ICE: still mutable

[matthiaskrgr]

auto-reduced (treereduce-rust):

struct Thingu {
    Thingux:  [X; -const {-X}]  match ,
    y: u32
}

original:

struct Thingu {
    Thingux:  [X; -const {-X}]  match ,
    y: u32
}

#[derive(Debug, Copy, Clnne)]struct std<'a, X> {
    X: [X; -const {-}],
    y: [[X; -const  continue {-X}]; -const {-X}]
}struct std {
    Thingx:   y: [[X; -const {-X}]; --X]
}

Version information

rustc 1.80.0-nightly (7717a306b 2024-05-28)
binary: rustc
commit-hash: 7717a306b2678ba9ece19b723c76a6b3a89ba931
commit-date: 2024-05-28
host: x86_64-unknown-linux-gnu
release: 1.80.0-nightly
LLVM version: 18.1.6

Command:
/home/matthias/.rustup/toolchains/master/bin/rustc

Program output

error: expected `,`, or `}`, found keyword `match`
 --> /tmp/icemaker_global_tempdir.RIXVA1mbOiVa/rustc_testrunner_tmpdir_reporting.UhMokt5Os0j1/mvce.rs:2:31
  |
2 |     Thingux:  [X; -const {-X}]  match ,
  |                               ^ help: try adding a comma: `,`

error: expected identifier, found keyword `match`
 --> /tmp/icemaker_global_tempdir.RIXVA1mbOiVa/rustc_testrunner_tmpdir_reporting.UhMokt5Os0j1/mvce.rs:2:33
  |
1 | struct Thingu {
  |        ------ while parsing this struct
2 |     Thingux:  [X; -const {-X}]  match ,
  |                                 ^^^^^ expected identifier, found keyword
  |
help: escape `match` to use it as an identifier
  |
2 |     Thingux:  [X; -const {-X}]  r#match ,
  |                                 ++

error[E0412]: cannot find type `X` in this scope
 --> /tmp/icemaker_global_tempdir.RIXVA1mbOiVa/rustc_testrunner_tmpdir_reporting.UhMokt5Os0j1/mvce.rs:2:16
  |
2 |     Thingux:  [X; -const {-X}]  match ,
  |                ^ not found in this scope
  |
help: you might be missing a type parameter
  |
1 | struct Thingu<X> {
  |              +++

error[E0425]: cannot find value `X` in this scope
 --> /tmp/icemaker_global_tempdir.RIXVA1mbOiVa/rustc_testrunner_tmpdir_reporting.UhMokt5Os0j1/mvce.rs:2:28
  |
2 |     Thingux:  [X; -const {-X}]  match ,
  |                            ^ not found in this scope
  |
help: you might be missing a const parameter
  |
1 | struct Thingu<const X: /* Type */> {
  |              +++++++++++++++++++++

error[E0601]: `main` function not found in crate `mvce`
 --> /tmp/icemaker_global_tempdir.RIXVA1mbOiVa/rustc_testrunner_tmpdir_reporting.UhMokt5Os0j1/mvce.rs:4:2
  |
4 | }
  |  ^ consider adding a `main` function to `/tmp/icemaker_global_tempdir.RIXVA1mbOiVa/rustc_testrunner_tmpdir_reporting.UhMokt5Os0j1/mvce.rs`

