assertion failed: trying to encode a dep node twice

As I've suspected #149916 revealed a bug in rustc's query system on multiple threads. I was trying to build rustc itself with the nightly toolchain as stage0 after doing git checkout build fails while trying to compile rustc_lint_defs.

Error

thread 'rustc' (199561) panicked at compiler/rustc_query_system/src/dep_graph/graph.rs:1392:9:
assertion `left == right` failed: trying to encode a dep node twice
  left: 64535
 right: 4294967295

backtrace

stack backtrace:
   0: __rustc::rust_begin_unwind
   1: core::panicking::panic_fmt
   2: core::panicking::assert_failed_inner
   3: core::panicking::assert_failed::<u32, u32>
   4: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::DynamicConfig<rustc_data_structures::vec_cache::VecCache<rustc_span::def_id::LocalDefId, rustc_middle::query::erase::Erased<[u8; 8]>, rustc_query_system::dep_graph::graph::DepNodeIndex>, false, false, false>, rustc_query_impl::plumbing::QueryCtxt, true>
   5: rustc_query_impl::plumbing::force_from_dep_node::<rustc_query_impl::DynamicConfig<rustc_data_structures::vec_cache::VecCache<rustc_span::def_id::LocalDefId, rustc_middle::query::erase::Erased<[u8; 8]>, rustc_query_system::dep_graph::graph::DepNodeIndex>, false, false, false>>
   6: <rustc_query_impl::plumbing::query_callback<rustc_query_impl::query_impl::mir_drops_elaborated_and_const_checked::QueryType>::{closure#0} as core::ops::function::FnOnce<(rustc_middle::ty::context::TyCtxt, rustc_query_system::dep_graph::dep_node::DepNode, rustc_query_system::dep_graph::serialized::SerializedDepNodeIndex)>>::call_once
   7: <rustc_query_system::dep_graph::graph::DepGraphData<rustc_middle::dep_graph::DepsType>>::try_mark_previous_green::<rustc_query_impl::plumbing::QueryCtxt>
   8: <rustc_query_system::dep_graph::graph::DepGraphData<rustc_middle::dep_graph::DepsType>>::try_mark_previous_green::<rustc_query_impl::plumbing::QueryCtxt>
   9: <rustc_query_system::dep_graph::graph::DepGraphData<rustc_middle::dep_graph::DepsType>>::try_mark_previous_green::<rustc_query_impl::plumbing::QueryCtxt>
  10: <rustc_query_system::dep_graph::graph::DepGraphData<rustc_middle::dep_graph::DepsType>>::try_mark_previous_green::<rustc_query_impl::plumbing::QueryCtxt>
  11: <rustc_query_system::dep_graph::graph::DepGraphData<rustc_middle::dep_graph::DepsType>>::try_mark_green::<rustc_query_impl::plumbing::QueryCtxt>
  12: rustc_query_system::query::plumbing::ensure_must_run::<rustc_query_impl::DynamicConfig<rustc_query_system::query::caches::DefIdCache<rustc_middle::query::erase::Erased<[u8; 32]>>, false, false, false>, rustc_query_impl::plumbing::QueryCtxt>
  13: <rustc_middle::ty::context::TyCtxt>::par_hir_body_owners::<rustc_hir_analysis::check_crate::{closure#2}>::{closure#0}
  14: rustc_data_structures::sync::parallel::par_slice::par_rec::<&rustc_span::def_id::LocalDefId, rustc_data_structures::sync::parallel::par_for_each_in<&rustc_span::def_id::LocalDefId, &[rustc_span::def_id::LocalDefId], <rustc_middle::ty::context::TyCtxt>::par_hir_body_owners<rustc_hir_analysis::check_crate::{closure#2}>::{closure#0}>::{closure#0}::{closure#0}>
  15: <rustc_thread_pool::job::StackJob<rustc_thread_pool::latch::SpinLatch, rustc_thread_pool::join::join_context<rustc_thread_pool::join::join::call<(), rustc_data_structures::sync::parallel::par_slice::par_rec<&rustc_span::def_id::LocalDefId, rustc_data_structures::sync::parallel::par_for_each_in<&rustc_span::def_id::LocalDefId, &[rustc_span::def_id::LocalDefId], <rustc_middle::ty::context::TyCtxt>::par_hir_body_owners<rustc_hir_analysis::check_crate::{closure#2}>::{closure#0}>::{closure#0}::{closure#0}>::{closure#1}>::{closure#0}, rustc_thread_pool::join::join::call<(), rustc_data_structures::sync::parallel::par_slice::par_rec<&rustc_span::def_id::LocalDefId, rustc_data_structures::sync::parallel::par_for_each_in<&rustc_span::def_id::LocalDefId, &[rustc_span::def_id::LocalDefId], <rustc_middle::ty::context::TyCtxt>::par_hir_body_owners<rustc_hir_analysis::check_crate::{closure#2}>::{closure#0}>::{closure#0}::{closure#0}>::{closure#2}>::{closure#0}, (), ()>::{closure#0}::{closure#0}, ()> as rustc_thread_pool::job::Job>::execute
  16: <rustc_thread_pool::registry::WorkerThread>::wait_or_steal_until_cold
  17: <rustc_thread_pool::registry::ThreadBuilder>::run
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.

