[ICE]: cannot decode `AttrId` with `CacheDecoder`

[ruriww]

Code

Not sure what caused it. Only happens on debug mode.

Meta

rustc --version --verbose:

rustc version: 1.96.0-nightly (900485642 2026-04-08)

thread 'rustc' panicked at /rustc-dev/900485642855f4729d926ecf24680a791f9293cf/compiler/rustc_middle/src/query/on_disk_cache.rs:663:9:
cannot decode `AttrId` with `CacheDecoder`
stack backtrace:
   0:        0x113521c08 - <std[cc2a4db2680813b8]::backtrace::Backtrace>::create
   1:        0x1113aeee0 - std[cc2a4db2680813b8]::panicking::update_hook::<alloc[5c025890d9b65067]::boxed::Box<rustc_driver_impl[a9b8195e93143871]::install_ice_hook::{closure#1}>>::{closure#0}
   2:        0x11353369c - std[cc2a4db2680813b8]::panicking::panic_with_hook
   3:        0x113517620 - std[cc2a4db2680813b8]::panicking::panic_handler::{closure#0}
   4:        0x11350df98 - std[cc2a4db2680813b8]::sys::backtrace::__rust_end_short_backtrace::<std[cc2a4db2680813b8]::panicking::panic_handler::{closure#0}, !>
   5:        0x113518bc4 - __rustc[9893dd7cded7045d]::rust_begin_unwind
   6:        0x116554044 - core[65d2295b482aced]::panicking::panic_fmt
   7:        0x11212ed30 - <rustc_middle[4fc8633060c41573]::query::on_disk_cache::OnDiskCache>::load_side_effect
   8:        0x112ca46d8 - <rustc_query_impl[95864d7e07eebc26]::dep_kind_vtables::non_query::SideEffect::{closure#0} as core[65d2295b482aced]::ops::function::FnOnce<(rustc_middle[4fc8633060c41573]::ty::context::TyCtxt, rustc_middle[4fc8633060c41573]::dep_graph::dep_node::DepNode, rustc_middle[4fc8633060c41573]::dep_graph::serialized::SerializedDepNodeIndex)>>::call_once
   9:        0x11215c2a4 - <rustc_middle[4fc8633060c41573]::dep_graph::graph::DepGraphData>::try_mark_previous_green
  10:        0x11215c258 - <rustc_middle[4fc8633060c41573]::dep_graph::graph::DepGraphData>::try_mark_previous_green
  11:        0x11215c258 - <rustc_middle[4fc8633060c41573]::dep_graph::graph::DepGraphData>::try_mark_previous_green
  12:        0x11215c118 - <rustc_middle[4fc8633060c41573]::dep_graph::graph::DepGraphData>::try_mark_green
  13:        0x112a38744 - rustc_query_impl[95864d7e07eebc26]::execution::ensure_can_skip_execution::<rustc_data_structures[abfc8eabe9c905b9]::vec_cache::VecCache<rustc_hir_id[185bbc009e60d6cf]::OwnerId, rustc_middle[4fc8633060c41573]::query::erase::ErasedData<[u8; 8usize]>, rustc_middle[4fc8633060c41573]::dep_graph::graph::DepNodeIndex>>
  14:        0x112b3c800 - rustc_query_impl[95864d7e07eebc26]::query_impl::check_unsafety::execute_query_incr::__rust_end_short_backtrace
  15:        0x111cbff88 - <rustc_middle[4fc8633060c41573]::ty::context::TyCtxt>::par_hir_body_owners::<rustc_interface[4d5dd335d36b1423]::passes::run_required_analyses::{closure#2}::{closure#0}>::{closure#0}
  16:        0x111d06540 - rustc_interface[4d5dd335d36b1423]::passes::analysis
  17:        0x1129b7a60 - rustc_query_impl[95864d7e07eebc26]::execution::try_execute_query::<rustc_middle[4fc8633060c41573]::query::caches::SingleCache<rustc_middle[4fc8633060c41573]::query::erase::ErasedData<[u8; 0usize]>>, true>
  18:        0x112b6e930 - rustc_query_impl[95864d7e07eebc26]::query_impl::analysis::execute_query_incr::__rust_end_short_backtrace
  19:        0x111366440 - rustc_interface[4d5dd335d36b1423]::passes::create_and_enter_global_ctxt::<core[65d2295b482aced]::option::Option<rustc_interface[4d5dd335d36b1423]::queries::Linker>, rustc_driver_impl[a9b8195e93143871]::run_compiler::{closure#0}::{closure#2}>
  20:        0x1113addc0 - rustc_interface[4d5dd335d36b1423]::interface::run_compiler::<(), rustc_driver_impl[a9b8195e93143871]::run_compiler::{closure#0}>::{closure#1}
  21:        0x1113a5948 - std[cc2a4db2680813b8]::sys::backtrace::__rust_begin_short_backtrace::<rustc_interface[4d5dd335d36b1423]::util::run_in_thread_with_globals<rustc_interface[4d5dd335d36b1423]::util::run_in_thread_pool_with_globals<rustc_interface[4d5dd335d36b1423]::interface::run_compiler<(), rustc_driver_impl[a9b8195e93143871]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>
  22:        0x1113b5ad0 - <std[cc2a4db2680813b8]::thread::lifecycle::spawn_unchecked<rustc_interface[4d5dd335d36b1423]::util::run_in_thread_with_globals<rustc_interface[4d5dd335d36b1423]::util::run_in_thread_pool_with_globals<rustc_interface[4d5dd335d36b1423]::interface::run_compiler<(), rustc_driver_impl[a9b8195e93143871]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>::{closure#1} as core[65d2295b482aced]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  23:        0x11353dee0 - <std[cc2a4db2680813b8]::sys::thread::unix::Thread>::new::thread_start
  24:        0x18250fbc8 - __pthread_cond_wait


rustc version: 1.96.0-nightly (900485642 2026-04-08)
platform: aarch64-apple-darwin

query stack during panic:
#0 [analysis] running analysis passes on crate `---`
end of query stack

Backtrace

<backtrace>

[spqr79]

have you tried cargo clean first and then doing a fresh build? the panic in
on_disk_cache.rs:663 usually means the incremental cache has something it
can't decode anymore, and nightly builds can invalidate it without warning.

if the ICE comes back on the next incremental build after that, it's more
likely a regression in 900485642. in that case it would be worth trying
rustup override set nightly-2026-04-07 to see if an earlier nightly avoids
it, since the check_unsafety path in the backtrace is a pretty specific clue
for bisecting.

[ruriww]

I have cleaned, and I believe it was happening in the 04-05 build as well.

[spqr79]

Good to know it's not just stale cache. If 04-05 also triggers it, try nightly-2026-04-01 to narrow the window before bisecting.

[ruriww]

Ok actually it is due to cache, but I wouldn't call it stale. Simply running two back to back builds after a clean consistently causes the error. 04-03 is the last version to work, 04-04 breaks.

[spqr79]

That's a precise reproduction. The window is tight enough that git log --oneline .. -- compiler/rustc_middle/src/query/on_disk_cache.rs might show the culprit directly without a full bisect.

[JonathanBrouwer]

Duplicate of #154878, fixed by #155056