ICE running cargo fmt in bevy repo

[TeamDman]

rustc-ice-2025-12-06T03_03_24-4684.txt

My repo at the time: https://github.com/TeamDman/bevy/tree/rust-ice-2025-12-05 (permalink)

bevywinicon on  rust-ice-2025-12-05 [$] is 📦 v0.18.0-dev via 🦀 v1.94.0-nightly 
❯ cargo fmt

thread 'main' (35988) panicked at compiler\rustc_parse\src\parser\item.rs:400:32:
called `Result::unwrap()` on an `Err` value: Some(DiagInner { level: Error, messages: [(FluentIdentifier("parse_expected_identifier_found_keyword_str", None), NoStyle)], code: None, lint_id: None, span: MultiSpan 
{ primary_spans: [Span { lo: BytePos(139697), hi: BytePos(139701), ctxt: #0 }], span_labels: [(Span { lo: BytePos(139697), hi: BytePos(139701), ctxt: #0 }, Translated("expected identifier, found keyword"))] }, children: [], suggestions: Enabled([]), args: {"token": Str("Self")}, reserved_args: {}, sort_span: Span { lo: BytePos(139697), hi: BytePos(139701), ctxt: #0 }, is_lint: None, long_ty_path: None, emitted_at: DiagLocation { file: "compiler\\rustc_parse\\src\\parser\\diagnostics.rs", line: 381, col: 34 } })

bevywinicon on  rust-ice-2025-12-05 [$] is 📦 v0.18.0-dev via 🦀 v1.94.0-nightly took 6s
❯ rustc --version
rustc 1.94.0-nightly (1aa9bab4e 2025-12-05)
bevywinicon on  rust-ice-2025-12-05 [$] is 📦 v0.18.0-dev via 🦀 v1.94.0-nightly 
❯ cargo --version
cargo 1.94.0-nightly (2c283a9a5 2025-12-04)
bevywinicon on  rust-ice-2025-12-05 [$] is 📦 v0.18.0-dev via 🦀 v1.94.0-nightly 
❯ rustup --version
rustup 1.28.2 (e4f3ad6f8 2025-04-28)
info: This is the version for the rustup toolchain manager, not the rustc compiler.
info: The currently active `rustc` version is `rustc 1.94.0-nightly (1aa9bab4e 2025-12-05)`
bevywinicon on  rust-ice-2025-12-05 [$] is 📦 v0.18.0-dev via 🦀 v1.94.0-nightly 
❯ pwd

Path
----
D:\bevywinicon

bevywinicon on  rust-ice-2025-12-05 [$] is 📦 v0.18.0-dev via 🦀 v1.94.0-nightly 
❯ git status
On branch rust-ice-2025-12-05
Your branch is up to date with 'mine/rust-ice-2025-12-05'.

nothing to commit, working tree clean
bevywinicon on  rust-ice-2025-12-05 [$] is 📦 v0.18.0-dev via 🦀 v1.94.0-nightly 
❯ git log   
commit ee86d092937e6f0f678c4773a309a2f0bd57f83f (HEAD -> rust-ice-2025-12-05, mine/rust-ice-2025-12-05, feat/window-icon-v3)
Author: TeamDman <TeamDman9201@gmail.com>
Date:   Fri Dec 5 22:06:46 2025 -0500

    Fix formatting

Observed this after doing rustup update after experiencing #5975 lol

[TeamDman]

still happens after cargo clean

[TeamDman]

narrowed it down, it only ICEs when the members being formatted includes bevy_reflect_derive

cargo fmt -p bevy_reflect_derive

[TeamDman]

Minimal reproduction:

bruh/repro2.rs:

use proc_macro2::{Ident, Span};
use quote::quote;

fn reproduce() {
    let __this = Ident::new("__this", Span::call_site());
    let _ = quote!(Self(#__this));
}

crates\bevy_reflect\derive on  rust-ice-2025-12-05 [$?⇡] is 📦 v0.18.0-dev via 🦀 v1.94.0-nightly 
❯ rustfmt .\bruh\repro2.rs