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: please attach the file at `/home/huawei/dev/rust/rustc-ice-2025-12-15T10_49_29-199385.txt` to your bug report

note: compiler flags: --crate-type lib -C opt-level=3 -C embed-bitcode=no -C debuginfo=line-tables-only -C debug-assertions=on -C incremental=[REDACTED] -C symbol-mangling-version=v0 -Z annotate-moves -Z unstable-options -Z macro-backtrace -C split-debuginfo=off -C force-frame-pointers=true -C llvm-args=-import-instr-limit=10 -C link-args=-Wl,-z,origin -C link-args=-Wl,-rpath,$ORIGIN/../lib -Z on-broken-pipe=kill -C lto=off -Z threads=24 -Z binary-dep-depinfo -Z tls-model=initial-exec -Z force-unstable-if-unmarked

note: some of the compiler flags provided by cargo are hidden

query stack during panic:
#0 [mir_drops_elaborated_and_const_checked] elaborating drops for `<impl at compiler/rustc_lint_defs/src/lib.rs:557:1: 557:10>::default_fields_for_macro`
#1 [analysis] running analysis passes on crate `rustc_lint_defs`
end of query stack
there was a panic while trying to force a dep node
try_mark_green dep node stack:
#0 mir_for_ctfe(rustc_lint_defs[912f]::{impl#9}::default_fields_for_macro)
#1 eval_to_allocation_raw(6a497d626948f9b4-2f772ebace64724b)
#2 eval_to_const_value_raw(6a497d626948f9b4-2f772ebace64724b)
#3 eval_static_initializer(rustc_lint_defs[912f]::builtin::UNCONDITIONAL_PANIC)
end of try_mark_green dep node stack
error: could not compile `rustc_lint_defs` (lib)

It is surprisingly persistent as and ~~I was unable to get it go away just by retriggering the incremental compilation using touch src/lib.rs but deleting incremental folder fixes this per usual~~ after some rebuilds goes away. We can infer from the error that compiler finds itself in a situation where it tries to mark one dep node as both green and red.

Rust version

Stage 0:

rustc 1.94.0-nightly (0208ee09b 2025-12-14)
binary: rustc
commit-hash: 0208ee09be465f69005a7a12c28d5eccac7d5f34
commit-date: 2025-12-14
host: x86_64-unknown-linux-gnu
release: 1.94.0-nightly
LLVM version: 21.1.5

Steps to reproduce

Do a clean build x build library --stage 1 at 52fda2e, then git checkout to ba45f0b and without cleaning try rebuilding it the same way again. And don't forget to set RUSTFLAGS_BOOTSTRAP to -Zthreads=n where n > 1.

Run ./x b rustc in a clean git worktree of rust-lang/rust with rust.incremental = true and rust.rustflags = "-Zthreads=8" set in bootstrap.toml. Then do a change from below diff to rustc source code:

diff --git a/compiler/rustc_data_structures/src/lib.rs b/compiler/rustc_data_structures/src/lib.rs
index 4467a281118..e79312458b3 100644
--- a/compiler/rustc_data_structures/src/lib.rs
+++ b/compiler/rustc_data_structures/src/lib.rs
@@ -162,3 +162,8 @@ fn fmt(&self, f: &mut ::std::fmt::Formatter<'_>) -> ::std::fmt::Result {
         }
     };
 }
+
+#[derive(Clone, Copy)]
+pub struct BadStruct {
+    int: u64,
+}

Finally run ./x b rustc again. It may sometimes not reproduce, in such case restore changes and ./x b rustc, then apply change and ./x b rustc until ICE is reproduced.

