ICE: type_alias_impl_trait: panic in a destructor during cleanup

[matthiaskrgr]

Code

#![feature(type_alias_impl_trait)]

trait Trait {
    type Gat<'lt>;
}

fn dyn_hoops<T: Trait>(_: T) -> *const dyn for<'b> Iterator<Item = impl Sized + Captures<'a>> {
    loop {}
}

mod typeck {
    use super::*;
    type Opaque = impl Sized;
    fn define() -> Option<Opaque> {
        let _: Opaque = dyn_hoops::<u8>(0);
        None
    }
}

fn main() {}

Meta

rustc --version --verbose:

rustc 1.82.0-nightly (80eb5a8e9 2024-08-13)
binary: rustc
commit-hash: 80eb5a8e910e5185d47cdefe3732d839c78a5e7e
commit-date: 2024-08-13
host: x86_64-unknown-linux-gnu
release: 1.82.0-nightly
LLVM version: 19.1.0

Error output

error[E0261]: use of undeclared lifetime name `'a`
 --> a.rs:7:90
  |
7 | fn dyn_hoops<T: Trait>(_: T) -> *const dyn for<'b> Iterator<Item = impl Sized + Captures<'a>> {
  |                                                                                          ^^ undeclared lifetime
  |
  = note: for more information on higher-ranked polymorphism, visit https://doc.rust-lang.org/nomicon/hrtb.html
help: consider making the bound lifetime-generic with a new `'a` lifetime
  |
7 | fn dyn_hoops<T: Trait>(_: T) -> *const dyn for<'b> Iterator<Item = impl Sized + for<'a> Captures<'a>> {
  |                                                                                 +++++++
help: consider making the bound lifetime-generic with a new `'a` lifetime
  |
7 | fn dyn_hoops<T: Trait>(_: T) -> *const dyn for<'a, 'b> Iterator<Item = impl Sized + Captures<'a>> {
  |                                                +++
help: consider introducing lifetime `'a` here
  |
7 | fn dyn_hoops<'a, T: Trait>(_: T) -> *const dyn for<'b> Iterator<Item = impl Sized + Captures<'a>> {
  |              +++

error[E0405]: cannot find trait `Captures` in this scope
 --> a.rs:7:81
  |
7 | fn dyn_hoops<T: Trait>(_: T) -> *const dyn for<'b> Iterator<Item = impl Sized + Captures<'a>> {
  |                                                                                 ^^^^^^^^ not found in this scope

Backtrace

thread 'rustc' panicked at core/src/panicking.rs:229:5:
panic in a destructor during cleanup

error: 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: please make sure that you have updated to the latest nightly

note: please attach the file at `/tmp/im/rustc-ice-2024-08-14T16_23_00-896091.txt` to your bug report

query stack during panic:
#0 [typeck] type-checking `typeck::define`
#1 [type_of_opaque] computing type of opaque `typeck::Opaque::{opaque#0}`
#2 [type_of] computing type of `typeck::Opaque::{opaque#0}`
#3 [check_well_formed] checking that `typeck::Opaque::{opaque#0}` is well-formed
#4 [check_mod_type_wf] checking that types are well-formed in module `typeck`
#5 [analysis] running analysis passes on this crate
end of query stack
thread caused non-unwinding panic. aborting.
[1]    896091 IOT instruction  RUST_BACKTRACE=full rustc a.rs

[matthiaskrgr]

Hmm this bisects to #125001 cc @compiler-errors

[matthiaskrgr]

bit smaller

#![feature(type_alias_impl_trait)]

fn dyn_hoops<T: Sized>() -> dyn for<'a> Iterator<Item = impl Captures<'a>> {
    loop {}
}

pub fn main() {
    type Opaque = impl Sized;
    fn define() -> Opaque {
        let x: Opaque = dyn_hoops::<()>(0);
        x
    }
}