ICE when assigning a method to a variable

[murarth]

I was curious whether it would be possible to treat a method like a function, so I gave it a try.

struct A;

impl A {
    fn foo(&self) { }
}

fn main() {
    let f = A::foo;
    f(&A);
}

This is the version of rustc:

$ rustc -v
rustc 0.13.0-nightly (bd7138dd6 2014-10-27 23:02:55 +0000)

And this is the error:

x.rs:8:13: 8:19 error: internal compiler error: uncategorized def for expr 26: DefMethod(DefId { krate: 0, node: 8 }, None, FromImpl(DefId { krate: 0, node: 7 }))
x.rs:8     let f = A::foo;
                   ^~~~~~
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 'Box<Any>', /home/rustbuild/src/rust-buildbot/slave/nightly-linux/build/src/libsyntax/diagnostic.rs:116

stack backtrace:
   1:     0x7ffe6856e070 - rt::backtrace::imp::write::h5a0997daa091452aAdq
   2:     0x7ffe68571160 - failure::on_fail::hc2bbfb16552a42a7Xyq
   3:     0x7ffe6caae180 - unwind::begin_unwind_inner::hba0c3c1372f5cb73PRd
   4:     0x7ffe692c39b0 - unwind::begin_unwind::h2734907025152909083
   5:     0x7ffe692c3930 - diagnostic::SpanHandler::span_bug::h963265597453565ah6F
   6:     0x7ffe6d4a4b10 - middle::ty::expr_kind::hdf6435478ca3d03fa9I
   7:     0x7ffe6d46cb30 - middle::trans::expr::trans_into::h59e7bbcc4d5362a6dG4
   8:     0x7ffe6d536370 - middle::trans::_match::store_local::closure.126275
   9:     0x7ffe6d536160 - middle::trans::_match::mk_binding_alloca::h7586589838283757987
  10:     0x7ffe6d505760 - middle::trans::_match::store_local::haee979a4ae164c29qwk
  11:     0x7ffe6d46c180 - middle::trans::base::init_local::h14997c0412bcab7fybg
  12:     0x7ffe6d46b540 - middle::trans::controlflow::trans_stmt::h0b313766085d2deenR0
  13:     0x7ffe6d46cf50 - middle::trans::controlflow::trans_block::he2d4b6f33ad56bdctW0
  14:     0x7ffe6d50c730 - middle::trans::base::trans_closure::hf302583eb5981ca2Y2g
  15:     0x7ffe6d460250 - middle::trans::base::trans_fn::h2698897672e52421meh
  16:     0x7ffe6d45d990 - middle::trans::base::trans_item::h108ceed97013196fFxh
  17:     0x7ffe6d516d10 - middle::trans::base::trans_crate::h2959ddec9d0661d4wvi
  18:     0x7ffe6d934da0 - driver::driver::phase_4_translate_to_llvm::h871e70ba7828df26FnA
  19:     0x7ffe6d92b610 - driver::driver::compile_input::hc2f03680b6cd2d08zUz
  20:     0x7ffe6d9ae5c0 - driver::run_compiler::h7d611b9a41d83191KHD
  21:     0x7ffe6d9ae4b0 - driver::run::closure.144980
  22:     0x7ffe6d12bfd0 - task::TaskBuilder<S>::try_future::closure.103244
  23:     0x7ffe6d12bdc0 - task::TaskBuilder<S>::spawn_internal::closure.103215
  24:     0x7ffe6cdf8a80 - task::NativeSpawner.Spawner::spawn::closure.8444
  25:     0x7ffe6cb07650 - rust_try_inner
  26:     0x7ffe6cb07640 - rust_try
  27:     0x7ffe6caab920 - unwind::try::hc0b42c9b6f96abb8xGd
  28:     0x7ffe6caab7b0 - task::Task::run::h1c3d2c1e07305f00nMc
  29:     0x7ffe6cdf87c0 - task::NativeSpawner.Spawner::spawn::closure.8382
  30:     0x7ffe6caad050 - thread::thread_start::h962311e4e7f76acfC7c
  31:     0x7ffe6791b0c0 - start_thread
  32:     0x7ffe6c775f89 - __clone
  33:                0x0 - <unknown>

[alexcrichton]

cc @nick29581

[bkoropoff]

#18177 doesn't seem to address this, but the fix appears simple