unexpected panic `unexpected ambiguity` at 'try_normalize_generic_arg_after_erasing_regions' query

[gmoshkin]

I'm running cargo clippy (Clippy version: clippy 0.1.65 (897e375 2022-11-02)) on my library and it panics.

The message is something like:
error: internal compiler error: compiler/rustc_trait_selection/src/traits/query/normalize.rs:258:21: unexpected ambiguity: Canonical { .. } (see bellow for more details)

Reproduce

Here's a link to my project and the commit on which clippy panics:
https://git.picodata.io/picodata/picodata/tarantool-module/-/commit/d417c97904ac614b577478df0b6aaaa5174a22c2

Simply do:

git clone https://git.picodata.io/picodata/picodata/tarantool-module.git
cd tarantool-module
git checkout d417c97904ac614b577478df0b6aaaa5174a22c2
cargo clippy

You'll get this:

    Updating crates.io index
   Compiling tlua-derive v0.1.3 (/home/gmoshkin/code/pd/tm3/tlua-derive)
   Compiling tarantool-proc v0.1.2 (/home/gmoshkin/code/pd/tm3/tarantool-proc)
    Checking tlua v0.6.3 (/home/gmoshkin/code/pd/tm3/tlua)
    Checking tarantool v0.6.4 (/home/gmoshkin/code/pd/tm3/tarantool)
    Checking easy v0.1.0 (/home/gmoshkin/code/pd/tm3/examples/easy)
    Checking harder v0.1.0 (/home/gmoshkin/code/pd/tm3/examples/harder)
    Checking read v0.1.0 (/home/gmoshkin/code/pd/tm3/examples/read)
    Checking tarantool-module-test-runner v0.1.0 (/home/gmoshkin/code/pd/tm3/tests)
    Checking hardest v0.1.0 (/home/gmoshkin/code/pd/tm3/examples/hardest)
    Checking write v0.1.0 (/home/gmoshkin/code/pd/tm3/examples/write)
warning: lint `clippy::blacklisted_name` has been renamed to `clippy::disallowed_names`
 --> tests/src/lib.rs:2:10
  |
2 | #![allow(clippy::blacklisted_name)]
  |          ^^^^^^^^^^^^^^^^^^^^^^^^ help: use the new name: `clippy::disallowed_names`
  |
  = note: `#[warn(renamed_and_removed_lints)]` on by default

warning: deref which would be done by auto-deref
  --> tests/src/bench_bulk_insert.rs:59:31
   |
59 |                         text: &*text.borrow(),
   |                               ^^^^^^^^^^^^^^^ help: try this: `&text.borrow()`
   |
   = note: `#[warn(clippy::explicit_auto_deref)]` on by default
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#explicit_auto_deref

error: internal compiler error: compiler/rustc_trait_selection/src/traits/query/normalize.rs:258:21: unexpected ambiguity: Canonical { max_universe: U0, variables: [], value: ParamEnvAnd { param_env: ParamEnv { caller_bounds: [], reveal: UserFacing, constness: NotConst }, value: ProjectionTy { substs: [tarantool::tlua::Function<fn() -> std::result::Result<i32, &str>, (), std::result::Result<i32, &str>>], item_def_id: DefId(33:1837 ~ tlua[df0d]::PushInto::Err) } } } Canonical { max_universe: U1, variables: [CanonicalVarInfo { kind: Region(U1) }, CanonicalVarInfo { kind: PlaceholderRegion(Placeholder { universe: U1, name: BrNamed(DefId(33:3158 ~ tlua[df0d]::functions_write::{impl#75}::'p), 'p) }) }, CanonicalVarInfo { kind: Region(U1) }], value: QueryResponse { var_values: CanonicalVarValues { var_values: [] }, region_constraints: QueryRegionConstraints { outlives: [(Binder(OutlivesPredicate(ReLateBound(DebruijnIndex(1), BoundRegion { var: 0, kind: BrAnon(0) }), ReLateBound(DebruijnIndex(1), BoundRegion { var: 1, kind: BrAnon(1) })), []), BoringNoLocation), (Binder(OutlivesPredicate(ReLateBound(DebruijnIndex(1), BoundRegion { var: 2, kind: BrAnon(2) }), ReErased), []), BoringNoLocation), (Binder(OutlivesPredicate(ReLateBound(DebruijnIndex(1), BoundRegion { var: 1, kind: BrAnon(1) }), ReLateBound(DebruijnIndex(1), BoundRegion { var: 0, kind: BrAnon(0) })), []), BoringNoLocation), (Binder(OutlivesPredicate(ReErased, ReLateBound(DebruijnIndex(1), BoundRegion { var: 2, kind: BrAnon(2) })), []), BoringNoLocation), (Binder(OutlivesPredicate(fn() -> std::result::Result<i32, &str>, ReStatic), []), BoringNoLocation), (Binder(OutlivesPredicate(std::result::Result<i32, &str>, ReStatic), []), BoringNoLocation)], member_constraints: [] }, certainty: Ambiguous, opaque_types: [], value: NormalizationResult { normalized_ty: tarantool::tlua::Void } } }

