ICE: Found unstable fingerprints for evaluate_obligation(4742c1b409da674c-2b2e292cfb3cefd9): Ok(EvaluatedToOk)

[1xX69]

Code

[package]
name = "rustc-bug1"
version = "0.1.0"
edition = "2024"

[dependencies]
bitcode = { version = "0.6.5", default-features = false, features = [
  "derive",
  "std",
] }

use bitcode::{Encode, Decode};

#[derive(Encode, Decode)]
pub struct HelpLink<'a> {
    link: &'a str,
}

/// Enum representing different types of error details.
#[derive(Encode, Decode)]
pub enum ErrorDetail<'a> {
    Help {
        links: Vec<HelpLink<'a>>,
    },

    LocalizedMessage {
        locale: &'a str,  // line 16
        message: &'a str,
    },
}

Meta

rustc --version --verbose:

rustc 1.87.0-nightly (8c392966a 2025-03-01)
binary: rustc
commit-hash: 8c392966a013fd8a09e6b78b3c8d6e442bc278e1
commit-date: 2025-03-01
host: x86_64-unknown-linux-gnu
release: 1.87.0-nightly
LLVM version: 20.1.0

Error output

Backtrace

user@work1:~/workspace/rustc-bug1$ cargo build
   Compiling proc-macro2 v1.0.94
   Compiling unicode-ident v1.0.18
   Compiling bytemuck v1.22.0
   Compiling quote v1.0.39
   Compiling syn v2.0.99
   Compiling bitcode_derive v0.6.5
   Compiling bitcode v0.6.5
   Compiling rustc-bug1 v0.1.0 (/home/user/workspace/rustc-bug1)
    Finished `dev` profile [unoptimized + debuginfo] target(s) in 3.21s
user@work1:~/workspace/rustc-bug1$ cat src/lib.rs
use bitcode::{Encode, Decode};

#[derive(Encode, Decode)]
pub struct HelpLink<'a> {
    link: &'a str,
}

/// Enum representing different types of error details.
#[derive(Encode, Decode)]
pub enum ErrorDetail<'a> {
    Help {
        links: Vec<HelpLink<'a>>,
    },

    LocalizedMessage {
        locale: &'a str,  // line 16
        message: &'a str,
    },
}
user@work1:~/workspace/rustc-bug1$ sed -i '16d' src/lib.rs
user@work1:~/workspace/rustc-bug1$ RUST_BACKTRACE=full cargo build
   Compiling rustc-bug1 v0.1.0 (/home/user/workspace/rustc-bug1)
error: internal compiler error: encountered incremental compilation error with evaluate_obligation(4742c1b409da674c-2b2e292cfb3cefd9)
  |
  = help: This is a known issue with the compiler. Run `cargo clean -p rustc_bug1` or `cargo clean` to allow your project to compile
  = note: Please follow the instructions below to create a bug report with the provided information
  = note: See <https://github.com/rust-lang/rust/issues/84970> for more information


