rust-lang / rust-lang/rust

ICE: `ConstArgHasType has escaping bound vars, so it cannot be wrapped in a dummy binder.`

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C-bug F-generic_const_exprs I-ICE P-low S-bug-has-test T-compiler
Dominant language
Rust
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Description

auto-reduced (treereduce-rust):

#![feature(generic_const_exprs)]
type Value<'v> = &[[u8; SIZE]];

trait Trait: Fn(Value) -> Value {}

original:


type Value<'v> = &[[u8; SIZE]];

trait Trait: Fn(Value) -> Value {}

impl<F: Indexer<Foo> + Indexer<Bar>> Trait for F {
    type A: Iterator<Item: Copy>;
    //~^ ERROR associated type bounds are unstable

    type B: Iterator<Item: 'static>;
    //~^ ERROR associated type bounds are unstable
}

fn main() {
    let _: Box<dyn Trait> = Box::new(|v: Value| v);
}

Version information

rustc 1.83.0-nightly (0321e73d1 2024-10-11)
binary: rustc
commit-hash: 0321e73d1cb3f739caa806927344eca6f96257b5
commit-date: 2024-10-11
host: x86_64-unknown-linux-gnu
release: 1.83.0-nightly
LLVM version: 19.1.1

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

Program output 

error[E0106]: missing lifetime specifier
 --> /tmp/icemaker_global_tempdir.P3GyuBNzInxV/rustc_testrunner_tmpdir_reporting.lgaymy8wn468/mvce.rs:1:18
  |
1 | type Value<'v> = &[[u8; SIZE]];
  |                  ^ expected named lifetime parameter
  |
help: consider using the `'v` lifetime
  |
1 | type Value<'v> = &'v [[u8; SIZE]];
  |                   ++

error[E0425]: cannot find value `SIZE` in this scope
 --> /tmp/icemaker_global_tempdir.P3GyuBNzInxV/rustc_testrunner_tmpdir_reporting.lgaymy8wn468/mvce.rs:1:25
  |
1 | type Value<'v> = &[[u8; SIZE]];
  |                         ^^^^ 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[E0601]: `main` function not found in crate `mvce`
 --> /tmp/icemaker_global_tempdir.P3GyuBNzInxV/rustc_testrunner_tmpdir_reporting.lgaymy8wn468/mvce.rs:3:35
  |
3 | trait Trait: Fn(Value) -> Value {}
  |                                   ^ consider adding a `main` function to `/tmp/icemaker_global_tempdir.P3GyuBNzInxV/rustc_testrunner_tmpdir_reporting.lgaymy8wn468/mvce.rs`