thread 'rustc' panicked at compiler/rustc_middle/src/ty/context.rs:1350:49:
still mutable
stack backtrace:
   0:     0x706b05a60ae5 - std::backtrace_rs::backtrace::libunwind::trace::h8e3ec5065424d28b
                               at /rustc/7717a306b2678ba9ece19b723c76a6b3a89ba931/library/std/src/../../backtrace/src/backtrace/libunwind.rs:116:5
   1:     0x706b05a60ae5 - std::backtrace_rs::backtrace::trace_unsynchronized::h882cf49e59475dbc
                               at /rustc/7717a306b2678ba9ece19b723c76a6b3a89ba931/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5
   2:     0x706b05a60ae5 - std::sys_common::backtrace::_print_fmt::h2c337a2c4b83dc01
                               at /rustc/7717a306b2678ba9ece19b723c76a6b3a89ba931/library/std/src/sys_common/backtrace.rs:68:5
   3:     0x706b05a60ae5 - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::h5fad958b7140a660
                               at /rustc/7717a306b2678ba9ece19b723c76a6b3a89ba931/library/std/src/sys_common/backtrace.rs:44:22
   4:     0x706b05ab15db - core::fmt::rt::Argument::fmt::h9f1efa968e340ff7
                               at /rustc/7717a306b2678ba9ece19b723c76a6b3a89ba931/library/core/src/fmt/rt.rs:165:63
   5:     0x706b05ab15db - core::fmt::write::hc4341e028d4aa04e
                               at /rustc/7717a306b2678ba9ece19b723c76a6b3a89ba931/library/core/src/fmt/mod.rs:1168:21
   6:     0x706b05a5586f - std::io::Write::write_fmt::hf3dd4197197b5730
                               at /rustc/7717a306b2678ba9ece19b723c76a6b3a89ba931/library/std/src/io/mod.rs:1835:15
   7:     0x706b05a608be - std::sys_common::backtrace::_print::hee589e8f95e333af
                               at /rustc/7717a306b2678ba9ece19b723c76a6b3a89ba931/library/std/src/sys_common/backtrace.rs:47:5
   8:     0x706b05a608be - std::sys_common::backtrace::print::hc6a85e053c1c7334
                               at /rustc/7717a306b2678ba9ece19b723c76a6b3a89ba931/library/std/src/sys_common/backtrace.rs:34:9
   9:     0x706b05a632e9 - std::panicking::default_hook::{{closure}}::he62a1676f96fee54
  10:     0x706b05a6308a - std::panicking::default_hook::h2ceb904f12dea8be
                               at /rustc/7717a306b2678ba9ece19b723c76a6b3a89ba931/library/std/src/panicking.rs:298:9
  11:     0x706b0238e6a0 - std[d6c1f98fb4e95ff7]::panicking::update_hook::<alloc[78b6f7e6bd40c475]::boxed::Box<rustc_driver_impl[c511ea10b869fcf7]::install_ice_hook::{closure#0}>>::{closure#0}
  12:     0x706b05a63a1b - <alloc::boxed::Box<F,A> as core::ops::function::Fn<Args>>::call::hc5b72f85a4688529
                               at /rustc/7717a306b2678ba9ece19b723c76a6b3a89ba931/library/alloc/src/boxed.rs:2077:9
  13:     0x706b05a63a1b - std::panicking::rust_panic_with_hook::h0a690364d46daaac
                               at /rustc/7717a306b2678ba9ece19b723c76a6b3a89ba931/library/std/src/panicking.rs:799:13
  14:     0x706b05a63794 - std::panicking::begin_panic_handler::{{closure}}::h9c10c03249dd0030
                               at /rustc/7717a306b2678ba9ece19b723c76a6b3a89ba931/library/std/src/panicking.rs:664:13
  15:     0x706b05a60fa9 - std::sys_common::backtrace::__rust_end_short_backtrace::h599802efea5774a9
                               at /rustc/7717a306b2678ba9ece19b723c76a6b3a89ba931/library/std/src/sys_common/backtrace.rs:171:18
  16:     0x706b05a634c7 - rust_begin_unwind
                               at /rustc/7717a306b2678ba9ece19b723c76a6b3a89ba931/library/std/src/panicking.rs:652:5
  17:     0x706b05aadb73 - core::panicking::panic_fmt::h16f8f3f4aae78ff5
                               at /rustc/7717a306b2678ba9ece19b723c76a6b3a89ba931/library/core/src/panicking.rs:72:14
  18:     0x706b05aad91b - core::panicking::panic_display::hd37bbef51df3a6ae
                               at /rustc/7717a306b2678ba9ece19b723c76a6b3a89ba931/library/core/src/panicking.rs:262:5
