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Internal compiler error when lifetime bound is unsatisfied for generic associated type defined with impl trait. #88595
Description
When implementing generic associated type using impl Trait, the compiler panics if the trait lifetime bound is not satisfied by duplicating the where clause.
UPDATE: seems like the compiler also panics if an appropriate where clause is included in the implementation.
Reproducible in a new cargo project on the latest nightly.
Code
#![feature(generic_associated_types)]
#![feature(type_alias_impl_trait)]
fn main() {
println!("Hello, world!");
}
trait A<'a> {
type B<'b>: Clone
where
'a: 'b;
fn a(&'a self) -> Self::B<'a>;
}
struct C;
impl<'a> A<'a> for C {
type B<'b> = impl Clone;
fn a(&'a self) -> Self::B<'a> {}
} Meta
rustc --version --verbose:
rustc 1.56.0-nightly (50171c310 2021-09-01)
binary: rustc
commit-hash: 50171c310cd15e1b2d3723766ce64e2e4d6696fc
commit-date: 2021-09-01
host: x86_64-unknown-linux-gnu
release: 1.56.0-nightly
LLVM version: 13.0.0
Error output
error[E0478]: lifetime bound not satisfied
--> src/main.rs:19:5
|
19 | type B<'b> = impl Clone;
| ^^^^^^^^^^^^^^^^^^^^^^^^
|
note: lifetime parameter instantiated with the lifetime `'a` as defined on the impl at 18:6
--> src/main.rs:18:6
|
18 | impl<'a> A<'a> for C {
| ^^
note: but lifetime parameter must outlive the lifetime `'b` as defined on the associated item at 19:12
--> src/main.rs:19:12
|
19 | type B<'b> = impl Clone;
| ^^
thread 'rustc' panicked at 'assertion failed: self.is_free_or_static(r_a) && self.is_free_or_static(r_b)', compiler/rustc_infer/src/infer/free_regions.rs:77:9
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
error: internal compiler error: unexpected panic
note: the compiler unexpectedly panicked. this is a bug.
note: we would appreciate a bug report: https://github.com/rust-lang/rust/issues/new?labels=C-bug%2C+I-ICE%2C+T-compiler&template=ice.md
note: rustc 1.56.0-nightly (50171c310 2021-09-01) running on x86_64-unknown-linux-gnu
note: compiler flags: -C embed-bitcode=no -C debuginfo=2 -C incremental --crate-type bin
note: some of the compiler flags provided by cargo are hidden
query stack during panic:
#0 [typeck] type-checking `<impl at src/main.rs:18:1: 22:2>::a`
#1 [type_of] computing type of `<impl at src/main.rs:18:1: 22:2>::B::{opaque#0}`
end of query stack
Backtrace
error[E0478]: lifetime bound not satisfied
--> src/main.rs:19:5
|
19 | type B<'b> = impl Clone;
| ^^^^^^^^^^^^^^^^^^^^^^^^
|
note: lifetime parameter instantiated with the lifetime `'a` as defined on the impl at 18:6
--> src/main.rs:18:6
|
18 | impl<'a> A<'a> for C {
| ^^
note: but lifetime parameter must outlive the lifetime `'b` as defined on the associated item at 19:12
--> src/main.rs:19:12
|
19 | type B<'b> = impl Clone;
| ^^
thread 'rustc' panicked at 'assertion failed: self.is_free_or_static(r_a) && self.is_free_or_static(r_b)', compiler/rustc_infer/src/infer/free_regions.rs:77:9
stack backtrace:
0: rust_begin_unwind
at /rustc/50171c310cd15e1b2d3723766ce64e2e4d6696fc/library/std/src/panicking.rs:517:5
1: core::panicking::panic_fmt
at /rustc/50171c310cd15e1b2d3723766ce64e2e4d6696fc/library/core/src/panicking.rs:101:14
2: core::panicking::panic
at /rustc/50171c310cd15e1b2d3723766ce64e2e4d6696fc/library/core/src/panicking.rs:50:5
3: <rustc_infer::infer::free_regions::FreeRegionMap as rustc_infer::infer::free_regions::FreeRegionRelations>::sub_free_regions
4: <rustc_infer::infer::InferCtxt as rustc_trait_selection::opaque_types::InferCtxtExt>::constrain_opaque_types
5: rustc_typeck::check::regionck::RegionCtxt::visit_fn_body
6: rustc_typeck::check::regionck::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::regionck_fn