thread 'rustc' panicked at /rustc/8c392966a013fd8a09e6b78b3c8d6e442bc278e1/compiler/rustc_query_system/src/query/plumbing.rs:731:9:
Found unstable fingerprints for evaluate_obligation(4742c1b409da674c-2b2e292cfb3cefd9): Ok(EvaluatedToOk)
stack backtrace:
   0:     0x77a7b5dbedf4 - <std::sys::backtrace::BacktraceLock::print::DisplayBacktrace as core::fmt::Display>::fmt::hdbd106d724e72c20
   1:     0x77a7b66057e2 - core::fmt::write::h861eecc74abebf7a
   2:     0x77a7b764dd51 - std::io::Write::write_fmt::h493b3152b071fba0
   3:     0x77a7b5dbec52 - std::sys::backtrace::BacktraceLock::print::h71f315c25fc266cb
   4:     0x77a7b5dc1532 - std::panicking::default_hook::{{closure}}::h8019dc6a2c6c0fe7
   5:     0x77a7b5dc1124 - std::panicking::default_hook::h497f769686a88dd6
   6:     0x77a7b4f18417 - std[e7ccd300aecc5933]::panicking::update_hook::<alloc[8cc49891b291256f]::boxed::Box<rustc_driver_impl[b622dd38a520489a]::install_ice_hook::{closure#1}>>::{closure#0}
   7:     0x77a7b5dc1da3 - std::panicking::rust_panic_with_hook::h98fc165e90ef379e
   8:     0x77a7b5dc1a9a - std::panicking::begin_panic_handler::{{closure}}::h2c1a60d0a908eaec
   9:     0x77a7b5dbf2c9 - std::sys::backtrace::__rust_end_short_backtrace::he8aba8f9b7ddf304
  10:     0x77a7b5dc175d - rust_begin_unwind
  11:     0x77a7b2a5a680 - core::panicking::panic_fmt::hcbf39f8c1e585f84
  12:     0x77a7b54b4a63 - rustc_query_system[18aefac76bbd956a]::query::plumbing::incremental_verify_ich_failed::<rustc_middle[464f7c4b782fc90]::ty::context::TyCtxt>
  13:     0x77a7b6e06018 - rustc_query_system[18aefac76bbd956a]::query::plumbing::try_execute_query::<rustc_query_impl[f11a5069a0fc322c]::DynamicConfig<rustc_query_system[18aefac76bbd956a]::query::caches::DefaultCache<rustc_type_ir[62a9722b2d8d5cac]::canonical::CanonicalQueryInput<rustc_middle[464f7c4b782fc90]::ty::context::TyCtxt, rustc_middle[464f7c4b782fc90]::ty::ParamEnvAnd<rustc_middle[464f7c4b782fc90]::ty::predicate::Predicate>>, rustc_middle[464f7c4b782fc90]::query::erase::Erased<[u8; 2usize]>>, false, false, false>, rustc_query_impl[f11a5069a0fc322c]::plumbing::QueryCtxt, true>
  14:     0x77a7b6af1dc5 - rustc_query_impl[f11a5069a0fc322c]::query_impl::evaluate_obligation::get_query_incr::__rust_end_short_backtrace
  15:     0x77a7b6e9bb11 - <rustc_trait_selection[4edfcc70fd15c568]::traits::fulfill::FulfillProcessor as rustc_data_structures[fa39f8fcd9225f43]::obligation_forest::ObligationProcessor>::process_obligation
  16:     0x77a7b6607529 - <rustc_data_structures[fa39f8fcd9225f43]::obligation_forest::ObligationForest<rustc_trait_selection[4edfcc70fd15c568]::traits::fulfill::PendingPredicateObligation>>::process_obligations::<rustc_trait_selection[4edfcc70fd15c568]::traits::fulfill::FulfillProcessor>
  17:     0x77a7b6a58387 - <rustc_trait_selection[4edfcc70fd15c568]::traits::fulfill::FulfillmentContext<rustc_trait_selection[4edfcc70fd15c568]::traits::FulfillmentError> as rustc_infer[c858f4b860ba366e]::traits::engine::TraitEngine<rustc_trait_selection[4edfcc70fd15c568]::traits::FulfillmentError>>::select_all_or_error
  18:     0x77a7b6d8a78f - rustc_hir_analysis[6dcb172f42838441]::check::compare_impl_item::check_type_bounds
  19:     0x77a7b6d9cd62 - rustc_hir_analysis[6dcb172f42838441]::check::compare_impl_item::compare_impl_item
  20:     0x77a7b6d9af47 - rustc_query_impl[f11a5069a0fc322c]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[f11a5069a0fc322c]::query_impl::compare_impl_item::dynamic_query::{closure#2}::{closure#0}, rustc_middle[464f7c4b782fc90]::query::erase::Erased<[u8; 1usize]>>
  21:     0x77a7b6aeccaa - rustc_query_system[18aefac76bbd956a]::query::plumbing::try_execute_query::<rustc_query_impl[f11a5069a0fc322c]::DynamicConfig<rustc_data_structures[fa39f8fcd9225f43]::vec_cache::VecCache<rustc_span[eeaf0b3b2812840a]::def_id::LocalDefId, rustc_middle[464f7c4b782fc90]::query::erase::Erased<[u8; 1usize]>, rustc_query_system[18aefac76bbd956a]::dep_graph::graph::DepNodeIndex>, false, false, false>, rustc_query_impl[f11a5069a0fc322c]::plumbing::QueryCtxt, true>
  22:     0x77a7b6af10b6 - rustc_query_impl[f11a5069a0fc322c]::query_impl::compare_impl_item::get_query_incr::__rust_end_short_backtrace
  23:     0x77a7b6e2690c - rustc_hir_analysis[6dcb172f42838441]::check::check::check_item_type
  24:     0x77a7b6db6d66 - rustc_hir_analysis[6dcb172f42838441]::check::wfcheck::check_well_formed
  25:     0x77a7b6db544d - rustc_query_impl[f11a5069a0fc322c]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[f11a5069a0fc322c]::query_impl::check_well_formed::dynamic_query::{closure#2}::{closure#0}, rustc_middle[464f7c4b782fc90]::query::erase::Erased<[u8; 1usize]>>
