Closed
Description
I found an ICE while attempting to use an impl type alias in a function pointer type while playing around with type_alias_impl_trait.
#![feature(type_alias_impl_trait)]
type Iter<'a> = impl Iterator<Item = u32> + 'a;
fn whee() -> for<'a> fn(&'a [u32]) -> Iter<'a> {
|a| a.iter().copied()
}Here's the playground link to the snippet above, which was running rustc 1.70.0-nightly (0c61c7a97 2023-03-25) running on x86_64-unknown-linux-gnu at the time of the panic.
The head of the panic is as follows:
error: internal compiler error: compiler/rustc_hir_typeck/src/inherited.rs:105:13: escaping bound vars in predicate Obligation(predicate=Binder(TraitPredicate(<Iter<'a> as std::marker::Sized>, polarity:Positive), []), depth=0)
--> src/lib.rs:5:14
|
5 | fn whee() -> for<'a> fn(&'a [u32]) -> Iter<'a> {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
thread 'rustc' panicked at 'Box<dyn Any>', /rustc/0c61c7a978fe9f7b77a1d667c77d2202dadd1c10/compiler/rustc_errors/src/lib.rs:995:33
stack backtrace:
...
Full Error Message
error: internal compiler error: compiler/rustc_hir_typeck/src/inherited.rs:105:13: escaping bound vars in predicate Obligation(predicate=Binder(TraitPredicate(<Iter<'a> as std::marker::Sized>, polarity:Positive), []), depth=0)
--> src/lib.rs:5:14
|
5 | fn whee() -> for<'a> fn(&'a [u32]) -> Iter<'a> {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
thread 'rustc' panicked at 'Box<dyn Any>', /rustc/0c61c7a978fe9f7b77a1d667c77d2202dadd1c10/compiler/rustc_errors/src/lib.rs:995:33
stack backtrace:
0: 0x7f75fd406b9a - std::backtrace_rs::backtrace::libunwind::trace::h33a8ebdd070a2849
at /rustc/0c61c7a978fe9f7b77a1d667c77d2202dadd1c10/library/std/src/../../backtrace/src/backtrace/libunwind.rs:93:5
1: 0x7f75fd406b9a - std::backtrace_rs::backtrace::trace_unsynchronized::hdcf243f187b50d8d
at /rustc/0c61c7a978fe9f7b77a1d667c77d2202dadd1c10/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5
2: 0x7f75fd406b9a - std::sys_common::backtrace::_print_fmt::h447195462962d9fa
at /rustc/0c61c7a978fe9f7b77a1d667c77d2202dadd1c10/library/std/src/sys_common/backtrace.rs:65:5
3: 0x7f75fd406b9a - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::h030527b6b1cd3ea0
at /rustc/0c61c7a978fe9f7b77a1d667c77d2202dadd1c10/library/std/src/sys_common/backtrace.rs:44:22
4: 0x7f75fd46ab3f - core::fmt::write::h820832a7aab88d9e
at /rustc/0c61c7a978fe9f7b77a1d667c77d2202dadd1c10/library/core/src/fmt/mod.rs:1254:17
5: 0x7f75fd3f96d5 - std::io::Write::write_fmt::h8f101bdb654e5017
at /rustc/0c61c7a978fe9f7b77a1d667c77d2202dadd1c10/library/std/src/io/mod.rs:1698:15
6: 0x7f75fd406965 - std::sys_common::backtrace::_print::h774dcd3ec539df8d
at /rustc/0c61c7a978fe9f7b77a1d667c77d2202dadd1c10/library/std/src/sys_common/backtrace.rs:47:5
7: 0x7f75fd406965 - std::sys_common::backtrace::print::hfb7ed7d7ba09efbc
at /rustc/0c61c7a978fe9f7b77a1d667c77d2202dadd1c10/library/std/src/sys_common/backtrace.rs:34:9
