ICE: did not expect inference variables here

[matthiaskrgr]

auto-reduced (treereduce-rust):

trait Owner {
    const C<const N: u32>: u32;
}

impl Owner for () {
    ;
}

fn take0<const N: u64>(_: impl Owner<C<N> = { N }>) {}

fn main() {
    take0::<f32, >(());
}

original:

trait Owner {
    const C<const N: u32>: u32;
}

impl Owner for () {
    const C<const N: u32>: u32 = N;
}

fn take0<const N: u64>(_: impl Owner<C<N> = { N }>) {}

fn main() {
    take0::<f32, {Dimension}>(());
}

Version information

rustc 1.84.0-nightly (251dc8ad8 2024-11-15)
binary: rustc
commit-hash: 251dc8ad84492c792a7600d8c5fef2ec868a36a7
commit-date: 2024-11-15
host: x86_64-unknown-linux-gnu
release: 1.84.0-nightly
LLVM version: 19.1.3

Possibly related line of code:

rust/compiler/rustc_middle/src/mir/interpret/queries.rs

Lines 99 to 111 in 251dc8a

	// variables. We reject those here since `resolve`
	// would fail otherwise.
	//
	// When trying to evaluate constants containing inference variables,
	// use `Infcx::const_eval_resolve` instead.
	if ct.args.has_non_region_infer() {
	bug!("did not expect inference variables here");
	}
	match ty::Instance::try_resolve(self, param_env, ct.def, ct.args) {
	Ok(Some(instance)) => {
	let cid = GlobalId { instance, promoted: None };
	self.const_eval_global_id_for_typeck(param_env, cid, span).inspect(|_| {

Command:
/home/matthias/.rustup/toolchains/master/bin/rustc

Program output

error: non-item in item list
 --> /tmp/icemaker_global_tempdir.LZacjKgHN0Cn/rustc_testrunner_tmpdir_reporting.fVFwgFbJn0St/mvce.rs:6:5
  |
5 | impl Owner for () {
  |                   - item list starts here
6 |     ;
  |     ^ non-item starts here
7 | }
  | - item list ends here

error[E0658]: associated const equality is incomplete
 --> /tmp/icemaker_global_tempdir.LZacjKgHN0Cn/rustc_testrunner_tmpdir_reporting.fVFwgFbJn0St/mvce.rs:9:38
  |
9 | fn take0<const N: u64>(_: impl Owner<C<N> = { N }>) {}
  |                                      ^^^^^^^^^^^^
  |
  = note: see issue #92827 <https://github.com/rust-lang/rust/issues/92827> for more information
  = help: add `#![feature(associated_const_equality)]` to the crate attributes to enable
  = note: this compiler was built on 2024-11-15; consider upgrading it if it is out of date

error[E0658]: generic const items are experimental
 --> /tmp/icemaker_global_tempdir.LZacjKgHN0Cn/rustc_testrunner_tmpdir_reporting.fVFwgFbJn0St/mvce.rs:2:12
  |
2 |     const C<const N: u32>: u32;
  |            ^^^^^^^^^^^^^^
  |
  = note: see issue #113521 <https://github.com/rust-lang/rust/issues/113521> for more information
  = help: add `#![feature(generic_const_items)]` to the crate attributes to enable
  = note: this compiler was built on 2024-11-15; consider upgrading it if it is out of date

error[E0046]: not all trait items implemented, missing: `C`
 --> /tmp/icemaker_global_tempdir.LZacjKgHN0Cn/rustc_testrunner_tmpdir_reporting.fVFwgFbJn0St/mvce.rs:5:1
  |
2 |     const C<const N: u32>: u32;
  |     -------------------------- `C` from trait
...
5 | impl Owner for () {
  | ^^^^^^^^^^^^^^^^^ missing `C` in implementation

