ICE `const parameter types cannot be generic`, generic_const_exprs

[matthiaskrgr]

Code

#![feature(generic_const_exprs)]
pub trait TraitWAssocConst {
  const A: TraitWAssocConst<A=0>;
}

fn main<A: TraitWAssocConst<A=32>>() {
  TraitWAssocConst<A=0>:: TraitWAssocConst<A=32> ();
}

Meta

rustc --version --verbose:

<version>

Error output

binary: rustc
commit-hash: f4f5fc3e5cc70b7a43bf7b518c455f3d9bada9e3
commit-date: 2023-02-17
host: x86_64-unknown-linux-gnu
release: 1.69.0-nightly
LLVM version: 15.0.7

Backtrace

error: comparison operators cannot be chained
 --> 692a8d4b478d8831cf921c7a69c2c613a807ed73.rs:7:23
  |
7 |   TraitWAssocConst<A=0>:: TraitWAssocConst<A=32> ();
  |                       ^                   ^

error[E0423]: expected value, found trait `TraitWAssocConst`
 --> 692a8d4b478d8831cf921c7a69c2c613a807ed73.rs:7:3
  |
7 |   TraitWAssocConst<A=0>:: TraitWAssocConst<A=32> ();
  |   ^^^^^^^^^^^^^^^^ not a value

error[E0423]: expected value, found type parameter `A`
 --> 692a8d4b478d8831cf921c7a69c2c613a807ed73.rs:7:20
  |
6 | fn main<A: TraitWAssocConst<A=32>>() {
  |         - found this type parameter
7 |   TraitWAssocConst<A=0>:: TraitWAssocConst<A=32> ();
  |                    ^ not a value

error[E0423]: expected value, found trait `TraitWAssocConst`
 --> 692a8d4b478d8831cf921c7a69c2c613a807ed73.rs:7:24
  |
7 |   TraitWAssocConst<A=0>:: TraitWAssocConst<A=32> ();
  |                        ^^^^^^^^^^^^^^^^^^^ not a value

error[E0423]: expected value, found type parameter `A`
 --> 692a8d4b478d8831cf921c7a69c2c613a807ed73.rs:7:44
  |
6 | fn main<A: TraitWAssocConst<A=32>>() {
  |         - found this type parameter
7 |   TraitWAssocConst<A=0>:: TraitWAssocConst<A=32> ();
  |                                            ^ not a value

error[E0658]: associated const equality is incomplete
 --> 692a8d4b478d8831cf921c7a69c2c613a807ed73.rs:3:29
  |
3 |   const A: TraitWAssocConst<A=0>;
  |                             ^^^
  |
  = 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

error[E0658]: associated const equality is incomplete
 --> 692a8d4b478d8831cf921c7a69c2c613a807ed73.rs:6:29
  |
6 | fn main<A: TraitWAssocConst<A=32>>() {
  |                             ^^^^
  |
  = 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

warning: the feature `generic_const_exprs` is incomplete and may not be safe to use and/or cause compiler crashes
 --> 692a8d4b478d8831cf921c7a69c2c613a807ed73.rs:1:12
  |
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

warning: trait objects without an explicit `dyn` are deprecated
 --> 692a8d4b478d8831cf921c7a69c2c613a807ed73.rs:3:12
  |
3 |   const A: TraitWAssocConst<A=0>;
  |            ^^^^^^^^^^^^^^^^^^^^^
  |
  = warning: this is accepted in the current edition (Rust 2015) but is a hard error in Rust 2021!
  = note: for more information, see <https://doc.rust-lang.org/nightly/edition-guide/rust-2021/warnings-promoted-to-error.html>
  = note: `#[warn(bare_trait_objects)]` on by default
help: use `dyn`
  |
3 |   const A: dyn TraitWAssocConst<A=0>;
  |            +++

