ICE: generic_const_exprs "range end index 2 out of range for slice of length 1"

[matthiaskrgr]

Code

rustc "-Zcrate-attr=feature(generic_const_exprs)"

trait Trait<const N: Trait = bar> {
    fn fnc<const N: Trait = u32>(&self) -> Trait {
        bar
    }
}

fn main() {}

Meta

rustc --version --verbose:

rustc 1.67.0-nightly (234151769 2022-12-03)
binary: rustc
commit-hash: 23415176968e81e0aac92d0218612a89c4e68a82
commit-date: 2022-12-03
host: x86_64-unknown-linux-gnu
release: 1.67.0-nightly
LLVM version: 15.0.4

Error output

error[E0403]: the name `N` is already used for a generic parameter in this item's generic parameters
 --> 152f764c6622dfef067008fe2bb5329872ae96ed.rs:2:18
  |
1 | trait Trait<const N: Trait = bar> {
  |                   - first use of `N`
2 |     fn fnc<const N: Trait = u32>(&self) -> Trait {
  |                  ^ already used

error[E0425]: cannot find value `bar` in this scope
 --> 152f764c6622dfef067008fe2bb5329872ae96ed.rs:1:30
  |
1 | trait Trait<const N: Trait = bar> {
  |                              ^^^ not found in this scope

error[E0423]: expected value, found builtin type `u32`
 --> 152f764c6622dfef067008fe2bb5329872ae96ed.rs:2:29
  |
2 |     fn fnc<const N: Trait = u32>(&self) -> Trait {
  |                             ^^^ not a value

error[E0425]: cannot find value `bar` in this scope
 --> 152f764c6622dfef067008fe2bb5329872ae96ed.rs:3:9
  |
3 |         bar
  |         ^^^ 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

warning: trait objects without an explicit `dyn` are deprecated
 --> 152f764c6622dfef067008fe2bb5329872ae96ed.rs:1:22
  |
1 | trait Trait<const N: Trait = bar> {
  |                      ^^^^^
  |
  = 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`
  |
1 | trait Trait<const N: dyn Trait = bar> {
  |                      +++

error[E0391]: cycle detected when computing type of `Trait::N`
 --> 152f764c6622dfef067008fe2bb5329872ae96ed.rs:1:22
  |
1 | trait Trait<const N: Trait = bar> {
  |                      ^^^^^
  |
  = note: ...which immediately requires computing type of `Trait::N` again
note: cycle used when computing explicit predicates of trait `Trait`
 --> 152f764c6622dfef067008fe2bb5329872ae96ed.rs:1:1
  |
1 | trait Trait<const N: Trait = bar> {
  | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

error[E0391]: cycle detected when computing type of `Trait::N`
 --> 152f764c6622dfef067008fe2bb5329872ae96ed.rs:1:13
  |
1 | trait Trait<const N: Trait = bar> {
  |             ^^^^^^^^^^^^^^^^^^^^
  |
  = note: ...which immediately requires computing type of `Trait::N` again
note: cycle used when computing explicit predicates of trait `Trait`
 --> 152f764c6622dfef067008fe2bb5329872ae96ed.rs:1:1
  |
1 | trait Trait<const N: Trait = bar> {
  | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

error: defaults for const parameters are only allowed in `struct`, `enum`, `type`, or `trait` definitions
 --> 152f764c6622dfef067008fe2bb5329872ae96ed.rs:2:12
  |
2 |     fn fnc<const N: Trait = u32>(&self) -> Trait {
  |            ^^^^^^^^^^^^^^^^^^^^

warning: trait objects without an explicit `dyn` are deprecated
 --> 152f764c6622dfef067008fe2bb5329872ae96ed.rs:2:21
  |
2 |     fn fnc<const N: Trait = u32>(&self) -> Trait {
  |                     ^^^^^
  |
  = 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>
help: use `dyn`
  |
2 |     fn fnc<const N: dyn Trait = u32>(&self) -> Trait {
  |                     +++

warning: trait objects without an explicit `dyn` are deprecated
 --> 152f764c6622dfef067008fe2bb5329872ae96ed.rs:2:44
  |
2 |     fn fnc<const N: Trait = u32>(&self) -> Trait {
  |                                            ^^^^^
  |
  = 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>
help: use `dyn`
  |
2 |     fn fnc<const N: Trait = u32>(&self) -> dyn Trait {
  |                                            +++

