[ICE]: Querying attributes on a constant expression causes assertion failure

[momvart]

I query attributes for any DefId that has a body. Upgrading to the latest nightly version is panicking because a constant expression that is not present in the attributes table is being queried.

Affected release channels

• Previous Stable
• Current Stable
• Current Beta
• Current Nightly

Rust Version

rustc 1.82.0-nightly (8bfcae730 2024-07-23)
binary: rustc
commit-hash: 8bfcae730a5db2438bbda72796175bba21427be1
commit-date: 2024-07-23
host: x86_64-unknown-linux-gnu
release: 1.82.0-nightly
LLVM version: 18.1.7

Current error output

thread 'rustc' panicked at compiler/rustc_metadata/src/rmeta/decoder.rs:1405:17:
assertion `left == right` failed
  left: AnonConst
 right: Ctor

Backtrace

thread 'rustc' panicked at compiler/rustc_metadata/src/rmeta/decoder.rs:1405:17:
assertion `left == right` failed
  left: AnonConst
 right: Ctor
stack backtrace:
   0:     0x7f5bb2446215 - std::backtrace_rs::backtrace::libunwind::trace::hc100fac9458ea61d
                               at /rustc/8bfcae730a5db2438bbda72796175bba21427be1/library/std/src/../../backtrace/src/backtrace/libunwind.rs:116:5
   1:     0x7f5bb2446215 - std::backtrace_rs::backtrace::trace_unsynchronized::hef55087fcdadf922
                               at /rustc/8bfcae730a5db2438bbda72796175bba21427be1/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5
   2:     0x7f5bb2446215 - std::sys::backtrace::_print_fmt::h1f2a4053eb374970
                               at /rustc/8bfcae730a5db2438bbda72796175bba21427be1/library/std/src/sys/backtrace.rs:68:9
   3:     0x7f5bb2446215 - <std::sys::backtrace::BacktraceLock::print::DisplayBacktrace as core::fmt::Display>::fmt::hf10c1ebc8bddc711
                               at /rustc/8bfcae730a5db2438bbda72796175bba21427be1/library/std/src/sys/backtrace.rs:41:26
   4:     0x7f5bb2495c8b - core::fmt::rt::Argument::fmt::hdc297574ec01e20b
                               at /rustc/8bfcae730a5db2438bbda72796175bba21427be1/library/core/src/fmt/rt.rs:173:76
   5:     0x7f5bb2495c8b - core::fmt::write::h1b95545231c46caf
                               at /rustc/8bfcae730a5db2438bbda72796175bba21427be1/library/core/src/fmt/mod.rs:1182:21
   6:     0x7f5bb243ad9f - std::io::Write::write_fmt::hb674a7403d96ce62
                               at /rustc/8bfcae730a5db2438bbda72796175bba21427be1/library/std/src/io/mod.rs:1827:15
   7:     0x7f5bb2448a01 - std::sys::backtrace::BacktraceLock::print::h97d31a6209887974
                               at /rustc/8bfcae730a5db2438bbda72796175bba21427be1/library/std/src/sys/backtrace.rs:44:9
   8:     0x7f5bb2448a01 - std::panicking::default_hook::{{closure}}::hed4257fd5a0db25c
                               at /rustc/8bfcae730a5db2438bbda72796175bba21427be1/library/std/src/panicking.rs:269:22
   9:     0x7f5bb24486dc - std::panicking::default_hook::h24ac2f43652a5d56
                               at /rustc/8bfcae730a5db2438bbda72796175bba21427be1/library/std/src/panicking.rs:296:9
  10:     0x7f5bae828dd9 - std[e4b7e4535017d5e1]::panicking::update_hook::<alloc[e6ec1d7ca0a399c5]::boxed::Box<rustc_driver_impl[febec7b9091e9110]::install_ice_hook::{closure#0}>>::{closure#0}
  11:     0x7f5bb24493cf - <alloc::boxed::Box<F,A> as core::ops::function::Fn<Args>>::call::h17698a3f854e57f1
                               at /rustc/8bfcae730a5db2438bbda72796175bba21427be1/library/alloc/src/boxed.rs:2163:9
  12:     0x7f5bb24493cf - std::panicking::rust_panic_with_hook::h1f9833954d467d48
                               at /rustc/8bfcae730a5db2438bbda72796175bba21427be1/library/std/src/panicking.rs:808:13
  13:     0x7f5bb2448ff7 - std::panicking::begin_panic_handler::{{closure}}::h1a936a87dc6e3105
