ICE: Normalizing ImplHeader, compiler/rustc_trait_selection/src/traits/project.rs

[chengniansun]

Code

struct ErrorKind;
struct Error(ErrorKind);
impl Fn(&isize) for Error {
    fn from() {}
}

Meta

rustc --version --verbose:

rustc 1.56.0-nightly (2faabf579 2021-07-27)
binary: rustc
commit-hash: 2faabf579323f5252329264cc53ba9ff803429a3
commit-date: 2021-07-27
host: x86_64-unknown-linux-gnu
release: 1.56.0-nightly
LLVM version: 12.0.1

Error output

error[E0407]: method `from` is not a member of trait `Fn`
 --> mutant.rs:4:5
  |
4 |     fn from() {}
  |     ^^^^^^^^^^^^ not a member of trait `Fn`

error[E0601]: `main` function not found in crate `mutant`
 --> mutant.rs:1:1
  |
1 | / struct ErrorKind;
2 | | struct Error(ErrorKind);
3 | | impl Fn(&isize) for Error {
4 | |     fn from() {}
5 | | }
  | |_^ consider adding a `main` function to `mutant.rs`

error[E0229]: associated type bindings are not allowed here
 --> mutant.rs:3:6
  |
3 | impl Fn(&isize) for Error {
  |      ^^^^^^^^^^ associated type not allowed here

thread 'rustc' panicked at 'Normalizing ImplHeader { impl_def_id: DefId(0:8 ~ mutant[57b0]::{impl#0}), self_ty: Error, trait_ref: Some(<Error as std::ops::Fn<(&isize,)>>), predicates: [] } without wrapping in a `Binder`', compiler/rustc_trait_selection/src/traits/project.rs:332:9
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 1.56.0-nightly (2faabf579 2021-07-27) running on x86_64-unknown-linux-gnu

query stack during panic:
#0 [specialization_graph_of] building specialization graph of trait `std::ops::Fn`
#1 [coherent_trait] coherence checking all impls of trait `std::ops::Fn`
end of query stack
error: aborting due to 3 previous errors

Some errors have detailed explanations: E0229, E0407, E0601.
For more information about an error, try `rustc --explain E0229`.

Backtrace

error[E0407]: method `from` is not a member of trait `Fn`
 --> mutant.rs:4:5
  |
4 |     fn from() {}
  |     ^^^^^^^^^^^^ not a member of trait `Fn`

error[E0601]: `main` function not found in crate `mutant`
 --> mutant.rs:1:1
  |
1 | / struct ErrorKind;
2 | | struct Error(ErrorKind);
3 | | impl Fn(&isize) for Error {
4 | |     fn from() {}
5 | | }
  | |_^ consider adding a `main` function to `mutant.rs`

error[E0229]: associated type bindings are not allowed here
 --> mutant.rs:3:6
  |
3 | impl Fn(&isize) for Error {
  |      ^^^^^^^^^^ associated type not allowed here

thread 'rustc' panicked at 'Normalizing ImplHeader { impl_def_id: DefId(0:8 ~ mutant[57b0]::{impl#0}), self_ty: Error, trait_ref: Some(<Error as std::ops::Fn<(&isize,)>>), predicates: [] } without wrapping in a `Binder`', compiler/rustc_trait_selection/src/traits/project.rs:332:9
stack backtrace:
   0: rust_begin_unwind
             at /rustc/2faabf579323f5252329264cc53ba9ff803429a3/library/std/src/panicking.rs:515:5
   1: std::panicking::begin_panic_fmt
             at /rustc/2faabf579323f5252329264cc53ba9ff803429a3/library/std/src/panicking.rs:457:5
   2: rustc_trait_selection::traits::project::AssocTypeNormalizer::fold
   3: rustc_trait_selection::traits::project::normalize
   4: rustc_trait_selection::traits::coherence::with_fresh_ty_vars
   5: rustc_trait_selection::traits::coherence::overlap_within_probe
   6: rustc_infer::infer::InferCtxtBuilder::enter
   7: rustc_trait_selection::traits::coherence::overlapping_impls
   8: <rustc_middle::traits::specialization_graph::Children as rustc_trait_selection::traits::specialize::specialization_graph::ChildrenExt>::insert
   9: <rustc_middle::traits::specialization_graph::Graph as rustc_trait_selection::traits::specialize::specialization_graph::GraphExt>::insert
  10: rustc_trait_selection::traits::specialize::specialization_graph_provider
  11: rustc_query_system::query::plumbing::get_query_impl
  12: <rustc_query_impl::Queries as rustc_middle::ty::query::QueryEngine>::specialization_graph_of
  13: rustc_typeck::coherence::coherent_trait
  14: rustc_query_system::query::plumbing::get_query_impl
  15: <rustc_query_impl::Queries as rustc_middle::ty::query::QueryEngine>::coherent_trait
  16: rustc_session::session::Session::track_errors
  17: rustc_typeck::check_crate
  18: rustc_interface::passes::analysis
  19: rustc_query_system::query::plumbing::get_query_impl
  20: <rustc_query_impl::Queries as rustc_middle::ty::query::QueryEngine>::analysis
  21: rustc_interface::queries::<impl rustc_interface::interface::Compiler>::enter
  22: rustc_span::with_source_map
  23: rustc_interface::interface::create_compiler_and_run
  24: scoped_tls::ScopedKey<T>::set
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose 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 1.56.0-nightly (2faabf579 2021-07-27) running on x86_64-unknown-linux-gnu

query stack during panic:
#0 [specialization_graph_of] building specialization graph of trait `std::ops::Fn`
#1 [coherent_trait] coherence checking all impls of trait `std::ops::Fn`
#2 [analysis] running analysis passes on this crate
end of query stack
error: aborting due to 3 previous errors

Some errors have detailed explanations: E0229, E0407, E0601.
For more information about an error, try `rustc --explain E0229`.

[jackh726]

So, #85499 will fix this ICE. But the coherence code should probably not be passing escaping bound vars to begin with.

As for prioritization, this is an ICE that occurs only after an error that, if fixed, will solve the ICE. I say low or medium.

[apiraino]

Assigning priority as discussed in the Zulip thread of the Prioritization Working Group.

@rustbot label -I-prioritize +P-low

[jackh726]

#85499 didn't fix this ICE; it's actually different than others and utterly broken (as expected)

[Alexendoo]

No longer ICEs since #92441