Triggering 'this path really should be doomed...' error

[AVee]

Code

Playground: https://play.rust-lang.org/?version=nightly&mode=debug&edition=2021&gist=42a62b185b3f54276c17e0c3560af875

use core::cell::RefCell;

pub struct SpinChar {
    current: RefCell<char>,
}

impl SpinChar {
    pub fn new() -> Self {
        SpinChar {
            current: RefCell::new('-'),
        }
    }

    pub fn next(&self) -> char {
        let current = self.current.try_borrow_mut();
        match current {
            Ok(mut c) => {
                *c = match *c {
                    '-' => '\\',
                    '\\' => '|',
                    '|' => '/',
                    _ => '-',
                }
                *c
            }
            Err(_) => '_',
        }
    }
}

The code (obviously) needs a semicolon on line 23. With that in place it compiles just fine.

Meta

Found in 1.77 initially, but it also exists in nightly.

rustc --version --verbose:

rustc 1.79.0-nightly (8b2459c1f 2024-04-09)
binary: rustc
commit-hash: 8b2459c1f21187f9792d99310171a15e64feb9cf
commit-date: 2024-04-09
host: x86_64-unknown-linux-gnu
release: 1.79.0-nightly
LLVM version: 18.1.3

Error output

note: no errors encountered even though delayed bugs were created

note: those delayed bugs will now be shown as internal compiler errors

error: internal compiler error: this path really should be doomed...
  --> src/bug.rs:24:21
   |
24 |                     *c
   |                     ^
   |
note: delayed at compiler/rustc_hir_typeck/src/op.rs:915:28
         0: <rustc_errors::DiagCtxtInner>::emit_diagnostic
         1: <rustc_errors::DiagCtxt>::emit_diagnostic
         2: <rustc_span::ErrorGuaranteed as rustc_errors::diagnostic::EmissionGuarantee>::emit_producing_guarantee
         3: <rustc_hir_typeck::fn_ctxt::FnCtxt>::check_overloaded_binop
         4: <rustc_hir_typeck::fn_ctxt::FnCtxt>::check_expr_with_expectation_and_args
         5: <rustc_hir_typeck::fn_ctxt::FnCtxt>::check_expr_with_expectation_and_args
         6: <rustc_hir_typeck::fn_ctxt::FnCtxt>::check_block_with_expected
         7: <rustc_hir_typeck::fn_ctxt::FnCtxt>::check_expr_with_expectation_and_args
         8: <rustc_hir_typeck::fn_ctxt::FnCtxt>::check_match
         9: <rustc_hir_typeck::fn_ctxt::FnCtxt>::check_expr_with_expectation_and_args
        10: <rustc_hir_typeck::fn_ctxt::FnCtxt>::check_block_with_expected
        11: <rustc_hir_typeck::fn_ctxt::FnCtxt>::check_expr_with_expectation_and_args
        12: rustc_hir_typeck::check::check_fn
        13: rustc_hir_typeck::typeck
        14: rustc_query_impl::plumbing::__rust_begin_short_backtrace::<rustc_query_impl::query_impl::typeck::dynamic_query::{closure#2}::{closure#0}, rustc_middle::query::erase::Erased<[u8; 8]>>
        15: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::DynamicConfig<rustc_query_system::query::caches::VecCache<rustc_span::def_id::LocalDefId, rustc_middle::query::erase::Erased<[u8; 8]>>, false, false, false>, rustc_query_impl::plumbing::QueryCtxt, false>