thread 'rustc' panicked at compiler/rustc_trait_selection/src/traits/wf.rs:687:21:
`ConstArgHasType(UnevaluatedConst { def: DefId(0:6 ~ mvce[ff9f]::Value::{constant#0}), args: ['^0.Named(DefId(0:7 ~ mvce[ff9f]::Trait::'_), "'_")] }, usize)` has escaping bound vars, so it cannot be wrapped in a dummy binder.
stack backtrace:
   0:     0x7d62025de57a - <std::sys::backtrace::BacktraceLock::print::DisplayBacktrace as core::fmt::Display>::fmt::h0c0d2e67483a7ce1
   1:     0x7d6202e034a6 - core::fmt::write::h19fbfdd1fd25c23b
   2:     0x7d62040c4091 - std::io::Write::write_fmt::hf8ab2da8ebc932a0
   3:     0x7d62025de3d2 - std::sys::backtrace::BacktraceLock::print::h3d864635116d695a
   4:     0x7d62025e08a6 - std::panicking::default_hook::{{closure}}::h2aa94d113a45cc15
   5:     0x7d62025e06f0 - std::panicking::default_hook::h97fbe8692dbb54b4
   6:     0x7d62016331df - std[b2c81c0a9485f2e4]::panicking::update_hook::<alloc[c9d20cda7901ded3]::boxed::Box<rustc_driver_impl[8c3cd927c140555]::install_ice_hook::{closure#0}>>::{closure#0}
   7:     0x7d62025e0fb8 - std::panicking::rust_panic_with_hook::hc4ff1f67175d51bb
   8:     0x7d62025e0d8a - std::panicking::begin_panic_handler::{{closure}}::h064adafafa3d3d91
   9:     0x7d62025dea29 - std::sys::backtrace::__rust_end_short_backtrace::hfd346037bc0f3979
  10:     0x7d62025e0a4c - rust_begin_unwind
  11:     0x7d620004cd00 - core::panicking::panic_fmt::hcd11b748a515a987
  12:     0x7d61ff2b7c5e - <rustc_trait_selection[9580d8cfdaacc399]::traits::wf::WfPredicates as rustc_type_ir[89eb6eb643500842]::visit::TypeVisitor<rustc_middle[3ffb7b0bf421448c]::ty::context::TyCtxt>>::visit_ty
  13:     0x7d620358cc09 - rustc_trait_selection[9580d8cfdaacc399]::traits::wf::clause_obligations
  14:     0x7d62035908bd - rustc_hir_analysis[94092c3b015c4ea3]::check::wfcheck::check_where_clauses
  15:     0x7d6203563b9c - rustc_hir_analysis[94092c3b015c4ea3]::check::wfcheck::check_trait
  16:     0x7d62007c1787 - rustc_hir_analysis[94092c3b015c4ea3]::check::wfcheck::check_well_formed
  17:     0x7d62037cee6b - rustc_query_impl[fa1174e4896087c1]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[fa1174e4896087c1]::query_impl::check_well_formed::dynamic_query::{closure#2}::{closure#0}, rustc_middle[3ffb7b0bf421448c]::query::erase::Erased<[u8; 1usize]>>
  18:     0x7d62037ce5d1 - rustc_query_system[3cba1a04b5b15b8a]::query::plumbing::try_execute_query::<rustc_query_impl[fa1174e4896087c1]::DynamicConfig<rustc_query_system[3cba1a04b5b15b8a]::query::caches::VecCache<rustc_span[6af75d8d312d6eec]::def_id::LocalDefId, rustc_middle[3ffb7b0bf421448c]::query::erase::Erased<[u8; 1usize]>>, false, false, false>, rustc_query_impl[fa1174e4896087c1]::plumbing::QueryCtxt, false>
  19:     0x7d62037ce250 - rustc_query_impl[fa1174e4896087c1]::query_impl::check_well_formed::get_query_non_incr::__rust_end_short_backtrace
  20:     0x7d62037cf0ff - rustc_hir_analysis[94092c3b015c4ea3]::check::wfcheck::check_mod_type_wf
  21:     0x7d62037cef25 - rustc_query_impl[fa1174e4896087c1]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[fa1174e4896087c1]::query_impl::check_mod_type_wf::dynamic_query::{closure#2}::{closure#0}, rustc_middle[3ffb7b0bf421448c]::query::erase::Erased<[u8; 1usize]>>
  22:     0x7d6203bb7b7b - rustc_query_system[3cba1a04b5b15b8a]::query::plumbing::try_execute_query::<rustc_query_impl[fa1174e4896087c1]::DynamicConfig<rustc_query_system[3cba1a04b5b15b8a]::query::caches::DefaultCache<rustc_span[6af75d8d312d6eec]::def_id::LocalModDefId, rustc_middle[3ffb7b0bf421448c]::query::erase::Erased<[u8; 1usize]>>, false, false, false>, rustc_query_impl[fa1174e4896087c1]::plumbing::QueryCtxt, false>
  23:     0x7d6203bb792d - rustc_query_impl[fa1174e4896087c1]::query_impl::check_mod_type_wf::get_query_non_incr::__rust_end_short_backtrace
  24:     0x7d62032340fb - rustc_hir_analysis[94092c3b015c4ea3]::check_crate
  25:     0x7d6203230e57 - rustc_interface[b91e754c6773c007]::passes::run_required_analyses