error[E0391]: cycle detected when computing type of `TraitWAssocConst::A`
 --> 692a8d4b478d8831cf921c7a69c2c613a807ed73.rs:3:3
  |
3 |   const A: TraitWAssocConst<A=0>;
  |   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  |
note: ...which requires computing type of `TraitWAssocConst::A::{constant#0}`...
 --> 692a8d4b478d8831cf921c7a69c2c613a807ed73.rs:3:31
  |
3 |   const A: TraitWAssocConst<A=0>;
  |                               ^
  = note: ...which again requires computing type of `TraitWAssocConst::A`, completing the cycle
note: cycle used when computing type of `main::{constant#0}`
 --> 692a8d4b478d8831cf921c7a69c2c613a807ed73.rs:6:31
  |
6 | fn main<A: TraitWAssocConst<A=32>>() {
  |                               ^^

thread 'rustc' panicked at 'const parameter types cannot be generic', compiler/rustc_middle/src/ty/consts.rs:79:14
stack backtrace:
   0:     0x7fed11f6aa5a - std::backtrace_rs::backtrace::libunwind::trace::hebe09041f884c65d
                               at /rustc/f4f5fc3e5cc70b7a43bf7b518c455f3d9bada9e3/library/std/src/../../backtrace/src/backtrace/libunwind.rs:93:5
   1:     0x7fed11f6aa5a - std::backtrace_rs::backtrace::trace_unsynchronized::h546f6c63cbbce5a9
                               at /rustc/f4f5fc3e5cc70b7a43bf7b518c455f3d9bada9e3/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5
   2:     0x7fed11f6aa5a - std::sys_common::backtrace::_print_fmt::h2559cb0cfed7a617
                               at /rustc/f4f5fc3e5cc70b7a43bf7b518c455f3d9bada9e3/library/std/src/sys_common/backtrace.rs:65:5
   3:     0x7fed11f6aa5a - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::h1fb4eaaaafa2d72a
                               at /rustc/f4f5fc3e5cc70b7a43bf7b518c455f3d9bada9e3/library/std/src/sys_common/backtrace.rs:44:22
   4:     0x7fed11fca9ae - core::fmt::write::hbaef4432b3c9d07b
                               at /rustc/f4f5fc3e5cc70b7a43bf7b518c455f3d9bada9e3/library/core/src/fmt/mod.rs:1232:17
   5:     0x7fed11f5ae05 - std::io::Write::write_fmt::h1f8dce362441faaa
                               at /rustc/f4f5fc3e5cc70b7a43bf7b518c455f3d9bada9e3/library/std/src/io/mod.rs:1684:15
   6:     0x7fed11f6a825 - std::sys_common::backtrace::_print::hc0e92ab849a4f4e1
                               at /rustc/f4f5fc3e5cc70b7a43bf7b518c455f3d9bada9e3/library/std/src/sys_common/backtrace.rs:47:5
   7:     0x7fed11f6a825 - std::sys_common::backtrace::print::h878cd11684ebdec3
                               at /rustc/f4f5fc3e5cc70b7a43bf7b518c455f3d9bada9e3/library/std/src/sys_common/backtrace.rs:34:9
   8:     0x7fed11f6d59f - std::panicking::default_hook::{{closure}}::h2ea8a6875aa6312d
                               at /rustc/f4f5fc3e5cc70b7a43bf7b518c455f3d9bada9e3/library/std/src/panicking.rs:267:22
   9:     0x7fed11f6d2db - std::panicking::default_hook::h9e42277a84072188
                               at /rustc/f4f5fc3e5cc70b7a43bf7b518c455f3d9bada9e3/library/std/src/panicking.rs:286:9
  10:     0x7fed1526e7b4 - <rustc_driver_impl[afa3c304d692170b]::DEFAULT_HOOK::{closure#0}::{closure#0} as core[ebab21900c9c0a2]::ops::function::FnOnce<(&core[ebab21900c9c0a2]::panic::panic_info::PanicInfo,)>>::call_once::{shim:vtable#0}
  11:     0x7fed11f6dddd - <alloc::boxed::Box<F,A> as core::ops::function::Fn<Args>>::call::h2c34f129ed413128
