Broken LLVM with GAT

[DutchGhost]

I tried this code:

#![feature(generic_associated_types)]
trait Fun {
    type F<'a>: ?Sized;
    
    fn identity<'a>(t: &'a Self::F<'a>) -> &'a Self::F<'a> { t }
}

impl <T> Fun for T {
    type F<'a> = i32;
}

fn bug<'a, T: ?Sized + Fun<F = [u8]>>(t: Box<T>) -> &'static T::F<'a> {
    let a = [0; 1];
    let x = T::identity(&a);
    todo!()
}


fn main() {
    let x = 10;
    
    bug(Box::new(x));
}

I expected to see this happen: Throw a bunch of error becouse I wrote wrong types

Instead, this happened: LLVM ERROR: Broken function found, compilation aborted!

Meta

rustc --version --verbose:

1.47.0-nightly (2020-07-22 bbebe7351fcd29af1eb9)

Backtrace

Invalid bitcast
  %10 = bitcast { [0 x i8]*, i64 } %9 to i32*, !dbg !1289
in function _ZN10playground3bug17h799acfa1e8492d55E
LLVM ERROR: Broken function found, compilation aborted!
error: could not compile `playground`.

Note that this issue may be very similar to #68642, which has been solved

[hellow554]

With rustc 1.46.0-nightly (346aec9b0 2020-07-11) I get an ICE

With cargo check I get the ICE below. With cargo build the LLVM ERROR from above 🤔

error: internal compiler error: impl item and trait item have different parameter counts
  |
  = note: delayed at /rustc/346aec9b02f3c74f3fce97fd6bda24709d220e49/src/librustc_session/session.rs:436:27

error: internal compiler error: TyKind::Error constructed but no error reported
  |
  = note: delayed at /rustc/346aec9b02f3c74f3fce97fd6bda24709d220e49/src/librustc_session/session.rs:436:27

thread 'rustc' panicked at 'no errors encountered even though `delay_span_bug` issued', src/librustc_errors/lib.rs:367:17
stack backtrace:
   0:     0x7f5c742468a5 - backtrace::backtrace::libunwind::trace::h34afbfad7fd770fc
                               at /cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.46/src/backtrace/libunwind.rs:86
   1:     0x7f5c742468a5 - backtrace::backtrace::trace_unsynchronized::h460d522b1619a600
                               at /cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.46/src/backtrace/mod.rs:66
   2:     0x7f5c742468a5 - std::sys_common::backtrace::_print_fmt::ha45fac10086813b4
                               at src/libstd/sys_common/backtrace.rs:78
   3:     0x7f5c742468a5 - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::hde84f63fcfd0e6de
                               at src/libstd/sys_common/backtrace.rs:59
   4:     0x7f5c7428332c - core::fmt::write::h540ac4a6a1232abc
                               at src/libcore/fmt/mod.rs:1076
   5:     0x7f5c74238622 - std::io::Write::write_fmt::hc344eafd6e850b4d
                               at src/libstd/io/mod.rs:1537
   6:     0x7f5c7424b740 - std::sys_common::backtrace::_print::h4db88ff15cb5d61d
                               at src/libstd/sys_common/backtrace.rs:62
   7:     0x7f5c7424b740 - std::sys_common::backtrace::print::h5fc39e1b1f610bd3
                               at src/libstd/sys_common/backtrace.rs:49
   8:     0x7f5c7424b740 - std::panicking::default_hook::{{closure}}::h59e55edacb1d974a
                               at src/libstd/panicking.rs:198
   9:     0x7f5c7424b48c - std::panicking::default_hook::heee4c8016dfbf328
                               at src/libstd/panicking.rs:217
  10:     0x7f5c749b6489 - rustc_driver::report_ice::h779cc1b2c44c51e9
  11:     0x7f5c7424beb8 - std::panicking::rust_panic_with_hook::h8405b6301c79fb5a
                               at src/libstd/panicking.rs:530
  12:     0x7f5c77503bde - std::panicking::begin_panic::h6ea7578d4a96992b
  13:     0x7f5c77537892 - <rustc_errors::HandlerInner as core::ops::drop::Drop>::drop::hbf11e6477c5496bc
  14:     0x7f5c749fc746 - core::ptr::drop_in_place::hf14317e84460e945
  15:     0x7f5c749ffdf6 - <alloc::rc::Rc<T> as core::ops::drop::Drop>::drop::hc7ca667378a494ce
  16:     0x7f5c74a145fd - core::ptr::drop_in_place::h04ba5b058b45842d
  17:     0x7f5c74a0ffeb - rustc_span::with_source_map::h276db6bb3fd85930
  18:     0x7f5c74971ae6 - rustc_interface::interface::create_compiler_and_run::h7654f3523c3fe4ef
  19:     0x7f5c7499c35d - scoped_tls::ScopedKey<T>::set::hec735e67099211f0
  20:     0x7f5c749c2542 - std::sys_common::backtrace::__rust_begin_short_backtrace::hc623bbd3fa27b625
  21:     0x7f5c7497f88e - core::ops::function::FnOnce::call_once{{vtable.shim}}::he5d650d3d699089a
  22:     0x7f5c7425ac7a - <alloc::boxed::Box<F> as core::ops::function::FnOnce<A>>::call_once::h13d34828db364579
                               at /rustc/346aec9b02f3c74f3fce97fd6bda24709d220e49/src/liballoc/boxed.rs:1081
  23:     0x7f5c7425ac7a - <alloc::boxed::Box<F> as core::ops::function::FnOnce<A>>::call_once::hd51b619e0f884abf
                               at /rustc/346aec9b02f3c74f3fce97fd6bda24709d220e49/src/liballoc/boxed.rs:1081
  24:     0x7f5c7425ac7a - std::sys::unix::thread::Thread::new::thread_start::h02c6e34c2c73f344
                               at src/libstd/sys/unix/thread.rs:87
  25:     0x7f5c74181422 - start_thread
  26:     0x7f5c7409fbf3 - __GI___clone
  27:                0x0 - <unknown>