7: rustc_infer::infer::InferCtxtBuilder::enter
8: rustc_typeck::check::typeck
9: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task_impl
10: rustc_data_structures::stack::ensure_sufficient_stack
11: rustc_query_system::query::plumbing::force_query_with_job
12: rustc_query_system::query::plumbing::get_query_impl
13: <rustc_query_impl::Queries as rustc_middle::ty::query::QueryEngine>::typeck
14: rustc_typeck::collect::type_of::find_opaque_ty_constraints::ConstraintLocator::check
15: <rustc_typeck::collect::type_of::find_opaque_ty_constraints::ConstraintLocator as rustc_hir::intravisit::Visitor>::visit_impl_item
16: rustc_hir::intravisit::Visitor::visit_nested_impl_item
17: rustc_hir::intravisit::walk_impl_item_ref
18: rustc_hir::intravisit::walk_item
19: rustc_typeck::collect::type_of::type_of
20: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task_impl
21: rustc_data_structures::stack::ensure_sufficient_stack
22: rustc_query_system::query::plumbing::force_query_with_job
23: rustc_query_system::query::plumbing::get_query_impl
24: <rustc_query_impl::Queries as rustc_middle::ty::query::QueryEngine>::type_of
25: rustc_typeck::check::check::check_item_type
26: rustc_middle::hir::map::Map::visit_item_likes_in_module
27: rustc_typeck::check::check::check_mod_item_types
28: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task_impl
29: rustc_data_structures::stack::ensure_sufficient_stack
30: rustc_query_system::query::plumbing::force_query_with_job
31: rustc_query_system::query::plumbing::get_query_impl
32: <rustc_query_impl::Queries as rustc_middle::ty::query::QueryEngine>::check_mod_item_types
33: rustc_session::utils::<impl rustc_session::session::Session>::time
34: rustc_typeck::check_crate
35: rustc_interface::passes::analysis
36: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task_impl
37: rustc_data_structures::stack::ensure_sufficient_stack
38: rustc_query_system::query::plumbing::force_query_with_job
39: rustc_query_system::query::plumbing::get_query_impl
40: <rustc_query_impl::Queries as rustc_middle::ty::query::QueryEngine>::analysis
41: rustc_interface::passes::QueryContext::enter
42: rustc_interface::queries::<impl rustc_interface::interface::Compiler>::enter
43: rustc_span::with_source_map
44: scoped_tls::ScopedKey<T>::set
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.
error: internal compiler error: unexpected panic
note: the compiler unexpectedly panicked. this is a bug.
note: we would appreciate a bug report: https://github.com/rust-lang/rust/issues/new?labels=C-bug%2C+I-ICE%2C+T-compiler&template=ice.md
note: rustc 1.56.0-nightly (50171c310 2021-09-01) running on x86_64-unknown-linux-gnu
note: compiler flags: -C embed-bitcode=no -C debuginfo=2 -C incremental --crate-type bin
note: some of the compiler flags provided by cargo are hidden
query stack during panic:
#0 [typeck] type-checking `<impl at src/main.rs:18:1: 22:2>::a`
#1 [type_of] computing type of `<impl at src/main.rs:18:1: 22:2>::B::{opaque#0}`
#2 [check_mod_item_types] checking item types in top-level module
#3 [analysis] running analysis passes on this crate
end of query stack
For more information about this error, try `rustc --explain E0478`.
error: could not compile `mre` due to previous error
Activity
add rust-lang/rust#88595
Luro02 commentedon Sep 20, 2021
I ran into this issue just now, reproducible code:
(note: this crashes on stable as well)
full backtrace
Luro02 commentedon Sep 20, 2021
Regression in `nightly-2021-07-17`
#87200
Alexendoo commentedon Oct 20, 2021
No longer ICEs since #89229
jackh726 commentedon Oct 23, 2021
GATs issue triage: not blocking. Fixed; needs test.
Rollup merge of rust-lang#90678 - JohnTitor:add-some-gats-tests, r=ja…