ICE: fast reject: `kind mismatch: {type error} 3_u8`

[matthiaskrgr]

auto-reduced (treereduce-rust):

#![feature(generic_const_exprs)]
trait Traitor<const N: u8 = 1, const M: u8 = repeat_36> {}

impl Traitor<2, 3> for bool {}

fn bar<const N: u8>(arg: &dyn Traitor<N>) -> u8 {
    arg.owo()
}

fn main() {
    bar(&true);
}

original:

trait Trait<const N: u8 = 12> {
    fn uwu(&self) -> u8 {
        N
    }
}

impl Trait<2> for u32 {}

fn foo(arg: &dyn Trait) -> isize {
    arg.uwu()
}

trait Traitor<const N: u8 = 1, const M: u8 = repeat_36> {
    fn owo(&self) -> u8 {
        M
    }
}

impl Traitor<2, 3> for bool {}

fn bar<const N: u8>(arg: &dyn Traitor<N>) -> u8 {
    arg.owo()
}

fn main() {
    foo(&10_u32);
    //~^ error: the trait bound `u32: Trait` is not satisfied
    bar(&true);
    //~^ error: the trait bound `bool: Traitor<_>` is not satisfied
}

Version information

rustc 1.86.0-nightly (203e6c127 2025-01-25)
binary: rustc
commit-hash: 203e6c127c50c499be53731a39fe36d24f544502
commit-date: 2025-01-25
host: x86_64-unknown-linux-gnu
release: 1.86.0-nightly
LLVM version: 19.1.7

Command:
/home/matthias/.rustup/toolchains/master/bin/rustc -Zcrate-attr=feature(generic_const_exprs)

Program output

error[E0425]: cannot find value `repeat_36` in this scope
 --> /tmp/icemaker_global_tempdir.WTfAIAh7lsb4/rustc_testrunner_tmpdir_reporting.MvFPhVMEvs6Q/mvce.rs:1:46
  |
1 | trait Traitor<const N: u8 = 1, const M: u8 = repeat_36> {}
  |                                              ^^^^^^^^^ not found in this scope

warning: the feature `generic_const_exprs` is incomplete and may not be safe to use and/or cause compiler crashes
 --> <crate attribute>:1:9
  |
1 | feature(generic_const_exprs)
  |         ^^^^^^^^^^^^^^^^^^^
  |
  = note: see issue #76560 <https://github.com/rust-lang/rust/issues/76560> for more information
  = note: `#[warn(incomplete_features)]` on by default

error[E0393]: the type parameter `M` must be explicitly specified
 --> /tmp/icemaker_global_tempdir.WTfAIAh7lsb4/rustc_testrunner_tmpdir_reporting.MvFPhVMEvs6Q/mvce.rs:5:31
  |
1 | trait Traitor<const N: u8 = 1, const M: u8 = repeat_36> {}
  | ------------------------------------------------------- type parameter `M` must be specified for this
...
5 | fn bar<const N: u8>(arg: &dyn Traitor<N>) -> u8 {
  |                               ^^^^^^^^^^ missing reference to `M`
  |
  = note: because the parameter default references `Self`, the parameter must be specified on the object type