  26:     0x77a7b6aed061 - rustc_query_system[18aefac76bbd956a]::query::plumbing::try_execute_query::<rustc_query_impl[f11a5069a0fc322c]::DynamicConfig<rustc_data_structures[fa39f8fcd9225f43]::vec_cache::VecCache<rustc_span[eeaf0b3b2812840a]::def_id::LocalDefId, rustc_middle[464f7c4b782fc90]::query::erase::Erased<[u8; 1usize]>, rustc_query_system[18aefac76bbd956a]::dep_graph::graph::DepNodeIndex>, false, false, false>, rustc_query_impl[f11a5069a0fc322c]::plumbing::QueryCtxt, true>
  27:     0x77a7b7693c94 - rustc_query_impl[f11a5069a0fc322c]::plumbing::force_from_dep_node::<rustc_query_impl[f11a5069a0fc322c]::DynamicConfig<rustc_data_structures[fa39f8fcd9225f43]::vec_cache::VecCache<rustc_span[eeaf0b3b2812840a]::def_id::LocalDefId, rustc_middle[464f7c4b782fc90]::query::erase::Erased<[u8; 1usize]>, rustc_query_system[18aefac76bbd956a]::dep_graph::graph::DepNodeIndex>, false, false, false>>
  28:     0x77a7b7693aed - <rustc_query_impl[f11a5069a0fc322c]::plumbing::query_callback<rustc_query_impl[f11a5069a0fc322c]::query_impl::check_well_formed::QueryType>::{closure#0} as core[9e5e7b8b77114b88]::ops::function::FnOnce<(rustc_middle[464f7c4b782fc90]::ty::context::TyCtxt, rustc_query_system[18aefac76bbd956a]::dep_graph::dep_node::DepNode)>>::call_once
  29:     0x77a7b66258ba - <rustc_query_system[18aefac76bbd956a]::dep_graph::graph::DepGraphData<rustc_middle[464f7c4b782fc90]::dep_graph::DepsType>>::try_mark_previous_green::<rustc_query_impl[f11a5069a0fc322c]::plumbing::QueryCtxt>
  30:     0x77a7b6624fee - <rustc_query_system[18aefac76bbd956a]::dep_graph::graph::DepGraphData<rustc_middle[464f7c4b782fc90]::dep_graph::DepsType>>::try_mark_green::<rustc_query_impl[f11a5069a0fc322c]::plumbing::QueryCtxt>
  31:     0x77a7b708fcbf - rustc_query_system[18aefac76bbd956a]::query::plumbing::ensure_must_run::<rustc_query_impl[f11a5069a0fc322c]::DynamicConfig<rustc_query_system[18aefac76bbd956a]::query::caches::DefaultCache<rustc_span[eeaf0b3b2812840a]::def_id::LocalModDefId, rustc_middle[464f7c4b782fc90]::query::erase::Erased<[u8; 0usize]>>, false, false, false>, rustc_query_impl[f11a5069a0fc322c]::plumbing::QueryCtxt>
  32:     0x77a7b759ac13 - rustc_query_impl[f11a5069a0fc322c]::query_impl::check_mod_type_wf::get_query_incr::__rust_end_short_backtrace
  33:     0x77a7b6b5e60f - rustc_hir_analysis[6dcb172f42838441]::check_crate
  34:     0x77a7b6b5831c - rustc_interface[f15b12210e2206a6]::passes::run_required_analyses
  35:     0x77a7b7649cfa - rustc_interface[f15b12210e2206a6]::passes::analysis
  36:     0x77a7b7649cd9 - rustc_query_impl[f11a5069a0fc322c]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[f11a5069a0fc322c]::query_impl::analysis::dynamic_query::{closure#2}::{closure#0}, rustc_middle[464f7c4b782fc90]::query::erase::Erased<[u8; 0usize]>>
  37:     0x77a7b76455aa - rustc_query_system[18aefac76bbd956a]::query::plumbing::try_execute_query::<rustc_query_impl[f11a5069a0fc322c]::DynamicConfig<rustc_query_system[18aefac76bbd956a]::query::caches::SingleCache<rustc_middle[464f7c4b782fc90]::query::erase::Erased<[u8; 0usize]>>, false, false, false>, rustc_query_impl[f11a5069a0fc322c]::plumbing::QueryCtxt, true>
  38:     0x77a7b7644fa2 - rustc_query_impl[f11a5069a0fc322c]::query_impl::analysis::get_query_incr::__rust_end_short_backtrace
  39:     0x77a7b7738b3d - rustc_interface[f15b12210e2206a6]::passes::create_and_enter_global_ctxt::<core[9e5e7b8b77114b88]::option::Option<rustc_interface[f15b12210e2206a6]::queries::Linker>, rustc_driver_impl[b622dd38a520489a]::run_compiler::{closure#0}::{closure#2}>::{closure#2}::{closure#0}
  40:     0x77a7b7703a20 - rustc_interface[f15b12210e2206a6]::interface::run_compiler::<(), rustc_driver_impl[b622dd38a520489a]::run_compiler::{closure#0}>::{closure#1}
  41:     0x77a7b7559bc8 - std[e7ccd300aecc5933]::sys::backtrace::__rust_begin_short_backtrace::<rustc_interface[f15b12210e2206a6]::util::run_in_thread_with_globals<rustc_interface[f15b12210e2206a6]::util::run_in_thread_pool_with_globals<rustc_interface[f15b12210e2206a6]::interface::run_compiler<(), rustc_driver_impl[b622dd38a520489a]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>
  42:     0x77a7b755a4b4 - <<std[e7ccd300aecc5933]::thread::Builder>::spawn_unchecked_<rustc_interface[f15b12210e2206a6]::util::run_in_thread_with_globals<rustc_interface[f15b12210e2206a6]::util::run_in_thread_pool_with_globals<rustc_interface[f15b12210e2206a6]::interface::run_compiler<(), rustc_driver_impl[b622dd38a520489a]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>::{closure#1} as core[9e5e7b8b77114b88]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  43:     0x77a7b755b8ab - std::sys::pal::unix::thread::Thread::new::thread_start::h20288ab9ea215a81
  44:     0x77a7b1698af3 - start_thread
  45:     0x77a7b1717f4c - __GI___clone3
  46:                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: please attach the file at `/home/user/workspace/rustc-bug1/rustc-ice-2025-03-08T06_34_07-266476.txt` to your bug report

