ICE when generating MIR

[tillarnold]

I tried to look at the MIR for the following code in the rust playground and got an internal compiler error. ( http://is.gd/oJVeYh )

fn main() {
  let t = 44;
  let r = 12;

  std::mem::swap(t,r)
}

<anon>:5:18: 5:19 error: mismatched types:
 expected `&mut _`,
    found `_`
(expected &-ptr,
    found integral variable) [E0308]
<anon>:5   std::mem::swap(t,r)
                          ^
<anon>:5:18: 5:19 help: see the detailed explanation for E0308
<anon>:5:20: 5:21 error: mismatched types:
 expected `&mut _`,
    found `_`
(expected &-ptr,
    found integral variable) [E0308]
<anon>:5   std::mem::swap(t,r)
                            ^
<anon>:5:20: 5:21 help: see the detailed explanation for 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 'called `Option::unwrap()` on a `None` value', ../src/libcore/option.rs:330
note: Run with `RUST_BACKTRACE=1` for a backtrace.

playpen: application terminated with error code 101

If I try to run this in the playground using Nightly (and not to generate the MIR) I only get the correct mismatched types error.

[nagisa]

Backtrace:

   1:     0x7f0b43b0b0d0 - sys::backtrace::tracing::imp::write::h605e9c1f7ada7ab7hbv
   2:     0x7f0b43b1448b - panicking::default_handler::_$u7b$$u7b$closure$u7d$$u7d$::closure.44444
   3:     0x7f0b43b13fe3 - panicking::default_handler::h6b489e2028b5422aFQz
   4:     0x7f0b43ad87bc - sys_common::unwind::begin_unwind_inner::h2bd8af3374a15fceAZt
   5:     0x7f0b43ad9258 - sys_common::unwind::begin_unwind_fmt::h3b596f09d971ea5eGYt
   6:     0x7f0b43b08ba1 - rust_begin_unwind
   7:     0x7f0b43b5b6bf - panicking::panic_fmt::h71118c177c5714b4lcM
   8:     0x7f0b43b5c1b8 - panicking::panic::h62d0499da58dfdf5SaM
   9:     0x7f0b440f7c51 - pretty::pretty_print_input::_$u7b$$u7b$closure$u7d$$u7d$::closure.36785
  10:     0x7f0b440f257c - driver::phase_3_run_analysis_passes::_$u7b$$u7b$closure$u7d$$u7d$::closure.36783
  11:     0x7f0b440f0bb8 - middle::ty::context::ctxt<'tcx>::create_and_enter::h10434081139749583753
  12:     0x7f0b440ee0e7 - driver::phase_3_run_analysis_passes::h5320998580799269994
  13:     0x7f0b43ffe847 - pretty::pretty_print_input::h5b47642c7d3d0daasdc
  14:     0x7f0b43ff36f6 - run_compiler::heb165938024abeeaHOc
  15:     0x7f0b43ff1061 - sys_common::unwind::try::try_fn::h10705131437883225394
  16:     0x7f0b43b08b2b - __rust_try
  17:     0x7f0b43b010dd - sys_common::unwind::inner_try::ha3e3bb972be5f331CWt
  18:     0x7f0b43ff18b0 - boxed::F.FnBox<A>::call_box::h15933834349413702402
  19:     0x7f0b43b12a59 - sys::thread::Thread::new::thread_start::h219f55ad3bfdbbebZNy
  20:     0x7f0b3c299423 - start_thread
  21:     0x7f0b4378acbc - clone
  22:                0x0 - <unknown>