ICE: compiler/rustc_infer/src/infer/at.rs:400:21: relating different kinds: '?20 utoipa::openapi::RefOr<utoipa::openapi::Schema>

[RocketRace]

Code

I hit this ICE while at work. I was unfortunately not able to reduce this example further as it was behaving unpredictably based on the toolchain and the version of utoipa installed (either =4.2.2 or =4.2.3).

use utoipa::ToSchema;

#[derive(ToSchema)]
struct A {
    #[schema(schema_with = B::schema)]
    b: B,
}
#[derive(ToSchema)]
struct B;

[package]
name = "example"
version = "0.1.0"
edition = "2021"

[dependencies]
utoipa = "=4.2.2"

Meta

I could repro the issue in beta but not in nightly.

rustc --version --verbose:

rustc 1.79.0 (129f3b996 2024-06-10)
binary: rustc
commit-hash: 129f3b9964af4d4a709d1383930ade12dfe7c081
commit-date: 2024-06-10
host: aarch64-apple-darwin
release: 1.79.0
LLVM version: 18.1.7

Error output

The ICE itself:

error: internal compiler error: compiler/rustc_infer/src/infer/at.rs:364:21: relating different kinds: '?6 utoipa::openapi::RefOr<utoipa::openapi::Schema>

Sometimes (in some toolchains and with some versions of the crate), instead of the ICE I get ~2000 lines of type errors:
https://pastebin.com/9hR6ruWY

On nightly (1.81.0-nightly (d8a38b000 2024-06-19)), and with utoipa = "=4.2.2", I managed to get the somewhat sane:

error[E0277]: the trait bound `(&str, utoipa::openapi::RefOr<Schema>): Into<utoipa::openapi::RefOr<Schema>>` is not satisfied
   --> src/lib.rs:3:10
    |
3   | #[derive(ToSchema)]
    |          ^^^^^^^^ the trait `ToSchema<'_>` is not implemented for `(&str, utoipa::openapi::RefOr<Schema>)`, which is required by `(&str, utoipa::openapi::RefOr<Schema>): Into<utoipa::openapi::RefOr<Schema>>`
    |
    = help: the trait `ToSchema<'_>` is implemented for `()`
    = help: for that trait implementation, expected `()`, found `(&str, utoipa::openapi::RefOr<Schema>)`
    = note: required for `utoipa::openapi::RefOr<Schema>` to implement `From<(&str, utoipa::openapi::RefOr<Schema>)>`
    = note: required for `(&str, utoipa::openapi::RefOr<Schema>)` to implement `Into<utoipa::openapi::RefOr<Schema>>`
note: required by a bound in `ObjectBuilder::property`
   --> /<home>/.cargo/registry/src/index.crates.io-6f17d22bba15001f/utoipa-4.2.2/src/openapi/schema.rs:876:41
    |
876 |     pub fn property<S: Into<String>, I: Into<RefOr<Schema>>>(
    |                                         ^^^^^^^^^^^^^^^^^^^ required by this bound in `ObjectBuilder::property`
    = note: this error originates in the derive macro `ToSchema` (in Nightly builds, run with -Z macro-backtrace for more info)
 
For more information about this error, try `rustc --explain E0277`.
error: could not compile `example` (lib) due to 1 previous error

