ICE `Subslice unexpected because it isn't captured` --edition=2021

[matthiaskrgr]

Code

#![crate_type="lib"]
fn arr_by_ref(mut x: [(); 3]) {
    let f = || {
        let [ref y, ref mut z @ ..] = x;
    };    
    f();
}

Meta

rustc --version --verbose:

rustc 1.70.0-nightly (13afbdaa0 2023-03-17)
binary: rustc
commit-hash: 13afbdaa0655dda23d7129e59ac48f1ec88b2084
commit-date: 2023-03-17
host: x86_64-unknown-linux-gnu
release: 1.70.0-nightly
LLVM version: 15.0.7

Error output

rustc file.rs --edition=2021

Backtrace

```warning: unused variable: y
--> treereduce.out:4:18
|
4 | let [ref y, ref mut z @ ..] = x;
| ^ help: if this is intentional, prefix it with an underscore: `_y`
|
= note: `#[warn(unused_variables)]` on by default

warning: unused variable: z
--> treereduce.out:4:29
|
4 | let [ref y, ref mut z @ ..] = x;
| ^ help: if this is intentional, prefix it with an underscore: _z

error: internal compiler error: compiler/rustc_middle/src/ty/closure.rs:372:21: Subslice unexpected because it isn't captured

thread 'rustc' panicked at 'Box', /rustc/13afbdaa0655dda23d7129e59ac48f1ec88b2084/compiler/rustc_errors/src/lib.rs:1644:9
stack backtrace:
0: 0x7f177a96739a - std::backtrace_rs::backtrace::libunwind::trace::h84d2711f38e4d049
at /rustc/13afbdaa0655dda23d7129e59ac48f1ec88b2084/library/std/src/../../backtrace/src/backtrace/libunwind.rs:93:5
1: 0x7f177a96739a - std::backtrace_rs::backtrace::trace_unsynchronized::h07f6ebc5344709db
at /rustc/13afbdaa0655dda23d7129e59ac48f1ec88b2084/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5
2: 0x7f177a96739a - std::sys_common::backtrace::_print_fmt::h05a29271ab24b307
at /rustc/13afbdaa0655dda23d7129e59ac48f1ec88b2084/library/std/src/sys_common/backtrace.rs:65:5
3: 0x7f177a96739a - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::h2badcaa62266c6d2
at /rustc/13afbdaa0655dda23d7129e59ac48f1ec88b2084/library/std/src/sys_common/backtrace.rs:44:22
4: 0x7f177a9ca9be - core::fmt::write::h029bd029dcf67de1
at /rustc/13afbdaa0655dda23d7129e59ac48f1ec88b2084/library/core/src/fmt/mod.rs:1254:17
5: 0x7f177a95a225 - std::io::Write::write_fmt::h80e1934b9bd451b8
at /rustc/13afbdaa0655dda23d7129e59ac48f1ec88b2084/library/std/src/io/mod.rs:1684:15
6: 0x7f177a967165 - std::sys_common::backtrace::_print::hd15e10f9274c89b0
at /rustc/13afbdaa0655dda23d7129e59ac48f1ec88b2084/library/std/src/sys_common/backtrace.rs:47:5
7: 0x7f177a967165 - std::sys_common::backtrace::print::h170965e4e66b5ee4
at /rustc/13afbdaa0655dda23d7129e59ac48f1ec88b2084/library/std/src/sys_common/backtrace.rs:34:9
8: 0x7f177a969edf - std::panicking::default_hook::{{closure}}::h0164004bb09e0366
at /rustc/13afbdaa0655dda23d7129e59ac48f1ec88b2084/library/std/src/panicking.rs:271:22
9: 0x7f177a969c1b - std::panicking::default_hook::h5e2940911ec5582f
at /rustc/13afbdaa0655dda23d7129e59ac48f1ec88b2084/library/std/src/panicking.rs:290:9
10: 0x7f177dbf2415 - rustc_driver_impl[bad2ed848d64dbdc]::DEFAULT_HOOK::{closure#0}::{closure#0}
11: 0x7f177a96a71d - <alloc::boxed::Box<F,A> as core::ops::function::Fn>::call::h0f3cc38fa49d6ba4
at /rustc/13afbdaa0655dda23d7129e59ac48f1ec88b2084/library/alloc/src/boxed.rs:2002:9
12: 0x7f177a96a71d - std::panicking::rust_panic_with_hook::h591d1df500c4db69
at /rustc/13afbdaa0655dda23d7129e59ac48f1ec88b2084/library/std/src/panicking.rs:696:13
13: 0x7f177e12aef1 - std[b4247acdb72724ff]::panicking::begin_panic::<rustc_errors[48bb1377a0478866]::ExplicitBug>::{closure#0}