If I do the these steps enough times without replacing stage0 I get #141540.

I've also got "assertion failed: tried to mark a red node as green" while messing around with the compiler. It is the same bug but it behaves a bit differently due to different orders of atomic ops. And its apparently the source of #148295.

thread 'rustc' (433110) panicked at compiler/rustc_query_system/src/dep_graph/graph.rs:1367:17:
assertion `left != right` failed: tried to mark a red node as green
  left: 4294967294
 right: 4294967294

backtrace

stack backtrace:
   0: __rustc::rust_begin_unwind
   1: core::panicking::panic_fmt
   2: core::panicking::assert_failed_inner
   3: core::panicking::assert_failed::<u32, u32>
   4: <rustc_query_system::dep_graph::graph::DepGraphData<rustc_middle::dep_graph::DepsType>>::try_mark_previous_green::<rustc_query_impl::plumbing::QueryCtxt>
   5: <rustc_query_system::dep_graph::graph::DepGraphData<rustc_middle::dep_graph::DepsType>>::try_mark_previous_green::<rustc_query_impl::plumbing::QueryCtxt>
   6: <rustc_query_system::dep_graph::graph::DepGraphData<rustc_middle::dep_graph::DepsType>>::try_mark_previous_green::<rustc_query_impl::plumbing::QueryCtxt>
   7: rustc_query_system::query::plumbing::ensure_must_run::<rustc_query_impl::DynamicConfig<rustc_data_structures::vec_cache::VecCache<rustc_span::def_id::LocalDefId, rustc_middle::query::erase::Erased<[u8; 0]>, rustc_query_system::dep_graph::graph::DepNodeIndex>, false, false, false>, rustc_query_impl::plumbing::QueryCtxt>
   8: <rustc_middle::ty::context::TyCtxt>::par_hir_body_owners::<rustc_interface::passes::run_required_analyses::{closure#1}::{closure#0}>::{closure#0}
   9: rustc_data_structures::sync::parallel::par_slice::par_rec::<&rustc_span::def_id::LocalDefId, rustc_data_structures::sync::parallel::par_for_each_in<&rustc_span::def_id::LocalDefId, &[rustc_span::def_id::LocalDefId], <rustc_middle::ty::context::TyCtxt>::par_hir_body_owners<rustc_interface::passes::run_required_analyses::{closure#1}::{closure#0}>::{closure#0}>::{closure#0}::{closure#0}>
  10: <rustc_thread_pool::job::StackJob<rustc_thread_pool::latch::SpinLatch, rustc_thread_pool::join::join_context<rustc_thread_pool::join::join::call<(), rustc_data_structures::sync::parallel::par_slice::par_rec<&rustc_span::def_id::LocalDefId, rustc_data_structures::sync::parallel::par_for_each_in<&rustc_span::def_id::LocalDefId, &[rustc_span::def_id::LocalDefId], <rustc_middle::ty::context::TyCtxt>::par_hir_body_owners<rustc_interface::passes::run_required_analyses::{closure#1}::{closure#0}>::{closure#0}>::{closure#0}::{closure#0}>::{closure#1}>::{closure#0}, rustc_thread_pool::join::join::call<(), rustc_data_structures::sync::parallel::par_slice::par_rec<&rustc_span::def_id::LocalDefId, rustc_data_structures::sync::parallel::par_for_each_in<&rustc_span::def_id::LocalDefId, &[rustc_span::def_id::LocalDefId], <rustc_middle::ty::context::TyCtxt>::par_hir_body_owners<rustc_interface::passes::run_required_analyses::{closure#1}::{closure#0}>::{closure#0}>::{closure#0}::{closure#0}>::{closure#2}>::{closure#0}, (), ()>::{closure#0}::{closure#0}, ()> as rustc_thread_pool::job::Job>::execute
  11: <rustc_thread_pool::registry::WorkerThread>::wait_or_steal_until_cold
  12: <rustc_thread_pool::registry::ThreadBuilder>::run
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.

