ICE with type_alias_impl_trait: ty_is_local invoked on unexpected type

[WaffleLapkin]

This code:

#![feature(type_alias_impl_trait)]

fn main() {
    let mut lazy = Wrap::default();
    let a: bool = lazy.call();
    assert_eq!(a, false);
}

type Closure<T> = impl FnOnce() -> T;

fn closure<T: Default>() -> Closure<T> {
    || T::default()
}

struct Wrap<T, F>(F, std::marker::PhantomData<dyn Fn() -> T>);

impl<T> Wrap<T, Closure<T>> {
    fn default() -> Self
    where
        T: Default,
    {
        Self(closure::<T>(), std::marker::PhantomData)
    }
}

impl<T, F> Wrap<T, F> {
    fn call(self) -> T 
    where
        F: FnOnce() -> T,
    {
        self.0()
    }
}

(playground)

Causes an ICE.

backtrace

   Compiling playground v0.0.1 (/playground)
error: internal compiler error: src/librustc/traits/coherence.rs:534: ty_is_local invoked on unexpected type: [closure@src/main.rs:12:5: 12:20]
thread 'rustc' panicked at 'Box', src/librustc_errors/lib.rs:892:9

stack backtrace:

0: backtrace::backtrace::libunwind::trace

at /cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.40/src/backtrace/libunwind.rs:88

1: backtrace::backtrace::trace_unsynchronized

at /cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.40/src/backtrace/mod.rs:66

2: std::sys_common::backtrace::_print_fmt

at src/libstd/sys_common/backtrace.rs:84

3: <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt

at src/libstd/sys_common/backtrace.rs:61

4: core::fmt::write

at src/libcore/fmt/mod.rs:1030

5: std::io::Write::write_fmt

at src/libstd/io/mod.rs:1412

6: std::sys_common::backtrace::_print

at src/libstd/sys_common/backtrace.rs:65

7: std::sys_common::backtrace::print

at src/libstd/sys_common/backtrace.rs:50

8: std::panicking::default_hook::{{closure}}

at src/libstd/panicking.rs:188

9: std::panicking::default_hook

at src/libstd/panicking.rs:205

10: rustc_driver::report_ice

11: std::panicking::rust_panic_with_hook

at src/libstd/panicking.rs:468

12: std::panicking::begin_panic

13: rustc_errors::HandlerInner::bug

14: rustc_errors::Handler::bug

15: rustc::util::bug::opt_span_bug_fmt::{{closure}}

16: rustc::ty::context::tls::with_opt::{{closure}}

17: rustc::ty::context::tls::with_context_opt

18: rustc::ty::context::tls::with_opt

19: rustc::util::bug::opt_span_bug_fmt

20: rustc::util::bug::bug_fmt

21: rustc::traits::coherence::ty_is_non_local_constructor

22: rustc::traits::coherence::ty_is_non_local

23: rustc::traits::coherence::orphan_check_trait_ref

24: rustc::traits::coherence::trait_ref_is_knowable

25: rustc::traits::select::SelectionContext::candidate_from_obligation_no_cache

26: rustc::dep_graph::graph::DepGraph::with_anon_task

27: rustc::traits::select::SelectionContext::candidate_from_obligation

28: rustc::traits::select::SelectionContext::evaluate_stack

29: rustc::dep_graph::graph::DepGraph::with_anon_task

30: rustc::traits::select::SelectionContext::evaluate_predicate_recursively

31: rustc::infer::InferCtxt::probe

32: core::ops::function::impls::<impl core::ops::function::FnMut for &mut F>::call_mut

33: <core::iter::adapters::chain::Chain<A,B> as core::iter::traits::iterator::Iterator>::try_fold

34: rustc::traits::coherence::overlap_within_probe

35: rustc::infer::InferCtxt::probe

36: rustc::traits::coherence::overlap

37: rustc::ty::context::GlobalCtxt::enter_local

38: rustc::traits::coherence::overlapping_impls

39: <rustc_typeck::coherence::inherent_impls_overlap::InherentOverlapChecker as rustc::hir::itemlikevisit::ItemLikeVisitor>::visit_item

40: rustc::hir::Crate::visit_all_item_likes

41: rustc_typeck::coherence::inherent_impls_overlap::crate_inherent_impls_overlap_check

42: rustc::ty::query::__query_compute::crate_inherent_impls_overlap_check

43: rustc::dep_graph::graph::DepGraph::with_task_impl

44: rustc::ty::query::plumbing::::get_query

45: rustc_typeck::check_crate::{{closure}}::{{closure}}

46: rustc::util::common::time

47: rustc_typeck::check_crate

48: rustc_interface::passes::analysis

49: rustc::ty::query::__query_compute::analysis

50: rustc::dep_graph::graph::DepGraph::with_task_impl

51: rustc::ty::query::plumbing::::get_query

52: rustc::ty::context::tls::enter_global

53: rustc_interface::passes::BoxedGlobalCtxt::access::{{closure}}

54: rustc_interface::passes::create_global_ctxt::{{closure}}

55: rustc_interface::passes::BoxedGlobalCtxt::enter

56: rustc_interface::interface::run_compiler_in_existing_thread_pool

57: std::thread::local::LocalKey::with

58: syntax::with_globals

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/blob/master/CONTRIBUTING.md#bug-reports
note: rustc 1.41.0-nightly (618b01f9f 2019-11-19) running on x86_64-unknown-linux-gnu
note: compiler flags: -C codegen-units=1 -C debuginfo=2 --crate-type bin
note: some of the compiler flags provided by cargo are hidden
query stack during panic:

#0 [crate_inherent_impls_overlap_check] check for overlap between inherent impls defined in this crate

#1 [analysis] running analysis passes on this crate

end of query stack

error: aborting due to previous error
error: could not compile playground.
To learn more, run the command again with --verbose.

[Centril]

Initial reduction (I cannot reduce more):

#![feature(type_alias_impl_trait)]

type Closure = impl FnOnce();

fn closure() -> Closure {
    || {}
}

struct Wrap<T> { f: T }

impl Wrap<Closure> {}

impl<T> Wrap<T> {}

[Centril]

cc @Aaron1011 @nikomatsakis (suggested by git blame)

[Aaron1011]

Something appears to have gone horribly wrong with PR #63934.

In my initial commit to the PR, I make coherence checking for opaque types check the underlying type to determine whether the opaque type is local or not.

After some feedback from @nikomatsakis, I changed the PR to always treat opaque types as foreign. This is what was supposed to get merged.

I then added some additional tests, force-pushing due to (I think) a rebase. However, I appear to have accidentally switched back to the orignal version of the PR. It's hard to tell from looking at the first push, because I added a new commit (adding the tests). However, the parent of 4eb3d8d is not a commit with the always-foreign behavior - instead, it's a commit with the content of the original PR.

Effectively, an earlier version of the PR got merged, along with some tests intended to go along with the later version of the PR (but which also happened.

I sincerely apologize for this mistake. I'm opening a PR with the proper, approved fix.

[Aaron1011]

I've opened #66590

[hellow554]

@rustbot modify labels: -requires-nightly

ICE also appears on stable (also on 1.38) and beta without feature flag. Backport worthy?