14: 0x7f177e128996 - std[b4247acdb72724ff]::sys_common::backtrace::__rust_end_short_backtrace::<std[b4247acdb72724ff]::panicking::begin_panic<rustc_errors[48bb1377a0478866]::ExplicitBug>::{closure#0}, !>
15: 0x7f177e13ec96 - std[b4247acdb72724ff]::panicking::begin_panic::<rustc_errors[48bb1377a0478866]::ExplicitBug>
16: 0x7f177e1a10d6 - std[b4247acdb72724ff]::panic::panic_any::<rustc_errors[48bb1377a0478866]::ExplicitBug>
17: 0x7f177e19e896 - <rustc_errors[48bb1377a0478866]::HandlerInner>::bug::<&alloc[c5857ad37805d36e]::string::String>
18: 0x7f177e19e560 - <rustc_errors[48bb1377a0478866]::Handler>::bug::<&alloc[c5857ad37805d36e]::string::String>
19: 0x7f177e19684b - rustc_middle[eaf6378de1cdbfa8]::util::bug::opt_span_bug_fmt::<rustc_span[4d522547309d7b79]::span_encoding::Span>::{closure#0}
20: 0x7f177e19529a - rustc_middle[eaf6378de1cdbfa8]::ty::context::tls::with_opt::<rustc_middle[eaf6378de1cdbfa8]::util::bug::opt_span_bug_fmt<rustc_span[4d522547309d7b79]::span_encoding::Span>::{closure#0}, !>::{closure#0}
21: 0x7f177e195266 - rustc_middle[eaf6378de1cdbfa8]::ty::context::tls::with_context_opt::<rustc_middle[eaf6378de1cdbfa8]::ty::context::tls::with_opt<rustc_middle[eaf6378de1cdbfa8]::util::bug::opt_span_bug_fmt<rustc_span[4d522547309d7b79]::span_encoding::Span>::{closure#0}, !>::{closure#0}, !>
22: 0x7f177e196796 - rustc_middle[eaf6378de1cdbfa8]::util::bug::opt_span_bug_fmt::<rustc_span[4d522547309d7b79]::span_encoding::Span>
23: 0x7f177c2874e3 - rustc_middle[eaf6378de1cdbfa8]::util::bug::bug_fmt
24: 0x7f177e1ab891 - rustc_middle[eaf6378de1cdbfa8]::ty::closure::place_to_string_for_capture
25: 0x7f177d8f01fa - <rustc_borrowck[3b5de70414a05ac6]::MirBorrowckCtxt>::show_mutating_upvar
26: 0x7f177c5a35a8 - <rustc_borrowck[3b5de70414a05ac6]::MirBorrowckCtxt>::report_mutability_error
27: 0x7f177c59baaf - <rustc_borrowck[3b5de70414a05ac6]::MirBorrowckCtxt>::access_place
28: 0x7f177c58707c - <rustc_borrowck[3b5de70414a05ac6]::MirBorrowckCtxt as rustc_mir_dataflow[60696dcf57ac1f12]::framework::visitor::ResultsVisitor>::visit_statement_before_primary_effect
29: 0x7f177c9829de - rustc_mir_dataflow[60696dcf57ac1f12]::framework::visitor::visit_results::<rustc_borrowck[3b5de70414a05ac6]::dataflow::BorrowckAnalyses<rustc_index[f2328b8185c300]::bit_set::BitSet<rustc_borrowck[3b5de70414a05ac6]::dataflow::BorrowIndex>, rustc_index[f2328b8185c300]::bit_set::ChunkedBitSet<rustc_mir_dataflow[60696dcf57ac1f12]::move_paths::MovePathIndex>, rustc_index[f2328b8185c300]::bit_set::ChunkedBitSet<rustc_mir_dataflow[60696dcf57ac1f12]::move_paths::InitIndex>>, rustc_borrowck[3b5de70414a05ac6]::dataflow::BorrowckAnalyses<rustc_mir_dataflow[60696dcf57ac1f12]::framework::engine::Results<rustc_borrowck[3b5de70414a05ac6]::dataflow::Borrows>, rustc_mir_dataflow[60696dcf57ac1f12]::framework::engine::Results<rustc_mir_dataflow[60696dcf57ac1f12]::impls::MaybeUninitializedPlaces>, rustc_mir_dataflow[60696dcf57ac1f12]::framework::engine::Results<rustc_mir_dataflow[60696dcf57ac1f12]::impls::EverInitializedPlaces>>, core[9847d4a2e8a02df2]::iter::adapters::map::Map<rustc_middle[eaf6378de1cdbfa8]::mir::traversal::ReversePostorderIter, rustc_borrowck[3b5de70414a05ac6]::do_mir_borrowck::{closure#2}>, rustc_borrowck[3b5de70414a05ac6]::MirBorrowckCtxt>
30: 0x7f177c933632 - rustc_borrowck[3b5de70414a05ac6]::do_mir_borrowck
31: 0x7f177c92c2be - rustc_borrowck[3b5de70414a05ac6]::mir_borrowck
32: 0x7f177cb8d296 - rustc_query_system[3b264ab6e948b942]::query::plumbing::try_execute_query::<rustc_query_impl[1cc93b35ef872c79]::queries::mir_borrowck, rustc_query_impl[1cc93b35ef872c79]::plumbing::QueryCtxt>
