rust-lang / rust-lang/rust

[ICE]: `Invalid MIR: bad LHS type for binop`

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C-bug F-generic_const_exprs F-min_generic_const_args I-ICE T-compiler
Dominant language
Rust
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PR metrics pending

Description

auto-reduced (treereduce-rust):

#![feature(generic_const_exprs, min_generic_const_args)]
struct Foo {
    field: isize,
}
fn foo<const N: usize, const M: usize = { N + 1 }>() {
    foo::<{ Foo { field: 1 } }>()
}

original:

#![feature(generic_const_exprs, min_generic_const_args)]
struct Foo {
    field: isize,
}
fn foo<const N: usize, const M: usize = { N + 1 }>() {
    foo::<{ Foo { field: 1 } }>()
}

fn main() {}

Version information

rustc 1.99.0-nightly (225e91c03 2026-07-13)
binary: rustc
commit-hash: 225e91c03da22cd4b9792b83c1cfc97967101614
commit-date: 2026-07-13
host: x86_64-unknown-linux-gnu
release: 1.99.0-nightly
LLVM version: 22.1.8

Possibly related line of code:
https://github.com/rust-lang/rust/blob/225e91c03da22cd4b9792b83c1cfc97967101614/compiler/rustc_const_eval/src/interpret/operator.rs#L417-L429

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

Program output 

warning: the feature `generic_const_exprs` is incomplete and may not be safe to use and/or cause compiler crashes
 --> /tmp/icemaker_global_tempdir.t2HbistEZJBr/rustc_testrunner_tmpdir_reporting.hutxlaBp0SfX/mvce.rs:1:12
  |
1 | #![feature(generic_const_exprs, min_generic_const_args)]
  |            ^^^^^^^^^^^^^^^^^^^
  |
  = note: see issue #76560 <https://github.com/rust-lang/rust/issues/76560> for more information
  = note: `#[warn(incomplete_features)]` on by default

warning: the feature `min_generic_const_args` is incomplete and may not be safe to use and/or cause compiler crashes
 --> /tmp/icemaker_global_tempdir.t2HbistEZJBr/rustc_testrunner_tmpdir_reporting.hutxlaBp0SfX/mvce.rs:1:33
  |
1 | #![feature(generic_const_exprs, min_generic_const_args)]
  |                                 ^^^^^^^^^^^^^^^^^^^^^^
  |
  = note: see issue #132980 <https://github.com/rust-lang/rust/issues/132980> for more information

error[E0601]: `main` function not found in crate `mvce`
 --> /tmp/icemaker_global_tempdir.t2HbistEZJBr/rustc_testrunner_tmpdir_reporting.hutxlaBp0SfX/mvce.rs:7:2
  |
7 | }
  |  ^ consider adding a `main` function to `/tmp/icemaker_global_tempdir.t2HbistEZJBr/rustc_testrunner_tmpdir_reporting.hutxlaBp0SfX/mvce.rs`

error: defaults for generic parameters are not allowed here
 --> /tmp/icemaker_global_tempdir.t2HbistEZJBr/rustc_testrunner_tmpdir_reporting.hutxlaBp0SfX/mvce.rs:5:24
  |
5 | fn foo<const N: usize, const M: usize = { N + 1 }>() {
  |                        ^^^^^^^^^^^^^^^^^^^^^^^^^^

error: internal compiler error: /rustc-dev/225e91c03da22cd4b9792b83c1cfc97967101614/compiler/rustc_const_eval/src/interpret/operator.rs:423:18: Invalid MIR: bad LHS type for binop: Foo
 --> /tmp/icemaker_global_tempdir.t2HbistEZJBr/rustc_testrunner_tmpdir_reporting.hutxlaBp0SfX/mvce.rs:5:43
  |
5 | fn foo<const N: usize, const M: usize = { N + 1 }>() {
  |                                           ^^^^^


