ICE: typeck: `no index for a field`

[matthiaskrgr]

snippet:

struct TestStruct {,}

fn edge_case_if() {
    let ts = TestStruct {};
    let _b = || { match ts {
        TestStruct{ x: 1, .. } | _ => (),
    }};
}

Version information

rustc 1.81.0-nightly (1ca578e68 2024-06-20)
binary: rustc
commit-hash: 1ca578e68eb715e772fc0c1b9e6ca7c5b122765a
commit-date: 2024-06-20
host: x86_64-unknown-linux-gnu
release: 1.81.0-nightly
LLVM version: 18.1.7

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

Program output

error: expected identifier, found `,`
 --> /tmp/icemaker_global_tempdir.hJLG4Uu9QCDq/rustc_testrunner_tmpdir_reporting.cVa4rm3LGIDH/mvce.rs:1:20
  |
1 | struct TestStruct {,}
  |        ----------  ^ expected identifier
  |        |
  |        while parsing this struct

error[E0601]: `main` function not found in crate `mvce`
 --> /tmp/icemaker_global_tempdir.hJLG4Uu9QCDq/rustc_testrunner_tmpdir_reporting.cVa4rm3LGIDH/mvce.rs:8:2
  |
8 | }
  |  ^ consider adding a `main` function to `/tmp/icemaker_global_tempdir.hJLG4Uu9QCDq/rustc_testrunner_tmpdir_reporting.cVa4rm3LGIDH/mvce.rs`