                               at /rustc/f4f5fc3e5cc70b7a43bf7b518c455f3d9bada9e3/library/alloc/src/boxed.rs:2002:9
  12:     0x7fed11f6dddd - std::panicking::rust_panic_with_hook::h4c799b8c4fc0a70b
                               at /rustc/f4f5fc3e5cc70b7a43bf7b518c455f3d9bada9e3/library/std/src/panicking.rs:692:13
  13:     0x7fed11f6db59 - std::panicking::begin_panic_handler::{{closure}}::h91f35d20f5c22591
                               at /rustc/f4f5fc3e5cc70b7a43bf7b518c455f3d9bada9e3/library/std/src/panicking.rs:579:13
  14:     0x7fed11f6aec6 - std::sys_common::backtrace::__rust_end_short_backtrace::hcc464c7f8476de7c
                               at /rustc/f4f5fc3e5cc70b7a43bf7b518c455f3d9bada9e3/library/std/src/sys_common/backtrace.rs:137:18
  15:     0x7fed11f6d862 - rust_begin_unwind
                               at /rustc/f4f5fc3e5cc70b7a43bf7b518c455f3d9bada9e3/library/std/src/panicking.rs:575:5
  16:     0x7fed11fc7353 - core::panicking::panic_fmt::hea21d570c6a5058a
                               at /rustc/f4f5fc3e5cc70b7a43bf7b518c455f3d9bada9e3/library/core/src/panicking.rs:64:14
  17:     0x7fed11fc74c1 - core::panicking::panic_display::h671d86309aadcfbd
                               at /rustc/f4f5fc3e5cc70b7a43bf7b518c455f3d9bada9e3/library/core/src/panicking.rs:147:5
  18:     0x7fed11fc746b - core::panicking::panic_str::h4d2e9b19fe17b3b5
                               at /rustc/f4f5fc3e5cc70b7a43bf7b518c455f3d9bada9e3/library/core/src/panicking.rs:131:5
  19:     0x7fed11fc70d6 - core::option::expect_failed::ha7447694ffe28900
                               at /rustc/f4f5fc3e5cc70b7a43bf7b518c455f3d9bada9e3/library/core/src/option.rs:1926:5
  20:     0x7fed1433313b - <rustc_middle[6caff671bb338453]::ty::consts::Const>::from_opt_const_arg_anon_const
  21:     0x7fed145a1a9b - <core[ebab21900c9c0a2]::iter::adapters::map::Map<core[ebab21900c9c0a2]::slice::iter::Iter<rustc_hir[f4a2ff38696703b5]::hir::TypeBinding>, <dyn rustc_hir_analysis[257f64c795d1d076]::astconv::AstConv>::create_assoc_bindings_for_generic_args::{closure#0}> as core[ebab21900c9c0a2]::iter::traits::iterator::Iterator>::fold::<(), core[ebab21900c9c0a2]::iter::traits::iterator::Iterator::for_each::call<rustc_hir_analysis[257f64c795d1d076]::astconv::ConvertedBinding, <alloc[d840872249f3dc84]::vec::Vec<rustc_hir_analysis[257f64c795d1d076]::astconv::ConvertedBinding>>::extend_trusted<core[ebab21900c9c0a2]::iter::adapters::map::Map<core[ebab21900c9c0a2]::slice::iter::Iter<rustc_hir[f4a2ff38696703b5]::hir::TypeBinding>, <dyn rustc_hir_analysis[257f64c795d1d076]::astconv::AstConv>::create_assoc_bindings_for_generic_args::{closure#0}>>::{closure#0}>::{closure#0}>
  22:     0x7fed1459d627 - <dyn rustc_hir_analysis[257f64c795d1d076]::astconv::AstConv>::instantiate_poly_trait_ref_inner
  23:     0x7fed1459c017 - <dyn rustc_hir_analysis[257f64c795d1d076]::astconv::AstConv>::instantiate_poly_trait_ref
  24:     0x7fed135b98ff - rustc_hir_analysis[257f64c795d1d076]::collect::predicates_of::gather_explicit_predicates_of
  25:     0x7fed13eea8bd - rustc_query_system[5ff89444bbfc32f5]::query::plumbing::get_query::<rustc_query_impl[ef929ccf3c28623b]::queries::explicit_predicates_of, rustc_query_impl[ef929ccf3c28623b]::plumbing::QueryCtxt, rustc_middle[6caff671bb338453]::dep_graph::dep_node::DepKind>
  26:     0x7fed13db2bf0 - rustc_hir_analysis[257f64c795d1d076]::collect::predicates_of::predicates_of
