rust-lang / rust-lang/rust

ICE: `overflow evaluating the requirement` / `impl was matchable against binder but now it is not`

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A-associated-items A-trait-system C-bug fixed-by-next-solver I-ICE S-bug-has-test S-has-bisection S-has-mcve T-types
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Rust
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Description

Code
trait a {
    type b;
}
impl<c> a for c
where
    c: d,
{
    type b = <(c,) as a>::b;
}
trait d {}
struct e;
impl d for <e as a>::b {}

pub fn main() {}
Meta

rustc --version --verbose:

rustc 1.89.0-nightly (16d2276fa 2025-05-16)
binary: rustc
commit-hash: 16d2276fa6fccb0cc239a542d4c3f0eb46f660ec
commit-date: 2025-05-16
host: x86_64-unknown-linux-gnu
release: 1.89.0-nightly
LLVM version: 20.1.4
Error output
warning: trait `a` should have an upper camel case name
 --> code.rs:1:7
  |
1 | trait a {
  |       ^ help: convert the identifier to upper camel case: `A`
  |
  = note: `#[warn(non_camel_case_types)]` on by default

warning: associated type `b` should have an upper camel case name
 --> code.rs:2:10
  |
2 |     type b;
  |          ^ help: convert the identifier to upper camel case: `B`

warning: type parameter `c` should have an upper camel case name
 --> code.rs:4:6
  |
4 | impl<c> a for c
  |      ^ help: convert the identifier to upper camel case (notice the capitalization): `C`

warning: trait `d` should have an upper camel case name
  --> code.rs:10:7
   |
10 | trait d {}
   |       ^ help: convert the identifier to upper camel case: `D`

warning: type `e` should have an upper camel case name
  --> code.rs:11:8
   |
11 | struct e;
   |        ^ help: convert the identifier to upper camel case: `E`

error[E0275]: overflow evaluating the requirement `(((((((...,),),),),),),): Sized`
 --> code.rs:8:14
  |
8 |     type b = <(c,) as a>::b;
  |              ^^^^^^^^^^^^^^
  |
  = help: consider increasing the recursion limit by adding a `#![recursion_limit = "256"]` attribute to your crate (`code`)
note: required for `(((((((((((((((((((((((((((((((((((((((((((((((((((...,),),),),),),),),),),),),),),),),),),),),),),),),),),),),),),),),),),),),),),),),),),),),),),),),),),)` to implement `a`
 --> code.rs:4:9
  |
4 | impl<c> a for c
  |      -  ^     ^
  |      |
  |      unsatisfied trait bound introduced here
  = note: the full name for the type has been written to 'code.long-type-5344617421428250298.txt'
  = note: consider using `--verbose` to print the full type name to the console
Backtrace 

error: internal compiler error: compiler/rustc_trait_selection/src/traits/select/mod.rs:2463:17: impl DefId(0:11 ~ code[7efa]::{impl#1}) was matchable against Binder { value: TraitPredicate(<((e,),) as d>, polarity:Positive), bound_vars: [] } but now is not


