panicked at 'mismatched kinds in substitution`, chalk-ir-0.82.0/src/fold/subst.rs:109:22

[Dirbaio]

Create a new crate, paste the following into lib.rs:

#![feature(generic_associated_types)]

pub trait Driver {}

pub trait OutType {
    type Reader<D: Driver>;
}

pub enum Out<const OUT_N: usize> {}
impl<const OUT_N: usize> OutType for Out<OUT_N> {
    type Reader<D: Driver> = ();
}

pub struct HidClass<D: Driver, OUT: OutType> {
    output: OUT::Reader<D>,
}

impl<D: Driver> HidClass<D, Out<4>> {
    pub fn new() -> Self {
        Self { output: () }
    }
}

Then try to hover stuff, for example Self. This causes errors like:

thread '<unnamed>' panicked at 'mismatched kinds in substitution', /home/runner/.cargo/registry/src/github.com-1ecc6299db9ec823/chalk-ir-0.82.0/src/fold/subst.rs:109:22
stack backtrace:
   0: std::panicking::begin_panic
   1: <chalk_ir::fold::subst::Subst<I> as chalk_ir::fold::Folder<I>>::fold_free_var_const
   2: <chalk_ir::Const<I> as chalk_ir::fold::SuperFold<I>>::super_fold_with
   3: chalk_ir::fold::boring_impls::<impl chalk_ir::fold::Fold<I> for chalk_ir::GenericArg<I>>::fold_with
   4: <smallvec::SmallVec<A> as core::iter::traits::collect::Extend<<A as smallvec::Array>::Item>>::extend
   5: chalk_ir::fold::boring_impls::<impl chalk_ir::fold::Fold<I> for chalk_ir::Substitution<I>>::fold_with
   6: <chalk_ir::Ty<I> as chalk_ir::fold::SuperFold<I>>::super_fold_with
   7: chalk_ir::fold::boring_impls::<impl chalk_ir::fold::Fold<I> for chalk_ir::GenericArg<I>>::fold_with
   8: <smallvec::SmallVec<A> as core::iter::traits::collect::Extend<<A as smallvec::Array>::Item>>::extend
   9: chalk_ir::fold::boring_impls::<impl chalk_ir::fold::Fold<I> for chalk_ir::Substitution<I>>::fold_with
  10: chalk_ir::fold::subst::Subst<I>::apply
  11: chalk_ir::Binders<T>::substitute
  12: chalk_solve::split::Split::impl_parameters_and_projection_from_associated_ty_value
  13: chalk_solve::clauses::builder::ClauseBuilder<I>::push_binders
  14: chalk_solve::clauses::push_program_clauses_for_associated_type_values_in_impls_of
  15: chalk_recursive::solve::SolveIterationHelpers::solve_from_clauses
  16: chalk_recursive::solve::SolveIteration::solve_iteration
  17: chalk_recursive::fixed_point::RecursiveContext<K,V>::solve_goal
  18: chalk_recursive::fulfill::Fulfill<I,Solver>::prove
  19: chalk_recursive::fulfill::Fulfill<I,Solver>::solve
  20: chalk_recursive::solve::SolveIterationHelpers::solve_from_clauses
  21: chalk_recursive::solve::SolveIteration::solve_iteration
  22: chalk_recursive::fixed_point::RecursiveContext<K,V>::solve_goal
  23: chalk_recursive::fixed_point::RecursiveContext<K,V>::solve_root_goal
  24: <hir_ty::db::TraitSolveQueryQuery as salsa::plumbing::QueryFunction>::execute
  25: salsa::runtime::Runtime::execute_query_implementation
  26: salsa::derived::slot::Slot<Q,MP>::read_upgrade
  27: salsa::derived::slot::Slot<Q,MP>::read
  28: salsa::QueryTable<Q>::get
  29: <DB as hir_ty::db::HirDatabase>::trait_solve_query
  30: hir_ty::db::trait_solve_wait
  31: <DB as hir_ty::db::HirDatabase>::trait_solve
  32: hir_ty::infer::unify::InferenceTable::register_obligation_in_env
  33: hir_ty::infer::coerce::<impl hir_ty::infer::unify::InferenceTable>::coerce
  34: hir_ty::infer::coerce::<impl hir_ty::infer::InferenceContext>::coerce
  35: hir_ty::infer::expr::<impl hir_ty::infer::InferenceContext>::infer_expr_coerce
  36: hir_ty::infer::expr::<impl hir_ty::infer::InferenceContext>::infer_expr_inner
  37: hir_ty::infer::expr::<impl hir_ty::infer::InferenceContext>::infer_expr_coerce
  38: hir_ty::infer::expr::<impl hir_ty::infer::InferenceContext>::infer_block
  39: hir_ty::infer::expr::<impl hir_ty::infer::InferenceContext>::infer_expr_inner
  40: hir_ty::infer::expr::<impl hir_ty::infer::InferenceContext>::infer_expr_coerce
  41: hir_ty::infer::infer_query
  42: salsa::runtime::Runtime::execute_query_implementation
  43: salsa::derived::slot::Slot<Q,MP>::read_upgrade
  44: salsa::derived::slot::Slot<Q,MP>::read
  45: salsa::QueryTable<Q>::get
  46: <DB as hir_ty::db::HirDatabase>::infer_query
  47: hir_ty::db::infer_wait
  48: hir::source_analyzer::SourceAnalyzer::new_for_body
  49: hir::semantics::SemanticsImpl::analyze_impl
  50: ide_db::defs::NameRefClass::classify
  51: ide_db::defs::IdentClass::classify_node
  52: core::ops::function::impls::<impl core::ops::function::FnMut<A> for &mut F>::call_mut
  53: <itertools::unique_impl::UniqueBy<I,V,F> as core::iter::traits::iterator::Iterator>::next
  54: ide::hover::hover
  55: std::panicking::try
  56: rust_analyzer::handlers::handle_hover
  57: std::panicking::try
  58: <F as threadpool::FnBox>::call_box
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.
[Error - 9:27:35 PM] Request textDocument/hover failed.
  Message: server panicked: mismatched kinds in substitution
  Code: -32603 

rust-analyzer version: 7ce3ca5 2022-04-15 nightly

rustc version: rustc 1.61.0-nightly (458262b 2022-03-09)

relevant settings: Nothing special

[lnicola]

Probably dupe of #11989.

[TennyZhuang]

same error on playing with https://github.com/matthieu-m/storage-poc

rust-analyzer version: 6262b6015 2022-05-03 nightly
rustc 1.62.0-nightly (bed05e996 2022-05-02)

[lowr]

This seems to be fixed (presumably by #13335). Feel free to reopen if you still experience the issue.