  27:     0x7fed13dafc9c - rustc_query_system[5ff89444bbfc32f5]::query::plumbing::get_query::<rustc_query_impl[ef929ccf3c28623b]::queries::predicates_of, rustc_query_impl[ef929ccf3c28623b]::plumbing::QueryCtxt, rustc_middle[6caff671bb338453]::dep_graph::dep_node::DepKind>
  28:     0x7fed13daf913 - <rustc_query_impl[ef929ccf3c28623b]::Queries as rustc_middle[6caff671bb338453]::ty::query::QueryEngine>::predicates_of
  29:     0x7fed138d6135 - <rustc_hir_analysis[257f64c795d1d076]::collect::CollectItemTypesVisitor as rustc_hir[f4a2ff38696703b5]::intravisit::Visitor>::visit_item
  30:     0x7fed138d4e75 - <rustc_middle[6caff671bb338453]::hir::map::Map>::visit_item_likes_in_module::<rustc_hir_analysis[257f64c795d1d076]::collect::CollectItemTypesVisitor>
  31:     0x7fed138d4d8c - rustc_hir_analysis[257f64c795d1d076]::collect::collect_mod_item_types
  32:     0x7fed1482f67f - rustc_query_system[5ff89444bbfc32f5]::query::plumbing::try_execute_query::<rustc_query_impl[ef929ccf3c28623b]::queries::collect_mod_item_types, rustc_query_impl[ef929ccf3c28623b]::plumbing::QueryCtxt>
  33:     0x7fed14c6e50d - <rustc_query_impl[ef929ccf3c28623b]::Queries as rustc_middle[6caff671bb338453]::ty::query::QueryEngine>::collect_mod_item_types
  34:     0x7fed137129dd - <rustc_middle[6caff671bb338453]::hir::map::Map>::for_each_module::<rustc_hir_analysis[257f64c795d1d076]::check_crate::{closure#0}::{closure#0}::{closure#0}>
  35:     0x7fed1371056c - rustc_hir_analysis[257f64c795d1d076]::check_crate
  36:     0x7fed13706062 - rustc_interface[686dab9608bc6033]::passes::analysis
  37:     0x7fed14a63d92 - rustc_query_system[5ff89444bbfc32f5]::query::plumbing::try_execute_query::<rustc_query_impl[ef929ccf3c28623b]::queries::analysis, rustc_query_impl[ef929ccf3c28623b]::plumbing::QueryCtxt>
  38:     0x7fed14c67e2a - <rustc_query_impl[ef929ccf3c28623b]::Queries as rustc_middle[6caff671bb338453]::ty::query::QueryEngine>::analysis
  39:     0x7fed14480303 - <rustc_interface[686dab9608bc6033]::queries::QueryResult<&rustc_middle[6caff671bb338453]::ty::context::GlobalCtxt>>::enter::<core[ebab21900c9c0a2]::result::Result<(), rustc_errors[faa449d960b5ce55]::ErrorGuaranteed>, rustc_driver_impl[afa3c304d692170b]::run_compiler::{closure#1}::{closure#2}::{closure#3}>
  40:     0x7fed1447f4d4 - <rustc_interface[686dab9608bc6033]::interface::Compiler>::enter::<rustc_driver_impl[afa3c304d692170b]::run_compiler::{closure#1}::{closure#2}, core[ebab21900c9c0a2]::result::Result<core[ebab21900c9c0a2]::option::Option<rustc_interface[686dab9608bc6033]::queries::Linker>, rustc_errors[faa449d960b5ce55]::ErrorGuaranteed>>
  41:     0x7fed1447a6f4 - rustc_span[1010a352e5466fad]::with_source_map::<core[ebab21900c9c0a2]::result::Result<(), rustc_errors[faa449d960b5ce55]::ErrorGuaranteed>, rustc_interface[686dab9608bc6033]::interface::run_compiler<core[ebab21900c9c0a2]::result::Result<(), rustc_errors[faa449d960b5ce55]::ErrorGuaranteed>, rustc_driver_impl[afa3c304d692170b]::run_compiler::{closure#1}>::{closure#0}::{closure#0}>
  42:     0x7fed1447a204 - <scoped_tls[d487b98c36b0d138]::ScopedKey<rustc_span[1010a352e5466fad]::SessionGlobals>>::set::<rustc_interface[686dab9608bc6033]::interface::run_compiler<core[ebab21900c9c0a2]::result::Result<(), rustc_errors[faa449d960b5ce55]::ErrorGuaranteed>, rustc_driver_impl[afa3c304d692170b]::run_compiler::{closure#1}>::{closure#0}, core[ebab21900c9c0a2]::result::Result<(), rustc_errors[faa449d960b5ce55]::ErrorGuaranteed>>
