rust-lang / rust-lang/rust

ICE `all spans must be disjoint`

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C-bug D-diagnostic-infra I-ICE T-compiler
Dominant language
Rust
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Description

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:
https://github.com/rust-lang/rust/blob/bd4a8004c2f3b73795cb4c03bf8e7634e4d89677/compiler/rustc_errors/src/lib.rs#L379-L391

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`.

Contributor guide

Open the contributing guide

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start with the minimized reproducer in /tmp/im/a.rs and the suggested section of compiler/rustc_errors/src/lib.rs around lines 379-391. Run it with the reported nightly or a current nightly, then trace how the resolver diagnostic creates overlapping substitutions. Done means the reproducer reports its errors without panicking on the all spans must be disjoint assertion.

Written by the indexing model from the issue text.

Assessment

Tech stack
rust
Domain
compilers
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
35/100

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