212bdec46f615ac8pds
  22:     0x7fbee32a7f36 - check::check_fn::h225bdd7ece966e55lSn
  23:     0x7fbee32bde27 - check::check_bare_fn::h8fed7360af87b5cbUHn
  24:     0x7fbee32c980c - check::check_method_body::h225a8a268d0d1168Ujo
  25:     0x7fbee32bbd85 - check::CheckItemBodiesVisitor&lt;'a, 'tcx&gt;.Visitor&lt;'tcx&gt;::visit_item::hb0162b7f82578cf4XEn
  26:     0x7fbee32bc1bf - check::CheckItemBodiesVisitor&lt;'a, 'tcx&gt;.Visitor&lt;'tcx&gt;::visit_item::hb0162b7f82578cf4XEn
  27:     0x7fbee3376c4a - check_crate::closure.38730
  28:     0x7fbee336ff80 - check_crate::hed85a8a5c9342eb05CC
  29:     0x7fbee4035c28 - driver::phase_3_run_analysis_passes::he0b331c645c77cdbtGa
  30:     0x7fbee401705c - driver::compile_input::h763ead6090436e8fQba
  31:     0x7fbee40cfeb1 - run_compiler::h711c4a29f8d270a365b
  32:     0x7fbee40cd702 - boxed::F.FnBox&lt;A&gt;::call_box::h12199818508070417299
  33:     0x7fbee40cccc9 - rt::unwind::try::try_fn::h5660428370877252098
  34:     0x7fbee3b62898 - rust_try_inner
  35:     0x7fbee3b62885 - rust_try
  36:     0x7fbee40ccf64 - boxed::F.FnBox&lt;A&gt;::call_box::h5514408293737026672
  37:     0x7fbee3aedca1 - sys::thread::Thread::new::thread_start::hfd3ca3d51ffcfe41QIv
  38:     0x7fbeddb82529 - start_thread
  39:     0x7fbee374022c - __clone
  40:                0x0 - &lt;unknown&gt;

Build failed, waiting for other jobs to finish...
error: internal compiler error: Impl DefId { krate: 2, node: 26942 } was matchable against Obligation(predicate=Binder(TraitPredicate(&lt;f32 as core::ops::Div&lt;_&gt;&gt;)),depth=1) but now is not
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 'Box&lt;Any&gt;', /home/rustbuild/src/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/libsyntax/diagnostic.rs:230

stack backtrace:
   1:     0x7f920f378f89 - sys::backtrace::write::h89d94970ae1bc478fhs
   2:     0x7f920f380f09 - panicking::on_panic::h314cddb0409059cbkXw
   3:     0x7f920f3410f2 - rt::unwind::begin_unwind_inner::hd6748515f1d9c0b2uCw
   4:     0x7f920c717fbd - rt::unwind::begin_unwind::h9184602946677297306
   5:     0x7f920c71867b - diagnostic::Handler::bug::h6d48c8060c15a3b4a2B
   6:     0x7f920d4c8304 - middle::traits::select::SelectionContext&lt;'cx, 'tcx&gt;::rematch_impl::h10b0cc0f4e83f0c3EuT
   7:     0x7f920d4c7c2f - middle::infer::InferCtxt&lt;'a, 'tcx&gt;::commit_if_ok::h17325861492725920879
   8:     0x7f920d4ae8a5 - middle::traits::select::SelectionContext&lt;'cx, 'tcx&gt;::confirm_candidate::hca3234a85605343cUMS
   9:     0x7f920d38ccc5 - middle::traits::select::SelectionContext&lt;'cx, 'tcx&gt;::select::hec5ba022f7c648beiPQ
  10:     0x7f920d49bd35 - middle::traits::project::project_type::h74992cfacc671364CwP
  11:     0x7f920d49a96b - middle::traits::project::opt_normalize_projection_type::ha8866d0a50189fbcepP
  12:     0x7f920d49799f - middle::traits::project::project_and_unify_type::h1300a4d0fa05187d87O
  13:     0x7f920d495970 - middle::infer::InferCtxt&lt;'a, 'tcx&gt;::commit_if_ok::h107823834106425565