note: compiler flags: --crate-type lib -C embed-bitcode=no -C debuginfo=2 -C incremental=[REDACTED]

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

query stack during panic:
#0 [evaluate_obligation] evaluating trait selection obligation `_::HelpLinkEncoder: core::marker::Sync`  |  = note: this failure-note originates in the derive macro `Encode` (in Nightly builds, run with -Z macro-backtrace for more info)

#1 [compare_impl_item] checking assoc item `_::<impl at src/lib.rs:9:10: 9:16>::Encoder` is compatible with trait definition
#2 [check_well_formed] checking that `_::<impl at src/lib.rs:9:10: 9:16>` is well-formed
#3 [analysis] running analysis passes on this crate
end of query stack
there was a panic while trying to force a dep node
try_mark_green dep node stack:
#0 check_mod_type_wf(rustc_bug1[c039])
end of try_mark_green dep node stack
error: could not compile `rustc-bug1` (lib) due to 1 previous error

rustc-ice-2025-03-08T06_34_07-266476.txt

thread 'rustc' panicked at /rustc/8c392966a013fd8a09e6b78b3c8d6e442bc278e1/compiler/rustc_query_system/src/query/plumbing.rs:731:9:
Found unstable fingerprints for evaluate_obligation(4742c1b409da674c-2b2e292cfb3cefd9): Ok(EvaluatedToOk)
stack backtrace:
   0:     0x77a7b7a1b4a5 - std::backtrace::Backtrace::create::h4caae72ea1d639e2
   1:     0x77a7b5da9495 - std::backtrace::Backtrace::force_capture::hed7edc9d6077f7f2
   2:     0x77a7b4f18b5e - std[e7ccd300aecc5933]::panicking::update_hook::<alloc[8cc49891b291256f]::boxed::Box<rustc_driver_impl[b622dd38a520489a]::install_ice_hook::{closure#1}>>::{closure#0}
   3:     0x77a7b5dc1da3 - std::panicking::rust_panic_with_hook::h98fc165e90ef379e
   4:     0x77a7b5dc1a9a - std::panicking::begin_panic_handler::{{closure}}::h2c1a60d0a908eaec
   5:     0x77a7b5dbf2c9 - std::sys::backtrace::__rust_end_short_backtrace::he8aba8f9b7ddf304
   6:     0x77a7b5dc175d - rust_begin_unwind
   7:     0x77a7b2a5a680 - core::panicking::panic_fmt::hcbf39f8c1e585f84
   8:     0x77a7b54b4a63 - rustc_query_system[18aefac76bbd956a]::query::plumbing::incremental_verify_ich_failed::<rustc_middle[464f7c4b782fc90]::ty::context::TyCtxt>
   9:     0x77a7b6e06018 - rustc_query_system[18aefac76bbd956a]::query::plumbing::try_execute_query::<rustc_query_impl[f11a5069a0fc322c]::DynamicConfig<rustc_query_system[18aefac76bbd956a]::query::caches::DefaultCache<rustc_type_ir[62a9722b2d8d5cac]::canonical::CanonicalQueryInput<rustc_middle[464f7c4b782fc90]::ty::context::TyCtxt, rustc_middle[464f7c4b782fc90]::ty::ParamEnvAnd<rustc_middle[464f7c4b782fc90]::ty::predicate::Predicate>>, rustc_middle[464f7c4b782fc90]::query::erase::Erased<[u8; 2usize]>>, false, false, false>, rustc_query_impl[f11a5069a0fc322c]::plumbing::QueryCtxt, true>
  10:     0x77a7b6af1dc5 - rustc_query_impl[f11a5069a0fc322c]::query_impl::evaluate_obligation::get_query_incr::__rust_end_short_backtrace
  11:     0x77a7b6e9bb11 - <rustc_trait_selection[4edfcc70fd15c568]::traits::fulfill::FulfillProcessor as rustc_data_structures[fa39f8fcd9225f43]::obligation_forest::ObligationProcessor>::process_obligation
  12:     0x77a7b6607529 - <rustc_data_structures[fa39f8fcd9225f43]::obligation_forest::ObligationForest<rustc_trait_selection[4edfcc70fd15c568]::traits::fulfill::PendingPredicateObligation>>::process_obligations::<rustc_trait_selection[4edfcc70fd15c568]::traits::fulfill::FulfillProcessor>