Backtrace

thread 'rustc' panicked at compiler/rustc_infer/src/infer/at.rs:400:21:
Box<dyn Any>
stack backtrace:
   0:        0x103165750 - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::h1f3776e0b5c7517d
   1:        0x1031a8470 - core::fmt::write::heedef092c8c0962e
   2:        0x10315ba1c - std::io::Write::write_fmt::h7178e8e2ea928914
   3:        0x1031655a8 - std::sys_common::backtrace::print::h417292deb95532ed
   4:        0x103167b2c - std::panicking::default_hook::{{closure}}::h0cb68f1228c4613a
   5:        0x103167820 - std::panicking::default_hook::h24535936bc1f51de
   6:        0x10c633828 - <alloc[d07bc629de031c28]::boxed::Box<rustc_driver_impl[17630cf877ef70bb]::install_ice_hook::{closure#0}> as core[fca7800875c611c6]::ops::function::Fn<(&dyn for<'a, 'b> core[fca7800875c611c6]::ops::function::Fn<(&'a core[fca7800875c611c6]::panic::panic_info::PanicInfo<'b>,), Output = ()> + core[fca7800875c611c6]::marker::Sync + core[fca7800875c611c6]::marker::Send, &core[fca7800875c611c6]::panic::panic_info::PanicInfo)>>::call
   7:        0x103168524 - std::panicking::rust_panic_with_hook::h5db4d2345b297bed
   8:        0x10c6bf198 - std[e84bc52996b8b382]::panicking::begin_panic::<rustc_errors[3520987c35dd2513]::ExplicitBug>::{closure#0}
   9:        0x10c6bdce0 - std[e84bc52996b8b382]::sys_common::backtrace::__rust_end_short_backtrace::<std[e84bc52996b8b382]::panicking::begin_panic<rustc_errors[3520987c35dd2513]::ExplicitBug>::{closure#0}, !>
  10:        0x11068b750 - std[e84bc52996b8b382]::panicking::begin_panic::<rustc_errors[3520987c35dd2513]::ExplicitBug>
  11:        0x10c6c00c0 - <rustc_errors[3520987c35dd2513]::diagnostic::BugAbort as rustc_errors[3520987c35dd2513]::diagnostic::EmissionGuarantee>::emit_producing_guarantee
  12:        0x10d123970 - rustc_middle[e187904418cf7088]::util::bug::opt_span_bug_fmt::<rustc_span[984a238feadb13f5]::span_encoding::Span>::{closure#0}
  13:        0x10d114d14 - rustc_middle[e187904418cf7088]::ty::context::tls::with_opt::<rustc_middle[e187904418cf7088]::util::bug::opt_span_bug_fmt<rustc_span[984a238feadb13f5]::span_encoding::Span>::{closure#0}, !>::{closure#0}
  14:        0x10d114ce0 - rustc_middle[e187904418cf7088]::ty::context::tls::with_context_opt::<rustc_middle[e187904418cf7088]::ty::context::tls::with_opt<rustc_middle[e187904418cf7088]::util::bug::opt_span_bug_fmt<rustc_span[984a238feadb13f5]::span_encoding::Span>::{closure#0}, !>::{closure#0}, !>
  15:        0x110724fdc - rustc_middle[e187904418cf7088]::util::bug::bug_fmt
  16:        0x10cc647a0 - <rustc_middle[e187904418cf7088]::ty::generic_args::GenericArg as rustc_infer[88fe184f288a0526]::infer::at::ToTrace>::to_trace
  17:        0x10deaf9b0 - <rustc_infer[88fe184f288a0526]::infer::at::At>::eq::<rustc_middle[e187904418cf7088]::ty::generic_args::GenericArg>
  18:        0x10debe430 - <rustc_trait_selection[67ea6c3922506dc7]::traits::engine::ObligationCtxt>::eq::<rustc_middle[e187904418cf7088]::ty::generic_args::GenericArg>
  19:        0x10df13fa4 - <rustc_infer[88fe184f288a0526]::infer::InferCtxt>::probe::<bool, <rustc_infer[88fe184f288a0526]::infer::error_reporting::TypeErrCtxt as rustc_trait_selection[67ea6c3922506dc7]::traits::error_reporting::type_err_ctxt_ext::InferCtxtPrivExt>::report_similar_impl_candidates::{closure#0}>
  20:        0x10dd6b30c - <rustc_infer[88fe184f288a0526]::infer::error_reporting::TypeErrCtxt as rustc_trait_selection[67ea6c3922506dc7]::traits::error_reporting::type_err_ctxt_ext::InferCtxtPrivExt>::report_similar_impl_candidates