thread 'rustc' panicked at /rustc/203e6c127c50c499be53731a39fe36d24f544502/compiler/rustc_type_ir/src/fast_reject.rs:254:22:
kind mismatch: {type error} 3_u8
stack backtrace:
   0:     0x7b60dde902a0 - <std::sys::backtrace::BacktraceLock::print::DisplayBacktrace as core::fmt::Display>::fmt::hdfdabc38b8669c9f
   1:     0x7b60de6150e6 - core::fmt::write::h85841a8a9f23dd59
   2:     0x7b60df5594d1 - std::io::Write::write_fmt::hf2e4fe8e168db1b7
   3:     0x7b60dde90102 - std::sys::backtrace::BacktraceLock::print::h14149197b7c0de32
   4:     0x7b60dde92582 - std::panicking::default_hook::{{closure}}::h9943e5f3f0626409
   5:     0x7b60dde9240a - std::panicking::default_hook::hdd3968de3a098232
   6:     0x7b60dd0459e9 - std[57730b54ef401f3]::panicking::update_hook::<alloc[f5830c3c5cfb9e11]::boxed::Box<rustc_driver_impl[238e9adc12ab3263]::install_ice_hook::{closure#1}>>::{closure#0}
   7:     0x7b60dde93103 - std::panicking::rust_panic_with_hook::h73ef51d9a205dc0a
   8:     0x7b60dde92dfa - std::panicking::begin_panic_handler::{{closure}}::hed515db6078dd255
   9:     0x7b60dde90789 - std::sys::backtrace::__rust_end_short_backtrace::h8ba760917d95b5b1
  10:     0x7b60dde92abd - rust_begin_unwind
  11:     0x7b60dab98400 - core::panicking::panic_fmt::h5ecc779537f0304d
  12:     0x7b60db43899b - <rustc_trait_selection[4ba0541b438290d2]::traits::select::SelectionContext>::assemble_candidates_from_impls
  13:     0x7b60db415705 - <rustc_trait_selection[4ba0541b438290d2]::traits::select::SelectionContext>::candidate_from_obligation::{closure#0}::{closure#0}
  14:     0x7b60dae5c32e - <rustc_trait_selection[4ba0541b438290d2]::traits::select::SelectionContext>::poly_select::{closure#0}
  15:     0x7b60deee6030 - <rustc_trait_selection[4ba0541b438290d2]::traits::fulfill::FulfillProcessor as rustc_data_structures[b1621f9a8426d32f]::obligation_forest::ObligationProcessor>::process_obligation
  16:     0x7b60de610882 - <rustc_data_structures[b1621f9a8426d32f]::obligation_forest::ObligationForest<rustc_trait_selection[4ba0541b438290d2]::traits::fulfill::PendingPredicateObligation>>::process_obligations::<rustc_trait_selection[4ba0541b438290d2]::traits::fulfill::FulfillProcessor>
  17:     0x7b60de79f0e4 - <rustc_hir_typeck[f3c634e21e25c7e1]::fn_ctxt::FnCtxt>::confirm_builtin_call
  18:     0x7b60df390bc8 - <rustc_hir_typeck[f3c634e21e25c7e1]::fn_ctxt::FnCtxt>::check_expr_with_expectation_and_args
  19:     0x7b60df389dcf - <rustc_hir_typeck[f3c634e21e25c7e1]::fn_ctxt::FnCtxt>::check_expr_block
  20:     0x7b60df3916d4 - <rustc_hir_typeck[f3c634e21e25c7e1]::fn_ctxt::FnCtxt>::check_expr_with_expectation_and_args
  21:     0x7b60dec88780 - rustc_hir_typeck[f3c634e21e25c7e1]::check::check_fn
  22:     0x7b60dec9163d - rustc_hir_typeck[f3c634e21e25c7e1]::typeck_with_inspect::{closure#0}
  23:     0x7b60dec8f64c - rustc_query_impl[db064f70679e7e57]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[db064f70679e7e57]::query_impl::typeck::dynamic_query::{closure#2}::{closure#0}, rustc_middle[e5994b11539d1088]::query::erase::Erased<[u8; 8usize]>>
  24:     0x7b60de981a4e - rustc_query_system[acb98781fee9c8ed]::query::plumbing::try_execute_query::<rustc_query_impl[db064f70679e7e57]::DynamicConfig<rustc_data_structures[b1621f9a8426d32f]::vec_cache::VecCache<rustc_span[573b00108592c307]::def_id::LocalDefId, rustc_middle[e5994b11539d1088]::query::erase::Erased<[u8; 8usize]>, rustc_query_system[acb98781fee9c8ed]::dep_graph::graph::DepNodeIndex>, false, false, false>, rustc_query_impl[db064f70679e7e57]::plumbing::QueryCtxt, false>
