ICE with Rust 1.9.0

[evanw]

I just hit a crash in the compiler. I'm not sure if it works with the nightly build or not because https://play.rust-lang.org is down (it currently says "502 Bad Gateway" after loading for a while).

Anyway, the following code:

use std::mem::swap;

fn foo<T>(a: &mut Vec<T>) {
  let mut b = Vec::new();
  swap(&mut a, &mut b);
}

fn main() {
}

crashes when compiled:

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 'index out of bounds: the len is 9 but the index is 11', ../src/libcollections/vec.rs:1166
stack backtrace:
   1:        0x10d8a83a8 - std::sys::backtrace::tracing::imp::write::h4c73fcd3363076f5
   2:        0x10d8b47f5 - std::panicking::default_hook::_$u7b$$u7b$closure$u7d$$u7d$::h0422dbb3077e6747
   3:        0x10d8b432f - std::panicking::default_hook::haac48fa641db8fa2
   4:        0x10d878f86 - std::sys_common::unwind::begin_unwind_inner::h39d40f52add53ef7
   5:        0x10d87b08e - std::sys_common::unwind::begin_unwind_fmt::h64c0ff793199cc1b
   6:        0x10d8a5ba7 - rust_begin_unwind
   7:        0x10d8f0df0 - core::panicking::panic_fmt::h73bf9d7e8e891a73
   8:        0x10d8f1000 - core::panicking::panic_bounds_check::hc30e971884568c27
   9:        0x10c36a6b9 - _<rustc_data_structures..unify..UnificationTable<K>>::get::he21ecf90e8e4f73a
  10:        0x10c2fea74 - rustc::infer::InferCtxt::shallow_resolve::he47cdea6677f40d2
  11:        0x10c467d91 - rustc::traits::fulfill::process_predicate::h8bbef05b37cf149a
  12:        0x10c466ba3 - _<rustc_data_structures..obligation_forest..ObligationForest<O, T>>::process_obligations::h824becaa5c013776
  13:        0x10c4621fc - rustc::traits::fulfill::FulfillmentContext::select_where_possible::hf3fc6484c301b5bb
  14:        0x10969afe4 - rustc_typeck::check::FnCtxt::select_obligations_where_possible::h623b6ae6ad660b2d
  15:        0x1096ad25c - rustc_typeck::check::FnCtxt::resolve_type_vars_if_possible::ha2a2b0468a33b7be
  16:        0x1096c25fa - rustc_typeck::check::demand::coerce::hd43013069440cf8a
  17:        0x1096bff00 - rustc_typeck::check::check_argument_types::ha726e4d47c9cf6ca
  18:        0x1097491ad - rustc_typeck::check::callee::confirm_builtin_call::h5c89fdde94ec7d50
  19:        0x1096dc632 - rustc_typeck::check::callee::check_call::h9d2b45441ce6bc57
  20:        0x1096c3c9a - rustc_typeck::check::check_expr_with_expectation_and_lvalue_pref::h76666174c4b17386
  21:        0x1096faed6 - rustc_typeck::check::check_stmt::h90d31dcbe73b93a2
  22:        0x1096a0d87 - rustc_typeck::check::check_block_with_expected::h17e4ec74708f2b9a
  23:        0x1096983c8 - rustc_typeck::check::check_fn::hab7334b30b5aec4a
  24:        0x109695c67 - rustc_typeck::check::check_bare_fn::h85926feaf1e6659d
  25:        0x109690b39 - rustc_typeck::check::check_item_body::h1895344155d5b2b2
  26:        0x1096889bb - rustc_typeck::check::check_item_bodies::h525c1aa0e1abb529
  27:        0x1096801eb - rustc_typeck::check_crate::h0ef96f4043e1e69a
  28:        0x109417158 - rustc_driver::driver::phase_3_run_analysis_passes::_$u7b$$u7b$closure$u7d$$u7d$::hc699330eb6f2bc1e
  29:        0x109415392 - rustc::ty::context::TyCtxt::create_and_enter::h656b2d3a4956519e
  30:        0x109411cdc - rustc_driver::driver::phase_3_run_analysis_passes::h83da042ec4b8ea10
  31:        0x1093e5571 - rustc_driver::driver::compile_input::h6491aaddd9e61258
  32:        0x1093cbd8f - rustc_driver::run_compiler::h80b2ba5e4d787c5f
  33:        0x1093c9122 - std::sys_common::unwind::try::try_fn::h34e27823ddd1d5e9
  34:        0x10d8a5b3b - __rust_try
  35:        0x10d8a5ac3 - std::sys_common::unwind::inner_try::h9eebd8dc83f388a6
  36:        0x1093c99b9 - _<F as std..boxed..FnBox<A>>::call_box::h3d5d78986dfac5b2
  37:        0x10d8b36c8 - std::sys::thread::Thread::new::thread_start::h471ad90789353b5b
  38:     0x7fff8c7fd059 - _pthread_body
  39:     0x7fff8c7fcfd6 - _pthread_start

Output of rustc --version --verbose:

rustc 1.9.0 (e4e8b6668 2016-05-18)
binary: rustc
commit-hash: e4e8b666850a763fdf1c3c2c142856ab51e32779
commit-date: 2016-05-18
host: x86_64-apple-darwin
release: 1.9.0

[Stebalien]

It works for me on nightly (rustc 1.11.0-nightly (bb4a79b08 2016-06-15)).

Edit: Well, spits out the correct error and doesn't crash:

tmp.rs:5:18: 5:24 error: mismatched types [E0308]
tmp.rs:5     swap(&mut a, &mut b);
                          ^~~~~~
tmp.rs:5:18: 5:24 help: run `rustc --explain E0308` to see a detailed explanation
tmp.rs:5:18: 5:24 note: expected type `&mut &mut std::vec::Vec<T>`
tmp.rs:5:18: 5:24 note:    found type `&mut std::vec::Vec<_>`
error: aborting due to previous error

[alexcrichton]

Fixed on nightly now, so closing