thread 'rustc' panicked at 'found unstable fingerprints for predicates_of(core[3998]::cmp::PartialEq)'

[arifd]

Code

#[no_mangle]
pub extern "C" fn double(x: i32) -> i32 {
    x * 2
}

#[cfg(test)]
mod tests {
    use super::*;
    #[test]
    fn double_test() {
        assert_eq!(double(2), 4);
    }
}

Meta

rustc --version --verbose:

rustc 1.52.0-nightly (107896c32 2021-03-15)
binary: rustc
commit-hash: 107896c32d5dda4db508968ff34997a39d286966
commit-date: 2021-03-15
host: x86_64-unknown-linux-gnu
release: 1.52.0-nightly
LLVM version: 12.0.0

Error output

cargo test
   Compiling patientprovider v0.1.0 (/home/arif/rust/patientprovider)
thread 'rustc' panicked at 'found unstable fingerprints for predicates_of(core[3998]::cmp::PartialEq)', /rustc/107896c32d5dda4db508968ff34997a39d286966/compiler/rustc_query_system/src/query/plumbing.rs:593:5

Backtrace

stack backtrace:
   0: rust_begin_unwind
             at /rustc/107896c32d5dda4db508968ff34997a39d286966/library/std/src/panicking.rs:493:5
   1: std::panicking::begin_panic_fmt
             at /rustc/107896c32d5dda4db508968ff34997a39d286966/library/std/src/panicking.rs:435:5
   2: rustc_query_system::query::plumbing::incremental_verify_ich
   3: rustc_query_system::query::plumbing::load_from_disk_and_cache_in_memory
   4: rustc_query_system::query::plumbing::get_query_impl
   5: <rustc_query_impl::Queries as rustc_middle::ty::query::QueryEngine>::predicates_of
   6: rustc_middle::ty::generics::GenericPredicates::instantiate_into
   7: rustc_middle::ty::generics::GenericPredicates::instantiate
   8: rustc_typeck::check::method::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::lookup_method_in_trait
   9: rustc_typeck::check::op::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::lookup_op_method
  10: rustc_typeck::check::op::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::check_overloaded_binop
  11: rustc_typeck::check::op::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::check_binop
  12: rustc_typeck::check::expr::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::check_expr_with_expectation
  13: rustc_typeck::check::expr::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::check_expr_kind
  14: rustc_typeck::check::expr::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::check_expr_with_expectation
  15: rustc_typeck::check::expr::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::check_expr_kind
  16: rustc_typeck::check::expr::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::check_expr_with_expectation
  17: rustc_typeck::check::fn_ctxt::checks::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::check_block_with_expected
  18: rustc_typeck::check::expr::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::check_expr_with_expectation
  19: rustc_typeck::check::_match::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::check_match
  20: rustc_typeck::check::expr::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::check_expr_kind
  21: rustc_typeck::check::expr::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::check_expr_with_expectation
  22: rustc_typeck::check::fn_ctxt::checks::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::check_block_with_expected
  23: rustc_typeck::check::expr::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::check_expr_with_expectation
  24: rustc_typeck::check::fn_ctxt::checks::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::check_stmt
  25: rustc_typeck::check::fn_ctxt::checks::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::check_block_with_expected
  26: rustc_typeck::check::expr::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::check_expr_with_expectation
  27: rustc_typeck::check::expr::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::check_return_expr
  28: rustc_typeck::check::check::check_fn
  29: rustc_infer::infer::InferCtxtBuilder::enter
  30: rustc_typeck::check::typeck
  31: rustc_middle::dep_graph::<impl rustc_query_system::dep_graph::DepKind for rustc_middle::dep_graph::dep_node::DepKind>::with_deps
  32: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task_impl
  33: rustc_query_system::query::plumbing::force_query_with_job
  34: rustc_query_system::query::plumbing::get_query_impl
  35: <rustc_query_impl::Queries as rustc_middle::ty::query::QueryEngine>::typeck
  36: rustc_middle::ty::<impl rustc_middle::ty::context::TyCtxt>::par_body_owners
  37: rustc_typeck::check::typeck_item_bodies
  38: rustc_middle::dep_graph::<impl rustc_query_system::dep_graph::DepKind for rustc_middle::dep_graph::dep_node::DepKind>::with_deps
  39: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task_impl
  40: rustc_data_structures::stack::ensure_sufficient_stack
  41: rustc_query_system::query::plumbing::force_query_with_job
  42: rustc_query_system::query::plumbing::get_query_impl
  43: <rustc_query_impl::Queries as rustc_middle::ty::query::QueryEngine>::typeck_item_bodies
  44: rustc_session::utils::<impl rustc_session::session::Session>::time
  45: rustc_typeck::check_crate
  46: rustc_interface::passes::analysis
  47: rustc_middle::dep_graph::<impl rustc_query_system::dep_graph::DepKind for rustc_middle::dep_graph::dep_node::DepKind>::with_deps
  48: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task_impl
  49: rustc_data_structures::stack::ensure_sufficient_stack
  50: rustc_query_system::query::plumbing::force_query_with_job
  51: rustc_query_system::query::plumbing::get_query_impl
  52: <rustc_query_impl::Queries as rustc_middle::ty::query::QueryEngine>::analysis
  53: rustc_interface::passes::QueryContext::enter
  54: rustc_interface::queries::<impl rustc_interface::interface::Compiler>::enter
  55: rustc_span::with_source_map
  56: scoped_tls::ScopedKey<T>::set
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.