thread 'rustc' panicked at compiler/rustc_hir_typeck/src/expr_use_visitor.rs:1697:26:
no index for a field
stack backtrace:
   0:     0x71e31da31915 - std::backtrace_rs::backtrace::libunwind::trace::h796e75e96c439f3e
                               at /rustc/1ca578e68eb715e772fc0c1b9e6ca7c5b122765a/library/std/src/../../backtrace/src/backtrace/libunwind.rs:116:5
   1:     0x71e31da31915 - std::backtrace_rs::backtrace::trace_unsynchronized::h57b5b13bb46e11ba
                               at /rustc/1ca578e68eb715e772fc0c1b9e6ca7c5b122765a/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5
   2:     0x71e31da31915 - std::sys::backtrace::_print_fmt::h11ce45f986076e87
                               at /rustc/1ca578e68eb715e772fc0c1b9e6ca7c5b122765a/library/std/src/sys/backtrace.rs:68:5
   3:     0x71e31da31915 - <std::sys::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::hcd09ba6a4fc236f1
                               at /rustc/1ca578e68eb715e772fc0c1b9e6ca7c5b122765a/library/std/src/sys/backtrace.rs:44:22
   4:     0x71e31da824bb - core::fmt::rt::Argument::fmt::h914f09f4a1c58d59
                               at /rustc/1ca578e68eb715e772fc0c1b9e6ca7c5b122765a/library/core/src/fmt/rt.rs:165:63
   5:     0x71e31da824bb - core::fmt::write::hc590b91d463e6a2c
                               at /rustc/1ca578e68eb715e772fc0c1b9e6ca7c5b122765a/library/core/src/fmt/mod.rs:1168:21
   6:     0x71e31da265af - std::io::Write::write_fmt::hc69b1d0ded026622
                               at /rustc/1ca578e68eb715e772fc0c1b9e6ca7c5b122765a/library/std/src/io/mod.rs:1835:15
   7:     0x71e31da316ee - std::sys::backtrace::_print::hc852e4497da27a95
                               at /rustc/1ca578e68eb715e772fc0c1b9e6ca7c5b122765a/library/std/src/sys/backtrace.rs:47:5
   8:     0x71e31da316ee - std::sys::backtrace::print::hc624de700d5fe576
                               at /rustc/1ca578e68eb715e772fc0c1b9e6ca7c5b122765a/library/std/src/sys/backtrace.rs:34:9
   9:     0x71e31da34129 - std::panicking::default_hook::{{closure}}::hf8d8481f1d9702fb
  10:     0x71e31da33ecc - std::panicking::default_hook::he469b58de751f8ee
                               at /rustc/1ca578e68eb715e772fc0c1b9e6ca7c5b122765a/library/std/src/panicking.rs:292:9
  11:     0x71e31a147870 - std[eca1b30e63fdea7a]::panicking::update_hook::<alloc[79c37403ec1ba474]::boxed::Box<rustc_driver_impl[93e75e0175b92285]::install_ice_hook::{closure#0}>>::{closure#0}
  12:     0x71e31da34a4f - <alloc::boxed::Box<F,A> as core::ops::function::Fn<Args>>::call::h7fb9108d23a6d563
                               at /rustc/1ca578e68eb715e772fc0c1b9e6ca7c5b122765a/library/alloc/src/boxed.rs:2076:9
  13:     0x71e31da34a4f - std::panicking::rust_panic_with_hook::h738066c73a52890f
                               at /rustc/1ca578e68eb715e772fc0c1b9e6ca7c5b122765a/library/std/src/panicking.rs:804:13
  14:     0x71e31da34677 - std::panicking::begin_panic_handler::{{closure}}::h8534a2aac695431b
                               at /rustc/1ca578e68eb715e772fc0c1b9e6ca7c5b122765a/library/std/src/panicking.rs:670:13
  15:     0x71e31da31dd9 - std::sys::backtrace::__rust_end_short_backtrace::h3420ee35d28bf807
                               at /rustc/1ca578e68eb715e772fc0c1b9e6ca7c5b122765a/library/std/src/sys/backtrace.rs:171:18
  16:     0x71e31da34304 - rust_begin_unwind
                               at /rustc/1ca578e68eb715e772fc0c1b9e6ca7c5b122765a/library/std/src/panicking.rs:661:5
  17:     0x71e31da7ea73 - core::panicking::panic_fmt::h51cb44e3a97167f8
                               at /rustc/1ca578e68eb715e772fc0c1b9e6ca7c5b122765a/library/core/src/panicking.rs:74:14
  18:     0x71e31da7e8cb - core::panicking::panic_display::h01c80b100e2db3b0
                               at /rustc/1ca578e68eb715e772fc0c1b9e6ca7c5b122765a/library/core/src/panicking.rs:264:5
  19:     0x71e31da7e8cb - core::option::expect_failed::h227980ecada19c49