  21:        0x10dd71444 - <rustc_infer[88fe184f288a0526]::infer::error_reporting::TypeErrCtxt as rustc_trait_selection[67ea6c3922506dc7]::traits::error_reporting::type_err_ctxt_ext::InferCtxtPrivExt>::try_to_add_help_message
  22:        0x10dd67fa4 - <rustc_infer[88fe184f288a0526]::infer::error_reporting::TypeErrCtxt as rustc_trait_selection[67ea6c3922506dc7]::traits::error_reporting::type_err_ctxt_ext::TypeErrCtxtExt>::report_selection_error
  23:        0x10dd739b4 - <rustc_infer[88fe184f288a0526]::infer::error_reporting::TypeErrCtxt as rustc_trait_selection[67ea6c3922506dc7]::traits::error_reporting::type_err_ctxt_ext::InferCtxtPrivExt>::report_fulfillment_error
  24:        0x10dd652c4 - <rustc_infer[88fe184f288a0526]::infer::error_reporting::TypeErrCtxt as rustc_trait_selection[67ea6c3922506dc7]::traits::error_reporting::type_err_ctxt_ext::TypeErrCtxtExt>::report_fulfillment_errors
  25:        0x10ca310d4 - <rustc_hir_typeck[8fa4488aa1bca511]::fn_ctxt::FnCtxt>::check_argument_types
  26:        0x10ca309c8 - <rustc_hir_typeck[8fa4488aa1bca511]::fn_ctxt::FnCtxt>::check_method_argument_types
  27:        0x10ca77f40 - <rustc_hir_typeck[8fa4488aa1bca511]::fn_ctxt::FnCtxt>::check_expr_kind
  28:        0x10ca1c228 - <rustc_hir_typeck[8fa4488aa1bca511]::fn_ctxt::FnCtxt>::check_expr_with_expectation_and_args
  29:        0x10ca6f874 - <rustc_hir_typeck[8fa4488aa1bca511]::fn_ctxt::FnCtxt>::check_expr_kind
  30:        0x10ca1c228 - <rustc_hir_typeck[8fa4488aa1bca511]::fn_ctxt::FnCtxt>::check_expr_with_expectation_and_args
  31:        0x10ca6f874 - <rustc_hir_typeck[8fa4488aa1bca511]::fn_ctxt::FnCtxt>::check_expr_kind
  32:        0x10ca1c228 - <rustc_hir_typeck[8fa4488aa1bca511]::fn_ctxt::FnCtxt>::check_expr_with_expectation_and_args
  33:        0x10cb82ccc - <&mut <rustc_hir_typeck[8fa4488aa1bca511]::fn_ctxt::FnCtxt>::check_expr_tuple::{closure#1} as core[fca7800875c611c6]::ops::function::FnOnce<((usize, &rustc_hir[8f63456841fca8c8]::hir::Expr),)>>::call_once
  34:        0x10cbacf68 - <rustc_middle[e187904418cf7088]::ty::Ty as rustc_type_ir[a6f4416129910f14]::interner::CollectAndApply<rustc_middle[e187904418cf7088]::ty::Ty, rustc_middle[e187904418cf7088]::ty::Ty>>::collect_and_apply::<core[fca7800875c611c6]::iter::adapters::map::Map<core[fca7800875c611c6]::iter::adapters::enumerate::Enumerate<core[fca7800875c611c6]::slice::iter::Iter<rustc_hir[8f63456841fca8c8]::hir::Expr>>, <rustc_hir_typeck[8fa4488aa1bca511]::fn_ctxt::FnCtxt>::check_expr_tuple::{closure#1}>, <rustc_middle[e187904418cf7088]::ty::Ty>::new_tup_from_iter<core[fca7800875c611c6]::iter::adapters::map::Map<core[fca7800875c611c6]::iter::adapters::enumerate::Enumerate<core[fca7800875c611c6]::slice::iter::Iter<rustc_hir[8f63456841fca8c8]::hir::Expr>>, <rustc_hir_typeck[8fa4488aa1bca511]::fn_ctxt::FnCtxt>::check_expr_tuple::{closure#1}>, rustc_middle[e187904418cf7088]::ty::Ty>::{closure#0}>
  35:        0x10ca73724 - <rustc_hir_typeck[8fa4488aa1bca511]::fn_ctxt::FnCtxt>::check_expr_kind
  36:        0x10ca1c228 - <rustc_hir_typeck[8fa4488aa1bca511]::fn_ctxt::FnCtxt>::check_expr_with_expectation_and_args
  37:        0x10ca389e8 - <rustc_hir_typeck[8fa4488aa1bca511]::fn_ctxt::FnCtxt>::check_block_with_expected
  38:        0x10ca1c228 - <rustc_hir_typeck[8fa4488aa1bca511]::fn_ctxt::FnCtxt>::check_expr_with_expectation_and_args
  39:        0x10ca1ccac - <rustc_hir_typeck[8fa4488aa1bca511]::fn_ctxt::FnCtxt>::check_return_expr