thread 'main' (14408) panicked at compiler\rustc_parse\src\parser\item.rs:400:32:
called `Result::unwrap()` on an `Err` value: Some(DiagInner { level: Error, messages: [(FluentIdentifier("parse_expected_identifier_found_keyword_str", None), NoStyle)], 
code: None, lint_id: None, span: MultiSpan { primary_spans: [Span { lo: BytePos(145), hi: BytePos(149), ctxt: #0 }], span_labels: [(Span { lo: BytePos(145), hi: BytePos(149), ctxt: #0 }, Translated("expected identifier, found keyword"))] }, children: [], suggestions: Enabled([]), args: {"token": Str("Self")}, reserved_args: {}, sort_span: Span { lo: BytePos(145), hi: BytePos(149), ctxt: #0 }, is_lint: None, long_ty_path: None, emitted_at: DiagLocation { file: "compiler\\rustc_parse\\src\\parser\\diagnostics.rs", line: 381, col: 34 } })
stack backtrace:
   0:     0x7ffd8acd4f92 - std::backtrace_rs::backtrace::win64::trace
                               at /rustc/1aa9bab4ecbce4859eaad53000f78158ebe2be2c/library\std\src\..\..\backtrace\src\backtrace\win64.rs:85
   1:     0x7ffd8acd4f92 - std::backtrace_rs::backtrace::trace_unsynchronized
                               at /rustc/1aa9bab4ecbce4859eaad53000f78158ebe2be2c/library\std\src\..\..\backtrace\src\backtrace\mod.rs:66
   2:     0x7ffd8acd4f92 - std::sys::backtrace::_print_fmt
                               at /rustc/1aa9bab4ecbce4859eaad53000f78158ebe2be2c/library\std\src\sys\backtrace.rs:68
   3:     0x7ffd8acd4f92 - std::sys::backtrace::impl$0::print::impl$0::fmt
                               at /rustc/1aa9bab4ecbce4859eaad53000f78158ebe2be2c/library\std\src\sys\backtrace.rs:38
   4:     0x7ffd8acfd241 - core::fmt::write
                               at /rustc/1aa9bab4ecbce4859eaad53000f78158ebe2be2c/library\core\src\fmt\mod.rs:0
   5:     0x7ffd8ace5144 - std::io::default_write_fmt
                               at /rustc/1aa9bab4ecbce4859eaad53000f78158ebe2be2c/library\std\src\io\mod.rs:614
   6:     0x7ffd8ace5144 - std::io::Write::write_fmt<std::sys::stdio::windows::Stderr>
                               at /rustc/1aa9bab4ecbce4859eaad53000f78158ebe2be2c/library\std\src\io\mod.rs:1969
   7:     0x7ffd8acaedce - std::sys::backtrace::BacktraceLock::print
                               at /rustc/1aa9bab4ecbce4859eaad53000f78158ebe2be2c/library\std\src\sys\backtrace.rs:41
   8:     0x7ffd8acaedce - std::panicking::default_hook::closure$0
                               at /rustc/1aa9bab4ecbce4859eaad53000f78158ebe2be2c/library\std\src\panicking.rs:292
   9:     0x7ffd8acc86d7 - std::panicking::default_hook
                               at /rustc/1aa9bab4ecbce4859eaad53000f78158ebe2be2c/library\std\src\panicking.rs:319
  10:     0x7ffd8c4a3c5d - core[9e425223ee68c027]::slice::sort::unstable::heapsort::heapsort::<((rustc_lint_defs[cf9623aa3d863903]::Level, &str), usize), <((rustc_lint_defs[cf9623aa3d863903]::Level, &str), usize) as core[9e425223ee68c027]::cmp::PartialOrd>::lt>
  11:     0x7ffd8acc89e1 - std::panicking::panic_with_hook
                               at /rustc/1aa9bab4ecbce4859eaad53000f78158ebe2be2c/library\std\src\panicking.rs:833
  12:     0x7ffd8acaeea4 - std::panicking::panic_handler::closure$0
                               at /rustc/1aa9bab4ecbce4859eaad53000f78158ebe2be2c/library\std\src\panicking.rs:698
  13:     0x7ffd8acac2ff - std::sys::backtrace::__rust_end_short_backtrace<std::panicking::panic_handler::closure_env$0,never$>