  14:     0x7f920d48d888 - middle::traits::fulfill::FulfillmentContext&lt;'tcx&gt;::select::hec0877a5f2e11ad0HHO
  15:     0x7f920d48d29b - middle::traits::fulfill::FulfillmentContext&lt;'tcx&gt;::select_where_possible::h301bc31d4e510c07VGO
  16:     0x7f920eacf048 - check::vtable::select_fcx_obligations_where_possible::h72b84a124c3a5b40I6b
  17:     0x7f920eaeb14a - check::FnCtxt&lt;'a, 'tcx&gt;::resolve_type_vars_if_possible::h74b2cbbcdf641686cPo
  18:     0x7f920eb4874e - check::op::check_binop::hba99f04615a48d79oYm
  19:     0x7f920eb7e9cd - check::check_expr_with_unifier::h12689752184703274217
  20:     0x7f920eba4c4b - check::check_decl_local::h28a2e7870f672b04j7r
  21:     0x7f920eb543f1 - check::check_block_with_expected::h212bdec46f615ac8pds
  22:     0x7f920eb39f36 - check::check_fn::h225bdd7ece966e55lSn
  23:     0x7f920eb4fe27 - check::check_bare_fn::h8fed7360af87b5cbUHn
  24:     0x7f920eb5b80c - check::check_method_body::h225a8a268d0d1168Ujo
  25:     0x7f920eb4dd85 - check::CheckItemBodiesVisitor&lt;'a, 'tcx&gt;.Visitor&lt;'tcx&gt;::visit_item::hb0162b7f82578cf4XEn
  26:     0x7f920eb4e1bf - check::CheckItemBodiesVisitor&lt;'a, 'tcx&gt;.Visitor&lt;'tcx&gt;::visit_item::hb0162b7f82578cf4XEn
  27:     0x7f920ec08c4a - check_crate::closure.38730
  28:     0x7f920ec01f80 - check_crate::hed85a8a5c9342eb05CC
  29:     0x7f920f8c7c28 - driver::phase_3_run_analysis_passes::he0b331c645c77cdbtGa
  30:     0x7f920f8a905c - driver::compile_input::h763ead6090436e8fQba
  31:     0x7f920f961eb1 - run_compiler::h711c4a29f8d270a365b
  32:     0x7f920f95f702 - boxed::F.FnBox&lt;A&gt;::call_box::h12199818508070417299
  33:     0x7f920f95ecc9 - rt::unwind::try::try_fn::h5660428370877252098
  34:     0x7f920f3f4898 - rust_try_inner
  35:     0x7f920f3f4885 - rust_try
  36:     0x7f920f95ef64 - boxed::F.FnBox&lt;A&gt;::call_box::h5514408293737026672
  37:     0x7f920f37fca1 - sys::thread::Thread::new::thread_start::hfd3ca3d51ffcfe41QIv
  38:     0x7f9209414529 - start_thread
  39:     0x7f920efd222c - __clone
  40:                0x0 - &lt;unknown&gt;

Could not compile `dumbmath`."><pre class="notranslate"><code class="notranslate">$ RUST_BACKTRACE=1 cargo test   
Compiling dumbmath v0.1.6 (file:///home/nicholasbishop/dumbmath)
error: internal compiler error: Impl DefId { krate: 2, node: 26942 } was matchable against Obligation(predicate=Binder(TraitPredicate(&lt;f32 as core::ops::Div&lt;_&gt;&gt;)),depth=1) but now is not
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 'Box&lt;Any&gt;', /home/rustbuild/src/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/libsyntax/diagnostic.rs:230

stack backtrace:
   1:     0x7fbee3ae6f89 - sys::backtrace::write::h89d94970ae1bc478fhs
   2:     0x7fbee3aeef09 - panicking::on_panic::h314cddb0409059cbkXw
   3:     0x7fbee3aaf0f2 - rt::unwind::begin_unwind_inner::hd6748515f1d9c0b2uCw
   4:     0x7fbee0e85fbd - rt::unwind::begin_unwind::h9184602946677297306
   5:     0x7fbee0e8667b - diagnostic::Handler::bug::h6d48c8060c15a3b4a2B
