Panic when using Self: Send constraint in impl parameter

[xrl]

Panic when trying to enforce Send on a impl parameter of type Self. Panics with meaningful error. Should perhaps just be a regular compiler error?

I tried this code:

pub trait SpawnableTaskTrait<Self: Send> {
    fn spawn(syncy_self: Arc<Mutex<Self>>) where Self: Send {
        let thread_this = syncy_self.clone();

        let signal = Arc::new(AtomicBool::new(false));
        let signal_clone = signal.clone();

        thread::spawn(move || {
            let this = thread_this;

            loop {
                {
                    let mut this = this.lock().unwrap();
                    let res = Self::werk()(&mut this);
                    match res {
                        Ok(_) => continue,
                        Err(err) => {
                            if err.description() == "Resource temporarily unavailable" || err.description() == "operation would block" {
                                continue
                            } else {
                                panic!("omg: {:?}", err)
                            }
                        }
                    }
                }

                if signal_clone.load(Ordering::Relaxed) {
                    break
                }
            }
        });
    }
}

I expected to see this happen: meaningful error or it would work!

Instead, this happened: panic in rustc

Meta

rustc --version --verbose:

Xaviers-MacBook-Pro-2:~ xavierlange$ rustc --version --verbose
rustc 1.13.0-nightly (a7b2232d2 2016-09-07)
binary: rustc
commit-hash: a7b2232d20320dc3b4044a2aec1d51a129e7e17d
commit-date: 2016-09-07
host: x86_64-apple-darwin
release: 1.13.0-nightly

Backtrace:

error: internal compiler error: ../src/librustc_typeck/collect.rs:1925: `Self` should not be the name of a regular parameter

thread 'rustc' panicked at 'Box<Any>', ../src/librustc_errors/lib.rs:590
stack backtrace:
   1:        0x10f45157a - std::sys::backtrace::tracing::imp::write::h46f28e67d38b4637
   2:        0x10f45fc7f - std::panicking::default_hook::{{closure}}::h1d3243f546573ff4
   3:        0x10f45e31d - std::panicking::default_hook::h96c288d728df3ebf
   4:        0x10f45e9b6 - std::panicking::rust_panic_with_hook::hb1322e5f2588b4db
   5:        0x10b102d1b - std::panicking::begin_panic::hb7c71bbc491f561c
   6:        0x10b2347d3 - rustc::session::opt_span_bug_fmt::{{closure}}::h0a2486f2fff54208
   7:        0x10b14b9a9 - rustc::session::span_bug_fmt::heb3fdb6acac8d0c7
   8:        0x10b16483e - <core::iter::Map<I, F> as core::iter::iterator::Iterator>::next::h1ff68e27aab0f019
   9:        0x10b21ab21 - rustc_typeck::collect::generics_of_def_id::h3a0f77e827110638
  10:        0x10b219ba9 - rustc_typeck::collect::trait_def_of_item::hed1ea083432e49c3
  11:        0x10b21547b - rustc_typeck::collect::convert_item::h293968d6650e9d0b
  12:        0x10b20f48e - rustc_typeck::collect::collect_item_types::ha4bc6b2aaead1c12
  13:        0x10b22fff6 - rustc_typeck::check_crate::h279dc52e9bc1b4c2
  14:        0x10b00b324 - rustc_driver::driver::phase_3_run_analysis_passes::{{closure}}::h2b062b0c671cd504
  15:        0x10afe18e7 - rustc_driver::driver::phase_3_run_analysis_passes::h2f1bd27ff2e4d8a0
  16:        0x10afd3c9f - rustc_driver::driver::compile_input::h7dacd98cd2fd7d2b
  17:        0x10affdc48 - rustc_driver::run_compiler::h37c4294ab73436f7
  18:        0x10af410a0 - std::panicking::try::do_call::h4d040997e2efdaf3
  19:        0x10f46685a - __rust_maybe_catch_panic
  20:        0x10af5f394 - <F as alloc::boxed::FnBox<A>>::call_box::hefd1c85fab3e6c31
  21:        0x10f45d194 - std::sys::thread::Thread::new::thread_start::h5b631f48cd23f128
  22:     0x7fff8745099c - _pthread_body
  23:     0x7fff87450919 - _pthread_start

[TimNN]

Reduced:

trait SpawnableTaskTrait<Self: Send> {}

The real error is the first one reported (tested on the latest nightly):

error: expected identifier, found keyword `Self`
 --> selsen_orig.rs:1:30
  |
1 | pub trait SpawnableTaskTrait<Self: Send> {
  |                              ^^^^

nightly-2016-08-16 is still good, nightly-2016-08-18 fails (Changes)

This is a regression from stable to nightly.

Probably an effect of #35605, cc @eddyb.

[eddyb]

Added the actual message to the backtrace in the description. Yeah, what I didn't expect is parser recovery to work, this is minor and easy to fix.