  13:     0x77a7b6a58387 - <rustc_trait_selection[4edfcc70fd15c568]::traits::fulfill::FulfillmentContext<rustc_trait_selection[4edfcc70fd15c568]::traits::FulfillmentError> as rustc_infer[c858f4b860ba366e]::traits::engine::TraitEngine<rustc_trait_selection[4edfcc70fd15c568]::traits::FulfillmentError>>::select_all_or_error
  14:     0x77a7b6d8a78f - rustc_hir_analysis[6dcb172f42838441]::check::compare_impl_item::check_type_bounds
  15:     0x77a7b6d9cd62 - rustc_hir_analysis[6dcb172f42838441]::check::compare_impl_item::compare_impl_item
  16:     0x77a7b6d9af47 - rustc_query_impl[f11a5069a0fc322c]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[f11a5069a0fc322c]::query_impl::compare_impl_item::dynamic_query::{closure#2}::{closure#0}, rustc_middle[464f7c4b782fc90]::query::erase::Erased<[u8; 1usize]>>
  17:     0x77a7b6aeccaa - rustc_query_system[18aefac76bbd956a]::query::plumbing::try_execute_query::<rustc_query_impl[f11a5069a0fc322c]::DynamicConfig<rustc_data_structures[fa39f8fcd9225f43]::vec_cache::VecCache<rustc_span[eeaf0b3b2812840a]::def_id::LocalDefId, rustc_middle[464f7c4b782fc90]::query::erase::Erased<[u8; 1usize]>, rustc_query_system[18aefac76bbd956a]::dep_graph::graph::DepNodeIndex>, false, false, false>, rustc_query_impl[f11a5069a0fc322c]::plumbing::QueryCtxt, true>
  18:     0x77a7b6af10b6 - rustc_query_impl[f11a5069a0fc322c]::query_impl::compare_impl_item::get_query_incr::__rust_end_short_backtrace
  19:     0x77a7b6e2690c - rustc_hir_analysis[6dcb172f42838441]::check::check::check_item_type
  20:     0x77a7b6db6d66 - rustc_hir_analysis[6dcb172f42838441]::check::wfcheck::check_well_formed
  21:     0x77a7b6db544d - rustc_query_impl[f11a5069a0fc322c]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[f11a5069a0fc322c]::query_impl::check_well_formed::dynamic_query::{closure#2}::{closure#0}, rustc_middle[464f7c4b782fc90]::query::erase::Erased<[u8; 1usize]>>
  22:     0x77a7b6aed061 - rustc_query_system[18aefac76bbd956a]::query::plumbing::try_execute_query::<rustc_query_impl[f11a5069a0fc322c]::DynamicConfig<rustc_data_structures[fa39f8fcd9225f43]::vec_cache::VecCache<rustc_span[eeaf0b3b2812840a]::def_id::LocalDefId, rustc_middle[464f7c4b782fc90]::query::erase::Erased<[u8; 1usize]>, rustc_query_system[18aefac76bbd956a]::dep_graph::graph::DepNodeIndex>, false, false, false>, rustc_query_impl[f11a5069a0fc322c]::plumbing::QueryCtxt, true>
  23:     0x77a7b7693c94 - rustc_query_impl[f11a5069a0fc322c]::plumbing::force_from_dep_node::<rustc_query_impl[f11a5069a0fc322c]::DynamicConfig<rustc_data_structures[fa39f8fcd9225f43]::vec_cache::VecCache<rustc_span[eeaf0b3b2812840a]::def_id::LocalDefId, rustc_middle[464f7c4b782fc90]::query::erase::Erased<[u8; 1usize]>, rustc_query_system[18aefac76bbd956a]::dep_graph::graph::DepNodeIndex>, false, false, false>>
  24:     0x77a7b7693aed - <rustc_query_impl[f11a5069a0fc322c]::plumbing::query_callback<rustc_query_impl[f11a5069a0fc322c]::query_impl::check_well_formed::QueryType>::{closure#0} as core[9e5e7b8b77114b88]::ops::function::FnOnce<(rustc_middle[464f7c4b782fc90]::ty::context::TyCtxt, rustc_query_system[18aefac76bbd956a]::dep_graph::dep_node::DepNode)>>::call_once
  25:     0x77a7b66258ba - <rustc_query_system[18aefac76bbd956a]::dep_graph::graph::DepGraphData<rustc_middle[464f7c4b782fc90]::dep_graph::DepsType>>::try_mark_previous_green::<rustc_query_impl[f11a5069a0fc322c]::plumbing::QueryCtxt>