33: 0x7f177bf473b2 - rustc_data_structures[8426954b093953dd]::sync::par_for_each_in::<&[rustc_span[4d522547309d7b79]::def_id::LocalDefId], <rustc_middle[eaf6378de1cdbfa8]::hir::map::Map>::par_body_owners<rustc_interface[dde792dfc5bb5edd]::passes::analysis::{closure#2}::{closure#0}>::{closure#0}>
34: 0x7f177bf46fde - <rustc_session[8656a7a78cf578e4]::session::Session>::time::<(), rustc_interface[dde792dfc5bb5edd]::passes::analysis::{closure#2}>
35: 0x7f177bf46780 - rustc_interface[dde792dfc5bb5edd]::passes::analysis
36: 0x7f177d411aec - rustc_query_system[3b264ab6e948b942]::query::plumbing::try_execute_query::<rustc_query_impl[1cc93b35ef872c79]::queries::analysis, rustc_query_impl[1cc93b35ef872c79]::plumbing::QueryCtxt>
37: 0x7f177d4117e0 - <rustc_query_impl[1cc93b35ef872c79]::Queries as rustc_middle[eaf6378de1cdbfa8]::ty::query::QueryEngine>::analysis
38: 0x7f177d26e109 - <rustc_middle[eaf6378de1cdbfa8]::ty::context::GlobalCtxt>::enter::<rustc_driver_impl[bad2ed848d64dbdc]::run_compiler::{closure#1}::{closure#2}::{closure#4}, core[9847d4a2e8a02df2]::result::Result<(), rustc_span[4d522547309d7b79]::ErrorGuaranteed>>
39: 0x7f177cdf852d - <rustc_interface[dde792dfc5bb5edd]::interface::Compiler>::enter::<rustc_driver_impl[bad2ed848d64dbdc]::run_compiler::{closure#1}::{closure#2}, core[9847d4a2e8a02df2]::result::Result<core[9847d4a2e8a02df2]::option::Option<rustc_interface[dde792dfc5bb5edd]::queries::Linker>, rustc_span[4d522547309d7b79]::ErrorGuaranteed>>
40: 0x7f177cdf6630 - rustc_span[4d522547309d7b79]::with_source_map::<core[9847d4a2e8a02df2]::result::Result<(), rustc_span[4d522547309d7b79]::ErrorGuaranteed>, rustc_interface[dde792dfc5bb5edd]::interface::run_compiler<core[9847d4a2e8a02df2]::result::Result<(), rustc_span[4d522547309d7b79]::ErrorGuaranteed>, rustc_driver_impl[bad2ed848d64dbdc]::run_compiler::{closure#1}>::{closure#0}::{closure#0}>
41: 0x7f177cdf5bd9 - std[b4247acdb72724ff]::sys_common::backtrace::_rust_begin_short_backtrace::<rustc_interface[dde792dfc5bb5edd]::util::run_in_thread_pool_with_globals<rustc_interface[dde792dfc5bb5edd]::interface::run_compiler<core[9847d4a2e8a02df2]::result::Result<(), rustc_span[4d522547309d7b79]::ErrorGuaranteed>, rustc_driver_impl[bad2ed848d64dbdc]::run_compiler::{closure#1}>::{closure#0}, core[9847d4a2e8a02df2]::result::Result<(), rustc_span[4d522547309d7b79]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[9847d4a2e8a02df2]::result::Result<(), rustc_span[4d522547309d7b79]::ErrorGuaranteed>>
42: 0x7f177d4e6afa - <<std[b4247acdb72724ff]::thread::Builder>::spawn_unchecked<rustc_interface[dde792dfc5bb5edd]::util::run_in_thread_pool_with_globals<rustc_interface[dde792dfc5bb5edd]::interface::run_compiler<core[9847d4a2e8a02df2]::result::Result<(), rustc_span[4d522547309d7b79]::ErrorGuaranteed>, rustc_driver_impl[bad2ed848d64dbdc]::run_compiler::{closure#1}>::{closure#0}, core[9847d4a2e8a02df2]::result::Result<(), rustc_span[4d522547309d7b79]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[9847d4a2e8a02df2]::result::Result<(), rustc_span[4d522547309d7b79]::ErrorGuaranteed>>::{closure#1} as core[9847d4a2e8a02df2]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
43: 0x7f177a9745f3 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce>::call_once::h51bca2043facf7d3
at /rustc/13afbdaa0655dda23d7129e59ac48f1ec88b2084/library/alloc/src/boxed.rs:1988:9
44: 0x7f177a9745f3 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce>::call_once::h365da710d54db7ab