Note, this bug does not exist in stable:

rustc 1.49.0 (e1884a8e3 2020-12-29)
binary: rustc
commit-hash: e1884a8e3c3e813aada8254edfa120e85bf5ffca
commit-date: 2020-12-29
host: x86_64-unknown-linux-gnu
release: 1.49.0

And in any case only occurs under cargo test, not cargo build

[Aaron1011]

This should be fixed by #83220

[Aaron1011]

@arifd: I'm not able to reproduce this locally. Did you make any modifications to the file between the first and second cargo test runs?

[arifd]

Wow. okay, I just tried:

• creating a new --lib with cargo
• switching rustup to nightly (nightly-x86_64-unknown-linux-gnu unchanged - rustc 1.52.0-nightly (107896c 2021-03-15))
• copy pasting the code and running cargo test

And it now runs fine! Sorry :(

I obviously didn't make up that bug. And I wish I had that project in the state it was then, perhaps a cargo clean would have sorted it?

But you're right, it's not reproducible from a fresh project. So, how do you wish to proceed? (I'm happy to delete this and pretend it never existed!)

Regarding:

Did you make any modifications to the file between the first and second cargo test runs?

I don't quite understand what you mean, but at the moment I was running cargo test and received that bug, that was the code and the only code in the project.

[Aaron1011]

I don't quite understand what you mean, but at the moment I was running cargo test and received that bug, that was the code and the only code in the project.

The backtrace you posted shows that cargo test was run with a pre-existing incremental cache (specifically, the load_from_disk_and_cache_in_memory line). Since I can't reproduce this issue, I suspect that crash was caused by a previous run of cargo test with a slightly different file.

[Aaron1011]

This issue is by far the simplest reproduction of the predicates_of crash that I've seen so far.
@arifd Was this snippet minimized from another project? Would you be able to share some previous steps of the minimization (or the original project) - it might allow me to reproduce this crash.

[arifd]

Umm okay, so, I don't know what minimized means, but what happened was I that I was interested in porting a module that I had written in Python over to Rust, so I was following this tutorial: https://bheisler.github.io/post/calling-rust-in-python/ I really hadn't got much farther than simply copy/pasting that double function and then writing the test for it. It happened REALLY soon after beginning the fresh project. The name of that project (patientprovider) is just what I might likely call it in the future.

I even tried going back into that project as it is now, with the code from above and hitting cargo test, but it tests fine now, even with nightly.

[XAMPPRocky]

Umm okay, so, I don't know what minimized means

Minimizing is taking a bug encountered in a large codebase, and converting the bug down into the smallest possible version of it. 🙂

---

FWIW I also just ran into this when working on a proc-macro for rust-gpu, and tested #83220 with rustup-toolchain-install-master and can confirm it did indeed fix the ICE.