thread 'rustc' panicked at compiler/rustc_trait_selection/src/traits/select/mod.rs:2463:17:
Box<dyn Any>
stack backtrace:
   0:     0x7f6eca165b33 - <std::sys::backtrace::BacktraceLock::print::DisplayBacktrace as core::fmt::Display>::fmt::h8ce760ad42a959df
   1:     0x7f6eca805977 - core::fmt::write::h17deacb9d093717d
   2:     0x7f6ecb85bdd1 - std::io::Write::write_fmt::h8edc637e3ed34e58
   3:     0x7f6eca165992 - std::sys::backtrace::BacktraceLock::print::hf4e931b5b8f47af6
   4:     0x7f6eca16958a - std::panicking::default_hook::{{closure}}::h1aa602af6f79c655
   5:     0x7f6eca16910f - std::panicking::default_hook::hb6d5039bf2b4cecd
   6:     0x7f6ec9194e13 - std[23b1014898398f3a]::panicking::update_hook::<alloc[189bd33173793ff9]::boxed::Box<rustc_driver_impl[c8796dbdb0a790d0]::install_ice_hook::{closure#1}>>::{closure#0}
   7:     0x7f6eca169e03 - std::panicking::rust_panic_with_hook::h1a38b2651d61b684
   8:     0x7f6ec91d1281 - std[23b1014898398f3a]::panicking::begin_panic::<rustc_errors[84d6361680d21c4f]::ExplicitBug>::{closure#0}
   9:     0x7f6ec91c5156 - std[23b1014898398f3a]::sys::backtrace::__rust_end_short_backtrace::<std[23b1014898398f3a]::panicking::begin_panic<rustc_errors[84d6361680d21c4f]::ExplicitBug>::{closure#0}, !>
  10:     0x7f6ec91c513b - std[23b1014898398f3a]::panicking::begin_panic::<rustc_errors[84d6361680d21c4f]::ExplicitBug>
  11:     0x7f6ec91db9f1 - <rustc_errors[84d6361680d21c4f]::diagnostic::BugAbort as rustc_errors[84d6361680d21c4f]::diagnostic::EmissionGuarantee>::emit_producing_guarantee
  12:     0x7f6ec984a14a - rustc_middle[3cba1f9493d37f78]::util::bug::opt_span_bug_fmt::<rustc_span[10508ddd74bd9d4e]::span_encoding::Span>::{closure#0}
  13:     0x7f6ec982394a - rustc_middle[3cba1f9493d37f78]::ty::context::tls::with_opt::<rustc_middle[3cba1f9493d37f78]::util::bug::opt_span_bug_fmt<rustc_span[10508ddd74bd9d4e]::span_encoding::Span>::{closure#0}, !>::{closure#0}
  14:     0x7f6ec98237bb - rustc_middle[3cba1f9493d37f78]::ty::context::tls::with_context_opt::<rustc_middle[3cba1f9493d37f78]::ty::context::tls::with_opt<rustc_middle[3cba1f9493d37f78]::util::bug::opt_span_bug_fmt<rustc_span[10508ddd74bd9d4e]::span_encoding::Span>::{closure#0}, !>::{closure#0}, !>
  15:     0x7f6ec6a87ff0 - rustc_middle[3cba1f9493d37f78]::util::bug::bug_fmt
  16:     0x7f6eca99b058 - <rustc_trait_selection[c3f3da74ab5cc5d9]::traits::select::SelectionContext>::confirm_candidate
  17:     0x7f6ecb2cc36f - <rustc_trait_selection[c3f3da74ab5cc5d9]::traits::fulfill::FulfillProcessor as rustc_data_structures[766a8a49e9a623b6]::obligation_forest::ObligationProcessor>::process_obligation
  18:     0x7f6eca807fd5 - <rustc_data_structures[766a8a49e9a623b6]::obligation_forest::ObligationForest<rustc_trait_selection[c3f3da74ab5cc5d9]::traits::fulfill::PendingPredicateObligation>>::process_obligations::<rustc_trait_selection[c3f3da74ab5cc5d9]::traits::fulfill::FulfillProcessor>
  19:     0x7f6ecafd43ab - <rustc_trait_selection[c3f3da74ab5cc5d9]::traits::fulfill::FulfillmentContext<rustc_trait_selection[c3f3da74ab5cc5d9]::traits::FulfillmentError> as rustc_infer[7388de4d28332a4e]::traits::engine::TraitEngine<rustc_trait_selection[c3f3da74ab5cc5d9]::traits::FulfillmentError>>::select_all_or_error
  20:     0x7f6ecb05fea8 - rustc_hir_analysis[2ff1991ffb30aa1a]::check::wfcheck::check_well_formed
  21:     0x7f6ecb05e90b - rustc_query_impl[efffa611636c8e5b]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[efffa611636c8e5b]::query_impl::check_well_formed::dynamic_query::{closure#2}::{closure#0}, rustc_middle[3cba1f9493d37f78]::query::erase::Erased<[u8; 1usize]>>
  22:     0x7f6ecb05e1b1 - rustc_query_system[194713339954f907]::query::plumbing::try_execute_query::<rustc_query_impl[efffa611636c8e5b]::DynamicConfig<rustc_data_structures[766a8a49e9a623b6]::vec_cache::VecCache<rustc_span[10508ddd74bd9d4e]::def_id::LocalDefId, rustc_middle[3cba1f9493d37f78]::query::erase::Erased<[u8; 1usize]>, rustc_query_system[194713339954f907]::dep_graph::graph::DepNodeIndex>, false, false, false>, rustc_query_impl[efffa611636c8e5b]::plumbing::QueryCtxt, false>
  23:     0x7f6ecb05dca6 - rustc_query_impl[efffa611636c8e5b]::query_impl::check_well_formed::get_query_non_incr::__rust_end_short_backtrace
  24:     0x7f6ecb05b225 - rustc_hir_analysis[2ff1991ffb30aa1a]::check::wfcheck::check_mod_type_wf
  25:     0x7f6ecb05b01f - rustc_query_impl[efffa611636c8e5b]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[efffa611636c8e5b]::query_impl::check_mod_type_wf::dynamic_query::{closure#2}::{closure#0}, rustc_middle[3cba1f9493d37f78]::query::erase::Erased<[u8; 1usize]>>