                               at /rustc/8bfcae730a5db2438bbda72796175bba21427be1/library/std/src/panicking.rs:674:13
  14:     0x7f5bb24466d9 - std::sys::backtrace::__rust_end_short_backtrace::hf33c2fe0a2870dfd
                               at /rustc/8bfcae730a5db2438bbda72796175bba21427be1/library/std/src/sys/backtrace.rs:172:18
  15:     0x7f5bb2448c84 - rust_begin_unwind
                               at /rustc/8bfcae730a5db2438bbda72796175bba21427be1/library/std/src/panicking.rs:665:5
  16:     0x7f5bb2492243 - core::panicking::panic_fmt::he12d0d7468628bb4
                               at /rustc/8bfcae730a5db2438bbda72796175bba21427be1/library/core/src/panicking.rs:74:14
  17:     0x7f5bb249274e - core::panicking::assert_failed_inner::ha97f4fea14e1772c
                               at /rustc/8bfcae730a5db2438bbda72796175bba21427be1/library/core/src/panicking.rs:410:17
  18:     0x7f5baed24f7b - core[54ddcb737db04b55]::panicking::assert_failed::<rustc_hir[1c74cf0c8dec4931]::definitions::DefPathData, rustc_hir[1c74cf0c8dec4931]::definitions::DefPathData>
  19:     0x7f5bb130eebd - <rustc_metadata[91f0e848ebb9135c]::creader::CrateMetadataRef>::get_item_attrs.cold
  20:     0x7f5bb00ff685 - rustc_metadata[91f0e848ebb9135c]::rmeta::decoder::cstore_impl::provide_extern::item_attrs
  21:     0x7f5bb00ff4aa - rustc_query_impl[24355b2398a17e2b]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[24355b2398a17e2b]::query_impl::item_attrs::dynamic_query::{closure#2}::{closure#0}, rustc_middle[fb2b7e38760c264]::query::erase::Erased<[u8; 16usize]>>
  22:     0x7f5bb00ff489 - <rustc_query_impl[24355b2398a17e2b]::query_impl::item_attrs::dynamic_query::{closure#2} as core[54ddcb737db04b55]::ops::function::FnOnce<(rustc_middle[fb2b7e38760c264]::ty::context::TyCtxt, rustc_span[4c8883a1b61e9c8d]::def_id::DefId)>>::call_once
  23:     0x7f5bb032a17a - rustc_query_system[8d1605f3b05757d1]::query::plumbing::try_execute_query::<rustc_query_impl[24355b2398a17e2b]::DynamicConfig<rustc_query_system[8d1605f3b05757d1]::query::caches::DefIdCache<rustc_middle[fb2b7e38760c264]::query::erase::Erased<[u8; 16usize]>>, false, false, false>, rustc_query_impl[24355b2398a17e2b]::plumbing::QueryCtxt, false>
  24:     0x7f5bb03299a3 - rustc_query_impl[24355b2398a17e2b]::query_impl::item_attrs::get_query_non_incr::__rust_end_short_backtrace
  25:     0x7f5bb05ba9f9 - rustc_middle[fb2b7e38760c264]::query::plumbing::query_get_at::<rustc_query_system[8d1605f3b05757d1]::query::caches::DefIdCache<rustc_middle[fb2b7e38760c264]::query::erase::Erased<[u8; 16usize]>>>
  26:     0x7f5bad1991e5 - <rustc_middle[fb2b7e38760c264]::ty::context::TyCtxt>::get_attrs_by_path

Anything else?

The DefId that was given to it:

DefId(1:12582 ~ std[f9c2]::sys::pal::unix::stack_overflow::imp::GUARD::{constant#0})

[momvart]

For a fix, I think we can change the assertion to a conditional and return an empty array (default) for any item absent in the table.

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

Lines 1391 to 1414 in 2ccafed

	fn get_item_attrs(
	self,
	id: DefIndex,
	sess: &'a Session,
	) -> impl Iterator<Item = ast::Attribute> + 'a {
	self.root
	.tables
	.attributes
	.get(self, id)
	.unwrap_or_else(|| {
	// Structure and variant constructors don't have any attributes encoded for them,
	// but we assume that someone passing a constructor ID actually wants to look at
	// the attributes on the corresponding struct or variant.
	let def_key = self.def_key(id);
	assert_eq!(def_key.disambiguated_data.data, DefPathData::Ctor);
	let parent_id = def_key.parent.expect("no parent for a constructor");
	self.root
	.tables
	.attributes
	.get(self, parent_id)
	.expect("no encoded attributes for a structure or variant")
	})
	.decode((self, sess))
	}

[petrochenkov]

Closing #128154 (comment)