error: the constant `N` is not of type `u32`
 --> /tmp/icemaker_global_tempdir.LZacjKgHN0Cn/rustc_testrunner_tmpdir_reporting.fVFwgFbJn0St/mvce.rs:9:38
  |
9 | fn take0<const N: u64>(_: impl Owner<C<N> = { N }>) {}
  |                                      ^^^^^^^^^^^^ expected `u32`, found `u64`
  |
note: required by a const generic parameter in `Owner::C`
 --> /tmp/icemaker_global_tempdir.LZacjKgHN0Cn/rustc_testrunner_tmpdir_reporting.fVFwgFbJn0St/mvce.rs:2:13
  |
2 |     const C<const N: u32>: u32;
  |             ^^^^^^^^^^^^ required by this const generic parameter in `Owner::C`

error[E0747]: type provided when a constant was expected
  --> /tmp/icemaker_global_tempdir.LZacjKgHN0Cn/rustc_testrunner_tmpdir_reporting.fVFwgFbJn0St/mvce.rs:12:13
   |
12 |     take0::<f32, >(());
   |             ^^^
   |
help: if this generic argument was intended as a const parameter, surround it with braces
   |
12 |     take0::<{ f32 }, >(());
   |             +     +

error: internal compiler error: compiler/rustc_middle/src/mir/interpret/queries.rs:105:13: did not expect inference variables here

