Unbalanced < and closure crash with "tuple pattern unexpected type Err(())"

[rardiol]

I tried this code:

fn main () {
    let sr: Vec<(u32, _, _) = vec![];
    let sr2: Vec<(u32, _, _)> = sr.iter().map(|(faction, th_sender, th_receiver)| {}).collect();
}

I expected to see this happen:

error: missing >

Instead, this happened:

> t.rs:2:29: 2:30 error: expected one of `+`, `,`, or `>`, found `=`
> t.rs:2     let sr: Vec<(u32, _, _) = vec![];
>                                    ^
> t.rs:3:33: 3:35 error: unresolved name `sr` [E0425]
> t.rs:3     let sr2: Vec<(u32, _, _)> = sr.iter().map(|(faction, th_sender, th_receiver)| {}).collect();
>                                        ^~
> t.rs:3:33: 3:35 help: run `rustc --explain E0425` to see a detailed explanation
> t.rs:3:48: 3:81 error: internal compiler error: src/librustc/middle/mem_categorization.rs:1300: tuple pattern unexpected type Err(())
> t.rs:3     let sr2: Vec<(u32, _, _)> = sr.iter().map(|(faction, th_sender, th_receiver)| {}).collect();
>                                                       ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> 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
> thread 'rustc' panicked at 'Box<Any>', src/libsyntax/errors/mod.rs:545
> note: Run with `RUST_BACKTRACE=1` for a backtrace.

Meta

rustc --version --verbose:

rustc 1.11.0-dev
binary: rustc
commit-hash: unknown
commit-date: unknown
host: x86_64-unknown-linux-gnu
release: 1.11.0-dev

Backtrace:

thread 'rustc' panicked at 'Box<Any>', src/libsyntax/errors/mod.rs:545
stack backtrace:
   1:     0x7f9f8901f0d4 - std::sys::backtrace::tracing::imp::write::hc6294d1e0e9044ff
   2:     0x7f9f8902d24b - std::panicking::default_hook::_$u7b$$u7b$closure$u7d$$u7d$::h695d4ae4d161909f
   3:     0x7f9f8902cdfc - std::panicking::default_hook::h369905e6af8b368f
   4:     0x7f9f88ff0f2d - std::panicking::rust_panic_with_hook::h021cdbac2b00d849
   5:     0x7f9f87d27ec8 - std::panicking::begin_panic::h7e9acd4fe05e4790
   6:     0x7f9f87d27d35 - rustc::session::opt_span_bug_fmt::_$u7b$$u7b$closure$u7d$$u7d$::hd2ee128532aebb8f
   7:     0x7f9f87d27b0f - rustc::session::span_bug_fmt::h89f92d121ede5b08
   8:     0x7f9f87dc4fb1 - rustc::middle::mem_categorization::MemCategorizationContext::cat_pattern_::hf21ea97e9711ea54
   9:     0x7f9f87dc380e - rustc_typeck::check::regionck::RegionCtxt::link_pattern::h70a3cd02a4321d1f
  10:     0x7f9f87dbfde8 - rustc_typeck::check::regionck::RegionCtxt::visit_fn_body::h5d3b7e4816fadba8
  11:     0x7f9f87dc27cf - rustc::hir::intravisit::walk_expr::h325cb1ca83c8a266
  12:     0x7f9f87dbdb4e - _<rustc_typeck..check..regionck..RegionCtxt<'a, 'gcx, 'tcx> as rustc..hir..intravisit..Visitor<'v>>::visit_expr::hd3645caaa0b0f045
  13:     0x7f9f87dc24e6 - rustc::hir::intravisit::walk_expr::h325cb1ca83c8a266
  14:     0x7f9f87dbd7ac - _<rustc_typeck..check..regionck..RegionCtxt<'a, 'gcx, 'tcx> as rustc..hir..intravisit..Visitor<'v>>::visit_expr::hd3645caaa0b0f045
  15:     0x7f9f87dc24e6 - rustc::hir::intravisit::walk_expr::h325cb1ca83c8a266
  16:     0x7f9f87dbd7ac - _<rustc_typeck..check..regionck..RegionCtxt<'a, 'gcx, 'tcx> as rustc..hir..intravisit..Visitor<'v>>::visit_expr::hd3645caaa0b0f045
  17:     0x7f9f87dc0ad1 - _<rustc_typeck..check..regionck..RegionCtxt<'a, 'gcx, 'tcx> as rustc..hir..intravisit..Visitor<'v>>::visit_local::h22e75c1a3f5047ed
  18:     0x7f9f87dbfe57 - rustc_typeck::check::regionck::RegionCtxt::visit_fn_body::h5d3b7e4816fadba8
  19:     0x7f9f87d47285 - rustc_typeck::check::regionck::_<impl rustc_typeck..check..FnCtxt<'a, 'gcx, 'tcx>>::regionck_fn::ha576d8a0a2255f8a
  20:     0x7f9f87d40b09 - rustc_typeck::check::check_bare_fn::h633487f778296e99
  21:     0x7f9f87d3c247 - rustc_typeck::check::check_item_body::ha7c59baac63cfc16
  22:     0x7f9f87d33888 - rustc_typeck::check::check_item_bodies::hc78013d54503f502
  23:     0x7f9f87d29653 - rustc_typeck::check_crate::hab8b45ac86a97257
  24:     0x7f9f895890d2 - rustc_driver::driver::phase_3_run_analysis_passes::_$u7b$$u7b$closure$u7d$$u7d$::h9ce010bf2f288e62
  25:     0x7f9f89586be5 - rustc::ty::context::TyCtxt::create_and_enter::h6d2f513f498cf199
  26:     0x7f9f8954d461 - rustc_driver::driver::compile_input::h5e5e4501615d7d4b
  27:     0x7f9f895343e0 - rustc_driver::run_compiler::h9bfe8b5b10d5224d
  28:     0x7f9f8953114f - std::panicking::try::call::h66750c51b011e8b9
  29:     0x7f9f8903a81b - __rust_try
  30:     0x7f9f8903a7be - __rust_maybe_catch_panic
  31:     0x7f9f89531cc1 - _<F as alloc..boxed..FnBox<A>>::call_box::h1dabc16042a72ead
  32:     0x7f9f8902b454 - std::sys::thread::Thread::new::thread_start::h00ab25479c85f368
  33:     0x7f9f83919413 - start_thread
  34:     0x7f9f88c78c3c - __clone
  35:                0x0 - <unknown>