ICE: encountered errors when checking RPITIT refinement (resolution) in rustc_hir_analysis/src/check/compare_impl_item/refine.rs

[cushionbadak]

Code

(hand-reduced)

pub trait A {}

pub trait Mirror {
    type Assoc: ?Sized;
}
impl<T: ?Sized> Mirror for dyn A {
    type Assoc = T;
}

pub trait First {
    async fn first() -> <dyn A + 'static as Mirror>::Assoc;
}

impl First for dyn A {
    async fn first() {}
}

fn main() {}

(original)

pub trait A {}
pub trait B: A {}

pub trait Mirror {
    type Assoc: ?Sized;
}
impl<T: ?Sized> Mirror for A {
    type Assoc = T;
}

pub fn foo<'a>(x: &'a <dyn A + 'static as Mirror>::Assoc) -> &'a <dyn B + 'static as Mirror>::Assoc {
    static
}


#![feature(async_fn_in_trait)]

fn main() {
    let _ = async {
        A.first().await.second().await;
    };
}

pub trait First {
    type Second: Second;
    async fn first(self) -> <dyn A + 'static as Mirror>::Assoc;
}

struct A;

impl First for A {
    type Second = A;
    async fn first(self) -> Self::Second {
        A
    }
}

pub trait Second {
    async fn second(self);
}

impl<C> Second for C
where
    C: First,
{
    async fn second(self) {
        self.first().await.second().await;
    }
}

Meta

rustc --version --verbose:

rustc 1.81.0-nightly (8fcd4dd08 2024-06-18)
binary: rustc
commit-hash: 8fcd4dd08e2ba3e922d917d819ba0be066bdb005
commit-date: 2024-06-18
host: x86_64-apple-darwin
release: 1.81.0-nightly
LLVM version: 18.1.7

Error output

Command: rustc --edition=2021

• I put the option --edition=2021 to remove "async fn" error, but I guess it is not an essential option to trigger ICE.

error[E0207]: the type parameter `T` is not constrained by the impl trait, self type, or predicates
 --> r_rpitit_0773A37F.rs:6:6
  |
6 | impl<T: ?Sized> Mirror for dyn A {
  |      ^ unconstrained type parameter

Backtrace

error: internal compiler error: encountered errors when checking RPITIT refinement (resolution)

thread 'rustc' panicked at compiler/rustc_hir_analysis/src/check/compare_impl_item/refine.rs:177:19:
Box<dyn Any>
stack backtrace:
   0: std::panicking::begin_panic::<rustc_errors::ExplicitBug>
   1: <rustc_errors::diagnostic::BugAbort as rustc_errors::diagnostic::EmissionGuarantee>::emit_producing_guarantee
   2: rustc_hir_analysis::check::compare_impl_item::refine::check_refining_return_position_impl_trait_in_trait
   3: rustc_hir_analysis::check::check::check_impl_items_against_trait
   4: rustc_hir_analysis::check::check::check_item_type
   5: rustc_hir_analysis::check::wfcheck::check_well_formed
      [... omitted 1 frame ...]
   6: rustc_middle::query::plumbing::query_ensure_error_guaranteed::<rustc_query_system::query::caches::VecCache<rustc_hir::hir_id::OwnerId, rustc_middle::query::erase::Erased<[u8; 1]>>, ()>
   7: rustc_hir_analysis::check::wfcheck::check_mod_type_wf
      [... omitted 1 frame ...]
   8: rustc_hir_analysis::check_crate
   9: rustc_interface::passes::run_required_analyses
  10: rustc_interface::passes::analysis
      [... omitted 1 frame ...]
  11: <rustc_interface::queries::QueryResult<&rustc_middle::ty::context::GlobalCtxt>>::enter::<core::result::Result<(), rustc_span::ErrorGuaranteed>, rustc_driver_impl::run_compiler::{closure#0}::{closure#1}::{closure#3}>
  12: rustc_interface::interface::run_compiler::<core::result::Result<(), rustc_span::ErrorGuaranteed>, rustc_driver_impl::run_compiler::{closure#0}>::{closure#1}
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.

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 `/Volumes/T7/workspace/240615_100chaos_tree_combine_typ/icefiles/rustc-ice-2024-06-19T07_28_40-72547.txt` to your bug report

query stack during panic:
#0 [check_well_formed] checking that `<impl at r_rpitit_0773A37F.rs:14:1: 14:21>` is well-formed
#1 [check_mod_type_wf] checking that types are well-formed in top-level module
#2 [analysis] running analysis passes on this crate
end of query stack
error: aborting due to 2 previous errors

For more information about this error, try `rustc --explain E0207`.

Note

• ICE location: compiler/rustc_hir_analysis/src/check/compare_impl_item/refine.rs#L177
  

  rust/compiler/rustc_hir_analysis/src/check/compare_impl_item/refine.rs

  Lines 173 to 178 in 8fcd4dd

  	let Ok((trait_bounds, impl_bounds)) = infcx.fully_resolve((trait_bounds, impl_bounds)) else {
  	// This code path is not reached in any tests, but may be reachable. If
  	// this is triggered, it should be converted to `delayed_bug` and the
  	// triggering case turned into a test.
  	tcx.dcx().bug("encountered errors when checking RPITIT refinement (resolution)");
  	};

[lqd]

@rustbot claim

[GrigorenkoPV]

searched nightlies: from nightly-2022-02-19 to nightly-2024-06-19
regressed nightly: nightly-2024-03-08
searched commit range: 7d3702e...9c3ad80
regressed commit: 8c9a75b (#121154)