  26:     0x77a7b6624fee - <rustc_query_system[18aefac76bbd956a]::dep_graph::graph::DepGraphData<rustc_middle[464f7c4b782fc90]::dep_graph::DepsType>>::try_mark_green::<rustc_query_impl[f11a5069a0fc322c]::plumbing::QueryCtxt>
  27:     0x77a7b708fcbf - rustc_query_system[18aefac76bbd956a]::query::plumbing::ensure_must_run::<rustc_query_impl[f11a5069a0fc322c]::DynamicConfig<rustc_query_system[18aefac76bbd956a]::query::caches::DefaultCache<rustc_span[eeaf0b3b2812840a]::def_id::LocalModDefId, rustc_middle[464f7c4b782fc90]::query::erase::Erased<[u8; 0usize]>>, false, false, false>, rustc_query_impl[f11a5069a0fc322c]::plumbing::QueryCtxt>
  28:     0x77a7b759ac13 - rustc_query_impl[f11a5069a0fc322c]::query_impl::check_mod_type_wf::get_query_incr::__rust_end_short_backtrace
  29:     0x77a7b6b5e60f - rustc_hir_analysis[6dcb172f42838441]::check_crate
  30:     0x77a7b6b5831c - rustc_interface[f15b12210e2206a6]::passes::run_required_analyses
  31:     0x77a7b7649cfa - rustc_interface[f15b12210e2206a6]::passes::analysis
  32:     0x77a7b7649cd9 - rustc_query_impl[f11a5069a0fc322c]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[f11a5069a0fc322c]::query_impl::analysis::dynamic_query::{closure#2}::{closure#0}, rustc_middle[464f7c4b782fc90]::query::erase::Erased<[u8; 0usize]>>
  33:     0x77a7b76455aa - rustc_query_system[18aefac76bbd956a]::query::plumbing::try_execute_query::<rustc_query_impl[f11a5069a0fc322c]::DynamicConfig<rustc_query_system[18aefac76bbd956a]::query::caches::SingleCache<rustc_middle[464f7c4b782fc90]::query::erase::Erased<[u8; 0usize]>>, false, false, false>, rustc_query_impl[f11a5069a0fc322c]::plumbing::QueryCtxt, true>
  34:     0x77a7b7644fa2 - rustc_query_impl[f11a5069a0fc322c]::query_impl::analysis::get_query_incr::__rust_end_short_backtrace
  35:     0x77a7b7738b3d - rustc_interface[f15b12210e2206a6]::passes::create_and_enter_global_ctxt::<core[9e5e7b8b77114b88]::option::Option<rustc_interface[f15b12210e2206a6]::queries::Linker>, rustc_driver_impl[b622dd38a520489a]::run_compiler::{closure#0}::{closure#2}>::{closure#2}::{closure#0}
  36:     0x77a7b7703a20 - rustc_interface[f15b12210e2206a6]::interface::run_compiler::<(), rustc_driver_impl[b622dd38a520489a]::run_compiler::{closure#0}>::{closure#1}
  37:     0x77a7b7559bc8 - std[e7ccd300aecc5933]::sys::backtrace::__rust_begin_short_backtrace::<rustc_interface[f15b12210e2206a6]::util::run_in_thread_with_globals<rustc_interface[f15b12210e2206a6]::util::run_in_thread_pool_with_globals<rustc_interface[f15b12210e2206a6]::interface::run_compiler<(), rustc_driver_impl[b622dd38a520489a]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>
  38:     0x77a7b755a4b4 - <<std[e7ccd300aecc5933]::thread::Builder>::spawn_unchecked_<rustc_interface[f15b12210e2206a6]::util::run_in_thread_with_globals<rustc_interface[f15b12210e2206a6]::util::run_in_thread_pool_with_globals<rustc_interface[f15b12210e2206a6]::interface::run_compiler<(), rustc_driver_impl[b622dd38a520489a]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>::{closure#1} as core[9e5e7b8b77114b88]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  39:     0x77a7b755b8ab - std::sys::pal::unix::thread::Thread::new::thread_start::h20288ab9ea215a81
  40:     0x77a7b1698af3 - start_thread
  41:     0x77a7b1717f4c - __GI___clone3
  42:                0x0 - <unknown>