thread 'rustc' (207135) panicked at /rustc-dev/225e91c03da22cd4b9792b83c1cfc97967101614/compiler/rustc_const_eval/src/interpret/operator.rs:423:18:
Box<dyn Any>
stack backtrace:
   0:     0x7fa06b60aa06 - <<std[f815c803b8bda7b3]::sys::backtrace::BacktraceLock>::print::DisplayBacktrace as core[a425eebf46758491]::fmt::Display>::fmt
   1:     0x7fa06bc10dc8 - core[a425eebf46758491]::fmt::write
   2:     0x7fa06b61fe7c - <std[f815c803b8bda7b3]::sys::stdio::unix::Stderr as core[a425eebf46758491]::io::write::Write>::write_fmt
   3:     0x7fa06b5ded8a - std[f815c803b8bda7b3]::panicking::default_hook::{closure#0}
   4:     0x7fa06b5fd123 - std[f815c803b8bda7b3]::panicking::default_hook
   5:     0x7fa06a5d4a2b - std[f815c803b8bda7b3]::panicking::update_hook::<alloc[2f076b677b3e1a3b]::boxed::Box<rustc_driver_impl[f6b68445f387381]::install_ice_hook::{closure#1}>>::{closure#0}
   6:     0x7fa06b5fd5c2 - std[f815c803b8bda7b3]::panicking::panic_with_hook
   7:     0x7fa06a601a81 - std[f815c803b8bda7b3]::panicking::begin_panic::<rustc_errors[17885d358a472364]::ExplicitBug>::{closure#0}
   8:     0x7fa06a5faa76 - std[f815c803b8bda7b3]::sys::backtrace::__rust_end_short_backtrace::<std[f815c803b8bda7b3]::panicking::begin_panic<rustc_errors[17885d358a472364]::ExplicitBug>::{closure#0}, !>
   9:     0x7fa06a5fa7db - std[f815c803b8bda7b3]::panicking::begin_panic::<rustc_errors[17885d358a472364]::ExplicitBug>
  10:     0x7fa06a60cc11 - <rustc_errors[17885d358a472364]::diagnostic::BugAbort as rustc_errors[17885d358a472364]::diagnostic::EmissionGuarantee>::emit_producing_guarantee
  11:     0x7fa06ab64cfc - <rustc_errors[17885d358a472364]::DiagCtxtHandle>::span_bug::<rustc_span[5e6c73db80a2ecda]::span_encoding::Span, alloc[2f076b677b3e1a3b]::string::String>
  12:     0x7fa06ab93916 - rustc_middle[83d6f6fa2ecd6292]::util::bug::opt_span_bug_fmt::<rustc_span[5e6c73db80a2ecda]::span_encoding::Span>::{closure#0}
  13:     0x7fa06ab93aa2 - rustc_middle[83d6f6fa2ecd6292]::ty::context::tls::with_opt::<rustc_middle[83d6f6fa2ecd6292]::util::bug::opt_span_bug_fmt<rustc_span[5e6c73db80a2ecda]::span_encoding::Span>::{closure#0}, !>::{closure#0}
  14:     0x7fa06ab7f27b - rustc_middle[83d6f6fa2ecd6292]::ty::context::tls::with_context_opt::<rustc_middle[83d6f6fa2ecd6292]::ty::context::tls::with_opt<rustc_middle[83d6f6fa2ecd6292]::util::bug::opt_span_bug_fmt<rustc_span[5e6c73db80a2ecda]::span_encoding::Span>::{closure#0}, !>::{closure#0}, !>
  15:     0x7fa068c20608 - rustc_middle[83d6f6fa2ecd6292]::util::bug::span_bug_fmt::<rustc_span[5e6c73db80a2ecda]::span_encoding::Span>
  16:     0x7fa06be73e48 - <rustc_const_eval[61e3780497d06163]::interpret::eval_context::InterpCx<rustc_const_eval[61e3780497d06163]::const_eval::machine::CompileTimeMachine>>::binary_op
  17:     0x7fa06cc2cafe - <rustc_const_eval[61e3780497d06163]::interpret::eval_context::InterpCx<rustc_const_eval[61e3780497d06163]::const_eval::machine::CompileTimeMachine>>::eval_rvalue_into_place
  18:     0x7fa06cc26510 - rustc_const_eval[61e3780497d06163]::const_eval::eval_queries::eval_to_allocation_raw_provider
  19:     0x7fa06cc24b96 - rustc_query_impl[68a2f365f9927c9b]::query_impl::eval_to_allocation_raw::invoke_provider_fn::__rust_begin_short_backtrace
