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A-dyn-traitArea: trait objects, vtable layoutArea: trait objects, vtable layoutC-bugCategory: This is a bug.Category: This is a bug.F-negative_bounds`#![feature(negative_bounds)]``#![feature(negative_bounds)]`I-ICEIssue: The compiler panicked, giving an Internal Compilation Error (ICE) ❄️Issue: The compiler panicked, giving an Internal Compilation Error (ICE) ❄️P-lowLow priorityLow priorityT-compilerRelevant to the compiler team, which will review and decide on the PR/issue.Relevant to the compiler team, which will review and decide on the PR/issue.
Description
auto-reduced (treereduce-rust):
//@compile-flags: --edition=2024
type _0 = dyn !Sized;
original:
// Test that `dyn ?Sized` (i.e., a trait object with only a maybe buond) is not allowed.
type _0 = dyn !Sized;
//~^ ERROR at least one trait is required for an object type [E0224]
//~| ERROR relaxed bounds are not permitted in trait object types
fn main() {}
Version information
rustc 1.90.0-nightly (e05ab47e6 2025-07-21)
binary: rustc
commit-hash: e05ab47e6c418fb2b9faa2eae9a7e70c65c98eaa
commit-date: 2025-07-21
host: x86_64-unknown-linux-gnu
release: 1.90.0-nightly
LLVM version: 20.1.8
Possibly related line of code:
rust/compiler/rustc_hir_analysis/src/hir_ty_lowering/dyn_compatibility.rs
Lines 158 to 170 in e05ab47
// We achieve a stable ordering by walking over the unsubstituted principal | |
// trait ref. | |
let mut ordered_associated_types = vec![]; | |
if let Some((principal_trait, ref spans)) = principal_trait { | |
let principal_trait = principal_trait.map_bound(|trait_pred| { | |
assert_eq!(trait_pred.polarity, ty::PredicatePolarity::Positive); | |
trait_pred.trait_ref | |
}); | |
for ClauseWithSupertraitSpan { clause, supertrait_span } in traits::elaborate( | |
tcx, | |
[ClauseWithSupertraitSpan::new( |
Command:
/home/matthias/.rustup/toolchains/master/bin/rustc --edition=2024
Program output
error: negative bounds are not supported
--> /tmp/icemaker_global_tempdir.Ism9jqXZadUU/rustc_testrunner_tmpdir_reporting.E7C0NMbYkVD9/mvce.rs:1:15
|
1 | type _0 = dyn !Sized;
| ^
error[E0601]: `main` function not found in crate `mvce`
--> /tmp/icemaker_global_tempdir.Ism9jqXZadUU/rustc_testrunner_tmpdir_reporting.E7C0NMbYkVD9/mvce.rs:1:22
|
1 | type _0 = dyn !Sized;
| ^ consider adding a `main` function to `/tmp/icemaker_global_tempdir.Ism9jqXZadUU/rustc_testrunner_tmpdir_reporting.E7C0NMbYkVD9/mvce.rs`
thread 'rustc' panicked at compiler/rustc_hir_analysis/src/hir_ty_lowering/dyn_compatibility.rs:164:17:
assertion `left == right` failed
left: Negative
right: Positive
stack backtrace:
0: 0x7d548f1aed13 - <std::sys::backtrace::BacktraceLock::print::DisplayBacktrace as core::fmt::Display>::fmt::h085efbd236febcbd
1: 0x7d548fa02cf7 - core::fmt::write::hdec995910d7cb82c
2: 0x7d548f1a4983 - std::io::Write::write_fmt::hdeaf768f2514aca6
3: 0x7d548f1aeb72 - std::sys::backtrace::BacktraceLock::print::h21329d1cea89715b
4: 0x7d548f1b2617 - std::panicking::default_hook::{{closure}}::h2b9a0773f7d3658d
5: 0x7d548f1b217b - std::panicking::default_hook::h6914ecce7597b75d
6: 0x7d548e23ce53 - std[c460a2864e85620a]::panicking::update_hook::<alloc[e5e1e0fb3e88a69e]::boxed::Box<rustc_driver_impl[5cdc508988eda417]::install_ice_hook::{closure#1}>>::{closure#0}
7: 0x7d548f1b2e5e - std::panicking::rust_panic_with_hook::hda79d560b2103b22
8: 0x7d548f1b2b5a - std::panicking::begin_panic_handler::{{closure}}::h11e64d6275db65a6
9: 0x7d548f1af1e9 - std::sys::backtrace::__rust_end_short_backtrace::heaac04fc129e000e
10: 0x7d548f1b283d - __rustc[8435b3fdf207ac82]::rust_begin_unwind
11: 0x7d548b8caf90 - core::panicking::panic_fmt::h00265bbaa0446d87
12: 0x7d548dc12d47 - core::panicking::assert_failed_inner::ha50e6f2acfdbea53
13: 0x7d548eefe55f - core[66948c5bc5ff115d]::panicking::assert_failed::<rustc_type_ir[206b20cbc4cc23b8]::predicate::PredicatePolarity, rustc_type_ir[206b20cbc4cc23b8]::predicate::PredicatePolarity>
