ICE: `missing associated_item_or_field_def_ids for DefId`

[matthiaskrgr]

auto-reduced (treereduce-rust):

fn main() {
    

    if let Some(<Map<I, F> as Iterator>::Item {_}) = foo {
    
    //
    
    //
    // where
    //
    // 'a: '0
    //
    
    
    
    (x, y)
}
    
}

original:

enum Foo {
    Bar { bar: u16 },
    Other,
}

fn main() {
    let foo = Some(Foo::Other);

    if let Some(<Map<I, F> as Iterator>::Item {_}) = foo {
    // Here we have a constraint that:
    //
    // (x, y) has type (&'0 u32, &'1 u32)
    //
    // where
    //
    // 'a: '0
    //
    // then we require that `('0 u32, &'1 u32): MultiRegionTrait<'a,
    // 'b>`, which winds up imposing a requirement that `'0 = 'a` and
    // `'1 = 'b`.
    (x, y)
}
    //~^ ERROR expected field pattern, found `_`
}

Version information

rustc 1.86.0-nightly (fb546ee09 2025-01-07)
binary: rustc
commit-hash: fb546ee09b226bc4dd4b712d35a372d923c4fa54
commit-date: 2025-01-07
host: x86_64-unknown-linux-gnu
release: 1.86.0-nightly
LLVM version: 19.1.6

Possibly related line of code:

rust/compiler/rustc_metadata/src/rmeta/decoder.rs

Lines 962 to 974 in fb546ee

	self.crate_deps.decode(metadata)
	}
	}
	impl<'a> CrateMetadataRef<'a> {
	fn missing(self, descr: &str, id: DefIndex) -> ! {
	bug!("missing `{descr}` for {:?}", self.local_def_id(id))
	}
	fn raw_proc_macro(self, id: DefIndex) -> &'a ProcMacro {
	// DefIndex's in root.proc_macro_data have a one-to-one correspondence
	// with items in 'raw_proc_macros'.
	let pos = self

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

Program output

error: expected field pattern, found `_`
 --> /tmp/icemaker_global_tempdir.k0zQgENfEqOy/rustc_testrunner_tmpdir_reporting.jj69jde1HiKo/mvce.rs:6:48
  |
6 |     if let Some(<Map<I, F> as Iterator>::Item {_}) = foo {
  |                                                ^
  |
help: to omit remaining fields, use `..`
  |
6 |     if let Some(<Map<I, F> as Iterator>::Item {..}) = foo {
  |                                                ~~

error: internal compiler error: compiler/rustc_metadata/src/rmeta/decoder.rs:968:9: missing `associated_item_or_field_def_ids` for DefId(2:8878 ~ core[465b]::iter::traits::iterator::Iterator::Item)