8: 0x7f75fd40960e - std::panicking::default_hook::{{closure}}::h1b562f555ed8e3e1
at /rustc/0c61c7a978fe9f7b77a1d667c77d2202dadd1c10/library/std/src/panicking.rs:271:22
9: 0x7f75fd4093b5 - std::panicking::default_hook::hc7a03bfdd14960de
at /rustc/0c61c7a978fe9f7b77a1d667c77d2202dadd1c10/library/std/src/panicking.rs:290:9
10: 0x7f76006bc025 - <rustc_driver_impl[92a15bc3e068e4f2]::DEFAULT_HOOK::{closure#0}::{closure#0} as core[a3d8d6709fc4f528]::ops::function::FnOnce<(&core[a3d8d6709fc4f528]::panic::panic_info::PanicInfo,)>>::call_once::{shim:vtable#0}
11: 0x7f75fd409e04 - <alloc::boxed::Box<F,A> as core::ops::function::Fn<Args>>::call::ha85a7263ce5c1565
at /rustc/0c61c7a978fe9f7b77a1d667c77d2202dadd1c10/library/alloc/src/boxed.rs:2002:9
12: 0x7f75fd409e04 - std::panicking::rust_panic_with_hook::hfd9594253b2174d9
at /rustc/0c61c7a978fe9f7b77a1d667c77d2202dadd1c10/library/std/src/panicking.rs:696:13
13: 0x7f76008aa6e1 - std[1bf61b140f607083]::panicking::begin_panic::<rustc_errors[7ae47b583acaa0c7]::ExplicitBug>::{closure#0}
14: 0x7f76008a8586 - std[1bf61b140f607083]::sys_common::backtrace::__rust_end_short_backtrace::<std[1bf61b140f607083]::panicking::begin_panic<rustc_errors[7ae47b583acaa0c7]::ExplicitBug>::{closure#0}, !>
15: 0x7f76008f2016 - std[1bf61b140f607083]::panicking::begin_panic::<rustc_errors[7ae47b583acaa0c7]::ExplicitBug>
16: 0x7f76008a5aa6 - std[1bf61b140f607083]::panic::panic_any::<rustc_errors[7ae47b583acaa0c7]::ExplicitBug>
17: 0x7f76008a5a42 - <rustc_errors[7ae47b583acaa0c7]::HandlerInner>::span_bug::<rustc_span[9f00524050a95850]::span_encoding::Span, &alloc[d60a5f910632ae0c]::string::String>
18: 0x7f76008a5777 - <rustc_errors[7ae47b583acaa0c7]::Handler>::span_bug::<rustc_span[9f00524050a95850]::span_encoding::Span, &alloc[d60a5f910632ae0c]::string::String>
19: 0x7f760092e56b - rustc_middle[e79c5042f5680516]::util::bug::opt_span_bug_fmt::<rustc_span[9f00524050a95850]::span_encoding::Span>::{closure#0}
20: 0x7f760092e5ba - rustc_middle[e79c5042f5680516]::ty::context::tls::with_opt::<rustc_middle[e79c5042f5680516]::util::bug::opt_span_bug_fmt<rustc_span[9f00524050a95850]::span_encoding::Span>::{closure#0}, !>::{closure#0}
21: 0x7f760092b586 - rustc_middle[e79c5042f5680516]::ty::context::tls::with_context_opt::<rustc_middle[e79c5042f5680516]::ty::context::tls::with_opt<rustc_middle[e79c5042f5680516]::util::bug::opt_span_bug_fmt<rustc_span[9f00524050a95850]::span_encoding::Span>::{closure#0}, !>::{closure#0}, !>
22: 0x7f760092b526 - rustc_middle[e79c5042f5680516]::util::bug::opt_span_bug_fmt::<rustc_span[9f00524050a95850]::span_encoding::Span>
23: 0x7f75fee948e4 - rustc_middle[e79c5042f5680516]::util::bug::span_bug_fmt::<rustc_span[9f00524050a95850]::span_encoding::Span>
24: 0x7f75fee977e6 - <rustc_hir_typeck[cd60bec5327d1575]::inherited::Inherited>::register_infer_ok_obligations::<rustc_middle[e79c5042f5680516]::ty::Ty>
25: 0x7f75ff6d2229 - rustc_hir_typeck[cd60bec5327d1575]::check::check_fn
26: 0x7f75ff6bd3af - rustc_hir_typeck[cd60bec5327d1575]::typeck
