ICE: in tokenstream with contracts in impl

[matthiaskrgr]

snippet:

impl T {
#[core::contracts::ensures]
  fn b() { (loop) }
}

Version information

rustc 1.88.0-nightly (243c5a35e 2025-05-05)
binary: rustc
commit-hash: 243c5a35e18b2634892fe7091d5ee888a18f77f5
commit-date: 2025-05-05
host: x86_64-unknown-linux-gnu
release: 1.88.0-nightly
LLVM version: 20.1.4

Possibly related line of code:

rust/compiler/rustc_ast/src/tokenstream.rs

Lines 370 to 382 in 243c5a3

	if let Some(delim) = kind.open_delim() {
	stack_rest.push(mem::replace(
	&mut stack_top,
	FrameData { open_delim_sp: Some((delim, span, spacing)), inner: vec![] },
	));
	} else if let Some(delim) = kind.close_delim() {
	let frame_data = mem::replace(&mut stack_top, stack_rest.pop().unwrap());
	let (open_delim, open_sp, open_spacing) = frame_data.open_delim_sp.unwrap();
	assert!(
	open_delim.eq_ignoring_invisible_origin(&delim),
	"Mismatched open/close delims: open={open_delim:?} close={span:?}"
	);
	let dspan = DelimSpan::from_pair(open_sp, span);

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

Program output

error: expected `{`, found `)`
 --> /tmp/icemaker_global_tempdir.QK3qBTtK0qNE/rustc_testrunner_tmpdir_reporting.enN8ewTmyed4/mvce.rs:3:17
  |
3 |   fn b() { (loop) }
  |             ----^ expected `{`
  |             |
  |             while parsing this `loop` expression

error: non-item in item list
 --> /tmp/icemaker_global_tempdir.QK3qBTtK0qNE/rustc_testrunner_tmpdir_reporting.enN8ewTmyed4/mvce.rs:4:1
  |
1 | impl T {
  |        - item list starts here
...
4 | }
  | ^
  | |
  | non-item starts here
  | item list ends here

error[E0658]: use of unstable library feature `contracts`
 --> /tmp/icemaker_global_tempdir.QK3qBTtK0qNE/rustc_testrunner_tmpdir_reporting.enN8ewTmyed4/mvce.rs:2:3
  |
2 | #[core::contracts::ensures]
  |   ^^^^^^^^^^^^^^^^^^^^^^^^
  |
  = note: see issue #128044 <https://github.com/rust-lang/rust/issues/128044> for more information
  = help: add `#![feature(contracts)]` to the crate attributes to enable
  = note: this compiler was built on 2025-05-05; consider upgrading it if it is out of date