thread 'rustc' panicked at compiler/rustc_metadata/src/rmeta/decoder.rs:968:9:
Box<dyn Any>
stack backtrace:
   0:     0x75323dae19ba - <std::sys::backtrace::BacktraceLock::print::DisplayBacktrace as core::fmt::Display>::fmt::h9bf89a0e5f11c1cf
   1:     0x75323e2135e6 - core::fmt::write::h761219e2be291c7a
   2:     0x75323f0d5991 - std::io::Write::write_fmt::h8032e22f9c3bd5b4
   3:     0x75323dae1812 - std::sys::backtrace::BacktraceLock::print::hebb5778cf40ee20f
   4:     0x75323dae3db7 - std::panicking::default_hook::{{closure}}::ha0fa1988f86f132d
   5:     0x75323dae3ba0 - std::panicking::default_hook::hc12d10b4cbb281ec
   6:     0x75323cc54a08 - std[a144ab5c1b85db5]::panicking::update_hook::<alloc[32a577d94c602890]::boxed::Box<rustc_driver_impl[c12604c6ccf9e768]::install_ice_hook::{closure#1}>>::{closure#0}
   7:     0x75323dae4643 - std::panicking::rust_panic_with_hook::hf8ade0577c2f95bc
   8:     0x75323cc8cf31 - std[a144ab5c1b85db5]::panicking::begin_panic::<rustc_errors[f4fe76fe817796ae]::ExplicitBug>::{closure#0}
   9:     0x75323cc82116 - std[a144ab5c1b85db5]::sys::backtrace::__rust_end_short_backtrace::<std[a144ab5c1b85db5]::panicking::begin_panic<rustc_errors[f4fe76fe817796ae]::ExplicitBug>::{closure#0}, !>
  10:     0x75323cc82103 - std[a144ab5c1b85db5]::panicking::begin_panic::<rustc_errors[f4fe76fe817796ae]::ExplicitBug>
  11:     0x75323cc96e91 - <rustc_errors[f4fe76fe817796ae]::diagnostic::BugAbort as rustc_errors[f4fe76fe817796ae]::diagnostic::EmissionGuarantee>::emit_producing_guarantee
  12:     0x75323d26b443 - rustc_middle[71fc52d0577df4e0]::util::bug::opt_span_bug_fmt::<rustc_span[80f3292a29acebce]::span_encoding::Span>::{closure#0}
  13:     0x75323d25044a - rustc_middle[71fc52d0577df4e0]::ty::context::tls::with_opt::<rustc_middle[71fc52d0577df4e0]::util::bug::opt_span_bug_fmt<rustc_span[80f3292a29acebce]::span_encoding::Span>::{closure#0}, !>::{closure#0}
  14:     0x75323d2502db - rustc_middle[71fc52d0577df4e0]::ty::context::tls::with_context_opt::<rustc_middle[71fc52d0577df4e0]::ty::context::tls::with_opt<rustc_middle[71fc52d0577df4e0]::util::bug::opt_span_bug_fmt<rustc_span[80f3292a29acebce]::span_encoding::Span>::{closure#0}, !>::{closure#0}, !>
  15:     0x75323b37e280 - rustc_middle[71fc52d0577df4e0]::util::bug::bug_fmt
  16:     0x75323d1cf5cf - <rustc_metadata[8c5f88d146413f0b]::creader::CrateMetadataRef>::missing
  17:     0x75323e41913a - rustc_metadata[8c5f88d146413f0b]::rmeta::decoder::cstore_impl::provide_extern::associated_item_def_ids
  18:     0x75323e418ad5 - rustc_query_impl[c60017a6d5ec95c8]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[c60017a6d5ec95c8]::query_impl::associated_item_def_ids::dynamic_query::{closure#2}::{closure#0}, rustc_middle[71fc52d0577df4e0]::query::erase::Erased<[u8; 16usize]>>
  19:     0x75323e418a65 - <rustc_query_impl[c60017a6d5ec95c8]::query_impl::associated_item_def_ids::dynamic_query::{closure#2} as core[465b72dbeda08b19]::ops::function::FnOnce<(rustc_middle[71fc52d0577df4e0]::ty::context::TyCtxt, rustc_span[80f3292a29acebce]::def_id::DefId)>>::call_once
  20:     0x75323e416e4a - rustc_query_system[e4307e8df47736e2]::query::plumbing::try_execute_query::<rustc_query_impl[c60017a6d5ec95c8]::DynamicConfig<rustc_query_system[e4307e8df47736e2]::query::caches::DefIdCache<rustc_middle[71fc52d0577df4e0]::query::erase::Erased<[u8; 16usize]>>, false, false, false>, rustc_query_impl[c60017a6d5ec95c8]::plumbing::QueryCtxt, false>
  21:     0x75323e4168ba - rustc_query_impl[c60017a6d5ec95c8]::query_impl::associated_item_def_ids::get_query_non_incr::__rust_end_short_backtrace
  22:     0x75323e4151f7 - rustc_middle[71fc52d0577df4e0]::query::plumbing::query_get_at::<rustc_query_system[e4307e8df47736e2]::query::caches::DefIdCache<rustc_middle[71fc52d0577df4e0]::query::erase::Erased<[u8; 16usize]>>>
  23:     0x75323d70f0c4 - <rustc_resolve[31f3b70b31eadbf7]::Resolver>::field_idents
  24:     0x75323d6e9e49 - <rustc_resolve[31f3b70b31eadbf7]::late::LateResolutionVisitor>::smart_resolve_report_errors
  25:     0x75323b265a24 - <rustc_resolve[31f3b70b31eadbf7]::late::LateResolutionVisitor>::smart_resolve_path_fragment::{closure#0}
  26:     0x75323ee87946 - <rustc_resolve[31f3b70b31eadbf7]::late::LateResolutionVisitor>::smart_resolve_path_fragment
  27:     0x75323ee70fbc - <rustc_resolve[31f3b70b31eadbf7]::late::LateResolutionVisitor>::resolve_expr
  28:     0x75323ee710e1 - <rustc_resolve[31f3b70b31eadbf7]::late::LateResolutionVisitor>::resolve_expr