  40:        0x10cb38fc8 - rustc_hir_typeck[8fa4488aa1bca511]::check::check_fn
  41:        0x10cad49e4 - rustc_hir_typeck[8fa4488aa1bca511]::typeck
  42:        0x10d869804 - rustc_query_impl[a9dcee21c1ea9187]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[a9dcee21c1ea9187]::query_impl::typeck::dynamic_query::{closure#2}::{closure#0}, rustc_middle[e187904418cf7088]::query::erase::Erased<[u8; 8usize]>>
  43:        0x10d9527d0 - <rustc_query_impl[a9dcee21c1ea9187]::query_impl::typeck::dynamic_query::{closure#2} as core[fca7800875c611c6]::ops::function::FnOnce<(rustc_middle[e187904418cf7088]::ty::context::TyCtxt, rustc_span[984a238feadb13f5]::def_id::LocalDefId)>>::call_once
  44:        0x10d818ef8 - rustc_query_system[3fe282a48bd1d9e8]::query::plumbing::try_execute_query::<rustc_query_impl[a9dcee21c1ea9187]::DynamicConfig<rustc_query_system[3fe282a48bd1d9e8]::query::caches::VecCache<rustc_span[984a238feadb13f5]::def_id::LocalDefId, rustc_middle[e187904418cf7088]::query::erase::Erased<[u8; 8usize]>>, false, false, false>, rustc_query_impl[a9dcee21c1ea9187]::plumbing::QueryCtxt, true>
  45:        0x10d8ca8c4 - rustc_query_impl[a9dcee21c1ea9187]::query_impl::typeck::get_query_incr::__rust_end_short_backtrace
  46:        0x10c914ec8 - std[e84bc52996b8b382]::panicking::try::<(), core[fca7800875c611c6]::panic::unwind_safe::AssertUnwindSafe<rustc_data_structures[d96e6b3ae716122c]::sync::parallel::disabled::par_for_each_in<&[rustc_span[984a238feadb13f5]::def_id::LocalDefId], <rustc_middle[e187904418cf7088]::hir::map::Map>::par_body_owners<rustc_hir_analysis[c1c0f42cf391c6f]::check_crate::{closure#4}>::{closure#0}>::{closure#0}::{closure#0}::{closure#0}>>
  47:        0x10c86d944 - rustc_data_structures[d96e6b3ae716122c]::sync::parallel::disabled::par_for_each_in::<&[rustc_span[984a238feadb13f5]::def_id::LocalDefId], <rustc_middle[e187904418cf7088]::hir::map::Map>::par_body_owners<rustc_hir_analysis[c1c0f42cf391c6f]::check_crate::{closure#4}>::{closure#0}>
  48:        0x10c98bbf0 - rustc_hir_analysis[c1c0f42cf391c6f]::check_crate
  49:        0x10cd8de3c - rustc_interface[617d4417f0fbb0b3]::passes::analysis
  50:        0x10d86989c - rustc_query_impl[a9dcee21c1ea9187]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[a9dcee21c1ea9187]::query_impl::analysis::dynamic_query::{closure#2}::{closure#0}, rustc_middle[e187904418cf7088]::query::erase::Erased<[u8; 1usize]>>
  51:        0x10d937bf4 - <rustc_query_impl[a9dcee21c1ea9187]::query_impl::analysis::dynamic_query::{closure#2} as core[fca7800875c611c6]::ops::function::FnOnce<(rustc_middle[e187904418cf7088]::ty::context::TyCtxt, ())>>::call_once
  52:        0x10d7cf194 - rustc_query_system[3fe282a48bd1d9e8]::query::plumbing::try_execute_query::<rustc_query_impl[a9dcee21c1ea9187]::DynamicConfig<rustc_query_system[3fe282a48bd1d9e8]::query::caches::SingleCache<rustc_middle[e187904418cf7088]::query::erase::Erased<[u8; 1usize]>>, false, false, false>, rustc_query_impl[a9dcee21c1ea9187]::plumbing::QueryCtxt, true>
  53:        0x10d8bca94 - rustc_query_impl[a9dcee21c1ea9187]::query_impl::analysis::get_query_incr::__rust_end_short_backtrace
  54:        0x10c624e38 - <rustc_middle[e187904418cf7088]::ty::context::GlobalCtxt>::enter::<rustc_driver_impl[17630cf877ef70bb]::run_compiler::{closure#0}::{closure#1}::{closure#3}, core[fca7800875c611c6]::result::Result<(), rustc_span[984a238feadb13f5]::ErrorGuaranteed>>
