A dep graph node (mir_drops_elaborated_and_const_checked) does not have an unique index

[dfaust]

The error has been occurring sporadically for like a week or two with recent nightly versions. Unfortunately I don't have more details, please let me know if I can help somehow.

Error output

thread 'rustc' panicked at /rustc/3e674b06b5c74adea662bd0b0b06450757994b16/compiler/rustc_query_system/src/dep_graph/serialized.rs:284:21:
Error: A dep graph node (mir_drops_elaborated_and_const_checked) does not have an unique index. Running a clean build on a nightly compiler with `-Z incremental-verify-ich` can help narrow down the issue for reporting. A clean build may also work around the issue.

                     DepNode: DepKind { variant: 55 }(66f52541bc7a3a54-9342199b53a1abb9)
stack backtrace:
   0:     0x7f110d0d9ee5 - std::backtrace::Backtrace::create::hfa425f8c6118c291
   1:     0x7f110b558655 - std::backtrace::Backtrace::force_capture::hc89ba712c3edf9d4
   2:     0x7f110a59b841 - std[dddea0bc0c38a8db]::panicking::update_hook::<alloc[ad07e7cbb7f1de4e]::boxed::Box<rustc_driver_impl[40f87d5870cfacca]::install_ice_hook::{closure#1}>>::{closure#0}
   3:     0x7f110b572583 - std::panicking::rust_panic_with_hook::hedd3f60f85824998
   4:     0x7f110b57227a - std::panicking::begin_panic_handler::{{closure}}::hf9de1d740cfa85c9
   5:     0x7f110b56e779 - std::sys::backtrace::__rust_end_short_backtrace::h60f7d5e7789cd81b
   6:     0x7f110b571f3d - __rustc[6241699db995e819]::rust_begin_unwind
   7:     0x7f1107e89ee0 - core::panicking::panic_fmt::h4e2563c759f41a6b
   8:     0x7f110cd6347f - rustc_incremental[e2943fc0bf579b13]::persist::load::setup_dep_graph
   9:     0x7f110cd1b204 - rustc_interface[3a0a2c43e50c5194]::interface::run_compiler::<(), rustc_driver_impl[40f87d5870cfacca]::run_compiler::{closure#0}>::{closure#1}
  10:     0x7f110a5af124 - <rayon_core[450d1f61637cc29a]::job::StackJob<rayon_core[450d1f61637cc29a]::latch::LatchRef<rayon_core[450d1f61637cc29a]::latch::LockLatch>, <rayon_core[450d1f61637cc29a]::registry::Registry>::in_worker_cold<<rayon_core[450d1f61637cc29a]::thread_pool::ThreadPool>::install<rustc_interface[3a0a2c43e50c5194]::util::run_in_thread_pool_with_globals<rustc_interface[3a0a2c43e50c5194]::interface::run_compiler<(), rustc_driver_impl[40f87d5870cfacca]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#5}::{closure#0}::{closure#1}::{closure#0}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()> as rayon_core[450d1f61637cc29a]::job::Job>::execute
  11:     0x7f110a04404e - <rayon_core[450d1f61637cc29a]::registry::WorkerThread>::wait_until_cold
  12:     0x7f110a0419d1 - <rayon_core[450d1f61637cc29a]::registry::ThreadBuilder>::run
  13:     0x7f110a59175d - std[dddea0bc0c38a8db]::sys::backtrace::__rust_begin_short_backtrace::<<rayon_core[450d1f61637cc29a]::ThreadPoolBuilder>::build_scoped<rustc_interface[3a0a2c43e50c5194]::util::run_in_thread_pool_with_globals<rustc_interface[3a0a2c43e50c5194]::interface::run_compiler<(), rustc_driver_impl[40f87d5870cfacca]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#5}::{closure#0}::{closure#0}, rustc_interface[3a0a2c43e50c5194]::util::run_in_thread_pool_with_globals<rustc_interface[3a0a2c43e50c5194]::interface::run_compiler<(), rustc_driver_impl[40f87d5870cfacca]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#5}::{closure#0}::{closure#1}, ()>::{closure#0}::{closure#0}::{closure#0}, ()>
  14:     0x7f110a59ffb2 - <<std[dddea0bc0c38a8db]::thread::Builder>::spawn_unchecked_<<rayon_core[450d1f61637cc29a]::ThreadPoolBuilder>::build_scoped<rustc_interface[3a0a2c43e50c5194]::util::run_in_thread_pool_with_globals<rustc_interface[3a0a2c43e50c5194]::interface::run_compiler<(), rustc_driver_impl[40f87d5870cfacca]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#5}::{closure#0}::{closure#0}, rustc_interface[3a0a2c43e50c5194]::util::run_in_thread_pool_with_globals<rustc_interface[3a0a2c43e50c5194]::interface::run_compiler<(), rustc_driver_impl[40f87d5870cfacca]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#5}::{closure#0}::{closure#1}, ()>::{closure#0}::{closure#0}::{closure#0}, ()>::{closure#1} as core[a1eebbb7364c739]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  15:     0x7f110ccc66fd - std::sys::pal::unix::thread::Thread::new::thread_start::h337190b46df16ff4
  16:     0x7f1106899546 - start_thread
  17:     0x7f110691d94c - __GI___clone3
  18:                0x0 - <unknown>


rustc version: 1.89.0-nightly (3e674b06b 2025-05-23)
platform: x86_64-unknown-linux-gnu

[nastynaz]

The same for me. It's really frustrating. A cargo clean sometimes fixes it but it randomly comes back. @dfaust did you ever figure it out?

[dfaust]

@nastynaz I disabled incremental compilation. No issues since.

[nastynaz]

@dfaust

This was the only thing that fixed it for me. Thanks for sharing. It's slightly annoying having longer compile times but better than the previous flakiness. Out of curiosity, are you using #![feature(generic_const_exprs)] anywhere in your code? The compiler had an issue with this in the past that was supposedly fixed and I wonder whether it's the same bug cropping up in a different form.

[dfaust]

@nastynaz

are you using #![feature(generic_const_exprs)] anywhere in your code?

No, I'm not.

[mirsella]

hey, still hapenning as of 12/06/2025.
personally it happens when multiples cargo commands are running at the same time (waiting for file lock on package cache). there might a be problem in the synchronization/lock system between cargo commands using the target dir ?