rustc version: 1.87.0-nightly (8c392966a 2025-03-01)
platform: x86_64-unknown-linux-gnu

query stack during panic:
#0 [evaluate_obligation] evaluating trait selection obligation `_::HelpLinkEncoder: core::marker::Sync`
#1 [compare_impl_item] checking assoc item `_::<impl at src/lib.rs:9:10: 9:16>::Encoder` is compatible with trait definition
#2 [check_well_formed] checking that `_::<impl at src/lib.rs:9:10: 9:16>` is well-formed
#3 [analysis] running analysis passes on this crate
end of query stack

Context

This bug is kinda tricky. Follow the instructions below to reproduce the issue:

1. Run cargo build. Should report success.
2. Remove line 16 from src/lib.rs.
3. Run cargo build once again. Should fail.

Related: matteopolak/axum-codec#10

[lqd]

An incremental bug with steps to reproduce omg thanks so much!

[lqd]

edit: scratch that, proc-macro2's nightly detection broke my bisection.

@rustbot label +E-needs-bisection

[cyrgani]

reduction:

pub trait Encoder<T>: Send {}

pub trait Encode {
    type Encoder;
}

impl Encode for &str {
    type Encoder = StrEncoder;
}
pub struct StrEncoder;

pub struct HelpLink {}

pub struct HelpLinkEncoder {
    link: <&'static str as Encode>::Encoder,
}
impl Encoder<HelpLink> for HelpLinkEncoder {}

pub struct ErrorDetail {
    /* START_REMOVE */ locale: u8,
    /* END_REMOVE */
}
pub struct ErrorDetailEncoder {
    a: HelpLinkEncoder,
    b: <&'static str as Encode>::Encoder,
}
impl Encoder<ErrorDetail> for ErrorDetailEncoder {}

reproduce by cargo clean, cargo build, removing the marked locale: u8 field and rerunning cargo build

@rustbot label S-has-mcve -E-needs-mcve