   6:     0x7fbee1c36304 - middle::traits::select::SelectionContext&lt;'cx, 'tcx&gt;::rematch_impl::h10b0cc0f4e83f0c3EuT
   7:     0x7fbee1c35c2f - middle::infer::InferCtxt&lt;'a, 'tcx&gt;::commit_if_ok::h17325861492725920879
   8:     0x7fbee1c1c8a5 - middle::traits::select::SelectionContext&lt;'cx, 'tcx&gt;::confirm_candidate::hca3234a85605343cUMS
   9:     0x7fbee1afacc5 - middle::traits::select::SelectionContext&lt;'cx, 'tcx&gt;::select::hec5ba022f7c648beiPQ
  10:     0x7fbee1c09d35 - middle::traits::project::project_type::h74992cfacc671364CwP
  11:     0x7fbee1c0896b - middle::traits::project::opt_normalize_projection_type::ha8866d0a50189fbcepP
  12:     0x7fbee1c0599f - middle::traits::project::project_and_unify_type::h1300a4d0fa05187d87O
  13:     0x7fbee1c03970 - middle::infer::InferCtxt&lt;'a, 'tcx&gt;::commit_if_ok::h107823834106425565
  14:     0x7fbee1bfb888 - middle::traits::fulfill::FulfillmentContext&lt;'tcx&gt;::select::hec0877a5f2e11ad0HHO
  15:     0x7fbee1bfb29b - middle::traits::fulfill::FulfillmentContext&lt;'tcx&gt;::select_where_possible::h301bc31d4e510c07VGO
  16:     0x7fbee323d048 - check::vtable::select_fcx_obligations_where_possible::h72b84a124c3a5b40I6b
  17:     0x7fbee325914a - check::FnCtxt&lt;'a, 'tcx&gt;::resolve_type_vars_if_possible::h74b2cbbcdf641686cPo
  18:     0x7fbee32b674e - check::op::check_binop::hba99f04615a48d79oYm
  19:     0x7fbee32ec9cd - check::check_expr_with_unifier::h12689752184703274217
  20:     0x7fbee3312c4b - check::check_decl_local::h28a2e7870f672b04j7r
  21:     0x7fbee32c23f1 - check::check_block_with_expected::h212bdec46f615ac8pds
  22:     0x7fbee32a7f36 - check::check_fn::h225bdd7ece966e55lSn
  23:     0x7fbee32bde27 - check::check_bare_fn::h8fed7360af87b5cbUHn
  24:     0x7fbee32c980c - check::check_method_body::h225a8a268d0d1168Ujo
  25:     0x7fbee32bbd85 - check::CheckItemBodiesVisitor&lt;'a, 'tcx&gt;.Visitor&lt;'tcx&gt;::visit_item::hb0162b7f82578cf4XEn
  26:     0x7fbee32bc1bf - check::CheckItemBodiesVisitor&lt;'a, 'tcx&gt;.Visitor&lt;'tcx&gt;::visit_item::hb0162b7f82578cf4XEn
  27:     0x7fbee3376c4a - check_crate::closure.38730
  28:     0x7fbee336ff80 - check_crate::hed85a8a5c9342eb05CC
  29:     0x7fbee4035c28 - driver::phase_3_run_analysis_passes::he0b331c645c77cdbtGa
  30:     0x7fbee401705c - driver::compile_input::h763ead6090436e8fQba
  31:     0x7fbee40cfeb1 - run_compiler::h711c4a29f8d270a365b
  32:     0x7fbee40cd702 - boxed::F.FnBox&lt;A&gt;::call_box::h12199818508070417299
  33:     0x7fbee40cccc9 - rt::unwind::try::try_fn::h5660428370877252098
  34:     0x7fbee3b62898 - rust_try_inner
  35:     0x7fbee3b62885 - rust_try
  36:     0x7fbee40ccf64 - boxed::F.FnBox&lt;A&gt;::call_box::h5514408293737026672
  37:     0x7fbee3aedca1 - sys::thread::Thread::new::thread_start::hfd3ca3d51ffcfe41QIv
  38:     0x7fbeddb82529 - start_thread
  39:     0x7fbee374022c - __clone
  40:                0x0 - &lt;unknown&gt;

Build failed, waiting for other jobs to finish...
