ICE when break and enum variants mixed in `match` arms

[KeenS]

I tried this code:

enum A {
    A1,
    A2,
    A3,
}

enum B {
    B1(String, String),
    B2(String, String),
}


fn consume_b(_b: B) {}

fn main() {
    let a = A::A1;
    loop {
        let ctor = match a {
            A3 => break,
            A1 => B::B1,
            A2 => B::B2,
        };
        consume_b(ctor("1".into(), "2".into()));
        break;
    }
}

then, rustc crashes with this message.

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 'assertion failed: !self.tables.borrow().adjustments.contains_key(&expr.id)', /buildslave/rust-buildbot/slave/stable-dist-rustc-linux/build/src/librustc_typeck/check/coercion.rs:695
stack backtrace:
   1:     0x7f363c0fe40c - std::sys::imp::backtrace::tracing::imp::write::hf33ae72d0baa11ed
                        at /buildslave/rust-buildbot/slave/stable-dist-rustc-linux/build/src/libstd/sys/unix/backtrace/tracing/gcc_s.rs:42
   2:     0x7f363c10c9ae - std::panicking::default_hook::{{closure}}::h59672b733cc6a455
                        at /buildslave/rust-buildbot/slave/stable-dist-rustc-linux/build/src/libstd/panicking.rs:351
   3:     0x7f363c10c553 - std::panicking::default_hook::h1670459d2f3f8843
                        at /buildslave/rust-buildbot/slave/stable-dist-rustc-linux/build/src/libstd/panicking.rs:361
   4:     0x7f363c10ce4b - std::panicking::rust_panic_with_hook::hcf0ddb069e7beee7
                        at /buildslave/rust-buildbot/slave/stable-dist-rustc-linux/build/src/libstd/panicking.rs:555
   5:     0x7f363aa3e1af - std::panicking::begin_panic::he1a21c7d2bfbc925
   6:     0x7f363aaa557b - rustc_typeck::check::_match::<impl rustc_typeck::check::FnCtxt<'a, 'gcx, 'tcx>>::check_match::h9b6e1aca41975d59
   7:     0x7f363ab1c936 - rustc_typeck::check::FnCtxt::check_expr_kind::h34a8082c3fb5738a
   8:     0x7f363ab1c1ed - rustc_typeck::check::FnCtxt::check_expr_with_expectation_and_lvalue_pref::h7ef9ef0888ee8a49
   9:     0x7f363ab2dbdd - rustc_typeck::check::FnCtxt::check_decl_initializer::haaea47c4d358654e
  10:     0x7f363ab2dce4 - rustc_typeck::check::FnCtxt::check_decl_local::h1b35be9466600360
  11:     0x7f363ab2e016 - rustc_typeck::check::FnCtxt::check_stmt::h432c28cb9771ab73
  12:     0x7f363ab2e36e - rustc_typeck::check::FnCtxt::check_block_with_expected::h5a97aba5369a0e70
  13:     0x7f363ab1c7db - rustc_typeck::check::FnCtxt::check_expr_kind::h34a8082c3fb5738a
  14:     0x7f363ab1c1ed - rustc_typeck::check::FnCtxt::check_expr_with_expectation_and_lvalue_pref::h7ef9ef0888ee8a49
  15:     0x7f363ab2e3b7 - rustc_typeck::check::FnCtxt::check_block_with_expected::h5a97aba5369a0e70
  16:     0x7f363ab1c62e - rustc_typeck::check::FnCtxt::check_expr_kind::h34a8082c3fb5738a
  17:     0x7f363ab1c1ed - rustc_typeck::check::FnCtxt::check_expr_with_expectation_and_lvalue_pref::h7ef9ef0888ee8a49
  18:     0x7f363ab02671 - rustc_typeck::check::check_fn::ha6fc77ffa200fbd2
  19:     0x7f363ab01684 - rustc_typeck::check::check_bare_fn::h9f0916104d636ee0
  20:     0x7f363aafe875 - rustc_typeck::check::check_item_bodies::hd9e8c6a8692f314b
  21:     0x7f363ab6c497 - rustc_typeck::check_crate::h8c159f70d1009b33
  22:     0x7f363c4aacd7 - rustc_driver::driver::phase_3_run_analysis_passes::{{closure}}::h040eea107b0d299b
  23:     0x7f363c4a76c6 - rustc_driver::driver::phase_3_run_analysis_passes::haec055f3322a38aa
  24:     0x7f363c48b150 - rustc_driver::driver::compile_input::hd9f060ee16a643fb
  25:     0x7f363c4d5844 - rustc_driver::run_compiler::h762802568c0e140e
  26:     0x7f363c3e1edb - std::panicking::try::do_call::h935e2f773deaf841
  27:     0x7f363c115c8a - __rust_maybe_catch_panic
                        at /buildslave/rust-buildbot/slave/stable-dist-rustc-linux/build/src/libpanic_unwind/lib.rs:98
  28:     0x7f363c40a112 - <F as alloc::boxed::FnBox<A>>::call_box::he43811d1f6894655
  29:     0x7f363c10b804 - std::sys::imp::thread::Thread::new::thread_start::he668872ac11287ba
                        at /buildslave/rust-buildbot/slave/stable-dist-rustc-linux/build/src/liballoc/boxed.rs:624
                        at /buildslave/rust-buildbot/slave/stable-dist-rustc-linux/build/src/libstd/sys_common/thread.rs:21
                        at /buildslave/rust-buildbot/slave/stable-dist-rustc-linux/build/src/libstd/sys/unix/thread.rs:84
  30:     0x7f3634bc66c9 - start_thread
  31:     0x7f363bdc50ae - __clone
  32:                0x0 - <unknown>

Meta

rustc --version --verbose:

rustc 1.16.0 (30cf806ef 2017-03-10)
binary: rustc
commit-hash: 30cf806ef8881c41821fbd43e5cf3699c5290c16
commit-date: 2017-03-10
host: x86_64-unknown-linux-gnu
release: 1.16.0
LLVM version: 3.9

Note

• When the break arm isn't the first, ICE doesn't occur.
• When the arms are only 2, ICE doesn't occure

[TimNN]

This was introduced between 1.11 and 1.12.

[eddyb]

cc @nikomatsakis @canndrew This looks like it has something to do with the ! -> _ coercion.

[arielb1]

looking at it.

[nikomatsakis]

Indeed, probably something I introduced.

[nikomatsakis]

@arielb1 are you going to have time to investigate, or you want me to?

[arielb1]

@nikomatsakis

Sorry. Was busy yesterday. I'll look at it today or tommorow.

[arielb1]

Wrong comment:

                    // No adjustments can produce a fn item, so this should never trip.