27: 0x7f75ff65e051 - rustc_query_system[c3c23202dfcd6b3e]::query::plumbing::try_execute_query::<rustc_query_impl[eb7c07aa1bc4986c]::queries::typeck, rustc_query_impl[eb7c07aa1bc4986c]::plumbing::QueryCtxt>
28: 0x7f75ff65da29 - <rustc_query_impl[eb7c07aa1bc4986c]::Queries as rustc_middle[e79c5042f5680516]::ty::query::QueryEngine>::typeck
29: 0x7f76007fb18b - <rustc_hir_analysis[513a04983a37f1da]::collect::type_of::find_opaque_ty_constraints_for_tait::ConstraintLocator>::check
30: 0x7f76007f9632 - <rustc_hir_analysis[513a04983a37f1da]::collect::type_of::find_opaque_ty_constraints_for_tait::ConstraintLocator as rustc_hir[1193c0d4d0a08a84]::intravisit::Visitor>::visit_nested_item
31: 0x7f76007e47c9 - rustc_hir[1193c0d4d0a08a84]::intravisit::walk_mod::<rustc_hir_analysis[513a04983a37f1da]::collect::type_of::find_opaque_ty_constraints_for_tait::ConstraintLocator>
32: 0x7f76007faae1 - rustc_hir_analysis[513a04983a37f1da]::collect::type_of::find_opaque_ty_constraints_for_tait
33: 0x7f75ffa0c1d0 - rustc_hir_analysis[513a04983a37f1da]::collect::type_of::type_of
34: 0x7f75feef2887 - rustc_query_system[c3c23202dfcd6b3e]::query::plumbing::try_execute_query::<rustc_query_impl[eb7c07aa1bc4986c]::queries::type_of, rustc_query_impl[eb7c07aa1bc4986c]::plumbing::QueryCtxt>
35: 0x7f75feef125d - <rustc_query_impl[eb7c07aa1bc4986c]::Queries as rustc_middle[e79c5042f5680516]::ty::query::QueryEngine>::type_of
36: 0x7f75ff53f461 - rustc_hir_analysis[513a04983a37f1da]::check::check::check_mod_item_types
37: 0x7f75ffcfdf09 - rustc_query_system[c3c23202dfcd6b3e]::query::plumbing::try_execute_query::<rustc_query_impl[eb7c07aa1bc4986c]::queries::check_mod_item_types, rustc_query_impl[eb7c07aa1bc4986c]::plumbing::QueryCtxt>
38: 0x7f75ffcfdab9 - <rustc_query_impl[eb7c07aa1bc4986c]::Queries as rustc_middle[e79c5042f5680516]::ty::query::QueryEngine>::check_mod_item_types
39: 0x7f75ffb7324e - <rustc_session[46f71b3d93718d91]::session::Session>::time::<(), rustc_hir_analysis[513a04983a37f1da]::check_crate::{closure#6}>
40: 0x7f75ffb70067 - rustc_hir_analysis[513a04983a37f1da]::check_crate
41: 0x7f75ffb6a131 - rustc_interface[8a54472d067ff82c]::passes::analysis
42: 0x7f75ffe86c32 - rustc_query_system[c3c23202dfcd6b3e]::query::plumbing::try_execute_query::<rustc_query_impl[eb7c07aa1bc4986c]::queries::analysis, rustc_query_impl[eb7c07aa1bc4986c]::plumbing::QueryCtxt>
43: 0x7f75ffe86940 - <rustc_query_impl[eb7c07aa1bc4986c]::Queries as rustc_middle[e79c5042f5680516]::ty::query::QueryEngine>::analysis
44: 0x7f75ffd18d99 - <rustc_middle[e79c5042f5680516]::ty::context::GlobalCtxt>::enter::<rustc_driver_impl[92a15bc3e068e4f2]::run_compiler::{closure#1}::{closure#2}::{closure#4}, core[a3d8d6709fc4f528]::result::Result<(), rustc_span[9f00524050a95850]::ErrorGuaranteed>>