thread 'rustc' panicked at 'Box<dyn Any>', /rustc/897e37553bba8b42751c67658967889d11ecd120/compiler/rustc_errors/src/lib.rs:1462:9
stack backtrace:
   0: std::panicking::begin_panic::<rustc_errors::ExplicitBug>
   1: std::panic::panic_any::<rustc_errors::ExplicitBug>
   2: <rustc_errors::HandlerInner>::bug::<&alloc::string::String>
   3: <rustc_errors::Handler>::bug::<&alloc::string::String>
   4: rustc_middle::ty::context::tls::with_context_opt::<rustc_middle::ty::context::tls::with_opt<rustc_middle::util::bug::opt_span_bug_fmt<rustc_span::span_encoding::Span>::{closure#0}, ()>::{closure#0}, ()>
   5: rustc_middle::util::bug::opt_span_bug_fmt::<rustc_span::span_encoding::Span>
   6: rustc_middle::util::bug::bug_fmt
   7: <rustc_trait_selection::traits::query::normalize::QueryNormalizer as rustc_middle::ty::fold::FallibleTypeFolder>::try_fold_ty
   8: <rustc_infer::infer::InferCtxtBuilder>::enter::<core::result::Result<rustc_middle::ty::subst::GenericArg, rustc_middle::traits::query::NoSolution>, rustc_traits::normalize_erasing_regions::try_normalize_after_erasing_regions<rustc_middle::ty::subst::GenericArg>::{closure#0}>
   9: <rustc_traits::normalize_erasing_regions::provide::{closure#0} as core::ops::function::FnOnce<(rustc_middle::ty::context::TyCtxt, rustc_middle::ty::ParamEnvAnd<rustc_middle::ty::subst::GenericArg>)>>::call_once
  10: <rustc_query_system::dep_graph::graph::DepGraph<rustc_middle::dep_graph::dep_node::DepKind>>::with_task::<rustc_middle::ty::context::TyCtxt, rustc_middle::ty::ParamEnvAnd<rustc_middle::ty::subst::GenericArg>, core::result::Result<rustc_middle::ty::subst::GenericArg, rustc_middle::traits::query::NoSolution>>
  11: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::plumbing::QueryCtxt, rustc_query_system::query::caches::DefaultCache<rustc_middle::ty::ParamEnvAnd<rustc_middle::ty::subst::GenericArg>, core::result::Result<rustc_middle::ty::subst::GenericArg, rustc_middle::traits::query::NoSolution>>>
  12: <rustc_query_impl::Queries as rustc_middle::ty::query::QueryEngine>::try_normalize_generic_arg_after_erasing_regions
  13: <rustc_middle::ty::normalize_erasing_regions::TryNormalizeAfterErasingRegionsFolder as rustc_middle::ty::fold::FallibleTypeFolder>::try_fold_ty
  14: clippy_lints::dereference::needless_borrow_impl_arg_position
  15: <&mut clippy_lints::dereference::walk_parents::{closure#0} as core::ops::function::FnMut<(rustc_hir::hir::Node, rustc_hir::hir_id::HirId)>>::call_mut
  16: clippy_utils::walk_to_expr_usage::<clippy_lints::dereference::Position, &mut clippy_lints::dereference::walk_parents::{closure#0}>
  17: <clippy_lints::dereference::Dereferencing as rustc_lint::passes::LateLintPass>::check_expr
  18: <rustc_lint::early::EarlyLintPassObjects as rustc_lint::passes::EarlyLintPass>::check_generic_arg
  19: <rustc_lint::late::LateContextAndPass<rustc_lint::late::LateLintPassObjects> as rustc_hir::intravisit::Visitor>::visit_expr
  20: rustc_hir::intravisit::walk_expr::<rustc_lint::late::LateContextAndPass<rustc_lint::late::LateLintPassObjects>>
  21: <rustc_lint::late::LateContextAndPass<rustc_lint::late::LateLintPassObjects> as rustc_hir::intravisit::Visitor>::visit_expr
  22: rustc_hir::intravisit::walk_block::<rustc_lint::late::LateContextAndPass<rustc_lint::late::LateLintPassObjects>>
  23: <rustc_lint::late::LateContextAndPass<rustc_lint::late::LateLintPassObjects> as rustc_hir::intravisit::Visitor>::visit_block