thread 'rustc' panicked at compiler/rustc_ast/src/tokenstream.rs:376:84:
called `Option::unwrap()` on a `None` value
stack backtrace:
   0:     0x7561c0316a23 - <std::sys::backtrace::BacktraceLock::print::DisplayBacktrace as core::fmt::Display>::fmt::h65551383c9634971
   1:     0x7561c0a059c7 - core::fmt::write::hd1d7d7de509062df
   2:     0x7561c1a3f891 - std::io::Write::write_fmt::h1a04e49834da160b
   3:     0x7561c0316882 - std::sys::backtrace::BacktraceLock::print::h793cee02245d5081
   4:     0x7561c031a6ca - std::panicking::default_hook::{{closure}}::h6ae00f240727be43
   5:     0x7561c031a24f - std::panicking::default_hook::h156478d29cf850ba
   6:     0x7561bf35bbc3 - std[cfdcd004f7c3d133]::panicking::update_hook::<alloc[88013fdaa6ac049f]::boxed::Box<rustc_driver_impl[a5b7631e7267f98a]::install_ice_hook::{closure#1}>>::{closure#0}
   7:     0x7561c031af43 - std::panicking::rust_panic_with_hook::h6ba9ecd60a752a68
   8:     0x7561c031ac06 - std::panicking::begin_panic_handler::{{closure}}::hed14983a4f5394ce
   9:     0x7561c0316ee9 - std::sys::backtrace::__rust_end_short_backtrace::h8d5f45e9eb074764
  10:     0x7561c031a8fd - __rustc[4726726be74f3c21]::rust_begin_unwind
  11:     0x7561bcc7d0a0 - core::panicking::panic_fmt::hecec6a54a644e96f
  12:     0x7561bcc811dc - core::panicking::panic::h76c2dcb84ba8059c
  13:     0x7561bcc7dad9 - core::option::unwrap_failed::hf1f8fd1804847760
  14:     0x7561c1580091 - <rustc_ast[ac699b453b946b68]::tokenstream::LazyAttrTokenStream>::to_attr_token_stream
  15:     0x7561c157a3f8 - rustc_ast[ac699b453b946b68]::tokenstream::attrs_and_tokens_to_token_trees
  16:     0x7561c149bfd6 - <rustc_expand[6b8c5499bcda7afa]::base::Annotatable>::to_tokens
  17:     0x7561c1dc08aa - <rustc_expand[6b8c5499bcda7afa]::expand::MacroExpander>::fully_expand_fragment
  18:     0x7561c1d67f37 - <rustc_expand[6b8c5499bcda7afa]::expand::MacroExpander>::expand_crate
  19:     0x7561c11cccf0 - rustc_interface[d28e3ca032370179]::passes::resolver_for_lowering_raw
  20:     0x7561c11cc08d - rustc_query_impl[a8d7657d34aae950]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[a8d7657d34aae950]::query_impl::resolver_for_lowering_raw::dynamic_query::{closure#2}::{closure#0}, rustc_middle[3bd5ba83e8545365]::query::erase::Erased<[u8; 16usize]>>
  21:     0x7561c11cc079 - <rustc_query_impl[a8d7657d34aae950]::query_impl::resolver_for_lowering_raw::dynamic_query::{closure#2} as core[f9132cdcabd89819]::ops::function::FnOnce<(rustc_middle[3bd5ba83e8545365]::ty::context::TyCtxt, ())>>::call_once
  22:     0x7561c1939bc7 - rustc_query_system[7470c717dfa77ba1]::query::plumbing::try_execute_query::<rustc_query_impl[a8d7657d34aae950]::DynamicConfig<rustc_query_system[7470c717dfa77ba1]::query::caches::SingleCache<rustc_middle[3bd5ba83e8545365]::query::erase::Erased<[u8; 16usize]>>, false, false, false>, rustc_query_impl[a8d7657d34aae950]::plumbing::QueryCtxt, false>
  23:     0x7561c193974f - rustc_query_impl[a8d7657d34aae950]::query_impl::resolver_for_lowering_raw::get_query_non_incr::__rust_end_short_backtrace
  24:     0x7561c1c462b1 - rustc_interface[d28e3ca032370179]::passes::create_and_enter_global_ctxt::<core[f9132cdcabd89819]::option::Option<rustc_interface[d28e3ca032370179]::queries::Linker>, rustc_driver_impl[a5b7631e7267f98a]::run_compiler::{closure#0}::{closure#2}>::{closure#2}::{closure#0}
  25:     0x7561c1a7e6a6 - rustc_interface[d28e3ca032370179]::interface::run_compiler::<(), rustc_driver_impl[a5b7631e7267f98a]::run_compiler::{closure#0}>::{closure#1}
  26:     0x7561c1a39dfe - std[cfdcd004f7c3d133]::sys::backtrace::__rust_begin_short_backtrace::<rustc_interface[d28e3ca032370179]::util::run_in_thread_with_globals<rustc_interface[d28e3ca032370179]::util::run_in_thread_pool_with_globals<rustc_interface[d28e3ca032370179]::interface::run_compiler<(), rustc_driver_impl[a5b7631e7267f98a]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>
  27:     0x7561c1a3a274 - <<std[cfdcd004f7c3d133]::thread::Builder>::spawn_unchecked_<rustc_interface[d28e3ca032370179]::util::run_in_thread_with_globals<rustc_interface[d28e3ca032370179]::util::run_in_thread_pool_with_globals<rustc_interface[d28e3ca032370179]::interface::run_compiler<(), rustc_driver_impl[a5b7631e7267f98a]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>::{closure#1} as core[f9132cdcabd89819]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  28:     0x7561c1a3b66b - std::sys::pal::unix::thread::Thread::new::thread_start::h7658bcd938bdd684
  29:     0x7561bb8a370a - <unknown>
  30:     0x7561bb927aac - <unknown>
  31:                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 1.88.0-nightly (243c5a35e 2025-05-05) running on x86_64-unknown-linux-gnu

query stack during panic:
#0 [resolver_for_lowering_raw] getting the resolver for lowering
end of query stack
error: aborting due to 3 previous errors

For more information about this error, try `rustc --explain E0658`.

[moxian]

• bisects to the initial implementation of contracts in #[contracts::requires(...)] + #[contracts::ensures(...)] #128045 (or technically its rollup #‍136564)

@rustbot label: +S-has-mcve +S-has-bisection +A-parser -needs-triage