45: 0x7f75ff84eb31 - <rustc_interface[8a54472d067ff82c]::interface::Compiler>::enter::<rustc_driver_impl[92a15bc3e068e4f2]::run_compiler::{closure#1}::{closure#2}, core[a3d8d6709fc4f528]::result::Result<core[a3d8d6709fc4f528]::option::Option<rustc_interface[8a54472d067ff82c]::queries::Linker>, rustc_span[9f00524050a95850]::ErrorGuaranteed>>
46: 0x7f75ff84cce1 - rustc_span[9f00524050a95850]::with_source_map::<core[a3d8d6709fc4f528]::result::Result<(), rustc_span[9f00524050a95850]::ErrorGuaranteed>, rustc_interface[8a54472d067ff82c]::interface::run_compiler<core[a3d8d6709fc4f528]::result::Result<(), rustc_span[9f00524050a95850]::ErrorGuaranteed>, rustc_driver_impl[92a15bc3e068e4f2]::run_compiler::{closure#1}>::{closure#0}::{closure#0}>
47: 0x7f75ff84c28f - std[1bf61b140f607083]::sys_common::backtrace::__rust_begin_short_backtrace::<rustc_interface[8a54472d067ff82c]::util::run_in_thread_pool_with_globals<rustc_interface[8a54472d067ff82c]::interface::run_compiler<core[a3d8d6709fc4f528]::result::Result<(), rustc_span[9f00524050a95850]::ErrorGuaranteed>, rustc_driver_impl[92a15bc3e068e4f2]::run_compiler::{closure#1}>::{closure#0}, core[a3d8d6709fc4f528]::result::Result<(), rustc_span[9f00524050a95850]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[a3d8d6709fc4f528]::result::Result<(), rustc_span[9f00524050a95850]::ErrorGuaranteed>>
48: 0x7f75fff65cbe - <<std[1bf61b140f607083]::thread::Builder>::spawn_unchecked_<rustc_interface[8a54472d067ff82c]::util::run_in_thread_pool_with_globals<rustc_interface[8a54472d067ff82c]::interface::run_compiler<core[a3d8d6709fc4f528]::result::Result<(), rustc_span[9f00524050a95850]::ErrorGuaranteed>, rustc_driver_impl[92a15bc3e068e4f2]::run_compiler::{closure#1}>::{closure#0}, core[a3d8d6709fc4f528]::result::Result<(), rustc_span[9f00524050a95850]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[a3d8d6709fc4f528]::result::Result<(), rustc_span[9f00524050a95850]::ErrorGuaranteed>>::{closure#1} as core[a3d8d6709fc4f528]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
49: 0x7f75fd413ed5 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::h009afec0196bee04
at /rustc/0c61c7a978fe9f7b77a1d667c77d2202dadd1c10/library/alloc/src/boxed.rs:1988:9
50: 0x7f75fd413ed5 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::ha6c4bb25884feef5
at /rustc/0c61c7a978fe9f7b77a1d667c77d2202dadd1c10/library/alloc/src/boxed.rs:1988:9
51: 0x7f75fd413ed5 - std::sys::unix::thread::Thread::new::thread_start::h6c0e7fa9b5646d29
at /rustc/0c61c7a978fe9f7b77a1d667c77d2202dadd1c10/library/std/src/sys/unix/thread.rs:108:17
52: 0x7f75fd2e1609 - start_thread
53: 0x7f75fd204133 - clone
54: 0x0 - <unknown>
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 1.70.0-nightly (0c61c7a97 2023-03-25) running on x86_64-unknown-linux-gnu
note: compiler flags: --crate-type lib -C embed-bitcode=no -C codegen-units=1 -C debuginfo=2
note: some of the compiler flags provided by cargo are hidden
query stack during panic:
#0 [typeck] type-checking `whee`
#1 [type_of] computing type of `Iter::{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
The error is also reproducible with HRTBs.