        16: rustc_query_impl::query_impl::typeck::get_query_non_incr::__rust_end_short_backtrace
        17: <rustc_middle::hir::map::Map>::par_body_owners::<rustc_hir_analysis::check_crate::{closure#4}>::{closure#0}
        18: rustc_hir_analysis::check_crate
        19: rustc_interface::passes::analysis
        20: rustc_query_impl::plumbing::__rust_begin_short_backtrace::<rustc_query_impl::query_impl::analysis::dynamic_query::{closure#2}::{closure#0}, rustc_middle::query::erase::Erased<[u8; 1]>>
        21: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::DynamicConfig<rustc_query_system::query::caches::SingleCache<rustc_middle::query::erase::Erased<[u8; 1]>>, false, false, false>, rustc_query_impl::plumbing::QueryCtxt, false>
        22: rustc_query_impl::query_impl::analysis::get_query_non_incr::__rust_end_short_backtrace
        23: rustc_interface::interface::run_compiler::<core::result::Result<(), rustc_span::ErrorGuaranteed>, rustc_driver_impl::run_compiler::{closure#0}>::{closure#0}
        24: std::sys_common::backtrace::__rust_begin_short_backtrace::<rustc_interface::util::run_in_thread_with_globals<rustc_interface::util::run_in_thread_pool_with_globals<rustc_interface::interface::run_compiler<core::result::Result<(), rustc_span::ErrorGuaranteed>, rustc_driver_impl::run_compiler::{closure#0}>::{closure#0}, core::result::Result<(), rustc_span::ErrorGuaranteed>>::{closure#0}, core::result::Result<(), rustc_span::ErrorGuaranteed>>::{closure#0}::{closure#0}, core::result::Result<(), rustc_span::ErrorGuaranteed>>
        25: <<std::thread::Builder>::spawn_unchecked_<rustc_interface::util::run_in_thread_with_globals<rustc_interface::util::run_in_thread_pool_with_globals<rustc_interface::interface::run_compiler<core::result::Result<(), rustc_span::ErrorGuaranteed>, rustc_driver_impl::run_compiler::{closure#0}>::{closure#0}, core::result::Result<(), rustc_span::ErrorGuaranteed>>::{closure#0}, core::result::Result<(), rustc_span::ErrorGuaranteed>>::{closure#0}::{closure#0}, core::result::Result<(), rustc_span::ErrorGuaranteed>>::{closure#1} as core::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
        26: <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once
                   at /rustc/8b2459c1f21187f9792d99310171a15e64feb9cf/library/alloc/src/boxed.rs:2018:9
        27: <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once
                   at /rustc/8b2459c1f21187f9792d99310171a15e64feb9cf/library/alloc/src/boxed.rs:2018:9
        28: std::sys::pal::unix::thread::Thread::new::thread_start
                   at /rustc/8b2459c1f21187f9792d99310171a15e64feb9cf/library/std/src/sys/pal/unix/thread.rs:108:17
        29: start_thread
                   at ./nptl/pthread_create.c:442:8
        30: __GI___clone3
                   at ./misc/../sysdeps/unix/sysv/linux/x86_64/clone3.S:81
  --> src/bug.rs:24:21
   |
24 |                     *c
   |                     ^

