ICE `all spans must be disjoint`

[matthiaskrgr]

auto-reduced (treereduce-rust):

fn main() {
    <&'a TDeref as IntoIterator>::IntoIter(vec![]);
}

original:

// check-pass

fn foo<T>(t: T) -> usize
where
    for<'a> &'a T: IntoIterator,
    for<'a> <&'a T as IntoIterator>::IntoIter: ExactSizeIterator,
{
    foo::<Vec<u32>>(vec![]).len()
}

fn main() {
    <&'a TDeref as IntoIterator>::IntoIter(vec![]);
}

mod another {
    use std::ops::Deref;

    fn test<T, TDeref>()
    where
        T: Deref<Target = TDeref>,
        TDeref: ?Sized,
        for<'a> &'a TDeref: IntoIterator,
        for<'a> &'a T: IntoIterator,
    {
    }

    fn main() {
        test::<Vec<u8>, _>();
    }
}

Version information

rustc 1.92.0-nightly (bd4a8004c 2025-10-20)
binary: rustc
commit-hash: bd4a8004c2f3b73795cb4c03bf8e7634e4d89677
commit-date: 2025-10-20
host: x86_64-unknown-linux-gnu
release: 1.92.0-nightly
LLVM version: 21.1.3

Possibly related line of code:

rust/compiler/rustc_errors/src/lib.rs

Lines 379 to 391 in bd4a800

	.cloned()
	.filter_map(|mut substitution| {
	// Assumption: all spans are in the same file, and all spans
	// are disjoint. Sort in ascending order.
	substitution.parts.sort_by_key(|part| part.span.lo());
	// Verify the assumption that all spans are disjoint
	assert_eq!(
	substitution.parts.array_windows().find(|[a, b]| a.span.overlaps(b.span)),
	None,
	"all spans must be disjoint",
	);
	// Account for cases where we are suggesting the same code that's already

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

Program output

error[E0261]: use of undeclared lifetime name `'a`
 --> /tmp/icemaker_global_tempdir.zT6DmWVt6amy/rustc_testrunner_tmpdir_reporting.gMs0r5JvGv5W/mvce.rs:2:7
  |
2 |     <&'a TDeref as IntoIterator>::IntoIter(vec![]);
  |       ^^ undeclared lifetime
  |
help: consider introducing lifetime `'a` here
  |
1 | fn main<'a>() {
  |        ++++

error[E0575]: expected method or associated constant, found associated type `IntoIterator::IntoIter`
 --> /tmp/icemaker_global_tempdir.zT6DmWVt6amy/rustc_testrunner_tmpdir_reporting.gMs0r5JvGv5W/mvce.rs:2:5
  |
2 |     <&'a TDeref as IntoIterator>::IntoIter(vec![]);
  |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  |
  = note: can't use a type alias as a constructor