                               at /rustc/1ca578e68eb715e772fc0c1b9e6ca7c5b122765a/library/core/src/option.rs:2023:5
  20:     0x71e31c05cd08 - <rustc_hir_typeck[3a3cc19eb2dfac16]::expr_use_visitor::ExprUseVisitor<&rustc_hir_typeck[3a3cc19eb2dfac16]::fn_ctxt::FnCtxt, &mut rustc_hir_typeck[3a3cc19eb2dfac16]::upvar::InferBorrowKind>>::cat_pattern::<<rustc_hir_typeck[3a3cc19eb2dfac16]::expr_use_visitor::ExprUseVisitor<&rustc_hir_typeck[3a3cc19eb2dfac16]::fn_ctxt::FnCtxt, &mut rustc_hir_typeck[3a3cc19eb2dfac16]::upvar::InferBorrowKind>>::maybe_read_scrutinee<core[daaba097f859fa28]::iter::adapters::map::Map<core[daaba097f859fa28]::slice::iter::Iter<rustc_hir[f2dc79efc6c2027e]::hir::Arm>, <rustc_hir_typeck[3a3cc19eb2dfac16]::expr_use_visitor::ExprUseVisitor<&rustc_hir_typeck[3a3cc19eb2dfac16]::fn_ctxt::FnCtxt, &mut rustc_hir_typeck[3a3cc19eb2dfac16]::upvar::InferBorrowKind>>::walk_expr::{closure#1}>>::{closure#0}>
  21:     0x71e31c05c919 - <rustc_hir_typeck[3a3cc19eb2dfac16]::expr_use_visitor::ExprUseVisitor<&rustc_hir_typeck[3a3cc19eb2dfac16]::fn_ctxt::FnCtxt, &mut rustc_hir_typeck[3a3cc19eb2dfac16]::upvar::InferBorrowKind>>::cat_pattern::<<rustc_hir_typeck[3a3cc19eb2dfac16]::expr_use_visitor::ExprUseVisitor<&rustc_hir_typeck[3a3cc19eb2dfac16]::fn_ctxt::FnCtxt, &mut rustc_hir_typeck[3a3cc19eb2dfac16]::upvar::InferBorrowKind>>::maybe_read_scrutinee<core[daaba097f859fa28]::iter::adapters::map::Map<core[daaba097f859fa28]::slice::iter::Iter<rustc_hir[f2dc79efc6c2027e]::hir::Arm>, <rustc_hir_typeck[3a3cc19eb2dfac16]::expr_use_visitor::ExprUseVisitor<&rustc_hir_typeck[3a3cc19eb2dfac16]::fn_ctxt::FnCtxt, &mut rustc_hir_typeck[3a3cc19eb2dfac16]::upvar::InferBorrowKind>>::walk_expr::{closure#1}>>::{closure#0}>
  22:     0x71e31c0669c0 - <rustc_hir_typeck[3a3cc19eb2dfac16]::expr_use_visitor::ExprUseVisitor<&rustc_hir_typeck[3a3cc19eb2dfac16]::fn_ctxt::FnCtxt, &mut rustc_hir_typeck[3a3cc19eb2dfac16]::upvar::InferBorrowKind>>::walk_expr
  23:     0x71e31c0656b0 - <rustc_hir_typeck[3a3cc19eb2dfac16]::expr_use_visitor::ExprUseVisitor<&rustc_hir_typeck[3a3cc19eb2dfac16]::fn_ctxt::FnCtxt, &mut rustc_hir_typeck[3a3cc19eb2dfac16]::upvar::InferBorrowKind>>::consume_expr
  24:     0x71e31c06404e - <rustc_hir_typeck[3a3cc19eb2dfac16]::expr_use_visitor::ExprUseVisitor<&rustc_hir_typeck[3a3cc19eb2dfac16]::fn_ctxt::FnCtxt, &mut rustc_hir_typeck[3a3cc19eb2dfac16]::upvar::InferBorrowKind>>::walk_block
  25:     0x71e31c0656b0 - <rustc_hir_typeck[3a3cc19eb2dfac16]::expr_use_visitor::ExprUseVisitor<&rustc_hir_typeck[3a3cc19eb2dfac16]::fn_ctxt::FnCtxt, &mut rustc_hir_typeck[3a3cc19eb2dfac16]::upvar::InferBorrowKind>>::consume_expr
  26:     0x71e31c05e887 - <rustc_hir_typeck[3a3cc19eb2dfac16]::fn_ctxt::FnCtxt>::analyze_closure
  27:     0x71e31900c688 - <rustc_hir_typeck[3a3cc19eb2dfac16]::upvar::InferBorrowKindVisitor as rustc_hir[f2dc79efc6c2027e]::intravisit::Visitor>::visit_expr
  28:     0x71e31b8a58ef - <rustc_hir_typeck[3a3cc19eb2dfac16]::upvar::InferBorrowKindVisitor as rustc_hir[f2dc79efc6c2027e]::intravisit::Visitor>::visit_block
  29:     0x71e31b8a780b - rustc_hir_typeck[3a3cc19eb2dfac16]::typeck
  30:     0x71e31b8a6ffb - rustc_query_impl[da2d3b64247f93f0]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[da2d3b64247f93f0]::query_impl::typeck::dynamic_query::{closure#2}::{closure#0}, rustc_middle[a7abdaade2c6424c]::query::erase::Erased<[u8; 8usize]>>
  31:     0x71e31ba031ee - rustc_query_system[5e65d9b3abdd3162]::query::plumbing::try_execute_query::<rustc_query_impl[da2d3b64247f93f0]::DynamicConfig<rustc_query_system[5e65d9b3abdd3162]::query::caches::VecCache<rustc_span[1efc0ab8e6bb0790]::def_id::LocalDefId, rustc_middle[a7abdaade2c6424c]::query::erase::Erased<[u8; 8usize]>>, false, false, false>, rustc_query_impl[da2d3b64247f93f0]::plumbing::QueryCtxt, false>
  32:     0x71e31ba01cdf - rustc_query_impl[da2d3b64247f93f0]::query_impl::typeck::get_query_non_incr::__rust_end_short_backtrace