Backtrace

thread '<unnamed>' panicked at 'range end index 2 out of range for slice of length 1', compiler/rustc_hir_analysis/src/collect/generics_of.rs:82:34
stack backtrace:
   0:     0x7f0a4a16625a - std::backtrace_rs::backtrace::libunwind::trace::h39c51bcedb139b44
                               at /rustc/23415176968e81e0aac92d0218612a89c4e68a82/library/std/src/../../backtrace/src/backtrace/libunwind.rs:93:5
   1:     0x7f0a4a16625a - std::backtrace_rs::backtrace::trace_unsynchronized::h9cf890f6f509d0c3
                               at /rustc/23415176968e81e0aac92d0218612a89c4e68a82/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5
   2:     0x7f0a4a16625a - std::sys_common::backtrace::_print_fmt::h4a0d7673c4689a86
                               at /rustc/23415176968e81e0aac92d0218612a89c4e68a82/library/std/src/sys_common/backtrace.rs:65:5
   3:     0x7f0a4a16625a - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::hed99d8097fd95926
                               at /rustc/23415176968e81e0aac92d0218612a89c4e68a82/library/std/src/sys_common/backtrace.rs:44:22
   4:     0x7f0a4a1c8e4e - core::fmt::write::hdab16ae0136a16af
                               at /rustc/23415176968e81e0aac92d0218612a89c4e68a82/library/core/src/fmt/mod.rs:1208:17
   5:     0x7f0a4a156675 - std::io::Write::write_fmt::h9619f0289bf5af21
                               at /rustc/23415176968e81e0aac92d0218612a89c4e68a82/library/std/src/io/mod.rs:1682:15
   6:     0x7f0a4a166025 - std::sys_common::backtrace::_print::h2fbe09348ca97657
                               at /rustc/23415176968e81e0aac92d0218612a89c4e68a82/library/std/src/sys_common/backtrace.rs:47:5
   7:     0x7f0a4a166025 - std::sys_common::backtrace::print::h72058f5ceb813403
                               at /rustc/23415176968e81e0aac92d0218612a89c4e68a82/library/std/src/sys_common/backtrace.rs:34:9
   8:     0x7f0a4a168d6f - std::panicking::default_hook::{{closure}}::h1542b395e584376b
                               at /rustc/23415176968e81e0aac92d0218612a89c4e68a82/library/std/src/panicking.rs:267:22
   9:     0x7f0a4a168aab - std::panicking::default_hook::hf92492522bb6bc51
                               at /rustc/23415176968e81e0aac92d0218612a89c4e68a82/library/std/src/panicking.rs:286:9
  10:     0x7f0a4a16958c - std::panicking::rust_panic_with_hook::h8e3ba576266d6126
                               at /rustc/23415176968e81e0aac92d0218612a89c4e68a82/library/std/src/panicking.rs:688:13
  11:     0x7f0a4a169329 - std::panicking::begin_panic_handler::{{closure}}::h5718d689762256a1
                               at /rustc/23415176968e81e0aac92d0218612a89c4e68a82/library/std/src/panicking.rs:579:13
  12:     0x7f0a4a16670c - std::sys_common::backtrace::__rust_end_short_backtrace::hb4469c61f2390e29
                               at /rustc/23415176968e81e0aac92d0218612a89c4e68a82/library/std/src/sys_common/backtrace.rs:137:18
  13:     0x7f0a4a169032 - rust_begin_unwind
                               at /rustc/23415176968e81e0aac92d0218612a89c4e68a82/library/std/src/panicking.rs:575:5
  14:     0x7f0a4a1c5863 - core::panicking::panic_fmt::h4dafe9d2577d7060
                               at /rustc/23415176968e81e0aac92d0218612a89c4e68a82/library/core/src/panicking.rs:64:14
  15:     0x7f0a4a1cc002 - core::slice::index::slice_end_index_len_fail_rt::h1d8f6c1e2b66432f
                               at /rustc/23415176968e81e0aac92d0218612a89c4e68a82/library/core/src/slice/index.rs:77:5
  16:     0x7f0a4a1cbf86 - core::slice::index::slice_end_index_len_fail::he6e8d5f4deaa626d
                               at /rustc/23415176968e81e0aac92d0218612a89c4e68a82/library/core/src/slice/index.rs:69:9