  24: <rustc_lint::late::LateContextAndPass<rustc_lint::late::LateLintPassObjects> as rustc_hir::intravisit::Visitor>::visit_expr
  25: <rustc_lint::late::LateContextAndPass<rustc_lint::late::LateLintPassObjects> as rustc_hir::intravisit::Visitor>::visit_nested_body
  26: <rustc_lint::late::LateContextAndPass<rustc_lint::late::LateLintPassObjects> as rustc_hir::intravisit::Visitor>::visit_fn
  27: rustc_hir::intravisit::walk_item::<rustc_lint::late::LateContextAndPass<rustc_lint::late::LateLintPassObjects>>
  28: <rustc_lint::late::LateContextAndPass<rustc_lint::late::LateLintPassObjects> as rustc_hir::intravisit::Visitor>::visit_nested_item
  29: rustc_hir::intravisit::walk_mod::<rustc_lint::late::LateContextAndPass<rustc_lint::late::LateLintPassObjects>>
  30: <rustc_lint::late::LateContextAndPass<rustc_lint::late::LateLintPassObjects> as rustc_hir::intravisit::Visitor>::visit_nested_item
  31: rustc_hir::intravisit::walk_mod::<rustc_lint::late::LateContextAndPass<rustc_lint::late::LateLintPassObjects>>
  32: <rustc_lint::late::LateContextAndPass<rustc_lint::late::LateLintPassObjects> as rustc_hir::intravisit::Visitor>::visit_nested_item
  33: rustc_hir::intravisit::walk_mod::<rustc_lint::late::LateContextAndPass<rustc_lint::late::LateLintPassObjects>>
  34: rustc_lint::late::late_lint_pass_crate::<rustc_lint::late::LateLintPassObjects>
  35: rustc_lint::late::late_lint_crate::<rustc_lint::BuiltinCombinedLateLintPass>
  36: <rustc_session::session::Session>::time::<(), rustc_lint::late::check_crate<rustc_lint::BuiltinCombinedLateLintPass, rustc_interface::passes::analysis::{closure#5}::{closure#1}::{closure#2}::{closure#0}::{closure#0}>::{closure#0}::{closure#0}>
  37: <rustc_session::session::Session>::time::<(), rustc_interface::passes::analysis::{closure#5}::{closure#1}::{closure#2}::{closure#0}>
  38: <core::panic::unwind_safe::AssertUnwindSafe<rustc_interface::passes::analysis::{closure#5}::{closure#1}> as core::ops::function::FnOnce<()>>::call_once
  39: <rustc_session::session::Session>::time::<(), rustc_interface::passes::analysis::{closure#5}>
  40: rustc_interface::passes::analysis
  41: <rustc_query_system::dep_graph::graph::DepGraph<rustc_middle::dep_graph::dep_node::DepKind>>::with_task::<rustc_mi
ddle::ty::context::TyCtxt, (), core::result::Result<(), rustc_errors::ErrorGuaranteed>>
  42: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::plumbing::QueryCtxt, rustc_query_system::query::caches::DefaultCache<(), core::result::Result<(), rustc_errors::ErrorGuaranteed>>>
  43: rustc_query_system::query::plumbing::get_query::<rustc_query_impl::queries::analysis, rustc_query_impl::plumbing::QueryCtxt>
  44: <rustc_interface::passes::QueryContext>::enter::<rustc_driver::run_compiler::{closure#1}::{closure#2}::{closure#3}, core::result::Result<(), rustc_errors::ErrorGuaranteed>>
  45: rustc_interface::interface::create_compiler_and_run::<core::result::Result<(), rustc_errors::ErrorGuaranteed>, rustc_driver::run_compiler::{closure#1}>
  46: <scoped_tls::ScopedKey<rustc_span::SessionGlobals>>::set::<rustc_interface::interface::run_compiler<core::result::Result<(), rustc_errors::ErrorGuaranteed>, rustc_driver::run_compiler::{closure#1}>::{closure#0}, core::result::Result<(), rustc_errors::ErrorGuaranteed>>
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.