  26:     0x7f6ecb7fc284 - rustc_query_system[194713339954f907]::query::plumbing::try_execute_query::<rustc_query_impl[efffa611636c8e5b]::DynamicConfig<rustc_query_system[194713339954f907]::query::caches::DefaultCache<rustc_span[10508ddd74bd9d4e]::def_id::LocalModDefId, rustc_middle[3cba1f9493d37f78]::query::erase::Erased<[u8; 1usize]>>, false, false, false>, rustc_query_impl[efffa611636c8e5b]::plumbing::QueryCtxt, false>
  27:     0x7f6ecb7fc011 - rustc_query_impl[efffa611636c8e5b]::query_impl::check_mod_type_wf::get_query_non_incr::__rust_end_short_backtrace
  28:     0x7f6ecaae36ae - rustc_hir_analysis[2ff1991ffb30aa1a]::check_crate
  29:     0x7f6ecac41245 - rustc_interface[88f95fb9e776d181]::passes::run_required_analyses
  30:     0x7f6ecb6f8ade - rustc_interface[88f95fb9e776d181]::passes::analysis
  31:     0x7f6ecb6f8ab5 - rustc_query_impl[efffa611636c8e5b]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[efffa611636c8e5b]::query_impl::analysis::dynamic_query::{closure#2}::{closure#0}, rustc_middle[3cba1f9493d37f78]::query::erase::Erased<[u8; 0usize]>>
  32:     0x7f6ecb6fabba - rustc_query_system[194713339954f907]::query::plumbing::try_execute_query::<rustc_query_impl[efffa611636c8e5b]::DynamicConfig<rustc_query_system[194713339954f907]::query::caches::SingleCache<rustc_middle[3cba1f9493d37f78]::query::erase::Erased<[u8; 0usize]>>, false, false, false>, rustc_query_impl[efffa611636c8e5b]::plumbing::QueryCtxt, false>
  33:     0x7f6ecb6fa88f - rustc_query_impl[efffa611636c8e5b]::query_impl::analysis::get_query_non_incr::__rust_end_short_backtrace
  34:     0x7f6ecb926607 - rustc_interface[88f95fb9e776d181]::passes::create_and_enter_global_ctxt::<core[64e60dbc053b37]::option::Option<rustc_interface[88f95fb9e776d181]::queries::Linker>, rustc_driver_impl[c8796dbdb0a790d0]::run_compiler::{closure#0}::{closure#2}>::{closure#2}::{closure#0}
  35:     0x7f6ecb879ba6 - rustc_interface[88f95fb9e776d181]::interface::run_compiler::<(), rustc_driver_impl[c8796dbdb0a790d0]::run_compiler::{closure#0}>::{closure#1}
  36:     0x7f6ecb8528be - std[23b1014898398f3a]::sys::backtrace::__rust_begin_short_backtrace::<rustc_interface[88f95fb9e776d181]::util::run_in_thread_with_globals<rustc_interface[88f95fb9e776d181]::util::run_in_thread_pool_with_globals<rustc_interface[88f95fb9e776d181]::interface::run_compiler<(), rustc_driver_impl[c8796dbdb0a790d0]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>
  37:     0x7f6ecb852d2b - <<std[23b1014898398f3a]::thread::Builder>::spawn_unchecked_<rustc_interface[88f95fb9e776d181]::util::run_in_thread_with_globals<rustc_interface[88f95fb9e776d181]::util::run_in_thread_pool_with_globals<rustc_interface[88f95fb9e776d181]::interface::run_compiler<(), rustc_driver_impl[c8796dbdb0a790d0]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>::{closure#1} as core[64e60dbc053b37]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  38:     0x7f6ecb85412b - std::sys::pal::unix::thread::Thread::new::thread_start::ha2537cf437130d92
  39:     0x7f6ec56a370a - <unknown>
  40:     0x7f6ec5727aac - <unknown>
  41:                0x0 - <unknown>

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 `/home/matthias/vcs/github/CRED/rustc-ice-2025-05-17T12_23_23-1960773.txt` to your bug report

query stack during panic:
#0 [check_well_formed] checking that `<impl at code.rs:12:1: 12:23>` is well-formed
#1 [check_mod_type_wf] checking that types are well-formed in top-level module
... and 1 other queries... use `env RUST_BACKTRACE=1` to see the full query stack
error: aborting due to 2 previous errors; 5 warnings emitted

For more information about this error, try `rustc --explain E0275`.

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  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Reproduce the supplied code.rs with the reported nightly compiler and inspect compiler/rustc_trait_selection/src/traits/select/mod.rs around line 2463, along with the check_well_formed query stack. Done means the example no longer triggers an internal compiler error and instead produces the intended compiler diagnostic or successfully compiles.

Written by the indexing model from the issue text.

Assessment

Tech stack
rust
Domain
compilers
Issue type
Bug
Difficulty
5/5
Estimated time
Over a week
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
25/100

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