  17:     0x7f0a4bfce5b5 - rustc_hir_analysis[df495fcaee2748ed]::collect::generics_of::generics_of
  18:     0x7f0a4bde7e8c - rustc_query_system[c6fc551e4ef2763b]::query::plumbing::get_query::<rustc_query_impl[935dec28a6523c17]::queries::generics_of, rustc_query_impl[935dec28a6523c17]::plumbing::QueryCtxt>
  19:     0x7f0a4b9e6196 - <rustc_middle[eef20b0c23bc8b9b]::ty::list::List<rustc_middle[eef20b0c23bc8b9b]::ty::subst::GenericArg>>::identity_for_item
  20:     0x7f0a4c5bebfa - <rustc_middle[eef20b0c23bc8b9b]::ty::consts::Const>::from_opt_const_arg_anon_const
  21:     0x7f0a4ce4b7fe - rustc_middle[eef20b0c23bc8b9b]::ty::consts::const_param_default
  22:     0x7f0a4cd4543b - rustc_query_system[c6fc551e4ef2763b]::query::plumbing::try_execute_query::<rustc_query_impl[935dec28a6523c17]::plumbing::QueryCtxt, rustc_query_system[c6fc551e4ef2763b]::query::caches::DefaultCache<rustc_span[653636119034ca50]::def_id::DefId, rustc_middle[eef20b0c23bc8b9b]::ty::consts::Const>>
  23:     0x7f0a4cd45134 - rustc_query_system[c6fc551e4ef2763b]::query::plumbing::get_query::<rustc_query_impl[935dec28a6523c17]::queries::const_param_default, rustc_query_impl[935dec28a6523c17]::plumbing::QueryCtxt>
  24:     0x7f0a4bd98bc0 - <rustc_hir_analysis[df495fcaee2748ed]::collect::CollectItemTypesVisitor as rustc_hir[ba83b4f9e64fc5a4]::intravisit::Visitor>::visit_generics
  25:     0x7f0a4bda0d3e - rustc_hir[ba83b4f9e64fc5a4]::intravisit::walk_trait_item::<rustc_hir_analysis[df495fcaee2748ed]::collect::CollectItemTypesVisitor>
  26:     0x7f0a4bd9ff36 - <rustc_hir_analysis[df495fcaee2748ed]::collect::CollectItemTypesVisitor as rustc_hir[ba83b4f9e64fc5a4]::intravisit::Visitor>::visit_trait_item
  27:     0x7f0a4bd95a82 - <rustc_middle[eef20b0c23bc8b9b]::hir::map::Map>::visit_item_likes_in_module::<rustc_hir_analysis[df495fcaee2748ed]::collect::CollectItemTypesVisitor>
  28:     0x7f0a4bd9579c - rustc_hir_analysis[df495fcaee2748ed]::collect::collect_mod_item_types
  29:     0x7f0a4bff3903 - rustc_query_system[c6fc551e4ef2763b]::query::plumbing::try_execute_query::<rustc_query_impl[935dec28a6523c17]::plumbing::QueryCtxt, rustc_query_system[c6fc551e4ef2763b]::query::caches::VecCache<rustc_span[653636119034ca50]::def_id::LocalDefId, ()>>
  30:     0x7f0a4c8aa833 - rustc_query_system[c6fc551e4ef2763b]::query::plumbing::get_query::<rustc_query_impl[935dec28a6523c17]::queries::collect_mod_item_types, rustc_query_impl[935dec28a6523c17]::plumbing::QueryCtxt>
  31:     0x7f0a4b8d3b05 - <rustc_middle[eef20b0c23bc8b9b]::hir::map::Map>::for_each_module::<rustc_hir_analysis[df495fcaee2748ed]::check_crate::{closure#0}::{closure#0}::{closure#0}>
  32:     0x7f0a4b8d3198 - <rustc_session[87f0d63408877899]::session::Session>::track_errors::<rustc_hir_analysis[df495fcaee2748ed]::check_crate::{closure#0}, ()>
  33:     0x7f0a4b8d2e8f - rustc_hir_analysis[df495fcaee2748ed]::check_crate
  34:     0x7f0a4b8d2bab - rustc_interface[c57545daadc3fa09]::passes::analysis
  35:     0x7f0a4cc9a3ba - rustc_query_system[c6fc551e4ef2763b]::query::plumbing::try_execute_query::<rustc_query_impl[935dec28a6523c17]::plumbing::QueryCtxt, rustc_query_system[c6fc551e4ef2763b]::query::caches::DefaultCache<(), core[ec9ef0a26f3cf28]::result::Result<(), rustc_errors[57b9e96b8e7428c]::ErrorGuaranteed>>>
  36:     0x7f0a4cc9a0b0 - rustc_query_system[c6fc551e4ef2763b]::query::plumbing::get_query::<rustc_query_impl[935dec28a6523c17]::queries::analysis, rustc_query_impl[935dec28a6523c17]::plumbing::QueryCtxt>