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: rustc 1.46.0-nightly (346aec9b0 2020-07-11) running on x86_64-unknown-linux-gnu

note: compiler flags: -C embed-bitcode=no -C debuginfo=2 -C incremental --crate-type bin

note: some of the compiler flags provided by cargo are hidden

query stack during panic:
end of query stack

[hellow554]

At lesat they are introduced at the very same day. Not sure, why the one ICEs and the other one not. Might be worth investigating?

searched toolchains nightly-2019-01-01 through nightly-2020-07-23

Regression in nightly-2019-12-23

fetching https://static.rust-lang.org/dist/2019-12-22/channel-rust-nightly-git-commit-hash.txt
nightly manifest 2019-12-22: 40 B / 40 B [==============================] 100.00 % 485.64 KB/s converted 2019-12-22 to fc5deca2143a448d10a1241a777275e59448c94d
fetching https://static.rust-lang.org/dist/2019-12-23/channel-rust-nightly-git-commit-hash.txt
nightly manifest 2019-12-23: 40 B / 40 B [==============================] 100.00 % 474.24 KB/s converted 2019-12-23 to 9b98af84c4aa66392236fff59c86da2130d46d46
looking for regression commit between 2019-12-22 and 2019-12-23
fetching (via remote github) commits from max(fc5deca2143a448d10a1241a777275e59448c94d, 2019-12-20) to 9b98af84c4aa66392236fff59c86da2130d46d46
ending github query because we found starting sha: fc5deca2143a448d10a1241a777275e59448c94d
get_commits_between returning commits, len: 8
  commit[0] 2019-12-21UTC: Auto merge of #67206 - ehuss:update-cargo-books, r=dtolnay
  commit[1] 2019-12-21UTC: Auto merge of #67495 - Centril:rollup-6aer3xg, r=Centril
  commit[2] 2019-12-22UTC: Auto merge of #66932 - rust-lang:pass-check-runfail, r=petrochenkov
  commit[3] 2019-12-22UTC: Auto merge of #67486 - matthiaskrgr:submodule_upd, r=oli-obk
  commit[4] 2019-12-22UTC: Auto merge of #67505 - Centril:rollup-7win7ty, r=Centril
  commit[5] 2019-12-22UTC: Auto merge of #66931 - cjgillot:hirene-preamble, r=eddyb
  commit[6] 2019-12-22UTC: Auto merge of #65939 - anp:incremental-rustfmt-rollout, r=Mark-Simulacrum
  commit[7] 2019-12-22UTC: Auto merge of #67532 - Centril:rollup-3duj42d, r=Centril
ERROR: no commits between fc5deca2143a448d10a1241a777275e59448c94d and 9b98af84c4aa66392236fff59c86da2130d46d46 within last 167 days

[DutchGhost]

@hellow554 your ice with cargo check seems similar to #68648