error: internal compiler error: Impl DefId { krate: 2, node: 26942 } was matchable against Obligation(predicate=Binder(TraitPredicate(&lt;f32 as core::ops::Div&lt;_&gt;&gt;)),depth=1) but now is not
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 'Box&lt;Any&gt;', /home/rustbuild/src/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/libsyntax/diagnostic.rs:230

stack backtrace:
   1:     0x7f920f378f89 - sys::backtrace::write::h89d94970ae1bc478fhs
   2:     0x7f920f380f09 - panicking::on_panic::h314cddb0409059cbkXw
   3:     0x7f920f3410f2 - rt::unwind::begin_unwind_inner::hd6748515f1d9c0b2uCw
   4:     0x7f920c717fbd - rt::unwind::begin_unwind::h9184602946677297306
   5:     0x7f920c71867b - diagnostic::Handler::bug::h6d48c8060c15a3b4a2B
   6:     0x7f920d4c8304 - middle::traits::select::SelectionContext&lt;'cx, 'tcx&gt;::rematch_impl::h10b0cc0f4e83f0c3EuT
   7:     0x7f920d4c7c2f - middle::infer::InferCtxt&lt;'a, 'tcx&gt;::commit_if_ok::h17325861492725920879
   8:     0x7f920d4ae8a5 - middle::traits::select::SelectionContext&lt;'cx, 'tcx&gt;::confirm_candidate::hca3234a85605343cUMS
   9:     0x7f920d38ccc5 - middle::traits::select::SelectionContext&lt;'cx, 'tcx&gt;::select::hec5ba022f7c648beiPQ
  10:     0x7f920d49bd35 - middle::traits::project::project_type::h74992cfacc671364CwP
  11:     0x7f920d49a96b - middle::traits::project::opt_normalize_projection_type::ha8866d0a50189fbcepP
  12:     0x7f920d49799f - middle::traits::project::project_and_unify_type::h1300a4d0fa05187d87O
  13:     0x7f920d495970 - middle::infer::InferCtxt&lt;'a, 'tcx&gt;::commit_if_ok::h107823834106425565
  14:     0x7f920d48d888 - middle::traits::fulfill::FulfillmentContext&lt;'tcx&gt;::select::hec0877a5f2e11ad0HHO
  15:     0x7f920d48d29b - middle::traits::fulfill::FulfillmentContext&lt;'tcx&gt;::select_where_possible::h301bc31d4e510c07VGO
  16:     0x7f920eacf048 - check::vtable::select_fcx_obligations_where_possible::h72b84a124c3a5b40I6b
  17:     0x7f920eaeb14a - check::FnCtxt&lt;'a, 'tcx&gt;::resolve_type_vars_if_possible::h74b2cbbcdf641686cPo
  18:     0x7f920eb4874e - check::op::check_binop::hba99f04615a48d79oYm
  19:     0x7f920eb7e9cd - check::check_expr_with_unifier::h12689752184703274217
  20:     0x7f920eba4c4b - check::check_decl_local::h28a2e7870f672b04j7r
  21:     0x7f920eb543f1 - check::check_block_with_expected::h212bdec46f615ac8pds
  22:     0x7f920eb39f36 - check::check_fn::h225bdd7ece966e55lSn
  23:     0x7f920eb4fe27 - check::check_bare_fn::h8fed7360af87b5cbUHn
  24:     0x7f920eb5b80c - check::check_method_body::h225a8a268d0d1168Ujo
  25:     0x7f920eb4dd85 - check::CheckItemBodiesVisitor&lt;'a, 'tcx&gt;.Visitor&lt;'tcx&gt;::visit_item::hb0162b7f82578cf4XEn
  26:     0x7f920eb4e1bf - check::CheckItemBodiesVisitor&lt;'a, 'tcx&gt;.Visitor&lt;'tcx&gt;::visit_item::hb0162b7f82578cf4XEn
  27:     0x7f920ec08c4a - check_crate::closure.38730
  28:     0x7f920ec01f80 - check_crate::hed85a8a5c9342eb05CC
  29:     0x7f920f8c7c28 - driver::phase_3_run_analysis_passes::he0b331c645c77cdbtGa
