Compiler error on cargo fix --edition

[HollayHorvath]

Hey folks,

I'm getting an ICE while trying to run cargo fix --edition.

Building or doing anything else with this code is fine. If I remove Rc but keep the internal type, it's also works.

Code

use std::rc::Rc;

pub fn ice<'a, T: 'a, Key, FKeyer>(
    iterable: &'a [Vec<T>],
    keyer: &FKeyer,
)
where
    FKeyer: Fn(&T) -> Key,
{
    let mut tree = Tree::new();
    iterable.iter().enumerate().for_each(|(index, item)| {
        tree.add(index, item.iter().map(keyer))
    });
}

pub struct Tree<K, E>
{
    pub(crate) _root: Rc<Node<K, E>>,
}

impl<K, E> Tree<K, E>
{
    pub fn new() -> Tree<K, E> {
        let _root = Node::new();

        Tree {
            _root,
        }
    }

    pub fn add<I>(&mut self, _: K, _: I)
    where
        I: Iterator<Item = E>,
    {
    }
}

pub struct Node<K, E>
{
    _k: std::marker::PhantomData<K>,
    _e: std::marker::PhantomData<E>,
}

impl<K, E> Node<K, E>
{
    pub fn new() -> Rc<Node<K, E>> {
        Rc::new(Node {
            _k: std::marker::PhantomData::default(),
            _e: std::marker::PhantomData::default(),
        })
    }
}

Meta

rustc --version --verbose:

rustc 1.56.0 (09c42c458 2021-10-18)
binary: rustc
commit-hash: 09c42c45858d5f3aedfa670698275303a3d19afa
commit-date: 2021-10-18
host: x86_64-unknown-linux-gnu
release: 1.56.0
LLVM version: 13.0.0

The same happens on nightly.

Error output

error: internal compiler error: compiler/rustc_middle/src/ty/subst.rs:534:17: type parameter `E/#1` (E/1) out of range when substituting, substs=[Node<K, E>]

thread 'rustc' panicked at 'Box<dyn Any>', /rustc/09c42c45858d5f3aedfa670698275303a3d19afa/compiler/rustc_errors/src/lib.rs:1093:9

...

query stack during panic:
#0 [adt_significant_drop_tys] computing when `Tree` has a significant destructor
#1 [has_significant_drop_raw] computing whether `Tree<usize, Key>` has a significant drop
end of query stack
error: build failed

Backtrace

thread 'rustc' panicked at 'Box<dyn Any>', /rustc/efd0483949496b067cd5f7569d1b28cd3d5d3c72/compiler/rustc_errors/src/lib.rs:1093:9
stack backtrace:
   0: std::panicking::begin_panic
   1: std::panic::panic_any
   2: rustc_errors::HandlerInner::span_bug
   3: rustc_errors::Handler::span_bug
   4: rustc_middle::ty::context::tls::with_opt
   5: rustc_middle::util::bug::opt_span_bug_fmt
   6: rustc_middle::util::bug::span_bug_fmt
   7: rustc_middle::ty::fold::TypeFoldable::fold_with
   8: rustc_middle::ty::structural_impls::<impl rustc_middle::ty::fold::TypeFoldable for &rustc_middle::ty::TyS>::super_fold_with
   9: <rustc_ty_utils::needs_drop::NeedsDropTypes<F> as core::iter::traits::iterator::Iterator>::next
  10: <core::iter::adapters::ResultShunt<I,E> as core::iter::traits::iterator::Iterator>::next
  11: <alloc::vec::Vec<T> as alloc::vec::spec_from_iter::SpecFromIter<T,I>>::from_iter
  12: core::iter::adapters::process_results
  13: rustc_ty_utils::needs_drop::adt_significant_drop_tys
  14: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task
  15: rustc_data_structures::stack::ensure_sufficient_stack
  16: rustc_query_system::query::plumbing::try_execute_query
  17: rustc_query_system::query::plumbing::get_query
  18: rustc_ty_utils::needs_drop::has_significant_drop_raw
  19: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task
  20: rustc_data_structures::stack::ensure_sufficient_stack
  21: rustc_query_system::query::plumbing::try_execute_query
  22: rustc_query_system::query::plumbing::get_query
  23: rustc_middle::ty::util::<impl rustc_middle::ty::TyS>::has_significant_drop
  24: rustc_typeck::check::upvar::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::analyze_closure
  25: <rustc_typeck::check::upvar::InferBorrowKindVisitor as rustc_hir::intravisit::Visitor>::visit_expr
  26: rustc_hir::intravisit::walk_expr
  27: rustc_hir::intravisit::walk_stmt
  28: rustc_hir::intravisit::walk_block
  29: rustc_hir::intravisit::walk_body
  30: rustc_infer::infer::InferCtxtBuilder::enter
  31: rustc_typeck::check::typeck
  32: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task
  33: rustc_data_structures::stack::ensure_sufficient_stack
  34: rustc_query_system::query::plumbing::try_execute_query
  35: <rustc_query_impl::Queries as rustc_middle::ty::query::QueryEngine>::typeck
  36: rustc_typeck::check::typeck
  37: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task
  38: rustc_data_structures::stack::ensure_sufficient_stack
  39: rustc_query_system::query::plumbing::try_execute_query
  40: <rustc_query_impl::Queries as rustc_middle::ty::query::QueryEngine>::typeck
  41: rustc_middle::hir::map::Map::par_body_owners
  42: rustc_typeck::check::typeck_item_bodies
  43: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task
  44: rustc_data_structures::stack::ensure_sufficient_stack
  45: rustc_query_system::query::plumbing::try_execute_query
  46: rustc_query_system::query::plumbing::get_query
  47: rustc_session::utils::<impl rustc_session::session::Session>::time
  48: rustc_typeck::check_crate
  49: rustc_interface::passes::analysis
  50: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task
  51: rustc_data_structures::stack::ensure_sufficient_stack
  52: rustc_query_system::query::plumbing::try_execute_query
  53: rustc_query_system::query::plumbing::get_query
  54: rustc_interface::passes::QueryContext::enter
  55: rustc_interface::queries::<impl rustc_interface::interface::Compiler>::enter
  56: rustc_span::with_source_map
  57: scoped_tls::ScopedKey<T>::set

If I should provide more details, please let me know!

Thank you very much!

[ehuss]

Thank you for the report! I believe this is a duplicate of #90024, so closing in favor of that.