  55:        0x10c5f7a88 - <rustc_interface[617d4417f0fbb0b3]::interface::Compiler>::enter::<rustc_driver_impl[17630cf877ef70bb]::run_compiler::{closure#0}::{closure#1}, core[fca7800875c611c6]::result::Result<core[fca7800875c611c6]::option::Option<rustc_interface[617d4417f0fbb0b3]::queries::Linker>, rustc_span[984a238feadb13f5]::ErrorGuaranteed>>
  56:        0x10c63b85c - <scoped_tls[710a08ee67d076ea]::ScopedKey<rustc_span[984a238feadb13f5]::SessionGlobals>>::set::<rustc_interface[617d4417f0fbb0b3]::util::run_in_thread_with_globals<rustc_interface[617d4417f0fbb0b3]::interface::run_compiler<core[fca7800875c611c6]::result::Result<(), rustc_span[984a238feadb13f5]::ErrorGuaranteed>, rustc_driver_impl[17630cf877ef70bb]::run_compiler::{closure#0}>::{closure#1}, core[fca7800875c611c6]::result::Result<(), rustc_span[984a238feadb13f5]::ErrorGuaranteed>>::{closure#0}::{closure#0}::{closure#0}, core[fca7800875c611c6]::result::Result<(), rustc_span[984a238feadb13f5]::ErrorGuaranteed>>
  57:        0x10c5f71d8 - rustc_span[984a238feadb13f5]::create_session_globals_then::<core[fca7800875c611c6]::result::Result<(), rustc_span[984a238feadb13f5]::ErrorGuaranteed>, rustc_interface[617d4417f0fbb0b3]::util::run_in_thread_with_globals<rustc_interface[617d4417f0fbb0b3]::interface::run_compiler<core[fca7800875c611c6]::result::Result<(), rustc_span[984a238feadb13f5]::ErrorGuaranteed>, rustc_driver_impl[17630cf877ef70bb]::run_compiler::{closure#0}>::{closure#1}, core[fca7800875c611c6]::result::Result<(), rustc_span[984a238feadb13f5]::ErrorGuaranteed>>::{closure#0}::{closure#0}::{closure#0}>
  58:        0x10c610400 - std[e84bc52996b8b382]::sys_common::backtrace::__rust_begin_short_backtrace::<rustc_interface[617d4417f0fbb0b3]::util::run_in_thread_with_globals<rustc_interface[617d4417f0fbb0b3]::interface::run_compiler<core[fca7800875c611c6]::result::Result<(), rustc_span[984a238feadb13f5]::ErrorGuaranteed>, rustc_driver_impl[17630cf877ef70bb]::run_compiler::{closure#0}>::{closure#1}, core[fca7800875c611c6]::result::Result<(), rustc_span[984a238feadb13f5]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[fca7800875c611c6]::result::Result<(), rustc_span[984a238feadb13f5]::ErrorGuaranteed>>
  59:        0x10c643808 - <<std[e84bc52996b8b382]::thread::Builder>::spawn_unchecked_<rustc_interface[617d4417f0fbb0b3]::util::run_in_thread_with_globals<rustc_interface[617d4417f0fbb0b3]::interface::run_compiler<core[fca7800875c611c6]::result::Result<(), rustc_span[984a238feadb13f5]::ErrorGuaranteed>, rustc_driver_impl[17630cf877ef70bb]::run_compiler::{closure#0}>::{closure#1}, core[fca7800875c611c6]::result::Result<(), rustc_span[984a238feadb13f5]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[fca7800875c611c6]::result::Result<(), rustc_span[984a238feadb13f5]::ErrorGuaranteed>>::{closure#2} as core[fca7800875c611c6]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  60:        0x103170edc - std::sys::pal::unix::thread::Thread::new::thread_start::h50a0ef5291b272f3
  61:        0x194a0ef94 - __pthread_joiner_wake

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: rustc 1.79.0 (129f3b996 2024-06-10) running on aarch64-apple-darwin

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

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

query stack during panic:
#0 [typeck] type-checking `<impl at src/lib.rs:3:10: 3:18>::schema`
#1 [analysis] running analysis passes on this crate
end of query stack

[RocketRace]

Found this: Probably duplicate. #127163