  30:     0x7f920f8a905c - driver::compile_input::h763ead6090436e8fQba
  31:     0x7f920f961eb1 - run_compiler::h711c4a29f8d270a365b
  32:     0x7f920f95f702 - boxed::F.FnBox&lt;A&gt;::call_box::h12199818508070417299
  33:     0x7f920f95ecc9 - rt::unwind::try::try_fn::h5660428370877252098
  34:     0x7f920f3f4898 - rust_try_inner
  35:     0x7f920f3f4885 - rust_try
  36:     0x7f920f95ef64 - boxed::F.FnBox&lt;A&gt;::call_box::h5514408293737026672
  37:     0x7f920f37fca1 - sys::thread::Thread::new::thread_start::hfd3ca3d51ffcfe41QIv
  38:     0x7f9209414529 - start_thread
  39:     0x7f920efd222c - __clone
  40:                0x0 - &lt;unknown&gt;

Could not compile `dumbmath`.
</code></pre></div>
<p dir="auto">I got an internal compiler error when <code class="notranslate">cargo test</code>ing my code, and I was unfortunately unable to reproduce on a small sample. The code is <a href="https://github.com/honzasp/spiral/tree/bf84c70e067a19c9da20cf1c088f304dd159e8df">here on Github</a>, to reproduce the error, change the literal on <a href="https://github.com/honzasp/spiral/blob/bf84c70e067a19c9da20cf1c088f304dd159e8df/src/spiral/to_spine.rs#L642">one line in test</a> from <code class="notranslate">42.0</code> to <code class="notranslate">42</code>.</p>
<div class="snippet-clipboard-content notranslate position-relative overflow-auto" data-snippet-clipboard-copy-content="$ rustc --version --verbose
rustc 1.0.0-nightly (522d09dfe 2015-02-19) (built 2015-02-21)
binary: rustc
commit-hash: 522d09dfecbeca1595f25ac58c6d0178bbd21d7d
commit-date: 2015-02-19
build-date: 2015-02-21
host: i686-unknown-linux-gnu
release: 1.0.0-nightly
$ RUST_BACKTRACE=1 cargo test --verbose
   Compiling spiral v0.0.1 (file:///[...]/spiral)
     Running `rustc src/main.rs --crate-name spiral --crate-type bin -g --test -C metadata=1ade813d3d860ac1 -C extra-filename=-1ade813d3d860ac1 --out-dir [...]/spiral/target --emit=dep-info,link -L dependency=[...]/spiral/target -L dependency=[...]/spiral/target/deps`
error: internal compiler error: Impl DefId { krate: 2, node: 74181 } was matchable against Obligation(predicate=Binder(TraitPredicate(core::cmp::PartialEq&lt;_&gt;)),depth=1) but now is not
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 'Box&lt;Any&gt;', /home/rustbuild/src/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/libsyntax/diagnostic.rs:189

stack backtrace:
   1: 0xb7231280 - sys::backtrace::write::hb58c665617e5cee2KlC
   2: 0xb725b8b0 - panicking::on_panic::hd4d4fc652390cdd8tXL
   3: 0xb7195ac0 - rt::unwind::begin_unwind_inner::h6797c7a781aac698RBL
   4: 0xb5656fd0 - rt::unwind::begin_unwind::h13117811778590822301
   5: 0xb5657800 - diagnostic::Handler::bug::h0b9167776bd8dc1aw4E
   6: 0xb61b5310 - middle::traits::select::SelectionContext&lt;'cx, 'tcx&gt;::rematch_impl::h7f3f2e654c4ffad9kHU
   7: 0xb61b4c30 - middle::infer::InferCtxt&lt;'a, 'tcx&gt;::try::h13523729267676866609
   8: 0xb619dd90 - middle::traits::select::SelectionContext&lt;'cx, 'tcx&gt;::confirm_candidate::ha4efb7af28b19263S8T
