Internal compiler error when matching a slice against two byte vectors.

[defnull]

rustc 0.11.0-pre-nightly (5d5c20647f45f2eb74f337e5434bbe63b0c43345 2014-07-03 21:46:47 +0000)

fn main() {
    let buf = vec!(1,2,3,4);
    match buf.slice(0,3) {
         b"abc" => {},
         b"def" => {}
    };
}

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 'internal error: entered unreachable code', /home/rustbuild/src/rust-buildbot/slave/nightly-linux/build/src/librustc/middle/check_match.rs:590

stack backtrace:
   1:     0x7fbffece45b0 - rt::backtrace::imp::write::h6c6320b7a331df2dPMp::v0.11.0.pre
   2:     0x7fbffece9ef0 - failure::on_fail::hf6739552e2d4569647p::v0.11.0.pre
   3:     0x7fbfff4c0e40 - unwind::begin_unwind_inner::h2c7e876dd7f351c8cZd::v0.11.0.pre
   4:     0x7fbfffb13670 - unwind::begin_unwind::h11965739027995047516::v0.11.0.pre
   5:     0x7fbffffb0cf0 - middle::check_match::constructor_arity::h2050d60f8fbae06f2LD::v0.11.0.pre
   6:     0x7fbffffb05d0 - middle::check_match::is_useful_specialized::h992f25e697ec2c46WCD::v0.11.0.pre
   7:     0x7fbffffb17e0 - middle::check_match::is_useful::closure.97228
   8:     0x7fbffffaf7b0 - iter::FilterMap<'a, A, B, T>.Iterator<B>::next::h8881800146787513647::v0.11.0.pre
   9:     0x7fbffffa87e0 - middle::check_match::is_useful::hffd126862233c547utD::v0.11.0.pre
  10:     0x7fbffffa3d10 - middle::check_match::check_expr::h26eb090c8b8376f6a0C::v0.11.0.pre
  11:     0x7fbffffa7b40 - visit::Visitor::visit_block::h16617548265022659780::v0.11.0.pre
  12:     0x7fbffffa5a80 - middle::check_match::check_fn::hb9f786c61dc71175N3D::v0.11.0.pre
  13:     0x7fbffffa69b0 - visit::walk_item::h8044846254511995900::v0.11.0.pre
  14:     0x7fbffffa5f60 - middle::check_match::check_crate::h6183dbc85399c897GZC::v0.11.0.pre
  15:     0x7fc00034bd70 - driver::driver::phase_3_run_analysis_passes::h71b62eba3117d76bxnq::v0.11.0.pre
  16:     0x7fc000347760 - driver::driver::compile_input::h0071edea40443948vaq::v0.11.0.pre
  17:     0x7fc0003fb2d0 - driver::run_compiler::ha74a95c4eb3cf9e43Vs::v0.11.0.pre
  18:     0x7fc0003fb1e0 - driver::main_args::closure.117612
  19:     0x7fc00040f380 - task::TaskBuilder<S>::try_future::closure.118754
  20:     0x7fc00040f070 - task::TaskBuilder<S>::spawn_internal::closure.118731
  21:     0x7fc0024f55f0 - task::spawn_opts::closure.7471
  22:     0x7fbfff519330 - rust_try
  23:     0x7fbfff4bd410 - unwind::try::h2d15e17f94c25bc4BNd::v0.11.0.pre
  24:     0x7fbfff4bd150 - task::Task::run::h5616d45120d2e1c1XYc::v0.11.0.pre
  25:     0x7fc0024f53b0 - task::spawn_opts::closure.7417
  26:     0x7fbfff4bfc70 - thread::thread_start::h18a2a671c7152c44vld::v0.11.0.pre
  27:     0x7fbffe764ea0 - start_thread
  28:     0x7fbfff17e999 - __clone
  29:                0x0 - <unknown>

[huonw]

cc @jakub-