  33:     0x71e31ba01915 - <rustc_middle[a7abdaade2c6424c]::hir::map::Map>::par_body_owners::<rustc_hir_analysis[74e881c9b9f2b37]::check_crate::{closure#4}>::{closure#0}
  34:     0x71e31ba003bc - rustc_hir_analysis[74e881c9b9f2b37]::check_crate
  35:     0x71e31bdf4f87 - rustc_interface[7fb7dc76513cf959]::passes::analysis
  36:     0x71e31bdf4ac7 - rustc_query_impl[da2d3b64247f93f0]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[da2d3b64247f93f0]::query_impl::analysis::dynamic_query::{closure#2}::{closure#0}, rustc_middle[a7abdaade2c6424c]::query::erase::Erased<[u8; 1usize]>>
  37:     0x71e31c433ea5 - rustc_query_system[5e65d9b3abdd3162]::query::plumbing::try_execute_query::<rustc_query_impl[da2d3b64247f93f0]::DynamicConfig<rustc_query_system[5e65d9b3abdd3162]::query::caches::SingleCache<rustc_middle[a7abdaade2c6424c]::query::erase::Erased<[u8; 1usize]>>, false, false, false>, rustc_query_impl[da2d3b64247f93f0]::plumbing::QueryCtxt, false>
  38:     0x71e31c433c0f - rustc_query_impl[da2d3b64247f93f0]::query_impl::analysis::get_query_non_incr::__rust_end_short_backtrace
  39:     0x71e31c2dd252 - rustc_interface[7fb7dc76513cf959]::interface::run_compiler::<core[daaba097f859fa28]::result::Result<(), rustc_span[1efc0ab8e6bb0790]::ErrorGuaranteed>, rustc_driver_impl[93e75e0175b92285]::run_compiler::{closure#0}>::{closure#1}
  40:     0x71e31c29dac9 - std[eca1b30e63fdea7a]::sys::backtrace::__rust_begin_short_backtrace::<rustc_interface[7fb7dc76513cf959]::util::run_in_thread_with_globals<rustc_interface[7fb7dc76513cf959]::util::run_in_thread_pool_with_globals<rustc_interface[7fb7dc76513cf959]::interface::run_compiler<core[daaba097f859fa28]::result::Result<(), rustc_span[1efc0ab8e6bb0790]::ErrorGuaranteed>, rustc_driver_impl[93e75e0175b92285]::run_compiler::{closure#0}>::{closure#1}, core[daaba097f859fa28]::result::Result<(), rustc_span[1efc0ab8e6bb0790]::ErrorGuaranteed>>::{closure#0}, core[daaba097f859fa28]::result::Result<(), rustc_span[1efc0ab8e6bb0790]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[daaba097f859fa28]::result::Result<(), rustc_span[1efc0ab8e6bb0790]::ErrorGuaranteed>>
  41:     0x71e31c29d880 - <<std[eca1b30e63fdea7a]::thread::Builder>::spawn_unchecked_<rustc_interface[7fb7dc76513cf959]::util::run_in_thread_with_globals<rustc_interface[7fb7dc76513cf959]::util::run_in_thread_pool_with_globals<rustc_interface[7fb7dc76513cf959]::interface::run_compiler<core[daaba097f859fa28]::result::Result<(), rustc_span[1efc0ab8e6bb0790]::ErrorGuaranteed>, rustc_driver_impl[93e75e0175b92285]::run_compiler::{closure#0}>::{closure#1}, core[daaba097f859fa28]::result::Result<(), rustc_span[1efc0ab8e6bb0790]::ErrorGuaranteed>>::{closure#0}, core[daaba097f859fa28]::result::Result<(), rustc_span[1efc0ab8e6bb0790]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[daaba097f859fa28]::result::Result<(), rustc_span[1efc0ab8e6bb0790]::ErrorGuaranteed>>::{closure#2} as core[daaba097f859fa28]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  42:     0x71e31da3e8cb - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::ha1ad2417ff4e2c89
                               at /rustc/1ca578e68eb715e772fc0c1b9e6ca7c5b122765a/library/alloc/src/boxed.rs:2062:9
  43:     0x71e31da3e8cb - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::ha5ab2243447620ef
                               at /rustc/1ca578e68eb715e772fc0c1b9e6ca7c5b122765a/library/alloc/src/boxed.rs:2062:9
  44:     0x71e31da3e8cb - std::sys::pal::unix::thread::Thread::new::thread_start::he00df2d38aeed7a5
                               at /rustc/1ca578e68eb715e772fc0c1b9e6ca7c5b122765a/library/std/src/sys/pal/unix/thread.rs:108:17
  45:     0x71e316ca6ded - <unknown>
  46:     0x71e316d2a0dc - <unknown>
  47:                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 1.81.0-nightly (1ca578e68 2024-06-20) running on x86_64-unknown-linux-gnu