   9: 0xb61784f0 - middle::traits::select::SelectionContext&lt;'cx, 'tcx&gt;::select::h5394e35b0e7c70a6lhS
  10: 0xb6174160 - middle::traits::fulfill::FulfillmentContext&lt;'tcx&gt;::select::hbef8233dc9336219B0P
  11: 0xb6173ac0 - middle::traits::fulfill::FulfillmentContext&lt;'tcx&gt;::select_where_possible::hbd71b9b88c61613cHZP
  12: 0xb6cdddc0 - check::vtable::select_fcx_obligations_where_possible::hffd3ec74dffa624eVRb
  13: 0xb6d1a6f0 - check::FnCtxt&lt;'a, 'tcx&gt;::resolve_type_vars_if_possible::he1da80c3c9c1dda2rJo
  14: 0xb6cca360 - check::structurally_resolved_type::hb6535b94e7bbe37bNPt
  15: 0xb6e00220 - check::check_expr_with_unifier::h9614455191220309796
  16: 0xb6dbad90 - check::check_expr_with_unifier::check_binop::hbf8de0ab08b2ba09JMq
  17: 0xb6df3370 - check::check_expr_with_unifier::h6092115828992963581
  18: 0xb6dd9240 - check::check_expr_with_unifier::h3884107362083173097
  19: 0xb6dbad90 - check::check_expr_with_unifier::check_binop::hbf8de0ab08b2ba09JMq
  20: 0xb6df3370 - check::check_expr_with_unifier::h6092115828992963581
  21: 0xb6df3370 - check::check_expr_with_unifier::h6092115828992963581
  22: 0xb6dd9240 - check::check_expr_with_unifier::h3884107362083173097
  23: 0xb6dd0200 - check::check_expr_with_unifier::check_then_else::h483da0d6a4f3eab2MEq
  24: 0xb6decc20 - check::check_expr_with_unifier::h17365000147061483630
  25: 0xb6da6d80 - check::check_block_with_expected::hf29cd5d4f1823991zys
  26: 0xb6decc20 - check::check_expr_with_unifier::h17365000147061483630
  27: 0xb6ccafe0 - check::_match::check_match::closure.29042
  28: 0xb6ccac10 - check::_match::check_match::h77807f1365a779d3V1a
  29: 0xb6decc20 - check::check_expr_with_unifier::h17365000147061483630
  30: 0xb6da6d80 - check::check_block_with_expected::hf29cd5d4f1823991zys
  31: 0xb6df9ad0 - check::check_expr_with_unifier::h14838318111108599859
  32: 0xb6da6d80 - check::check_block_with_expected::hf29cd5d4f1823991zys
  33: 0xb6d85a80 - check::check_fn::h9733b23b5bb31869JKn
  34: 0xb6da3700 - check::check_bare_fn::hc0a904b0aabec0a4Wzn
  35: 0xb6d9aa00 - check::check_item::heaa17bb09891b8a9nTn
  36: 0xb6da19f0 - visit::walk_item::h334270929839752142
  37: 0xb6da19f0 - visit::walk_item::h334270929839752142
  38: 0xb6da19f0 - visit::walk_item::h334270929839752142
  39: 0xb6e7f750 - check_crate::closure.35867
  40: 0xb6e78b60 - check_crate::h74f1efb9c9ad0cecVjC
  41: 0xb769c480 - driver::phase_3_run_analysis_passes::ha81485be033381d8gHa
  42: 0xb7680c20 - driver::compile_input::h55e2c5089100dcc0Gba
  43: 0xb7760430 - run_compiler::h7c1df0ae32ef6a57Zbc
  44: 0xb775e810 - thunk::F.Invoke&lt;A, R&gt;::invoke::h4956589150906656218
  45: 0xb775d680 - rt::unwind::try::try_fn::h3108213307196454525
  46: 0xb72d5b30 - rust_try_inner
  47: 0xb72d5b00 - rust_try
  48: 0xb775d9b0 - thunk::F.Invoke&lt;A, R&gt;::invoke::h9387302087009601825
  49: 0xb72474c0 - sys::thread::thread_start::hb380b1da46a95e5393G
  50: 0xb2f29ea0 - start_thread
  51: 0xb7049502 - clone
  52:        0x0 - &lt;unknown&gt;

Could not compile `spiral`.