  43:     0x7fed14479902 - std[dc63ca99f82ce43d]::sys_common::backtrace::__rust_begin_short_backtrace::<rustc_interface[686dab9608bc6033]::util::run_in_thread_pool_with_globals<rustc_interface[686dab9608bc6033]::interface::run_compiler<core[ebab21900c9c0a2]::result::Result<(), rustc_errors[faa449d960b5ce55]::ErrorGuaranteed>, rustc_driver_impl[afa3c304d692170b]::run_compiler::{closure#1}>::{closure#0}, core[ebab21900c9c0a2]::result::Result<(), rustc_errors[faa449d960b5ce55]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[ebab21900c9c0a2]::result::Result<(), rustc_errors[faa449d960b5ce55]::ErrorGuaranteed>>
  44:     0x7fed144796ac - <<std[dc63ca99f82ce43d]::thread::Builder>::spawn_unchecked_<rustc_interface[686dab9608bc6033]::util::run_in_thread_pool_with_globals<rustc_interface[686dab9608bc6033]::interface::run_compiler<core[ebab21900c9c0a2]::result::Result<(), rustc_errors[faa449d960b5ce55]::ErrorGuaranteed>, rustc_driver_impl[afa3c304d692170b]::run_compiler::{closure#1}>::{closure#0}, core[ebab21900c9c0a2]::result::Result<(), rustc_errors[faa449d960b5ce55]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[ebab21900c9c0a2]::result::Result<(), rustc_errors[faa449d960b5ce55]::ErrorGuaranteed>>::{closure#1} as core[ebab21900c9c0a2]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  45:     0x7fed11f77c63 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::h9fd36c4a0ba5b15d
                               at /rustc/f4f5fc3e5cc70b7a43bf7b518c455f3d9bada9e3/library/alloc/src/boxed.rs:1988:9
  46:     0x7fed11f77c63 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::hd37d267854c7434f
                               at /rustc/f4f5fc3e5cc70b7a43bf7b518c455f3d9bada9e3/library/alloc/src/boxed.rs:1988:9
  47:     0x7fed11f77c63 - std::sys::unix::thread::Thread::new::thread_start::h1ff24d5a09f2a8be
                               at /rustc/f4f5fc3e5cc70b7a43bf7b518c455f3d9bada9e3/library/std/src/sys/unix/thread.rs:108:17
  48:     0x7fed11d07bb5 - <unknown>
  49:     0x7fed11d89d90 - <unknown>
  50:                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: rustc 1.69.0-nightly (f4f5fc3e5 2023-02-17) running on x86_64-unknown-linux-gnu

query stack during panic:
#0 [explicit_predicates_of] computing explicit predicates of `main`
#1 [predicates_defined_on] computing predicates of `main`
#2 [predicates_of] computing predicates of `main`
#3 [collect_mod_item_types] collecting item types in top-level module
#4 [analysis] running analysis passes on this crate
end of query stack
error: aborting due to 8 previous errors; 2 warnings emitted

Some errors have detailed explanations: E0391, E0423, E0658.
For more information about an error, try `rustc --explain E0391`.

[kylematsuda]

This is from #107753, we added expect("const parameter types cannot be generic") there.

@rustbot claim

[BoxyUwU]

closing this in favor of #108271

[BoxyUwU]

@matthiaskrgr ?

[compiler-errors]

Unclear why this PR was re-opened when this issue is already being tracked in #108271. Feel free to augment that issue with additional information if you find that one hard to search for when looking for pre-existing ICEs, since I really don't think we need to have two main issues for the same GCE ICE.