                               at /rustc/1aa9bab4ecbce4859eaad53000f78158ebe2be2c/library\std\src\sys\backtrace.rs:176
  14:     0x7ffd8acafa5e - std::panicking::panic_handler
                               at /rustc/1aa9bab4ecbce4859eaad53000f78158ebe2be2c/library\std\src\panicking.rs:689
  15:     0x7ffd8edaf95d - core::panicking::panic_fmt
                               at /rustc/1aa9bab4ecbce4859eaad53000f78158ebe2be2c/library\core\src\panicking.rs:80
  16:     0x7ffd8edaf5f7 - core::result::unwrap_failed
                               at /rustc/1aa9bab4ecbce4859eaad53000f78158ebe2be2c/library\core\src\result.rs:1867
  17:     0x7ffd8c22917f - <rustc_parse[917f9efb9f2b7a86]::parser::Parser>::parse_item
  18:     0x7ffd8c211da7 - <rustc_parse[917f9efb9f2b7a86]::parser::Parser>::parse_item
  19:     0x7ffd8c211832 - <rustc_parse[917f9efb9f2b7a86]::parser::Parser>::parse_item
  20:     0x7ffd8c21f8eb - <rustc_parse[917f9efb9f2b7a86]::parser::Parser>::parse_item
  21:     0x7ffd8c205fb6 - <rustc_parse[917f9efb9f2b7a86]::parser::Parser>::parse_item
  22:     0x7ff75f0e3a09 - <unknown>
  23:     0x7ff75f0c660f - <unknown>
  24:     0x7ff75f09ff0b - <unknown>
  25:     0x7ff75efe069b - <unknown>
  26:     0x7ff75efe374e - <unknown>
  27:     0x7ff75f0e6c13 - <unknown>
  28:     0x7ff75f0ab2a0 - <unknown>
  29:     0x7ff75f038cbd - <unknown>
  30:     0x7ff75f039456 - <unknown>
  31:     0x7ff75f03c918 - <unknown>
  32:     0x7ff75f03ed6e - <unknown>
  33:     0x7ff75f03763f - <unknown>
  34:     0x7ff75f08ffc3 - <unknown>
  35:     0x7ff75f03d579 - <unknown>
  36:     0x7ff75f03e0cf - <unknown>
  37:     0x7ff75ef86bbd - <unknown>
  38:     0x7ff75ef811b1 - <unknown>
  39:     0x7ff75ef987f7 - <unknown>
  40:     0x7ff75ef94a23 - <unknown>
  41:     0x7ff75ef934d6 - <unknown>
  42:     0x7ff75ef93b5c - <unknown>
  43:     0x7ffd8acc627f - std::rt::lang_start_internal::closure$0
                               at /rustc/1aa9bab4ecbce4859eaad53000f78158ebe2be2c/library\std\src\rt.rs:175
  44:     0x7ffd8acc627f - std::panicking::catch_unwind::do_call
                               at /rustc/1aa9bab4ecbce4859eaad53000f78158ebe2be2c/library\std\src\panicking.rs:581
  45:     0x7ffd8acc627f - std::panicking::catch_unwind
                               at /rustc/1aa9bab4ecbce4859eaad53000f78158ebe2be2c/library\std\src\panicking.rs:544
  46:     0x7ffd8acc627f - std::panic::catch_unwind
                               at /rustc/1aa9bab4ecbce4859eaad53000f78158ebe2be2c/library\std\src\panic.rs:359
  47:     0x7ffd8acc627f - std::rt::lang_start_internal
                               at /rustc/1aa9bab4ecbce4859eaad53000f78158ebe2be2c/library\std\src\rt.rs:171
  48:     0x7ff75efa563c - <unknown>
  49:     0x7ff75f299960 - <unknown>
  50:     0x7ffe89e57374 - BaseThreadInitThunk
  51:     0x7ffe8ad7cc91 - RtlUserThreadStart

error: the compiler unexpectedly panicked. this is a bug.

note: we would appreciate a bug report: https://github.com/rust-lang/rustfmt/issues/new?labels=bug

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

note: please attach the file at `D:\bevywinicon\crates\bevy_reflect\derive\rustc-ice-2025-12-06T04_47_18-37484.txt` to your bug report

query stack during panic:
end of query stack
crates\bevy_reflect\derive on  rust-ice-2025-12-05 [$?⇡] is 📦 v0.18.0-dev via 🦀 v1.94.0-nightly