thread 'rustc' panicked at compiler/rustc_middle/src/mir/interpret/queries.rs:105:13:
Box<dyn Any>
stack backtrace:
   0:     0x767693e5a3ba - <std::sys::backtrace::BacktraceLock::print::DisplayBacktrace as core::fmt::Display>::fmt::h3e8890c320687803
   1:     0x76769460414a - core::fmt::write::h8e02e323e721d5d3
   2:     0x767695a2cc51 - std::io::Write::write_fmt::hfa5fc2d5ad51eab4
   3:     0x767693e5a212 - std::sys::backtrace::BacktraceLock::print::hef9ddff43c45c466
   4:     0x767693e5c716 - std::panicking::default_hook::{{closure}}::he4ae1ef11715c038
   5:     0x767693e5c560 - std::panicking::default_hook::h4571154760051e3a
   6:     0x767692ee4281 - std[575dabc3fc23637d]::panicking::update_hook::<alloc[488fcebc54bee2fb]::boxed::Box<rustc_driver_impl[530468506af41d6d]::install_ice_hook::{closure#0}>>::{closure#0}
   7:     0x767693e5ce28 - std::panicking::rust_panic_with_hook::h99e29fee3fbc2974
   8:     0x767692f1e5d1 - std[575dabc3fc23637d]::panicking::begin_panic::<rustc_errors[6fe58dffe56bd7e6]::ExplicitBug>::{closure#0}
   9:     0x767692f115a6 - std[575dabc3fc23637d]::sys::backtrace::__rust_end_short_backtrace::<std[575dabc3fc23637d]::panicking::begin_panic<rustc_errors[6fe58dffe56bd7e6]::ExplicitBug>::{closure#0}, !>
  10:     0x767692f0ce1d - std[575dabc3fc23637d]::panicking::begin_panic::<rustc_errors[6fe58dffe56bd7e6]::ExplicitBug>
  11:     0x767692f282e1 - <rustc_errors[6fe58dffe56bd7e6]::diagnostic::BugAbort as rustc_errors[6fe58dffe56bd7e6]::diagnostic::EmissionGuarantee>::emit_producing_guarantee
  12:     0x7676935a86d3 - rustc_middle[c94631e3827a547d]::util::bug::opt_span_bug_fmt::<rustc_span[9778d555244491c7]::span_encoding::Span>::{closure#0}
  13:     0x76769358ef1a - rustc_middle[c94631e3827a547d]::ty::context::tls::with_opt::<rustc_middle[c94631e3827a547d]::util::bug::opt_span_bug_fmt<rustc_span[9778d555244491c7]::span_encoding::Span>::{closure#0}, !>::{closure#0}
  14:     0x76769358edab - rustc_middle[c94631e3827a547d]::ty::context::tls::with_context_opt::<rustc_middle[c94631e3827a547d]::ty::context::tls::with_opt<rustc_middle[c94631e3827a547d]::util::bug::opt_span_bug_fmt<rustc_span[9778d555244491c7]::span_encoding::Span>::{closure#0}, !>::{closure#0}, !>
  15:     0x76769195b280 - rustc_middle[c94631e3827a547d]::util::bug::bug_fmt
  16:     0x7676960ab035 - <rustc_middle[c94631e3827a547d]::ty::context::TyCtxt>::const_eval_resolve_for_typeck.cold
  17:     0x76769503e581 - rustc_trait_selection[ae5754708a8b3a46]::traits::try_evaluate_const
  18:     0x767694f92383 - <rustc_trait_selection[ae5754708a8b3a46]::traits::normalize::AssocTypeNormalizer as rustc_type_ir[83e8cfe6e15c3590]::fold::TypeFolder<rustc_middle[c94631e3827a547d]::ty::context::TyCtxt>>::fold_const
  19:     0x7676928336de - <rustc_trait_selection[ae5754708a8b3a46]::traits::normalize::AssocTypeNormalizer>::fold::<rustc_middle[c94631e3827a547d]::ty::Term>
  20:     0x767693d1a9bd - rustc_trait_selection[ae5754708a8b3a46]::traits::normalize::normalize_with_depth_to::<rustc_middle[c94631e3827a547d]::ty::Term>
  21:     0x767693d0f792 - <rustc_trait_selection[ae5754708a8b3a46]::error_reporting::TypeErrCtxt>::report_fulfillment_error
  22:     0x767693cdc889 - <rustc_trait_selection[ae5754708a8b3a46]::error_reporting::TypeErrCtxt>::report_fulfillment_errors
  23:     0x767690d25711 - <rustc_hir_typeck[37bfb0076054673b]::fn_ctxt::FnCtxt>::confirm_builtin_call
  24:     0x76769536b6d8 - <rustc_hir_typeck[37bfb0076054673b]::fn_ctxt::FnCtxt>::check_expr_with_expectation_and_args
  25:     0x767695365c35 - <rustc_hir_typeck[37bfb0076054673b]::fn_ctxt::FnCtxt>::check_expr_block
  26:     0x76769536bfba - <rustc_hir_typeck[37bfb0076054673b]::fn_ctxt::FnCtxt>::check_expr_with_expectation_and_args
  27:     0x76769485789c - rustc_hir_typeck[37bfb0076054673b]::check::check_fn
  28:     0x76769484d2ec - rustc_hir_typeck[37bfb0076054673b]::typeck
  29:     0x76769484cc93 - rustc_query_impl[bf1c9f3baad9eabf]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[bf1c9f3baad9eabf]::query_impl::typeck::dynamic_query::{closure#2}::{closure#0}, rustc_middle[c94631e3827a547d]::query::erase::Erased<[u8; 8usize]>>
  30:     0x767694d12001 - rustc_query_system[d5846f7a9cb2c23f]::query::plumbing::try_execute_query::<rustc_query_impl[bf1c9f3baad9eabf]::DynamicConfig<rustc_query_system[d5846f7a9cb2c23f]::query::caches::VecCache<rustc_span[9778d555244491c7]::def_id::LocalDefId, rustc_middle[c94631e3827a547d]::query::erase::Erased<[u8; 8usize]>>, false, false, false>, rustc_query_impl[bf1c9f3baad9eabf]::plumbing::QueryCtxt, false>