  20:     0x7fa06cc205ac - rustc_query_impl[68a2f365f9927c9b]::execution::try_execute_query::<rustc_middle[83d6f6fa2ecd6292]::query::caches::DefaultCache<rustc_middle[83d6f6fa2ecd6292]::ty::PseudoCanonicalInput<rustc_middle[83d6f6fa2ecd6292]::mir::interpret::GlobalId>, rustc_middle[83d6f6fa2ecd6292]::query::erase::ErasedData<[u8; 24usize]>>, false>
  21:     0x7fa06cc1f9ff - rustc_query_impl[68a2f365f9927c9b]::query_impl::eval_to_allocation_raw::execute_query_non_incr::__rust_end_short_backtrace
  22:     0x7fa06cc1d76d - rustc_const_eval[61e3780497d06163]::const_eval::valtrees::eval_to_valtree
  23:     0x7fa06cc1d526 - <rustc_const_eval[61e3780497d06163]::provide::{closure#0} as core[a425eebf46758491]::ops::function::FnOnce<(rustc_middle[83d6f6fa2ecd6292]::ty::context::TyCtxt, rustc_middle[83d6f6fa2ecd6292]::ty::PseudoCanonicalInput<rustc_middle[83d6f6fa2ecd6292]::mir::interpret::GlobalId>)>>::call_once
  24:     0x7fa06cc1d4d8 - rustc_query_impl[68a2f365f9927c9b]::query_impl::eval_to_valtree::invoke_provider_fn::__rust_begin_short_backtrace
  25:     0x7fa06cc16460 - rustc_query_impl[68a2f365f9927c9b]::execution::try_execute_query::<rustc_middle[83d6f6fa2ecd6292]::query::caches::DefaultCache<rustc_middle[83d6f6fa2ecd6292]::ty::PseudoCanonicalInput<rustc_middle[83d6f6fa2ecd6292]::mir::interpret::GlobalId>, rustc_middle[83d6f6fa2ecd6292]::query::erase::ErasedData<[u8; 16usize]>>, false>
  26:     0x7fa06cc16108 - rustc_query_impl[68a2f365f9927c9b]::query_impl::eval_to_valtree::execute_query_non_incr::__rust_end_short_backtrace
  27:     0x7fa06c946818 - <rustc_middle[83d6f6fa2ecd6292]::ty::context::TyCtxt>::const_eval_resolve_for_typeck
  28:     0x7fa06c945a67 - rustc_trait_selection[9953319ec50c4b70]::traits::try_evaluate_const
  29:     0x7fa06d53bd53 - rustc_trait_selection[9953319ec50c4b70]::traits::const_evaluatable::is_const_evaluatable.cold
  30:     0x7fa06c2e70bc - <rustc_trait_selection[9953319ec50c4b70]::traits::fulfill::FulfillProcessor as rustc_data_structures[d208358c53517434]::obligation_forest::ObligationProcessor>::process_obligation
  31:     0x7fa06bc05c51 - <rustc_data_structures[d208358c53517434]::obligation_forest::ObligationForest<rustc_trait_selection[9953319ec50c4b70]::traits::fulfill::PendingPredicateObligation>>::process_obligations::<rustc_trait_selection[9953319ec50c4b70]::traits::fulfill::FulfillProcessor>
  32:     0x7fa06bedc227 - <rustc_hir_typeck[f0e17d0ac8b05531]::fn_ctxt::FnCtxt>::check_expr_call
  33:     0x7fa06bf03d19 - <rustc_hir_typeck[f0e17d0ac8b05531]::fn_ctxt::FnCtxt>::check_expr_with_expectation_and_args
  34:     0x7fa06bf0e4b0 - <rustc_hir_typeck[f0e17d0ac8b05531]::fn_ctxt::FnCtxt>::check_expr_block
  35:     0x7fa06bf03cc4 - <rustc_hir_typeck[f0e17d0ac8b05531]::fn_ctxt::FnCtxt>::check_expr_with_expectation_and_args
  36:     0x7fa06bf30818 - rustc_hir_typeck[f0e17d0ac8b05531]::check::check_fn
  37:     0x7fa06ce60cd2 - rustc_hir_typeck[f0e17d0ac8b05531]::typeck_with_inspect::{closure#0}
  38:     0x7fa06ce5f5f0 - rustc_query_impl[68a2f365f9927c9b]::query_impl::typeck_root::invoke_provider_fn::__rust_begin_short_backtrace
  39:     0x7fa06c26f4e9 - rustc_query_impl[68a2f365f9927c9b]::execution::try_execute_query::<rustc_data_structures[d208358c53517434]::vec_cache::VecCache<rustc_span[5e6c73db80a2ecda]::def_id::LocalDefId, rustc_middle[83d6f6fa2ecd6292]::query::erase::ErasedData<[u8; 8usize]>, rustc_middle[83d6f6fa2ecd6292]::dep_graph::graph::DepNodeIndex>, false>