  19:     0x706b05aad91b - core::option::expect_failed::hded3cd93e8782a18
                               at /rustc/7717a306b2678ba9ece19b723c76a6b3a89ba931/library/core/src/option.rs:1997:5
  20:     0x706b0118113e - <rustc_middle[b8101328ceeb956a]::ty::context::TyCtxt>::create_def
  21:     0x706b00ad25c8 - <rustc_hir_typeck[1894e698386f9cd2]::writeback::WritebackCx as rustc_hir[aafb8b6f15759b0a]::intravisit::Visitor>::visit_expr
  22:     0x706b00ad0df0 - <rustc_hir_typeck[1894e698386f9cd2]::writeback::WritebackCx as rustc_hir[aafb8b6f15759b0a]::intravisit::Visitor>::visit_expr
  23:     0x706b04270447 - <rustc_hir_typeck[1894e698386f9cd2]::fn_ctxt::FnCtxt>::resolve_type_vars_in_body
  24:     0x706b03b836c2 - rustc_hir_typeck[1894e698386f9cd2]::typeck
  25:     0x706b03b825d1 - rustc_query_impl[a43b8a3fae63a645]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[a43b8a3fae63a645]::query_impl::typeck::dynamic_query::{closure#2}::{closure#0}, rustc_middle[b8101328ceeb956a]::query::erase::Erased<[u8; 8usize]>>
  26:     0x706b039c212e - rustc_query_system[ef4de90281b6d444]::query::plumbing::try_execute_query::<rustc_query_impl[a43b8a3fae63a645]::DynamicConfig<rustc_query_system[ef4de90281b6d444]::query::caches::VecCache<rustc_span[8ae10af61471f323]::def_id::LocalDefId, rustc_middle[b8101328ceeb956a]::query::erase::Erased<[u8; 8usize]>>, false, false, false>, rustc_query_impl[a43b8a3fae63a645]::plumbing::QueryCtxt, false>
  27:     0x706b039c0c55 - rustc_query_impl[a43b8a3fae63a645]::query_impl::typeck::get_query_non_incr::__rust_end_short_backtrace
  28:     0x706b039c34a1 - rustc_query_impl[a43b8a3fae63a645]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[a43b8a3fae63a645]::query_impl::used_trait_imports::dynamic_query::{closure#2}::{closure#0}, rustc_middle[b8101328ceeb956a]::query::erase::Erased<[u8; 8usize]>>
  29:     0x706b039c212e - rustc_query_system[ef4de90281b6d444]::query::plumbing::try_execute_query::<rustc_query_impl[a43b8a3fae63a645]::DynamicConfig<rustc_query_system[ef4de90281b6d444]::query::caches::VecCache<rustc_span[8ae10af61471f323]::def_id::LocalDefId, rustc_middle[b8101328ceeb956a]::query::erase::Erased<[u8; 8usize]>>, false, false, false>, rustc_query_impl[a43b8a3fae63a645]::plumbing::QueryCtxt, false>
  30:     0x706b039c1acd - rustc_query_impl[a43b8a3fae63a645]::query_impl::used_trait_imports::get_query_non_incr::__rust_end_short_backtrace
  31:     0x706b039c14fb - rustc_hir_analysis[4a9f7cb3dd37a3dc]::check_unused::check_unused_traits
  32:     0x706b039c1363 - rustc_query_impl[a43b8a3fae63a645]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[a43b8a3fae63a645]::query_impl::check_unused_traits::dynamic_query::{closure#2}::{closure#0}, rustc_middle[b8101328ceeb956a]::query::erase::Erased<[u8; 0usize]>>
  33:     0x706b04599f01 - rustc_query_system[ef4de90281b6d444]::query::plumbing::try_execute_query::<rustc_query_impl[a43b8a3fae63a645]::DynamicConfig<rustc_query_system[ef4de90281b6d444]::query::caches::SingleCache<rustc_middle[b8101328ceeb956a]::query::erase::Erased<[u8; 0usize]>>, false, false, false>, rustc_query_impl[a43b8a3fae63a645]::plumbing::QueryCtxt, false>
  34:     0x706b04599cab - rustc_query_impl[a43b8a3fae63a645]::query_impl::check_unused_traits::get_query_non_incr::__rust_end_short_backtrace
  35:     0x706b039bf2fb - rustc_hir_analysis[4a9f7cb3dd37a3dc]::check_crate
  36:     0x706b041683fe - rustc_interface[3320d9bec8b3433a]::passes::analysis
  37:     0x706b04167f5b - rustc_query_impl[a43b8a3fae63a645]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[a43b8a3fae63a645]::query_impl::analysis::dynamic_query::{closure#2}::{closure#0}, rustc_middle[b8101328ceeb956a]::query::erase::Erased<[u8; 1usize]>>