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: please attach the file at `/home/huawei/dev/rust/rustc-ice-2025-12-15T12_09_14-432905.txt` to your bug report

note: compiler flags: --crate-type lib -C opt-level=3 -C embed-bitcode=no -C debuginfo=line-tables-only -C debug-assertions=on -C incremental=[REDACTED] -C symbol-mangling-version=v0 -Z annotate-moves -Z unstable-options -Z macro-backtrace -C split-debuginfo=off -C force-frame-pointers=true -C llvm-args=-import-instr-limit=10 -C link-args=-Wl,-z,origin -C link-args=-Wl,-rpath,$ORIGIN/../lib -Z on-broken-pipe=kill -C lto=off -Z threads=24 -Z binary-dep-depinfo -Z tls-model=initial-exec -Z force-unstable-if-unmarked

note: some of the compiler flags provided by cargo are hidden

query stack during panic:
#0 [analysis] running analysis passes on crate `rustc_ast_pretty`
end of query stack
error: could not compile `rustc_ast_pretty` (lib)

Issue debugged, a solution is proposed in #150156.

Are there any workarounds other than doing cargo clean? Do we know which nightly / toolchain version/date this originally appeared in?

Are there any workarounds other than doing cargo clean?

I usually

rm -r .\target\debug\incremental\

Are there any workarounds other than doing cargo clean?

You can kinda brute-force it by doing your cargo build command again and again. At least that works when compiling rustc.

Do we know which nightly / toolchain version/date this originally appeared in?

This exact issue appeared sometime around nightly-2025-12-13. However downgrading would only get you either #142778 or #141540. The latter issue will corrupt your incremental cache and so brute-force won't be able to help you any longer.

I'm also seeing these two quite frequently (nightly 2026-01-03)

thread 'rustc' panicked at /rustc-dev/7ecabfaaf1a58172cdd71f7661cf6589ddf7928f/compiler/rustc_query_system/src/dep_graph/graph.rs:1367:17:
assertion `left != right` failed: tried to mark a red node as green
  left: 4294967294
 right: 4294967294

thread 'rustc' panicked at /rustc-dev/7ecabfaaf1a58172cdd71f7661cf6589ddf7928f/compiler/rustc_query_system/src/dep_graph/graph.rs:1392:9:
assertion `left == right` failed: trying to encode a dep node twice
  left: 180797
 right: 4294967295

a few full logs from yesterday:

Archiv.zip

You can kinda brute-force it by doing your cargo build command again and again. At least that works when compiling rustc.

I am on rustc version: 1.94.0-nightly (4f14395 2025-12-22), bruteforcing it does not seem to work for me, or at least not for the first 7 times. It seems like I have to completely rebuild it which sucks since it takes like 10 minutes.

You can kinda brute-force it by doing your cargo build command again and again. At least that works when compiling rustc.

I am on rustc version: 1.94.0-nightly (4f14395 2025-12-22), bruteforcing it does not seem to work for me, or at least not for the first 7 times. It seems like I have to completely rebuild it which sucks since it takes like 10 minutes.

In that case rm -r target/debug/incremental should be your best second option until #150156 is merged.

Auto merge of #151509 - Zoxc:gen-color-race, r=zetanumbers,petrochenkov

Turbopack: Update rust toolchain to nightly-2026-02-18 (#89974)

Auto merge of #151509 - Zoxc:gen-color-race, r=zetanumbers,petrochenkov

Turbopack: Update rust toolchain to nightly-2026-02-18 (vercel#89974)

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assertion failed: trying to encode a dep node twice #150018

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assertion failed: trying to encode a dep node twice #150018

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zetanumbers commented on Dec 15, 2025

zetanumbers commented on Dec 15, 2025

petrochenkov commented on Dec 19, 2025

luxalpa commented on Dec 29, 2025

TeamDman commented on Jan 5, 2026

zetanumbers commented on Jan 12, 2026

mischnic commented on Jan 15, 2026

luxalpa commented on Jan 18, 2026

zetanumbers commented on Jan 18, 2026

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