#![feature(type_alias_impl_trait)]
type Iter<'a> = impl Iterator<Item = u32> + 'a;
fn whee() -> Box<dyn for<'a> FnOnce(&'a [u32]) -> Iter<'a>> {
|a| a.iter().copied()
}Here's the playground link to the above snippet, which was running note: rustc 1.70.0-nightly (0c61c7a97 2023-03-25) running on x86_64-unknown-linux-gnu at the time of the panic.
The head of the panic is identical to the head of the first panic.
Full Error Message
error: internal compiler error: compiler/rustc_hir_typeck/src/inherited.rs:105:13: escaping bound vars in predicate Obligation(predicate=Binder(TraitPredicate(<Iter<'a> as std::marker::Sized>, polarity:Positive), []), depth=0)
--> src/lib.rs:5:14
|
5 | fn whee() -> Box<dyn for<'a> FnOnce(&'a [u32]) -> Iter<'a>> {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
thread 'rustc' panicked at 'Box<dyn Any>', /rustc/0c61c7a978fe9f7b77a1d667c77d2202dadd1c10/compiler/rustc_errors/src/lib.rs:995:33
stack backtrace:
0: 0x7f02c7c98b9a - std::backtrace_rs::backtrace::libunwind::trace::h33a8ebdd070a2849
at /rustc/0c61c7a978fe9f7b77a1d667c77d2202dadd1c10/library/std/src/../../backtrace/src/backtrace/libunwind.rs:93:5
1: 0x7f02c7c98b9a - std::backtrace_rs::backtrace::trace_unsynchronized::hdcf243f187b50d8d
at /rustc/0c61c7a978fe9f7b77a1d667c77d2202dadd1c10/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5
2: 0x7f02c7c98b9a - std::sys_common::backtrace::_print_fmt::h447195462962d9fa
at /rustc/0c61c7a978fe9f7b77a1d667c77d2202dadd1c10/library/std/src/sys_common/backtrace.rs:65:5
3: 0x7f02c7c98b9a - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::h030527b6b1cd3ea0
at /rustc/0c61c7a978fe9f7b77a1d667c77d2202dadd1c10/library/std/src/sys_common/backtrace.rs:44:22
4: 0x7f02c7cfcb3f - core::fmt::write::h820832a7aab88d9e
at /rustc/0c61c7a978fe9f7b77a1d667c77d2202dadd1c10/library/core/src/fmt/mod.rs:1254:17
5: 0x7f02c7c8b6d5 - std::io::Write::write_fmt::h8f101bdb654e5017
at /rustc/0c61c7a978fe9f7b77a1d667c77d2202dadd1c10/library/std/src/io/mod.rs:1698:15
6: 0x7f02c7c98965 - std::sys_common::backtrace::_print::h774dcd3ec539df8d
at /rustc/0c61c7a978fe9f7b77a1d667c77d2202dadd1c10/library/std/src/sys_common/backtrace.rs:47:5
7: 0x7f02c7c98965 - std::sys_common::backtrace::print::hfb7ed7d7ba09efbc
at /rustc/0c61c7a978fe9f7b77a1d667c77d2202dadd1c10/library/std/src/sys_common/backtrace.rs:34:9
8: 0x7f02c7c9b60e - std::panicking::default_hook::{{closure}}::h1b562f555ed8e3e1
at /rustc/0c61c7a978fe9f7b77a1d667c77d2202dadd1c10/library/std/src/panicking.rs:271:22
9: 0x7f02c7c9b3b5 - std::panicking::default_hook::hc7a03bfdd14960de
at /rustc/0c61c7a978fe9f7b77a1d667c77d2202dadd1c10/library/std/src/panicking.rs:290:9
10: 0x7f02caf4e025 - <rustc_driver_impl[92a15bc3e068e4f2]::DEFAULT_HOOK::{closure#0}::{closure#0} as core[a3d8d6709fc4f528]::ops::function::FnOnce<(&core[a3d8d6709fc4f528]::panic::panic_info::PanicInfo,)>>::call_once::{shim:vtable#0}