query stack during panic:
#0 [typeck] type-checking `edge_case_if`
#1 [analysis] running analysis passes on this crate
end of query stack
error: aborting due to 2 previous errors

For more information about this error, try `rustc --explain E0601`.

[matthiaskrgr]

#126320 cc @oli-obk :D

[oli-obk]

wtf. why does that wrong comma cause the struct to be different from a struct with no fields

[matthiaskrgr]

minimized

struct X {,}

fn main() {
    || {
        if let X { x: 1,} = (X {}) {}
    };
}

[chenyukang]

wtf. why does that wrong comma cause the struct to be different from a struct with no fields

An extra , is a recovered struct variant, and it is skipped here:

rust/compiler/rustc_hir_typeck/src/pat.rs

Line 1533 in 382148d

let inexistent_fields_err = if !(inexistent_fields.is_empty() || variant.is_recovered())

so we didn't emit the error like an empty struct:

rust/compiler/rustc_hir_typeck/src/pat.rs

Line 1610 in 382148d

(Some(err), None) => Err(err.emit()),

error[E0026]: struct `X` does not have a field named `x`
 --> src/main.rs:5:20
  |
5 |         if let X { x: 1,} = (X {}) {}
  |                    ^ struct `X` does not have this field

So the compiler continues until the ICE point.

I think a trivial fix will be ok here?

[oli-obk]

Hmm... I'd look into reporting that error even for recovered structs and figuring out how to avoid it just for the cases that this skip was intended to avoid

[chenyukang]

seems there is nothing else we are trying to avoid:

2ea2bb4

I'd prefer not to report the no-field error, since the first error in parsing will point out the root cause, and there is a case like #126344, which may introduce noise when there are too many type errors, it's also applied to this issue.

[oli-obk]

Oh... we can probably just replace the is_recovered method with a new tainted_by_errors method and return an Result<(), ErrorGuaranteed>. This way we act as if we reported an error, and thus not continue to the ICE