error: internal compiler error[E0369]: cannot multiply `char` by `RefMut<'_, char>`
  --> src/bug.rs:24:21
   |
18 |                   *c = match *c {
   |  ______________________-
19 | |                     '-' => '\\',
20 | |                     '\\' => '|',
21 | |                     '|' => '/',
22 | |                     _ => '-',
23 | |                 }
   | |_________________- char
24 |                       *c
   |                       ^- RefMut<'_, char>
   |
note: delayed at compiler/rustc_hir_typeck/src/op.rs:375:29
         0: <rustc_errors::DiagCtxtInner>::emit_diagnostic
         1: <rustc_errors::DiagCtxt>::emit_diagnostic
         2: <rustc_span::ErrorGuaranteed as rustc_errors::diagnostic::EmissionGuarantee>::emit_producing_guarantee
         3: <rustc_hir_typeck::fn_ctxt::FnCtxt>::check_overloaded_binop
         4: <rustc_hir_typeck::fn_ctxt::FnCtxt>::check_expr_with_expectation_and_args
         5: <rustc_hir_typeck::fn_ctxt::FnCtxt>::check_expr_with_expectation_and_args
         6: <rustc_hir_typeck::fn_ctxt::FnCtxt>::check_block_with_expected
         7: <rustc_hir_typeck::fn_ctxt::FnCtxt>::check_expr_with_expectation_and_args
         8: <rustc_hir_typeck::fn_ctxt::FnCtxt>::check_match
         9: <rustc_hir_typeck::fn_ctxt::FnCtxt>::check_expr_with_expectation_and_args
        10: <rustc_hir_typeck::fn_ctxt::FnCtxt>::check_block_with_expected
        11: <rustc_hir_typeck::fn_ctxt::FnCtxt>::check_expr_with_expectation_and_args
        12: rustc_hir_typeck::check::check_fn
        13: rustc_hir_typeck::typeck
        14: rustc_query_impl::plumbing::__rust_begin_short_backtrace::<rustc_query_impl::query_impl::typeck::dynamic_query::{closure#2}::{closure#0}, rustc_middle::query::erase::Erased<[u8; 8]>>
        15: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::DynamicConfig<rustc_query_system::query::caches::VecCache<rustc_span::def_id::LocalDefId, rustc_middle::query::erase::Erased<[u8; 8]>>, false, false, false>, rustc_query_impl::plumbing::QueryCtxt, false>
        16: rustc_query_impl::query_impl::typeck::get_query_non_incr::__rust_end_short_backtrace
        17: <rustc_middle::hir::map::Map>::par_body_owners::<rustc_hir_analysis::check_crate::{closure#4}>::{closure#0}
        18: rustc_hir_analysis::check_crate
        19: rustc_interface::passes::analysis
        20: rustc_query_impl::plumbing::__rust_begin_short_backtrace::<rustc_query_impl::query_impl::analysis::dynamic_query::{closure#2}::{closure#0}, rustc_middle::query::erase::Erased<[u8; 1]>>
        21: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::DynamicConfig<rustc_query_system::query::caches::SingleCache<rustc_middle::query::erase::Erased<[u8; 1]>>, false, false, false>, rustc_query_impl::plumbing::QueryCtxt, false>
        22: rustc_query_impl::query_impl::analysis::get_query_non_incr::__rust_end_short_backtrace
        23: rustc_interface::interface::run_compiler::<core::result::Result<(), rustc_span::ErrorGuaranteed>, rustc_driver_impl::run_compiler::{closure#0}>::{closure#0}
        24: std::sys_common::backtrace::__rust_begin_short_backtrace::<rustc_interface::util::run_in_thread_with_globals<rustc_interface::util::run_in_thread_pool_with_globals<rustc_interface::interface::run_compiler<core::result::Result<(), rustc_span::ErrorGuaranteed>, rustc_driver_impl::run_compiler::{closure#0}>::{closure#0}, core::result::Result<(), rustc_span::ErrorGuaranteed>>::{closure#0}, core::result::Result<(), rustc_span::ErrorGuaranteed>>::{closure#0}::{closure#0}, core::result::Result<(), rustc_span::ErrorGuaranteed>>
        25: <<std::thread::Builder>::spawn_unchecked_<rustc_interface::util::run_in_thread_with_globals<rustc_interface::util::run_in_thread_pool_with_globals<rustc_interface::interface::run_compiler<core::result::Result<(), rustc_span::ErrorGuaranteed>, rustc_driver_impl::run_compiler::{closure#0}>::{closure#0}, core::result::Result<(), rustc_span::ErrorGuaranteed>>::{closure#0}, core::result::Result<(), rustc_span::ErrorGuaranteed>>::{closure#0}::{closure#0}, core::result::Result<(), rustc_span::ErrorGuaranteed>>::{closure#1} as core::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
        26: <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once
                   at /rustc/8b2459c1f21187f9792d99310171a15e64feb9cf/library/alloc/src/boxed.rs:2018:9
        27: <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once
                   at /rustc/8b2459c1f21187f9792d99310171a15e64feb9cf/library/alloc/src/boxed.rs:2018:9
        28: std::sys::pal::unix::thread::Thread::new::thread_start
                   at /rustc/8b2459c1f21187f9792d99310171a15e64feb9cf/library/std/src/sys/pal/unix/thread.rs:108:17
        29: start_thread
                   at ./nptl/pthread_create.c:442:8
        30: __GI___clone3
                   at ./misc/../sysdeps/unix/sysv/linux/x86_64/clone3.S:81
  --> src/bug.rs:24:21
   |
24 |                     *c
   |                     ^
help: you might have meant to write a semicolon here
   |
23 |                 };
   |                  +

note: it seems that this compiler `1.79.0-nightly (8b2459c1f 2024-04-09)` is outdated, a newer nightly should have been released in the meantime
  |
  = note: please consider running `rustup update nightly` to update the nightly channel and check if this problem still persists
  = note: if the problem still persists, 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 attach the file at `/home/avee/source/playground/tztest/rustc-ice-2024-04-10T13_14_12-25919.txt` to your bug report

query stack during panic:
end of query stack

rustc-ice-2024-04-10T13_14_12-25919.txt