11: 0x7f02c7c9be04 - <alloc::boxed::Box<F,A> as core::ops::function::Fn<Args>>::call::ha85a7263ce5c1565
at /rustc/0c61c7a978fe9f7b77a1d667c77d2202dadd1c10/library/alloc/src/boxed.rs:2002:9
12: 0x7f02c7c9be04 - std::panicking::rust_panic_with_hook::hfd9594253b2174d9
at /rustc/0c61c7a978fe9f7b77a1d667c77d2202dadd1c10/library/std/src/panicking.rs:696:13
13: 0x7f02cb13c6e1 - std[1bf61b140f607083]::panicking::begin_panic::<rustc_errors[7ae47b583acaa0c7]::ExplicitBug>::{closure#0}
14: 0x7f02cb13a586 - std[1bf61b140f607083]::sys_common::backtrace::__rust_end_short_backtrace::<std[1bf61b140f607083]::panicking::begin_panic<rustc_errors[7ae47b583acaa0c7]::ExplicitBug>::{closure#0}, !>
15: 0x7f02cb184016 - std[1bf61b140f607083]::panicking::begin_panic::<rustc_errors[7ae47b583acaa0c7]::ExplicitBug>
16: 0x7f02cb137aa6 - std[1bf61b140f607083]::panic::panic_any::<rustc_errors[7ae47b583acaa0c7]::ExplicitBug>
17: 0x7f02cb137a42 - <rustc_errors[7ae47b583acaa0c7]::HandlerInner>::span_bug::<rustc_span[9f00524050a95850]::span_encoding::Span, &alloc[d60a5f910632ae0c]::string::String>
18: 0x7f02cb137777 - <rustc_errors[7ae47b583acaa0c7]::Handler>::span_bug::<rustc_span[9f00524050a95850]::span_encoding::Span, &alloc[d60a5f910632ae0c]::string::String>
19: 0x7f02cb1c056b - rustc_middle[e79c5042f5680516]::util::bug::opt_span_bug_fmt::<rustc_span[9f00524050a95850]::span_encoding::Span>::{closure#0}
20: 0x7f02cb1c05ba - rustc_middle[e79c5042f5680516]::ty::context::tls::with_opt::<rustc_middle[e79c5042f5680516]::util::bug::opt_span_bug_fmt<rustc_span[9f00524050a95850]::span_encoding::Span>::{closure#0}, !>::{closure#0}
21: 0x7f02cb1bd586 - rustc_middle[e79c5042f5680516]::ty::context::tls::with_context_opt::<rustc_middle[e79c5042f5680516]::ty::context::tls::with_opt<rustc_middle[e79c5042f5680516]::util::bug::opt_span_bug_fmt<rustc_span[9f00524050a95850]::span_encoding::Span>::{closure#0}, !>::{closure#0}, !>
22: 0x7f02cb1bd526 - rustc_middle[e79c5042f5680516]::util::bug::opt_span_bug_fmt::<rustc_span[9f00524050a95850]::span_encoding::Span>
23: 0x7f02c97268e4 - rustc_middle[e79c5042f5680516]::util::bug::span_bug_fmt::<rustc_span[9f00524050a95850]::span_encoding::Span>
24: 0x7f02c97297e6 - <rustc_hir_typeck[cd60bec5327d1575]::inherited::Inherited>::register_infer_ok_obligations::<rustc_middle[e79c5042f5680516]::ty::Ty>
25: 0x7f02c9f64229 - rustc_hir_typeck[cd60bec5327d1575]::check::check_fn
26: 0x7f02c9f4f3af - rustc_hir_typeck[cd60bec5327d1575]::typeck
27: 0x7f02c9ef0051 - rustc_query_system[c3c23202dfcd6b3e]::query::plumbing::try_execute_query::<rustc_query_impl[eb7c07aa1bc4986c]::queries::typeck, rustc_query_impl[eb7c07aa1bc4986c]::plumbing::QueryCtxt>
28: 0x7f02c9eefa29 - <rustc_query_impl[eb7c07aa1bc4986c]::Queries as rustc_middle[e79c5042f5680516]::ty::query::QueryEngine>::typeck
29: 0x7f02cb08d18b - <rustc_hir_analysis[513a04983a37f1da]::collect::type_of::find_opaque_ty_constraints_for_tait::ConstraintLocator>::check