  38:     0x706b0459c225 - rustc_query_system[ef4de90281b6d444]::query::plumbing::try_execute_query::<rustc_query_impl[a43b8a3fae63a645]::DynamicConfig<rustc_query_system[ef4de90281b6d444]::query::caches::SingleCache<rustc_middle[b8101328ceeb956a]::query::erase::Erased<[u8; 1usize]>>, false, false, false>, rustc_query_impl[a43b8a3fae63a645]::plumbing::QueryCtxt, false>
  39:     0x706b0459bf8f - rustc_query_impl[a43b8a3fae63a645]::query_impl::analysis::get_query_non_incr::__rust_end_short_backtrace
  40:     0x706b043f9f5c - rustc_interface[3320d9bec8b3433a]::interface::run_compiler::<core[5e8023d66ded8339]::result::Result<(), rustc_span[8ae10af61471f323]::ErrorGuaranteed>, rustc_driver_impl[c511ea10b869fcf7]::run_compiler::{closure#0}>::{closure#1}
  41:     0x706b043c0609 - std[d6c1f98fb4e95ff7]::sys_common::backtrace::__rust_begin_short_backtrace::<rustc_interface[3320d9bec8b3433a]::util::run_in_thread_with_globals<rustc_interface[3320d9bec8b3433a]::util::run_in_thread_pool_with_globals<rustc_interface[3320d9bec8b3433a]::interface::run_compiler<core[5e8023d66ded8339]::result::Result<(), rustc_span[8ae10af61471f323]::ErrorGuaranteed>, rustc_driver_impl[c511ea10b869fcf7]::run_compiler::{closure#0}>::{closure#1}, core[5e8023d66ded8339]::result::Result<(), rustc_span[8ae10af61471f323]::ErrorGuaranteed>>::{closure#0}, core[5e8023d66ded8339]::result::Result<(), rustc_span[8ae10af61471f323]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[5e8023d66ded8339]::result::Result<(), rustc_span[8ae10af61471f323]::ErrorGuaranteed>>
  42:     0x706b043c03b2 - <<std[d6c1f98fb4e95ff7]::thread::Builder>::spawn_unchecked_<rustc_interface[3320d9bec8b3433a]::util::run_in_thread_with_globals<rustc_interface[3320d9bec8b3433a]::util::run_in_thread_pool_with_globals<rustc_interface[3320d9bec8b3433a]::interface::run_compiler<core[5e8023d66ded8339]::result::Result<(), rustc_span[8ae10af61471f323]::ErrorGuaranteed>, rustc_driver_impl[c511ea10b869fcf7]::run_compiler::{closure#0}>::{closure#1}, core[5e8023d66ded8339]::result::Result<(), rustc_span[8ae10af61471f323]::ErrorGuaranteed>>::{closure#0}, core[5e8023d66ded8339]::result::Result<(), rustc_span[8ae10af61471f323]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[5e8023d66ded8339]::result::Result<(), rustc_span[8ae10af61471f323]::ErrorGuaranteed>>::{closure#2} as core[5e8023d66ded8339]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  43:     0x706b05a6d9eb - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::ha3f12f701ab217ba
                               at /rustc/7717a306b2678ba9ece19b723c76a6b3a89ba931/library/alloc/src/boxed.rs:2063:9
  44:     0x706b05a6d9eb - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::hbabc732018734ba3
                               at /rustc/7717a306b2678ba9ece19b723c76a6b3a89ba931/library/alloc/src/boxed.rs:2063:9
  45:     0x706b05a6d9eb - std::sys::pal::unix::thread::Thread::new::thread_start::h25b845304e0b166b
                               at /rustc/7717a306b2678ba9ece19b723c76a6b3a89ba931/library/std/src/sys/pal/unix/thread.rs:108:17
  46:     0x706aff0aa1cf - <unknown>
  47:     0x706aff12b6ec - <unknown>
  48:                0x0 - <unknown>

error: 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: please make sure that you have updated to the latest nightly

note: rustc 1.80.0-nightly (7717a306b 2024-05-28) running on x86_64-unknown-linux-gnu

query stack during panic:
#0 [typeck] type-checking `Thingu::Thingux::{constant#0}`
#1 [used_trait_imports] finding used_trait_imports `Thingu::Thingux::{constant#0}`
end of query stack
error: aborting due to 5 previous errors

Some errors have detailed explanations: E0412, E0425, E0601.
For more information about an error, try `rustc --explain E0412`.

[matthiaskrgr]

mvce: type A = [u32; const { X }];

[theemathas]

The undeclared variable isn't needed for the ICE. This code also causes an ICE: type A = [i32; const { 2 }];