Caused by:
  Process didn't exit successfully: `rustc src/main.rs --crate-name spiral --crate-type bin -g --test -C metadata=1ade813d3d860ac1 -C extra-filename=-1ade813d3d860ac1 --out-dir [...]/spiral/target --emit=dep-info,link -L dependency=[...]/spiral/target -L dependency=[...]/spiral/target/deps` (status=101)"><pre class="notranslate"><code class="notranslate">$ rustc --version --verbose
rustc 1.0.0-nightly (522d09dfe 2015-02-19) (built 2015-02-21)
binary: rustc
commit-hash: 522d09dfecbeca1595f25ac58c6d0178bbd21d7d
commit-date: 2015-02-19
build-date: 2015-02-21
host: i686-unknown-linux-gnu
release: 1.0.0-nightly
$ RUST_BACKTRACE=1 cargo test --verbose
   Compiling spiral v0.0.1 (file:///[...]/spiral)
     Running `rustc src/main.rs --crate-name spiral --crate-type bin -g --test -C metadata=1ade813d3d860ac1 -C extra-filename=-1ade813d3d860ac1 --out-dir [...]/spiral/target --emit=dep-info,link -L dependency=[...]/spiral/target -L dependency=[...]/spiral/target/deps`
error: internal compiler error: Impl DefId { krate: 2, node: 74181 } was matchable against Obligation(predicate=Binder(TraitPredicate(core::cmp::PartialEq&lt;_&gt;)),depth=1) but now is not
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 'Box&lt;Any&gt;', /home/rustbuild/src/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/libsyntax/diagnostic.rs:189

stack backtrace:
   1: 0xb7231280 - sys::backtrace::write::hb58c665617e5cee2KlC
   2: 0xb725b8b0 - panicking::on_panic::hd4d4fc652390cdd8tXL
   3: 0xb7195ac0 - rt::unwind::begin_unwind_inner::h6797c7a781aac698RBL
   4: 0xb5656fd0 - rt::unwind::begin_unwind::h13117811778590822301
   5: 0xb5657800 - diagnostic::Handler::bug::h0b9167776bd8dc1aw4E
   6: 0xb61b5310 - middle::traits::select::SelectionContext&lt;'cx, 'tcx&gt;::rematch_impl::h7f3f2e654c4ffad9kHU
   7: 0xb61b4c30 - middle::infer::InferCtxt&lt;'a, 'tcx&gt;::try::h13523729267676866609
   8: 0xb619dd90 - middle::traits::select::SelectionContext&lt;'cx, 'tcx&gt;::confirm_candidate::ha4efb7af28b19263S8T
   9: 0xb61784f0 - middle::traits::select::SelectionContext&lt;'cx, 'tcx&gt;::select::h5394e35b0e7c70a6lhS
  10: 0xb6174160 - middle::traits::fulfill::FulfillmentContext&lt;'tcx&gt;::select::hbef8233dc9336219B0P
  11: 0xb6173ac0 - middle::traits::fulfill::FulfillmentContext&lt;'tcx&gt;::select_where_possible::hbd71b9b88c61613cHZP
  12: 0xb6cdddc0 - check::vtable::select_fcx_obligations_where_possible::hffd3ec74dffa624eVRb
  13: 0xb6d1a6f0 - check::FnCtxt&lt;'a, 'tcx&gt;::resolve_type_vars_if_possible::he1da80c3c9c1dda2rJo
  14: 0xb6cca360 - check::structurally_resolved_type::hb6535b94e7bbe37bNPt
  15: 0xb6e00220 - check::check_expr_with_unifier::h9614455191220309796
  16: 0xb6dbad90 - check::check_expr_with_unifier::check_binop::hbf8de0ab08b2ba09JMq