  25:     0x7b60de97ff51 - rustc_query_impl[db064f70679e7e57]::query_impl::typeck::get_query_non_incr::__rust_end_short_backtrace
  26:     0x7b60de97fc0b - <rustc_middle[e5994b11539d1088]::hir::map::Map>::par_body_owners::<rustc_hir_analysis[f7ab43cc31358404]::check_crate::{closure#4}>::{closure#0}
  27:     0x7b60de97dcbf - rustc_hir_analysis[f7ab43cc31358404]::check_crate
  28:     0x7b60de97a2e2 - rustc_interface[a9a02922dc001c32]::passes::run_required_analyses
  29:     0x7b60df554bde - rustc_interface[a9a02922dc001c32]::passes::analysis
  30:     0x7b60df554baf - rustc_query_impl[db064f70679e7e57]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[db064f70679e7e57]::query_impl::analysis::dynamic_query::{closure#2}::{closure#0}, rustc_middle[e5994b11539d1088]::query::erase::Erased<[u8; 0usize]>>
  31:     0x7b60df541b55 - rustc_query_system[acb98781fee9c8ed]::query::plumbing::try_execute_query::<rustc_query_impl[db064f70679e7e57]::DynamicConfig<rustc_query_system[acb98781fee9c8ed]::query::caches::SingleCache<rustc_middle[e5994b11539d1088]::query::erase::Erased<[u8; 0usize]>>, false, false, false>, rustc_query_impl[db064f70679e7e57]::plumbing::QueryCtxt, false>
  32:     0x7b60df54188e - rustc_query_impl[db064f70679e7e57]::query_impl::analysis::get_query_non_incr::__rust_end_short_backtrace
  33:     0x7b60df603969 - rustc_interface[a9a02922dc001c32]::passes::create_and_enter_global_ctxt::<core[bef17dfe197dbeb2]::option::Option<rustc_interface[a9a02922dc001c32]::queries::Linker>, rustc_driver_impl[238e9adc12ab3263]::run_compiler::{closure#0}::{closure#2}>::{closure#2}::{closure#0}
  34:     0x7b60df5ad513 - rustc_interface[a9a02922dc001c32]::interface::run_compiler::<(), rustc_driver_impl[238e9adc12ab3263]::run_compiler::{closure#0}>::{closure#1}
  35:     0x7b60df4a7235 - std[57730b54ef401f3]::sys::backtrace::__rust_begin_short_backtrace::<rustc_interface[a9a02922dc001c32]::util::run_in_thread_with_globals<rustc_interface[a9a02922dc001c32]::util::run_in_thread_pool_with_globals<rustc_interface[a9a02922dc001c32]::interface::run_compiler<(), rustc_driver_impl[238e9adc12ab3263]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>
  36:     0x7b60df4a6f19 - <<std[57730b54ef401f3]::thread::Builder>::spawn_unchecked_<rustc_interface[a9a02922dc001c32]::util::run_in_thread_with_globals<rustc_interface[a9a02922dc001c32]::util::run_in_thread_pool_with_globals<rustc_interface[a9a02922dc001c32]::interface::run_compiler<(), rustc_driver_impl[238e9adc12ab3263]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>::{closure#1} as core[bef17dfe197dbeb2]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  37:     0x7b60df4a66af - std::sys::pal::unix::thread::Thread::new::thread_start::h58ab2ce80d2171c1
  38:     0x7b60d98a339d - <unknown>
  39:     0x7b60d992849c - <unknown>
  40:                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: rustc 1.86.0-nightly (203e6c127 2025-01-25) running on x86_64-unknown-linux-gnu

note: compiler flags: -Z crate-attr=feature(generic_const_exprs) -Z dump-mir-dir=dir

query stack during panic:
#0 [typeck] type-checking `main`
#1 [analysis] running analysis passes on this crate
end of query stack
error: aborting due to 2 previous errors; 1 warning emitted

Some errors have detailed explanations: E0393, E0425.
For more information about an error, try `rustc --explain E0393`.

@rustbot label +F-generic_const_exprs

[matthiaskrgr]

#![feature(generic_const_exprs)]
trait A<const B: u8 = X> {}
impl A<1> for bool {}
fn bar(arg : &dyn A<x>) { bar(true) }
pub fn main() {}

bisects to #135971