30: 0x7f02cb08b632 - <rustc_hir_analysis[513a04983a37f1da]::collect::type_of::find_opaque_ty_constraints_for_tait::ConstraintLocator as rustc_hir[1193c0d4d0a08a84]::intravisit::Visitor>::visit_nested_item
31: 0x7f02cb0767c9 - rustc_hir[1193c0d4d0a08a84]::intravisit::walk_mod::<rustc_hir_analysis[513a04983a37f1da]::collect::type_of::find_opaque_ty_constraints_for_tait::ConstraintLocator>
32: 0x7f02cb08cae1 - rustc_hir_analysis[513a04983a37f1da]::collect::type_of::find_opaque_ty_constraints_for_tait
33: 0x7f02ca29e1d0 - rustc_hir_analysis[513a04983a37f1da]::collect::type_of::type_of
34: 0x7f02c9784887 - rustc_query_system[c3c23202dfcd6b3e]::query::plumbing::try_execute_query::<rustc_query_impl[eb7c07aa1bc4986c]::queries::type_of, rustc_query_impl[eb7c07aa1bc4986c]::plumbing::QueryCtxt>
35: 0x7f02c978325d - <rustc_query_impl[eb7c07aa1bc4986c]::Queries as rustc_middle[e79c5042f5680516]::ty::query::QueryEngine>::type_of
36: 0x7f02c9dd1461 - rustc_hir_analysis[513a04983a37f1da]::check::check::check_mod_item_types
37: 0x7f02ca58ff09 - rustc_query_system[c3c23202dfcd6b3e]::query::plumbing::try_execute_query::<rustc_query_impl[eb7c07aa1bc4986c]::queries::check_mod_item_types, rustc_query_impl[eb7c07aa1bc4986c]::plumbing::QueryCtxt>
38: 0x7f02ca58fab9 - <rustc_query_impl[eb7c07aa1bc4986c]::Queries as rustc_middle[e79c5042f5680516]::ty::query::QueryEngine>::check_mod_item_types
39: 0x7f02ca40524e - <rustc_session[46f71b3d93718d91]::session::Session>::time::<(), rustc_hir_analysis[513a04983a37f1da]::check_crate::{closure#6}>
40: 0x7f02ca402067 - rustc_hir_analysis[513a04983a37f1da]::check_crate
41: 0x7f02ca3fc131 - rustc_interface[8a54472d067ff82c]::passes::analysis
42: 0x7f02ca718c32 - rustc_query_system[c3c23202dfcd6b3e]::query::plumbing::try_execute_query::<rustc_query_impl[eb7c07aa1bc4986c]::queries::analysis, rustc_query_impl[eb7c07aa1bc4986c]::plumbing::QueryCtxt>
43: 0x7f02ca718940 - <rustc_query_impl[eb7c07aa1bc4986c]::Queries as rustc_middle[e79c5042f5680516]::ty::query::QueryEngine>::analysis
44: 0x7f02ca5aad99 - <rustc_middle[e79c5042f5680516]::ty::context::GlobalCtxt>::enter::<rustc_driver_impl[92a15bc3e068e4f2]::run_compiler::{closure#1}::{closure#2}::{closure#4}, core[a3d8d6709fc4f528]::result::Result<(), rustc_span[9f00524050a95850]::ErrorGuaranteed>>
45: 0x7f02ca0e0b31 - <rustc_interface[8a54472d067ff82c]::interface::Compiler>::enter::<rustc_driver_impl[92a15bc3e068e4f2]::run_compiler::{closure#1}::{closure#2}, core[a3d8d6709fc4f528]::result::Result<core[a3d8d6709fc4f528]::option::Option<rustc_interface[8a54472d067ff82c]::queries::Linker>, rustc_span[9f00524050a95850]::ErrorGuaranteed>>
46: 0x7f02ca0dece1 - rustc_span[9f00524050a95850]::with_source_map::<core[a3d8d6709fc4f528]::result::Result<(), rustc_span[9f00524050a95850]::ErrorGuaranteed>, rustc_interface[8a54472d067ff82c]::interface::run_compiler<core[a3d8d6709fc4f528]::result::Result<(), rustc_span[9f00524050a95850]::ErrorGuaranteed>, rustc_driver_impl[92a15bc3e068e4f2]::run_compiler::{closure#1}>::{closure#0}::{closure#0}>