thread 'rustc' (1082747) panicked at compiler/rustc_errors/src/lib.rs:385:17:
assertion `left == right` failed: all spans must be disjoint
  left: Some([SubstitutionPart { span: /home/matthias/.rustup/toolchains/master/lib/rustlib/src/rust/library/alloc/src/macros.rs:44:9: 44:32 (#4), snippet: " { 0: " }, SubstitutionPart { span: /home/matthias/.rustup/toolchains/master/lib/rustlib/src/rust/library/alloc/src/macros.rs:44:9: 44:32 (#4), snippet: " }" }])
 right: None
stack backtrace:
   0:     0x7f2daf21bad3 - <std::sys::backtrace::BacktraceLock::print::DisplayBacktrace as core::fmt::Display>::fmt::h7ce1817dc787ae2a
   1:     0x7f2daf801ad8 - core::fmt::write::h4b44684f3eb278fd
   2:     0x7f2daf1cfc43 - std::io::Write::write_fmt::hce8030c46a5cc224
   3:     0x7f2daf1e1192 - std::sys::backtrace::BacktraceLock::print::h96e3511f9684deb2
   4:     0x7f2daf1e7269 - std::panicking::default_hook::{{closure}}::h8f19c297eed9b282
   5:     0x7f2daf1e6d93 - std::panicking::default_hook::h419be45792712020
   6:     0x7f2dae1f3d07 - std[77a4331de3222898]::panicking::update_hook::<alloc[b29b593dea949441]::boxed::Box<rustc_driver_impl[5267ee30c81b0e]::install_ice_hook::{closure#1}>>::{closure#0}
   7:     0x7f2daf1e768f - std::panicking::panic_with_hook::hb1a2dc8e6eebd27b
   8:     0x7f2daf1e744a - std::panicking::panic_handler::{{closure}}::hd5af40f7328a8837
   9:     0x7f2daf1e12c9 - std::sys::backtrace::__rust_end_short_backtrace::h43c84acb4bc43c12
  10:     0x7f2daf1c1e5d - __rustc[3e962e80ec1fc39a]::rust_begin_unwind
  11:     0x7f2dac161890 - core::panicking::panic_fmt::h87f499a557a86b6c
  12:     0x7f2dadbd2833 - core::panicking::assert_failed_inner::h7a36df2f7aa52825
  13:     0x7f2dae221838 - core[98aea282fc88ea4b]::panicking::assert_failed::<core[98aea282fc88ea4b]::option::Option<&[rustc_errors[2c8b44d91033c985]::SubstitutionPart; 2usize]>, core[98aea282fc88ea4b]::option::Option<&[rustc_errors[2c8b44d91033c985]::SubstitutionPart; 2usize]>>
  14:     0x7f2db0b5c027 - <core[98aea282fc88ea4b]::iter::adapters::filter_map::FilterMap<core[98aea282fc88ea4b]::iter::adapters::cloned::Cloned<core[98aea282fc88ea4b]::iter::adapters::filter::Filter<core[98aea282fc88ea4b]::slice::iter::Iter<rustc_errors[2c8b44d91033c985]::Substitution>, <rustc_errors[2c8b44d91033c985]::CodeSuggestion>::splice_lines::{closure#0}>>, <rustc_errors[2c8b44d91033c985]::CodeSuggestion>::splice_lines::{closure#1}> as core[98aea282fc88ea4b]::iter::traits::iterator::Iterator>::next
  15:     0x7f2db0b57c8b - <rustc_errors[2c8b44d91033c985]::emitter::HumanEmitter>::emit_suggestion_default
  16:     0x7f2db0cf3649 - <rustc_errors[2c8b44d91033c985]::emitter::HumanEmitter as rustc_errors[2c8b44d91033c985]::emitter::Emitter>::emit_diagnostic
  17:     0x7f2db0cef326 - <rustc_errors[2c8b44d91033c985]::DiagCtxtInner>::emit_diagnostic::{closure#3}
  18:     0x7f2db0cece04 - rustc_interface[e8534005bd5cee03]::callbacks::track_diagnostic::<core[98aea282fc88ea4b]::option::Option<rustc_span[235b32e56945d136]::ErrorGuaranteed>>
  19:     0x7f2db0cebe36 - <rustc_errors[2c8b44d91033c985]::DiagCtxtInner>::emit_diagnostic
  20:     0x7f2db0cebcff - <rustc_errors[2c8b44d91033c985]::DiagCtxtHandle>::emit_diagnostic
  21:     0x7f2dac54749e - <rustc_span[235b32e56945d136]::ErrorGuaranteed as rustc_errors[2c8b44d91033c985]::diagnostic::EmissionGuarantee>::emit_producing_guarantee
  22:     0x7f2dafd0d6dd - <rustc_resolve[f580584eb261ff18]::Resolver>::resolve_crate::{closure#0}
  23:     0x7f2dafd02f8b - <rustc_resolve[f580584eb261ff18]::Resolver>::resolve_crate
  24:     0x7f2db0379d15 - rustc_interface[e8534005bd5cee03]::passes::configure_and_expand
  25:     0x7f2db091f615 - rustc_interface[e8534005bd5cee03]::passes::resolver_for_lowering_raw
  26:     0x7f2db091f38d - rustc_query_impl[4f9b9f05dcc10e6c]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[4f9b9f05dcc10e6c]::query_impl::resolver_for_lowering_raw::dynamic_query::{closure#2}::{closure#0}, rustc_middle[57c44cee7187e787]::query::erase::Erased<[u8; 16usize]>>
  27:     0x7f2db091f367 - <rustc_query_impl[4f9b9f05dcc10e6c]::query_impl::resolver_for_lowering_raw::dynamic_query::{closure#2} as core[98aea282fc88ea4b]::ops::function::FnOnce<(rustc_middle[57c44cee7187e787]::ty::context::TyCtxt, ())>>::call_once