  40:     0x7fa06c26ef43 - rustc_query_impl[68a2f365f9927c9b]::query_impl::typeck_root::execute_query_non_incr::__rust_end_short_backtrace
  41:     0x7fa06c271629 - <rustc_middle[83d6f6fa2ecd6292]::ty::context::TyCtxt>::par_hir_body_owners::<rustc_hir_analysis[d14ae22442f42ae1]::check_crate::{closure#1}>::{closure#0}
  42:     0x7fa06c270f30 - rustc_hir_analysis[d14ae22442f42ae1]::check_crate
  43:     0x7fa06c26bc0b - rustc_interface[daa1f9eccb307e6d]::passes::analysis
  44:     0x7fa06cdf2687 - rustc_query_impl[68a2f365f9927c9b]::execution::try_execute_query::<rustc_middle[83d6f6fa2ecd6292]::query::caches::SingleCache<rustc_middle[83d6f6fa2ecd6292]::query::erase::ErasedData<[u8; 0usize]>>, false>
  45:     0x7fa06cdf2369 - rustc_query_impl[68a2f365f9927c9b]::query_impl::analysis::execute_query_non_incr::__rust_end_short_backtrace
  46:     0x7fa06cd85d1b - rustc_interface[daa1f9eccb307e6d]::interface::run_compiler::<(), rustc_driver_impl[f6b68445f387381]::run_compiler::{closure#0}>::{closure#1}
  47:     0x7fa06cddd0ba - std[f815c803b8bda7b3]::sys::backtrace::__rust_begin_short_backtrace::<rustc_interface[daa1f9eccb307e6d]::util::run_in_thread_with_globals<rustc_interface[daa1f9eccb307e6d]::util::run_in_thread_pool_with_globals<rustc_interface[daa1f9eccb307e6d]::interface::run_compiler<(), rustc_driver_impl[f6b68445f387381]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>
  48:     0x7fa06cddce6d - <std[f815c803b8bda7b3]::thread::lifecycle::spawn_unchecked<rustc_interface[daa1f9eccb307e6d]::util::run_in_thread_with_globals<rustc_interface[daa1f9eccb307e6d]::util::run_in_thread_pool_with_globals<rustc_interface[daa1f9eccb307e6d]::interface::run_compiler<(), rustc_driver_impl[f6b68445f387381]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>::{closure#1} as core[a425eebf46758491]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  49:     0x7fa06cde1290 - <std[f815c803b8bda7b3]::sys::thread::unix::Thread>::new::thread_start
  50:     0x7fa066697739 - <unknown>
  51:     0x7fa06671bedc - <unknown>
  52:                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 1.99.0-nightly (225e91c03 2026-07-13) running on x86_64-unknown-linux-gnu

query stack during panic:
#0 [eval_to_allocation_raw] const-evaluating + checking `foo::{constant#0}`
#1 [eval_to_valtree] evaluating type-level constant
#2 [typeck_root] type-checking `foo`
#3 [analysis] running analysis passes on crate `mvce`
end of query stack
error: aborting due to 3 previous errors; 2 warnings emitted

For more information about this error, try `rustc --explain E0601`.

@rustbot label +F-generic_const_exprs +F-min_generic_const_args

Contributor guide

Open the contributing guide

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Reproduce the reduced program in a.rs with the nightly rustc command shown in the issue, then read compiler/rustc_const_eval/src/interpret/operator.rs around lines 417-429 and follow the binary_op call in the backtrace. Determine why the Foo constant reaches the invalid MIR check; done means the reproducer no longer triggers an internal compiler error and instead produces valid diagnostics or evaluation behavior.

Written by the indexing model from the issue text.

Assessment

Tech stack
rust
Domain
compilers
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Active
Clarity
Mostly clear
Newbie friendliness
48/100

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