  26:     0x7d620391fb1e - rustc_interface[b91e754c6773c007]::passes::analysis
  27:     0x7d620391faf1 - rustc_query_impl[fa1174e4896087c1]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[fa1174e4896087c1]::query_impl::analysis::dynamic_query::{closure#2}::{closure#0}, rustc_middle[3ffb7b0bf421448c]::query::erase::Erased<[u8; 1usize]>>
  28:     0x7d6203d26dae - rustc_query_system[3cba1a04b5b15b8a]::query::plumbing::try_execute_query::<rustc_query_impl[fa1174e4896087c1]::DynamicConfig<rustc_query_system[3cba1a04b5b15b8a]::query::caches::SingleCache<rustc_middle[3ffb7b0bf421448c]::query::erase::Erased<[u8; 1usize]>>, false, false, false>, rustc_query_impl[fa1174e4896087c1]::plumbing::QueryCtxt, false>
  29:     0x7d6203d26a8f - rustc_query_impl[fa1174e4896087c1]::query_impl::analysis::get_query_non_incr::__rust_end_short_backtrace
  30:     0x7d6203b4edde - rustc_interface[b91e754c6773c007]::interface::run_compiler::<core[15204f05ba262a1b]::result::Result<(), rustc_span[6af75d8d312d6eec]::ErrorGuaranteed>, rustc_driver_impl[8c3cd927c140555]::run_compiler::{closure#0}>::{closure#1}
  31:     0x7d6203c32d10 - std[b2c81c0a9485f2e4]::sys::backtrace::__rust_begin_short_backtrace::<rustc_interface[b91e754c6773c007]::util::run_in_thread_with_globals<rustc_interface[b91e754c6773c007]::util::run_in_thread_pool_with_globals<rustc_interface[b91e754c6773c007]::interface::run_compiler<core[15204f05ba262a1b]::result::Result<(), rustc_span[6af75d8d312d6eec]::ErrorGuaranteed>, rustc_driver_impl[8c3cd927c140555]::run_compiler::{closure#0}>::{closure#1}, core[15204f05ba262a1b]::result::Result<(), rustc_span[6af75d8d312d6eec]::ErrorGuaranteed>>::{closure#0}, core[15204f05ba262a1b]::result::Result<(), rustc_span[6af75d8d312d6eec]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[15204f05ba262a1b]::result::Result<(), rustc_span[6af75d8d312d6eec]::ErrorGuaranteed>>
  32:     0x7d6203c333d7 - <<std[b2c81c0a9485f2e4]::thread::Builder>::spawn_unchecked_<rustc_interface[b91e754c6773c007]::util::run_in_thread_with_globals<rustc_interface[b91e754c6773c007]::util::run_in_thread_pool_with_globals<rustc_interface[b91e754c6773c007]::interface::run_compiler<core[15204f05ba262a1b]::result::Result<(), rustc_span[6af75d8d312d6eec]::ErrorGuaranteed>, rustc_driver_impl[8c3cd927c140555]::run_compiler::{closure#0}>::{closure#1}, core[15204f05ba262a1b]::result::Result<(), rustc_span[6af75d8d312d6eec]::ErrorGuaranteed>>::{closure#0}, core[15204f05ba262a1b]::result::Result<(), rustc_span[6af75d8d312d6eec]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[15204f05ba262a1b]::result::Result<(), rustc_span[6af75d8d312d6eec]::ErrorGuaranteed>>::{closure#1} as core[15204f05ba262a1b]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  33:     0x7d6203c342c1 - std::sys::pal::unix::thread::Thread::new::thread_start::h4694c2beab690665
  34:     0x7d62053ab39d - <unknown>
  35:     0x7d620543049c - <unknown>
  36:                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 1.83.0-nightly (0321e73d1 2024-10-11) 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 [check_well_formed] checking that `Trait` is well-formed
#1 [check_mod_type_wf] checking that types are well-formed in top-level module
end of query stack
error: aborting due to 3 previous errors; 1 warning emitted

Some errors have detailed explanations: E0106, E0425, E0601.
For more information about an error, try `rustc --explain E0106`.

@rustbot label +F-generic_const_exprs

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

Start by compiling the reduced example in /tmp/im/a.rs with the reported nightly flags and confirm the ICE in compiler/rustc_trait_selection/src/traits/wf.rs:687. Trace the check_well_formed and check_mod_type_wf query path shown in the report. Done means the example no longer panics and regression coverage preserves that 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
Stale
Clarity
Mostly clear
Newbie friendliness
35/100

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