  28:     0x7f2db088859f - rustc_query_system[ee3fd6b41b5cadc9]::query::plumbing::try_execute_query::<rustc_query_impl[4f9b9f05dcc10e6c]::DynamicConfig<rustc_query_system[ee3fd6b41b5cadc9]::query::caches::SingleCache<rustc_middle[57c44cee7187e787]::query::erase::Erased<[u8; 16usize]>>, false, false, false>, rustc_query_impl[4f9b9f05dcc10e6c]::plumbing::QueryCtxt, false>
  29:     0x7f2db08880fc - rustc_query_impl[4f9b9f05dcc10e6c]::query_impl::resolver_for_lowering_raw::get_query_non_incr::__rust_end_short_backtrace
  30:     0x7f2db0a64931 - <rustc_interface[e8534005bd5cee03]::passes::create_and_enter_global_ctxt<core[98aea282fc88ea4b]::option::Option<rustc_interface[e8534005bd5cee03]::queries::Linker>, rustc_driver_impl[5267ee30c81b0e]::run_compiler::{closure#0}::{closure#2}>::{closure#2} as core[98aea282fc88ea4b]::ops::function::FnOnce<(&rustc_session[39b43f51f4446db8]::session::Session, rustc_middle[57c44cee7187e787]::ty::context::CurrentGcx, alloc[b29b593dea949441]::sync::Arc<rustc_data_structures[738b40c7f5a39734]::jobserver::Proxy>, &std[77a4331de3222898]::sync::once_lock::OnceLock<rustc_middle[57c44cee7187e787]::ty::context::GlobalCtxt>, &rustc_data_structures[738b40c7f5a39734]::sync::worker_local::WorkerLocal<rustc_middle[57c44cee7187e787]::arena::Arena>, &rustc_data_structures[738b40c7f5a39734]::sync::worker_local::WorkerLocal<rustc_hir[4616985d3bd4a1e2]::Arena>, rustc_driver_impl[5267ee30c81b0e]::run_compiler::{closure#0}::{closure#2})>>::call_once::{shim:vtable#0}
  31:     0x7f2db089c895 - rustc_interface[e8534005bd5cee03]::interface::run_compiler::<(), rustc_driver_impl[5267ee30c81b0e]::run_compiler::{closure#0}>::{closure#1}
  32:     0x7f2db08fa6c7 - std[77a4331de3222898]::sys::backtrace::__rust_begin_short_backtrace::<rustc_interface[e8534005bd5cee03]::util::run_in_thread_with_globals<rustc_interface[e8534005bd5cee03]::util::run_in_thread_pool_with_globals<rustc_interface[e8534005bd5cee03]::interface::run_compiler<(), rustc_driver_impl[5267ee30c81b0e]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>
  33:     0x7f2db08fa3a8 - <<std[77a4331de3222898]::thread::Builder>::spawn_unchecked_<rustc_interface[e8534005bd5cee03]::util::run_in_thread_with_globals<rustc_interface[e8534005bd5cee03]::util::run_in_thread_pool_with_globals<rustc_interface[e8534005bd5cee03]::interface::run_compiler<(), rustc_driver_impl[5267ee30c81b0e]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>::{closure#1} as core[98aea282fc88ea4b]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  34:     0x7f2db09009ef - std::sys::thread::unix::Thread::new::thread_start::h5d7739f30ff88cb2
  35:     0x7f2daa2969cb - <unknown>
  36:     0x7f2daa31aa0c - <unknown>
  37:                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 1.92.0-nightly (bd4a8004c 2025-10-20) 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 2 previous errors

Some errors have detailed explanations: E0261, E0575.
For more information about an error, try `rustc --explain E0261`.

[matthiaskrgr]

the offending diagnostic on stable:

error[E0575]: expected method or associated constant, found associated type `IntoIterator::IntoIter`
 --> oo.rs:2:5
  |
2 |     <&'a TDeref as IntoIterator>::IntoIter(vec![]);
  |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  |
  = note: can't use a type alias as a constructor
help: use struct expression instead
 --> /home/matthias/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/alloc/src/macros.rs:44:9
  |
44-         $crate::vec::Vec::new()
44+          { 0:  }
  |

[GoldsteinE]

Regression appears in commit that just adds this assertion, so presumably bad spans were there all along. Suggestions that point into macro expansions shouldn’t be generated anyway, I’ll try to see how it could be filtered.

searched nightlies: from nightly-2025-08-02 to nightly-2025-10-19
regressed nightly: nightly-2025-09-06
searched commit range: af00ff2...6c699a3
regressed commit: 99317ef

bisected with cargo-bisect-rustc v0.6.10

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

cargo bisect-rustc --start 1.90.0 --end 2025-10-19 --regress ice -- check 

[GoldsteinE]

Will be fixed by #147849.

[lqd]

cc @Muscraft