47: 0x7f02ca0de28f - std[1bf61b140f607083]::sys_common::backtrace::__rust_begin_short_backtrace::<rustc_interface[8a54472d067ff82c]::util::run_in_thread_pool_with_globals<rustc_interface[8a54472d067ff82c]::interface::run_compiler<core[a3d8d6709fc4f528]::result::Result<(), rustc_span[9f00524050a95850]::ErrorGuaranteed>, rustc_driver_impl[92a15bc3e068e4f2]::run_compiler::{closure#1}>::{closure#0}, core[a3d8d6709fc4f528]::result::Result<(), rustc_span[9f00524050a95850]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[a3d8d6709fc4f528]::result::Result<(), rustc_span[9f00524050a95850]::ErrorGuaranteed>>
48: 0x7f02ca7f7cbe - <<std[1bf61b140f607083]::thread::Builder>::spawn_unchecked_<rustc_interface[8a54472d067ff82c]::util::run_in_thread_pool_with_globals<rustc_interface[8a54472d067ff82c]::interface::run_compiler<core[a3d8d6709fc4f528]::result::Result<(), rustc_span[9f00524050a95850]::ErrorGuaranteed>, rustc_driver_impl[92a15bc3e068e4f2]::run_compiler::{closure#1}>::{closure#0}, core[a3d8d6709fc4f528]::result::Result<(), rustc_span[9f00524050a95850]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[a3d8d6709fc4f528]::result::Result<(), rustc_span[9f00524050a95850]::ErrorGuaranteed>>::{closure#1} as core[a3d8d6709fc4f528]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
49: 0x7f02c7ca5ed5 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::h009afec0196bee04
at /rustc/0c61c7a978fe9f7b77a1d667c77d2202dadd1c10/library/alloc/src/boxed.rs:1988:9
50: 0x7f02c7ca5ed5 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::ha6c4bb25884feef5
at /rustc/0c61c7a978fe9f7b77a1d667c77d2202dadd1c10/library/alloc/src/boxed.rs:1988:9
51: 0x7f02c7ca5ed5 - std::sys::unix::thread::Thread::new::thread_start::h6c0e7fa9b5646d29
at /rustc/0c61c7a978fe9f7b77a1d667c77d2202dadd1c10/library/std/src/sys/unix/thread.rs:108:17
52: 0x7f02c7b73609 - start_thread
53: 0x7f02c7a96133 - clone
54: 0x0 - <unknown>
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 1.70.0-nightly (0c61c7a97 2023-03-25) running on x86_64-unknown-linux-gnu
note: compiler flags: --crate-type lib -C embed-bitcode=no -C codegen-units=1 -C debuginfo=2
note: some of the compiler flags provided by cargo are hidden
query stack during panic:
#0 [typeck] type-checking `whee`
#1 [type_of] computing type of `Iter::{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
If, however, the lifetime provided to the type alias is not higher-ranked (is this appropriate terminology??), but rather originates from the function itself, the compiler does not panic.
#![feature(type_alias_impl_trait)]
type Iter<'a> = impl Iterator<Item = u32> + 'a;
fn whee<'a>() -> for<'b> fn(&'b [u32]) -> Iter<'a> {
|_a| [1, 2, 3].into_iter()
}Here's the playground link to the above snippet, which was presumably also running rustc 1.70.0-nightly (0c61c7a97 2023-03-25) running on x86_64-unknown-linux-gnu at the time of the panicn't.