at /rustc/13afbdaa0655dda23d7129e59ac48f1ec88b2084/library/alloc/src/boxed.rs:1988:9
45: 0x7f177a9745f3 - std::sys::unix::thread::Thread::new::thread_start::hb322f3a535acf0fe
at /rustc/13afbdaa0655dda23d7129e59ac48f1ec88b2084/library/std/src/sys/unix/thread.rs:108:17
46: 0x7f177a706bb5 -
47: 0x7f177a788d90 -
48: 0x0 -

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 (13afbda 2023-03-17) running on x86_64-unknown-linux-gnu

query stack during panic:
#0 [mir_borrowck] borrow-checking arr_by_ref
#1 [analysis] running analysis passes on this crate
end of query stack
error: aborting due to previous error; 2 warnings emitted

</p>
</details>


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[Noratrieb]

Probably fixed by #108705 (@clubby789)

[matthiaskrgr]

searched nightlies: from nightly-2022-12-30 to nightly-2023-03-18
regressed nightly: nightly-2023-01-01
searched commit range: ce85c98...574b64a
regressed commit: 247e44e

bisected with cargo-bisect-rustc v0.6.5

Host triple: x86_64-unknown-linux-gnu
Reproduce with:

cargo bisect-rustc --script=/home/matthias/vcs/github/rust_bisect/script.sh --test-dir=/home/matthias/vcs/github/rust_bisect/foo

Regression in rust-lang-ci@e3e79ed

same as #109297 ..?

[Noratrieb]

You should update your cargo-bisect-rustc version to make it bisect the contents of rollups as well^^

[matthiaskrgr]

I already have the git version installed :o

[matthiaskrgr]

Note that we don't have the artifacts for all rollups. I think it requires a perf bisection to be run on the pr or something?

[matthiaskrgr]

Regression in nightly-2021-09-01

found 9 bors merge commits in the specified range
  commit[0] 2021-08-30UTC: Auto merge of #88466 - sexxi-goose:issue-88372, r=nikomatsakis
  commit[1] 2021-08-30UTC: Auto merge of #88369 - lcnr:cec-rename, r=oli-obk
  commit[2] 2021-08-31UTC: Auto merge of #88100 - HTG-YT:edition2021-compopt-stabilization, r=m-ou-se
  commit[3] 2021-08-31UTC: Auto merge of #88414 - Aaron1011:guess-foreign-head-span, r=estebank
  commit[4] 2021-08-31UTC: Auto merge of #88467 - sexxi-goose:issue-88431, r=nikomatsakis
  commit[5] 2021-08-31UTC: Auto merge of #88491 - RalfJung:miri, r=RalfJung
  commit[6] 2021-08-31UTC: Auto merge of #88527 - m-ou-se:rollup-az6xtc5, r=m-ou-se
  commit[7] 2021-08-31UTC: Auto merge of #88535 - m-ou-se:rollup-jeusxbo, r=m-ou-se
  commit[8] 2021-08-31UTC: Auto merge of #88506 - Mark-Simulacrum:fix-rlibs, r=ehuss
ERROR: no CI builds available between 5d6804469d80aaf26f98090ae016af45e267f58f and 29ef6cf1637aa8317f8911f93f14e18d404c1b0e within last 167 days

[Noratrieb]

Ah, the rollup predates unrolled builds.

[clubby789]

I think this is a different issue, it's not fixed by that PR anyway. I'll try and investigate anyway

@rustbot claim

---

The ICE occurs while trying to report this error

error[E0596]: cannot borrow `f` as mutable, as it is not declared as mutable
 --> poc.rs:6:5
  |
4 |         let [ref y, ref mut z @ ..] = x;
  |                                       - calling `f` requires mutable binding due to mutable borrow of `x`
5 |     };
6 |     f();
  |     ^ cannot borrow as mutable
  |
help: consider changing this to be mutable
  |
3 |     let mut f = || {
  |     

Changing to let [ref mut b @ ..] = x; fails earlier: compiler/rustc_middle/src/ty/closure.rs:178:25: Unexpected projection Subslice in captured place

[clubby789]

Actually this can be reduced further -

pub fn capture_slice(x: [u8; 3]) {
    || {
        let [_x @ ..] = x;
    };
}