  31:     0x767694d1048d - rustc_query_impl[bf1c9f3baad9eabf]::query_impl::typeck::get_query_non_incr::__rust_end_short_backtrace
  32:     0x767694d10107 - <rustc_middle[c94631e3827a547d]::hir::map::Map>::par_body_owners::<rustc_hir_analysis[19f2f9b7f430108f]::check_crate::{closure#4}>::{closure#0}
  33:     0x767694d0e0d9 - rustc_hir_analysis[19f2f9b7f430108f]::check_crate
  34:     0x767694b44fca - rustc_interface[c18496298df4cf52]::passes::run_required_analyses
  35:     0x76769542961e - rustc_interface[c18496298df4cf52]::passes::analysis
  36:     0x7676954295ef - rustc_query_impl[bf1c9f3baad9eabf]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[bf1c9f3baad9eabf]::query_impl::analysis::dynamic_query::{closure#2}::{closure#0}, rustc_middle[c94631e3827a547d]::query::erase::Erased<[u8; 1usize]>>
  37:     0x7676955dee6e - rustc_query_system[d5846f7a9cb2c23f]::query::plumbing::try_execute_query::<rustc_query_impl[bf1c9f3baad9eabf]::DynamicConfig<rustc_query_system[d5846f7a9cb2c23f]::query::caches::SingleCache<rustc_middle[c94631e3827a547d]::query::erase::Erased<[u8; 1usize]>>, false, false, false>, rustc_query_impl[bf1c9f3baad9eabf]::plumbing::QueryCtxt, false>
  38:     0x7676955deb4e - rustc_query_impl[bf1c9f3baad9eabf]::query_impl::analysis::get_query_non_incr::__rust_end_short_backtrace
  39:     0x7676954d963a - rustc_interface[c18496298df4cf52]::interface::run_compiler::<core[678332cb0ee15b78]::result::Result<(), rustc_span[9778d555244491c7]::ErrorGuaranteed>, rustc_driver_impl[530468506af41d6d]::run_compiler::{closure#0}>::{closure#1}
  40:     0x767695532e50 - std[575dabc3fc23637d]::sys::backtrace::__rust_begin_short_backtrace::<rustc_interface[c18496298df4cf52]::util::run_in_thread_with_globals<rustc_interface[c18496298df4cf52]::util::run_in_thread_pool_with_globals<rustc_interface[c18496298df4cf52]::interface::run_compiler<core[678332cb0ee15b78]::result::Result<(), rustc_span[9778d555244491c7]::ErrorGuaranteed>, rustc_driver_impl[530468506af41d6d]::run_compiler::{closure#0}>::{closure#1}, core[678332cb0ee15b78]::result::Result<(), rustc_span[9778d555244491c7]::ErrorGuaranteed>>::{closure#0}, core[678332cb0ee15b78]::result::Result<(), rustc_span[9778d555244491c7]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[678332cb0ee15b78]::result::Result<(), rustc_span[9778d555244491c7]::ErrorGuaranteed>>
  41:     0x76769553326b - <<std[575dabc3fc23637d]::thread::Builder>::spawn_unchecked_<rustc_interface[c18496298df4cf52]::util::run_in_thread_with_globals<rustc_interface[c18496298df4cf52]::util::run_in_thread_pool_with_globals<rustc_interface[c18496298df4cf52]::interface::run_compiler<core[678332cb0ee15b78]::result::Result<(), rustc_span[9778d555244491c7]::ErrorGuaranteed>, rustc_driver_impl[530468506af41d6d]::run_compiler::{closure#0}>::{closure#1}, core[678332cb0ee15b78]::result::Result<(), rustc_span[9778d555244491c7]::ErrorGuaranteed>>::{closure#0}, core[678332cb0ee15b78]::result::Result<(), rustc_span[9778d555244491c7]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[678332cb0ee15b78]::result::Result<(), rustc_span[9778d555244491c7]::ErrorGuaranteed>>::{closure#1} as core[678332cb0ee15b78]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  42:     0x767695533d39 - std::sys::pal::unix::thread::Thread::new::thread_start::h1176f996a4a1b888
  43:     0x767696d5f39d - <unknown>
  44:     0x767696de449c - <unknown>
  45:                0x0 - <unknown>

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 1.84.0-nightly (251dc8ad8 2024-11-15) running on x86_64-unknown-linux-gnu

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 7 previous errors

Some errors have detailed explanations: E0046, E0658, E0747.
For more information about an error, try `rustc --explain E0046`.

[matthiaskrgr]

bisects to #132927 cc @BoxyUwU

[cyrgani]

Isn't this the same as #131406?

[matthiaskrgr]

stacktrace is different, query stack is different, code is different, bisection points to a different PR, so I'm inclined to say its a different case

[oli-obk]

Needs an error minimization.

[moxian]

Error-minimized:

#![feature(generic_const_items)]
#![feature(associated_const_equality)]
trait Trait {
    const C<const N: u32>: u32;
}

impl Trait for () {
    const C<const N: u32>: u32 = 0;
}

fn take0<const N: u64>(_: impl Trait<C<N> = 0>){
}

fn main() {
    take0(());
}

Which is essentially the same as what BoxyUwU already has in the pending #137972

@rustbot label: -E-needs-mcve