ICE unexpected ambiguity: CanonicalQueryInput

[matthiaskrgr]

Summary

RUST_BACKTRACE=full ~/.rustup/toolchains/master/bin/clippy-driver a.rs -Wclippy::pedantic

code

//@ check-pass
//! This is a reproducer for the ICE 6840: https://github.com/rust-lang/rust-clippy/issues/6840.
//! The ICE is caused by `TyCtxt::layout_of` and `is_normalizable` not being strict enough
#![allow(dead_code)]
use std::collections::HashMap;

pub trait Rule {
    type DependencyKey;
}

pub struct RuleEdges<R: Rule> {
    dependencies: R::DependencyKey,
}

type RuleDependencyEdges<R> = HashMap<u32, RuleEdges<R>>;

// reproducer from the GitHub issue ends here
//   but check some additional variants
type RuleDependencyEdgesArray<R> = HashMap<u32, [RuleEdges<R>; 8]>;
type RuleDependencyEdgesSlice<R> = HashMap<u32, &'static [RuleEdges<R>]>;
type RuleDependencyEdgesRef<R> = HashMap<u32, &'static RuleEdges<R>>;
type RuleDependencyEdgesRaw<R> = HashMap<u32, *const RuleEdges<R>>;
type RuleDependencyEdgesTuple<R> = HashMap<u32, (RuleEdges<R>, RuleEdges<R>)>;

// and an additional checks to make sure fix doesn't have stack-overflow issue
//   on self-containing types
pub struct SelfContaining {
    inner: Box<SelfContaining>,
}
type SelfContainingEdges = HashMap<u32, SelfContaining>;

fn main() {}

Version

rustc 1.89.0-nightly (36ad75bce 2025-05-16)
binary: rustc
commit-hash: 36ad75bcebece482b9980c72541469a4a8af9dbb
commit-date: 2025-05-16
host: x86_64-unknown-linux-gnu
release: 1.89.0-nightly
LLVM version: 20.1.4

Error output

Backtrace

warning: you should put bare URLs between `<`/`>` or make a proper Markdown link
--> a.rs:2:44
|
2 | //! This is a reproducer for the ICE 6840: https://github.com/rust-lang/rust-clippy/issues/6840.
|                                            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `<https://github.com/rust-lang/rust-clippy/issues/6840>`
|
= help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#doc_markdown
= note: `-W clippy::doc-markdown` implied by `-W clippy::pedantic`
= help: to override `-W clippy::pedantic` add `#[allow(clippy::doc_markdown)]`