  37:     0x7f0a4c64bfab - <rustc_interface[c57545daadc3fa09]::passes::QueryContext>::enter::<rustc_driver[d87acf87108c2deb]::run_compiler::{closure#1}::{closure#2}::{closure#2}, core[ec9ef0a26f3cf28]::result::Result<(), rustc_errors[57b9e96b8e7428c]::ErrorGuaranteed>>
  38:     0x7f0a4c64395e - <rustc_interface[c57545daadc3fa09]::interface::Compiler>::enter::<rustc_driver[d87acf87108c2deb]::run_compiler::{closure#1}::{closure#2}, core[ec9ef0a26f3cf28]::result::Result<core[ec9ef0a26f3cf28]::option::Option<rustc_interface[c57545daadc3fa09]::queries::Linker>, rustc_errors[57b9e96b8e7428c]::ErrorGuaranteed>>
  39:     0x7f0a4c63e978 - rustc_span[653636119034ca50]::with_source_map::<core[ec9ef0a26f3cf28]::result::Result<(), rustc_errors[57b9e96b8e7428c]::ErrorGuaranteed>, rustc_interface[c57545daadc3fa09]::interface::run_compiler<core[ec9ef0a26f3cf28]::result::Result<(), rustc_errors[57b9e96b8e7428c]::ErrorGuaranteed>, rustc_driver[d87acf87108c2deb]::run_compiler::{closure#1}>::{closure#0}::{closure#0}>
  40:     0x7f0a4c63e465 - <scoped_tls[2510ce566f7fd87d]::ScopedKey<rustc_span[653636119034ca50]::SessionGlobals>>::set::<rustc_interface[c57545daadc3fa09]::interface::run_compiler<core[ec9ef0a26f3cf28]::result::Result<(), rustc_errors[57b9e96b8e7428c]::ErrorGuaranteed>, rustc_driver[d87acf87108c2deb]::run_compiler::{closure#1}>::{closure#0}, core[ec9ef0a26f3cf28]::result::Result<(), rustc_errors[57b9e96b8e7428c]::ErrorGuaranteed>>
  41:     0x7f0a4c63da52 - std[b988c8daa9554a2a]::sys_common::backtrace::__rust_begin_short_backtrace::<rustc_interface[c57545daadc3fa09]::util::run_in_thread_pool_with_globals<rustc_interface[c57545daadc3fa09]::interface::run_compiler<core[ec9ef0a26f3cf28]::result::Result<(), rustc_errors[57b9e96b8e7428c]::ErrorGuaranteed>, rustc_driver[d87acf87108c2deb]::run_compiler::{closure#1}>::{closure#0}, core[ec9ef0a26f3cf28]::result::Result<(), rustc_errors[57b9e96b8e7428c]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[ec9ef0a26f3cf28]::result::Result<(), rustc_errors[57b9e96b8e7428c]::ErrorGuaranteed>>
  42:     0x7f0a4cda6848 - <<std[b988c8daa9554a2a]::thread::Builder>::spawn_unchecked_<rustc_interface[c57545daadc3fa09]::util::run_in_thread_pool_with_globals<rustc_interface[c57545daadc3fa09]::interface::run_compiler<core[ec9ef0a26f3cf28]::result::Result<(), rustc_errors[57b9e96b8e7428c]::ErrorGuaranteed>, rustc_driver[d87acf87108c2deb]::run_compiler::{closure#1}>::{closure#0}, core[ec9ef0a26f3cf28]::result::Result<(), rustc_errors[57b9e96b8e7428c]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[ec9ef0a26f3cf28]::result::Result<(), rustc_errors[57b9e96b8e7428c]::ErrorGuaranteed>>::{closure#1} as core[ec9ef0a26f3cf28]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  43:     0x7f0a4e2b07f3 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::hd24e4095bea58fc3
                               at /rustc/23415176968e81e0aac92d0218612a89c4e68a82/library/alloc/src/boxed.rs:2000:9
  44:     0x7f0a4e2b07f3 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::h7c7f47af88aff778
                               at /rustc/23415176968e81e0aac92d0218612a89c4e68a82/library/alloc/src/boxed.rs:2000:9
  45:     0x7f0a4e2b07f3 - std::sys::unix::thread::Thread::new::thread_start::h8d5de08b8b3f2cac
                               at /rustc/23415176968e81e0aac92d0218612a89c4e68a82/library/std/src/sys/unix/thread.rs:108:17
  46:     0x7f0a49f068fd - <unknown>
  47:     0x7f0a49f88a60 - <unknown>
  48:                0x0 - <unknown>
error: aborting due to 7 previous errors; 4 warnings emitted

[TaKO8Ki]

A little bit smaller example:

#![feature(generic_const_exprs)]
#![allow(incomplete_features)]

trait Trait<T> {
    fn fnc<const N: usize = "">(&self) {}
}

fn main() {}

playground