ICE: glacier 65918.rs with -Zmir-opt-level=2

[matthiaskrgr]

Code

Code is from glaciers 65918.rs, original ticket: #65918
The code still ICEs when checking with -Zmir-opt-level=2

#![feature(type_alias_impl_trait)]

use std::marker::PhantomData;

/* copied Index and TryFrom for convinience (and simplicity) */
trait MyIndex<T> {
    type O;
    fn my_index(self) -> Self::O;
}
trait MyFrom<T>: Sized {
    type Error;
    fn my_from(value: T) -> Result<Self, Self::Error>;
}

/* MCVE starts here */
trait F {}
impl F for () {}
type DummyT<T> = impl F;
fn _dummy_t<T>() -> DummyT<T> {}

struct Phantom1<T>(PhantomData<T>);
struct Phantom2<T>(PhantomData<T>);
struct Scope<T>(Phantom2<DummyT<T>>);

impl<T> Scope<T> {
    fn new() -> Self {
        unimplemented!()
    }
}

impl<T> MyFrom<Phantom2<T>> for Phantom1<T> {
    type Error = ();
    fn my_from(_: Phantom2<T>) -> Result<Self, Self::Error> {
        unimplemented!()
    }
}

impl<T: MyFrom<Phantom2<DummyT<U>>>, U> MyIndex<Phantom1<T>> for Scope<U> {
    type O = T;
    fn my_index(self) -> Self::O {
        MyFrom::my_from(self.0).ok().unwrap()
    }
}

fn main() {
    let _pos: Phantom1<DummyT<()>> = Scope::new().my_index();
}

Meta

repo is @ 12799ad

Error output

error: internal compiler error: Encountered error `Unimplemented` selecting `Binder(<T as MyFrom<Phantom2<impl F>>>)` during codegen
  |
  = note: delayed at /home/matthias/vcs/github/rust/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:366:17
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

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/issues/new?labels=C-bug%2C+I-ICE%2C+T-compiler&template=ice.md

note: rustc 1.47.0-dev running on x86_64-unknown-linux-gnu

note: compiler flags: -Z mir-opt-level=2

Backtrace

error: internal compiler error: Encountered error `Unimplemented` selecting `Binder(<T as MyFrom<Phantom2<impl F>>>)` during codegen
  |
  = note: delayed at /home/matthias/vcs/github/rust/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:366:17
stack backtrace:
   0:     0x7f0523b945a0 - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::he42d29a748bbbd1e
   1:     0x7f0523c32a1c - core::fmt::write::hc3de054a6627b208
   2:     0x7f0523bb3753 - std::io::Write::write_fmt::h0f31a08a1acea6c9
   3:     0x7f0523bad080 - std::panicking::default_hook::{{closure}}::h500bdbd0f32aff44
   4:     0x7f0523baccbd - std::panicking::default_hook::h0dc2e03bf7be0812
   5:     0x7f0524c9be69 - rustc_driver::report_ice::h39a24bccd856358c
   6:     0x7f0523bad706 - std::panicking::rust_panic_with_hook::h8248fec3d52a4e49
   7:     0x7f052760554e - std::panicking::begin_panic::h6ec4b207f043b463
   8:     0x7f05275d273e - <rustc_errors::HandlerInner as core::ops::drop::Drop>::drop::h8580a5b14d9a09b5
   9:     0x7f0524b16046 - core::ptr::drop_in_place::h8e2a841ebc57267b
  10:     0x7f0524b1a700 - core::ptr::drop_in_place::hb3d9f649584de58e
  11:     0x7f0524b21e9d - core::ptr::drop_in_place::hf58666ccabfba218
  12:     0x7f0524aea720 - rustc_interface::interface::create_compiler_and_run::ha17d896c1829f0ee
  13:     0x7f0524c5c0de - scoped_tls::ScopedKey<T>::set::he92bf0fa18655a94
  14:     0x7f0524b0315c - std::sys_common::backtrace::__rust_begin_short_backtrace::h04546cabc08d32c7
  15:     0x7f0524c6773e - core::ops::function::FnOnce::call_once{{vtable.shim}}::h9dd17cde02219cce
  16:     0x7f0523baec38 - std::sys::unix::thread::Thread::new::thread_start::h66120da06ca148b6
  17:     0x7f05209af422 - start_thread
  18:     0x7f05239b2bf3 - __clone
  19:                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/issues/new?labels=C-bug%2C+I-ICE%2C+T-compiler&template=ice.md

note: rustc 1.47.0-dev running on x86_64-unknown-linux-gnu

note: compiler flags: -Z mir-opt-level=2

query stack during panic:
end of query stack

[JohnTitor]

Triage: It's now compiled fine with the latest nightly, perhaps it's fixed by #77306.