  29:     0x75323ee70647 - <rustc_resolve[31f3b70b31eadbf7]::late::LateResolutionVisitor>::resolve_block
  30:     0x75323ee71936 - <rustc_resolve[31f3b70b31eadbf7]::late::LateResolutionVisitor>::resolve_expr
  31:     0x75323ee70647 - <rustc_resolve[31f3b70b31eadbf7]::late::LateResolutionVisitor>::resolve_block
  32:     0x75323ee7a16a - <rustc_resolve[31f3b70b31eadbf7]::late::LateResolutionVisitor as rustc_ast[4ef52985ee0a86ba]::visit::Visitor>::visit_fn
  33:     0x75323ee91a77 - rustc_ast[4ef52985ee0a86ba]::visit::walk_item_ctxt::<rustc_resolve[31f3b70b31eadbf7]::late::LateResolutionVisitor, rustc_ast[4ef52985ee0a86ba]::ast::ItemKind>
  34:     0x75323ee9a993 - <rustc_resolve[31f3b70b31eadbf7]::late::LateResolutionVisitor as rustc_ast[4ef52985ee0a86ba]::visit::Visitor>::visit_item
  35:     0x75323f4162b5 - <rustc_resolve[31f3b70b31eadbf7]::Resolver>::resolve_crate::{closure#0}
  36:     0x75323f41227f - <rustc_resolve[31f3b70b31eadbf7]::Resolver>::resolve_crate
  37:     0x75323e734d57 - rustc_interface[26e69c7fcb6d2c01]::passes::resolver_for_lowering_raw
  38:     0x75323e733d9f - rustc_query_impl[c60017a6d5ec95c8]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[c60017a6d5ec95c8]::query_impl::resolver_for_lowering_raw::dynamic_query::{closure#2}::{closure#0}, rustc_middle[71fc52d0577df4e0]::query::erase::Erased<[u8; 16usize]>>
  39:     0x75323e733d8d - <rustc_query_impl[c60017a6d5ec95c8]::query_impl::resolver_for_lowering_raw::dynamic_query::{closure#2} as core[465b72dbeda08b19]::ops::function::FnOnce<(rustc_middle[71fc52d0577df4e0]::ty::context::TyCtxt, ())>>::call_once
  40:     0x75323f1b6c36 - rustc_query_system[e4307e8df47736e2]::query::plumbing::try_execute_query::<rustc_query_impl[c60017a6d5ec95c8]::DynamicConfig<rustc_query_system[e4307e8df47736e2]::query::caches::SingleCache<rustc_middle[71fc52d0577df4e0]::query::erase::Erased<[u8; 16usize]>>, false, false, false>, rustc_query_impl[c60017a6d5ec95c8]::plumbing::QueryCtxt, false>
  41:     0x75323f1b68e0 - rustc_query_impl[c60017a6d5ec95c8]::query_impl::resolver_for_lowering_raw::get_query_non_incr::__rust_end_short_backtrace
  42:     0x75323f104265 - rustc_interface[26e69c7fcb6d2c01]::passes::create_and_enter_global_ctxt::<core[465b72dbeda08b19]::option::Option<rustc_interface[26e69c7fcb6d2c01]::queries::Linker>, rustc_driver_impl[c12604c6ccf9e768]::run_compiler::{closure#0}::{closure#2}>::{closure#2}::{closure#0}
  43:     0x75323f177724 - rustc_interface[26e69c7fcb6d2c01]::interface::run_compiler::<(), rustc_driver_impl[c12604c6ccf9e768]::run_compiler::{closure#0}>::{closure#1}
  44:     0x75323eff8007 - std[a144ab5c1b85db5]::sys::backtrace::__rust_begin_short_backtrace::<rustc_interface[26e69c7fcb6d2c01]::util::run_in_thread_with_globals<rustc_interface[26e69c7fcb6d2c01]::util::run_in_thread_pool_with_globals<rustc_interface[26e69c7fcb6d2c01]::interface::run_compiler<(), rustc_driver_impl[c12604c6ccf9e768]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>
  45:     0x75323eff84a4 - <<std[a144ab5c1b85db5]::thread::Builder>::spawn_unchecked_<rustc_interface[26e69c7fcb6d2c01]::util::run_in_thread_with_globals<rustc_interface[26e69c7fcb6d2c01]::util::run_in_thread_pool_with_globals<rustc_interface[26e69c7fcb6d2c01]::interface::run_compiler<(), rustc_driver_impl[c12604c6ccf9e768]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>::{closure#1} as core[465b72dbeda08b19]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  46:     0x75323eff9a6f - std::sys::pal::unix::thread::Thread::new::thread_start::hf3e31ce7c291fa9b
  47:     0x75323946439d - <unknown>
  48:     0x7532394e949c - <unknown>
  49:                0x0 - <unknown>

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 1.86.0-nightly (fb546ee09 2025-01-07) running on x86_64-unknown-linux-gnu

query stack during panic:
#0 [associated_item_def_ids] collecting associated items or fields of `core::iter::traits::iterator::Iterator::Item`
#1 [resolver_for_lowering_raw] getting the resolver for lowering
end of query stack
error: aborting due to 2 previous errors

[matthiaskrgr]

fn main() {
	if let <Map<I, F> as Iterator>::Item {_} = _ {
		(x)
	}
}

[matthiaskrgr]

bisection points to #134284 cc @estebank

[theemathas]

fn main() {
    if let Iterator::Item { .. } = 1 {
        x
    }
}

@rustbot label +regression-from-stable-to-nightly

[apiraino]

WG-prioritization assigning priority (Zulip discussion).

@rustbot label -I-prioritize +P-low