warning: 1 warning emitted

note: no errors encountered even though delayed bugs were created

note: those delayed bugs will now be shown as internal compiler errors

error: internal compiler error: unexpected ambiguity: CanonicalQueryInput { canonical: Canonical { value: ParamEnvAnd { param_env: ParamEnv { caller_bounds: [Binder { value: TraitPredicate(<R as std::marker::Sized>, polarity:Positive), bound_vars: [] }] }, value: AliasTy { args: [RuleEdges<R/#0>], def_id: DefId(2:2442 ~ core[dfa7]::ptr::metadata::Pointee::Metadata), .. } }, max_universe: U0, variables: [] }, typing_mode: PostAnalysis } Canonical { value: QueryResponse { var_values: CanonicalVarValues { var_values: [] }, region_constraints: QueryRegionConstraints { outlives: [] }, certainty: Ambiguous, opaque_types: [], value: NormalizationResult { normalized_ty: ^0 } }, max_universe: U0, variables: [CanonicalVarInfo { kind: Ty(General(U0)) }] }
|
= note: delayed at compiler/rustc_trait_selection/src/traits/query/normalize.rs:288:30
           0: <rustc_errors::DiagCtxtInner>::emit_diagnostic
           1: <rustc_errors::DiagCtxtHandle>::emit_diagnostic
           2: <rustc_span::ErrorGuaranteed as rustc_errors::diagnostic::EmissionGuarantee>::emit_producing_guarantee
           3: <rustc_errors::DiagCtxtHandle>::delayed_bug::<alloc::string::String>
           4: <rustc_trait_selection::traits::query::normalize::QueryNormalizer as rustc_type_ir::fold::FallibleTypeFolder<rustc_middle::ty::context::TyCtxt>>::try_fold_ty
           5: <rustc_traits::normalize_erasing_regions::provide::{closure#0} as core::ops::function::FnOnce<(rustc_middle::ty::context::TyCtxt, rustc_middle::ty::PseudoCanonicalInput<rustc_middle::ty::generic_args::GenericArg>)>>::call_once
           6: rustc_query_impl::plumbing::__rust_begin_short_backtrace::<rustc_query_impl::query_impl::try_normalize_generic_arg_after_erasing_regions::dynamic_query::{closure#2}::{closure#0}, rustc_middle::query::erase::Erased<[u8; 8]>>
           7: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::DynamicConfig<rustc_query_system::query::caches::DefaultCache<rustc_middle::ty::PseudoCanonicalInput<rustc_middle::ty::generic_args::GenericArg>, rustc_middle::query::erase::Erased<[u8; 8]>>, false, false, false>, rustc_query_impl::plumbing::QueryCtxt, false>
           8: rustc_query_impl::query_impl::try_normalize_generic_arg_after_erasing_regions::get_query_non_incr::__rust_end_short_backtrace
           9: <rustc_middle::ty::normalize_erasing_regions::TryNormalizeAfterErasingRegionsFolder as rustc_type_ir::fold::FallibleTypeFolder<rustc_middle::ty::context::TyCtxt>>::try_fold_ty
          10: rustc_ty_utils::layout::layout_of_uncached
          11: rustc_ty_utils::layout::layout_of
          12: rustc_query_impl::plumbing::__rust_begin_short_backtrace::<rustc_query_impl::query_impl::layout_of::dynamic_query::{closure#2}::{closure#0}, rustc_middle::query::erase::Erased<[u8; 16]>>
          13: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::DynamicConfig<rustc_query_system::query::caches::DefaultCache<rustc_middle::ty::PseudoCanonicalInput<rustc_middle::ty::Ty>, rustc_middle::query::erase::Erased<[u8; 16]>>, false, true, false>, rustc_query_impl::plumbing::QueryCtxt, false>
          14: rustc_query_impl::query_impl::layout_of::get_query_non_incr::__rust_end_short_backtrace
          15: rustc_ty_utils::layout::layout_of
          16: rustc_query_impl::plumbing::__rust_begin_short_backtrace::<rustc_query_impl::query_impl::layout_of::dynamic_query::{closure#2}::{closure#0}, rustc_middle::query::erase::Erased<[u8; 16]>>
          17: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::DynamicConfig<rustc_query_system::query::caches::DefaultCache<rustc_middle::ty::PseudoCanonicalInput<rustc_middle::ty::Ty>, rustc_middle::query::erase::Erased<[u8; 16]>>, false, true, false>, rustc_query_impl::plumbing::QueryCtxt, false>
          18: rustc_query_impl::query_impl::layout_of::get_query_non_incr::__rust_end_short_backtrace
          19: <clippy_lints::zero_sized_map_values::ZeroSizedMapValues as rustc_lint::passes::LateLintPass>::check_ty
          20: <rustc_lint::late::LateContextAndPass<rustc_lint::late::RuntimeCombinedLateLintPass> as rustc_hir::intravisit::Visitor>::visit_ty
          21: <rustc_lint::late::LateContextAndPass<rustc_lint::late::RuntimeCombinedLateLintPass> as rustc_hir::intravisit::Visitor>::visit_nested_item
          22: rustc_lint::late::check_crate::{closure#0}
          23: rustc_lint::late::check_crate
          24: rustc_interface::passes::analysis
          25: rustc_query_impl::plumbing::__rust_begin_short_backtrace::<rustc_query_impl::query_impl::analysis::dynamic_query::{closure#2}::{closure#0}, rustc_middle::query::erase::Erased<[u8; 0]>>
          26: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::DynamicConfig<rustc_query_system::query::caches::SingleCache<rustc_middle::query::erase::Erased<[u8; 0]>>, false, false, false>, rustc_query_impl::plumbing::QueryCtxt, false>
          27: rustc_query_impl::query_impl::analysis::get_query_non_incr::__rust_end_short_backtrace
          28: rustc_interface::passes::create_and_enter_global_ctxt::<core::option::Option<rustc_interface::queries::Linker>, rustc_driver_impl::run_compiler::{closure#0}::{closure#2}>::{closure#2}::{closure#0}
          29: rustc_interface::interface::run_compiler::<(), rustc_driver_impl::run_compiler::{closure#0}>::{closure#1}
          30: std::sys::backtrace::__rust_begin_short_backtrace::<rustc_interface::util::run_in_thread_with_globals<rustc_interface::util::run_in_thread_pool_with_globals<rustc_interface::interface::run_compiler<(), rustc_driver_impl::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>
          31: <<std::thread::Builder>::spawn_unchecked_<rustc_interface::util::run_in_thread_with_globals<rustc_interface::util::run_in_thread_pool_with_globals<rustc_interface::interface::run_compiler<(), rustc_driver_impl::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>::{closure#1} as core::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
          32: std::sys::pal::unix::thread::Thread::new::thread_start
          33: <unknown>
          34: <unknown>


note: we would appreciate a bug report: https://github.com/rust-lang/rust-clippy/issues/new?template=ice.yml

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

note: please attach the file at `/tmp/im/rustc-ice-2025-05-16T20_35_29-3540417.txt` to your bug report

query stack during panic:
end of query stack
note: Clippy version: clippy 0.1.89 (36ad75bceb 2025-05-16)

[profetia]

@rustbot claim

[profetia]

Regression of #6840, caused by #14717 @Jarcho

[samueltardieu]

@profetia I'll open a PR for this one, I'd like to get it fixed rapidly