  17: 0xb6df3370 - check::check_expr_with_unifier::h6092115828992963581
  18: 0xb6dd9240 - check::check_expr_with_unifier::h3884107362083173097
  19: 0xb6dbad90 - check::check_expr_with_unifier::check_binop::hbf8de0ab08b2ba09JMq
  20: 0xb6df3370 - check::check_expr_with_unifier::h6092115828992963581
  21: 0xb6df3370 - check::check_expr_with_unifier::h6092115828992963581
  22: 0xb6dd9240 - check::check_expr_with_unifier::h3884107362083173097
  23: 0xb6dd0200 - check::check_expr_with_unifier::check_then_else::h483da0d6a4f3eab2MEq
  24: 0xb6decc20 - check::check_expr_with_unifier::h17365000147061483630
  25: 0xb6da6d80 - check::check_block_with_expected::hf29cd5d4f1823991zys
  26: 0xb6decc20 - check::check_expr_with_unifier::h17365000147061483630
  27: 0xb6ccafe0 - check::_match::check_match::closure.29042
  28: 0xb6ccac10 - check::_match::check_match::h77807f1365a779d3V1a
  29: 0xb6decc20 - check::check_expr_with_unifier::h17365000147061483630
  30: 0xb6da6d80 - check::check_block_with_expected::hf29cd5d4f1823991zys
  31: 0xb6df9ad0 - check::check_expr_with_unifier::h14838318111108599859
  32: 0xb6da6d80 - check::check_block_with_expected::hf29cd5d4f1823991zys
  33: 0xb6d85a80 - check::check_fn::h9733b23b5bb31869JKn
  34: 0xb6da3700 - check::check_bare_fn::hc0a904b0aabec0a4Wzn
  35: 0xb6d9aa00 - check::check_item::heaa17bb09891b8a9nTn
  36: 0xb6da19f0 - visit::walk_item::h334270929839752142
  37: 0xb6da19f0 - visit::walk_item::h334270929839752142
  38: 0xb6da19f0 - visit::walk_item::h334270929839752142
  39: 0xb6e7f750 - check_crate::closure.35867
  40: 0xb6e78b60 - check_crate::h74f1efb9c9ad0cecVjC
  41: 0xb769c480 - driver::phase_3_run_analysis_passes::ha81485be033381d8gHa
  42: 0xb7680c20 - driver::compile_input::h55e2c5089100dcc0Gba
  43: 0xb7760430 - run_compiler::h7c1df0ae32ef6a57Zbc
  44: 0xb775e810 - thunk::F.Invoke&lt;A, R&gt;::invoke::h4956589150906656218
  45: 0xb775d680 - rt::unwind::try::try_fn::h3108213307196454525
  46: 0xb72d5b30 - rust_try_inner
  47: 0xb72d5b00 - rust_try
  48: 0xb775d9b0 - thunk::F.Invoke&lt;A, R&gt;::invoke::h9387302087009601825
  49: 0xb72474c0 - sys::thread::thread_start::hb380b1da46a95e5393G
  50: 0xb2f29ea0 - start_thread
  51: 0xb7049502 - clone
  52:        0x0 - &lt;unknown&gt;

Could not compile `spiral`.

Caused by:
  Process didn't exit successfully: `rustc src/main.rs --crate-name spiral --crate-type bin -g --test -C metadata=1ade813d3d860ac1 -C extra-filename=-1ade813d3d860ac1 --out-dir [...]/spiral/target --emit=dep-info,link -L dependency=[...]/spiral/target -L dependency=[...]/spiral/target/deps` (status=101)
</code></pre></div>
<p dir="auto">I am sorry for such a crude report, but I could not come with a better sample, as the origin of the error is a bit unclear to me.</p>