note: the compiler unexpectedly panicked. this is a bug.

note: we would appreciate a bug report: https://github.com/rust-lang/rust-clippy/issues/new

note: Clippy version: clippy 0.1.65 (897e375 2022-11-02)

query stack during panic:
#0 [try_normalize_generic_arg_after_erasing_regions] normalizing `tlua::PushInto::Err`
#1 [analysis] running analysis passes on this crate
end of query stack
warning: `tarantool-module-test-runner` (lib) generated 2 warnings
error: could not compile `tarantool-module-test-runner`; 2 warnings emitted

Can't add any more context at this point

[e-ivkov]

In 1.64 and earlier versions cargo clippy seems to work fine on this tarantool-module commit. This panic starts only on 1.65

[e-ivkov]

Also interestingly it doesn't panic if we give it cargo clippy --tests flag

[smoelius]

From what I can tell, either one of these triggers the error (I don't understand why, though):

• https://git.picodata.io/picodata/picodata/tarantool-module/-/blob/d417c97904ac614b577478df0b6aaaa5174a22c2/tests/src/tlua/functions_write.rs#L68
• https://git.picodata.io/picodata/picodata/tarantool-module/-/blob/d417c97904ac614b577478df0b6aaaa5174a22c2/tests/src/tlua/values.rs#L877

Also, here is where the error is triggered within the compiler:
https://github.com/rust-lang/rust/blob/02b64c5d2689fad8360d83f3bcd58f5dbbd2f303/compiler/rustc_trait_selection/src/traits/query/normalize.rs#L268-L271

[gmoshkin]

@smoelius yes, the panic goes away for me if I remove the & on line https://git.picodata.io/picodata/picodata/tarantool-module/-/blob/d417c97904ac614b577478df0b6aaaa5174a22c2/tests/src/tlua/functions_write.rs#L68
like this:

     let f: function![() -> Result<i32, &'static str>] = function0(always_fails);
-    lua.set("always_fails", &f);
+    lua.set("always_fails", f);

Thus changing the deduced generic argument to the Lua::set function

But what I noticed is that it also goes aways if I change the signature of Lua::set (defined at https://git.picodata.io/picodata/picodata/tarantool-module/-/blob/d417c97904ac614b577478df0b6aaaa5174a22c2/tlua/src/lib.rs#L1281) in a seemingly unrelated way:

-    pub fn set<'lua, I, V, E>(&'lua self, index: I, value: V)
+    pub fn set<'lua, I, V>(&'lua self, index: I, value: V)
     where
         I: Borrow<str>,
-        V: PushOneInto<&'lua Self, Err = E>,
-        E: Into<Void>,
+        V: PushOneInto<&'lua Self>,
+        <V as PushInto<&'lua Self>>::Err: Into<Void>,

Not sure if this is of any help

[matthiaskrgr]

Getting the same ICE when running clippy on the git-repository gitoxide crate :/