14: 0x7d5490957bee - <dyn rustc_hir_analysis[7dd98ded1e59e61f]::hir_ty_lowering::HirTyLowerer>::lower_trait_object_ty
15: 0x7d54903913ae - <dyn rustc_hir_analysis[7dd98ded1e59e61f]::hir_ty_lowering::HirTyLowerer>::lower_ty
16: 0x7d54903a198d - rustc_hir_analysis[7dd98ded1e59e61f]::collect::type_of::type_of
17: 0x7d548fa1936c - rustc_query_impl[e2149f423b14ff5d]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[e2149f423b14ff5d]::query_impl::type_of::dynamic_query::{closure#2}::{closure#0}, rustc_middle[966becd38e69f903]::query::erase::Erased<[u8; 8usize]>>
18: 0x7d548fa18025 - rustc_query_system[4d6471456bd701ae]::query::plumbing::try_execute_query::<rustc_query_impl[e2149f423b14ff5d]::DynamicConfig<rustc_query_system[4d6471456bd701ae]::query::caches::DefIdCache<rustc_middle[966becd38e69f903]::query::erase::Erased<[u8; 8usize]>>, false, false, false>, rustc_query_impl[e2149f423b14ff5d]::plumbing::QueryCtxt, false>
19: 0x7d548fa17bdd - rustc_query_impl[e2149f423b14ff5d]::query_impl::type_of::get_query_non_incr::__rust_end_short_backtrace
20: 0x7d54908be0ea - rustc_hir_analysis[7dd98ded1e59e61f]::check::check::check_item_type
21: 0x7d54908b7e35 - rustc_hir_analysis[7dd98ded1e59e61f]::check::wfcheck::check_well_formed
22: 0x7d54908b7e17 - rustc_query_impl[e2149f423b14ff5d]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[e2149f423b14ff5d]::query_impl::check_well_formed::dynamic_query::{closure#2}::{closure#0}, rustc_middle[966becd38e69f903]::query::erase::Erased<[u8; 1usize]>>
23: 0x7d54908b764c - rustc_query_system[4d6471456bd701ae]::query::plumbing::try_execute_query::<rustc_query_impl[e2149f423b14ff5d]::DynamicConfig<rustc_data_structures[8223ad205e246b01]::vec_cache::VecCache<rustc_span[854d2ff5fa944bc2]::def_id::LocalDefId, rustc_middle[966becd38e69f903]::query::erase::Erased<[u8; 1usize]>, rustc_query_system[4d6471456bd701ae]::dep_graph::graph::DepNodeIndex>, false, false, false>, rustc_query_impl[e2149f423b14ff5d]::plumbing::QueryCtxt, false>
24: 0x7d54908b7182 - rustc_query_impl[e2149f423b14ff5d]::query_impl::check_well_formed::get_query_non_incr::__rust_end_short_backtrace
25: 0x7d54908b48a3 - rustc_hir_analysis[7dd98ded1e59e61f]::check::wfcheck::check_type_wf
26: 0x7d54908b47b9 - rustc_query_impl[e2149f423b14ff5d]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[e2149f423b14ff5d]::query_impl::check_type_wf::dynamic_query::{closure#2}::{closure#0}, rustc_middle[966becd38e69f903]::query::erase::Erased<[u8; 1usize]>>
27: 0x7d5490adbe3c - rustc_query_system[4d6471456bd701ae]::query::plumbing::try_execute_query::<rustc_query_impl[e2149f423b14ff5d]::DynamicConfig<rustc_query_system[4d6471456bd701ae]::query::caches::SingleCache<rustc_middle[966becd38e69f903]::query::erase::Erased<[u8; 1usize]>>, false, false, false>, rustc_query_impl[e2149f423b14ff5d]::plumbing::QueryCtxt, false>
28: 0x7d5490adbc36 - rustc_query_impl[e2149f423b14ff5d]::query_impl::check_type_wf::get_query_non_incr::__rust_end_short_backtrace
29: 0x7d54900e509b - rustc_hir_analysis[7dd98ded1e59e61f]::check_crate
30: 0x7d54900e9dc4 - rustc_interface[21031aeca52a62ab]::passes::analysis
31: 0x7d54900e9a87 - rustc_query_impl[e2149f423b14ff5d]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[e2149f423b14ff5d]::query_impl::analysis::dynamic_query::{closure#2}::{closure#0}, rustc_middle[966becd38e69f903]::query::erase::Erased<[u8; 0usize]>>
32: 0x7d5490add5bc - rustc_query_system[4d6471456bd701ae]::query::plumbing::try_execute_query::<rustc_query_impl[e2149f423b14ff5d]::DynamicConfig<rustc_query_system[4d6471456bd701ae]::query::caches::SingleCache<rustc_middle[966becd38e69f903]::query::erase::Erased<[u8; 0usize]>>, false, false, false>, rustc_query_impl[e2149f423b14ff5d]::plumbing::QueryCtxt, false>
33: 0x7d5490add184 - rustc_query_impl[e2149f423b14ff5d]::query_impl::analysis::get_query_non_incr::__rust_end_short_backtrace
34: 0x7d5490d55d4b - rustc_interface[21031aeca52a62ab]::passes::create_and_enter_global_ctxt::<core[66948c5bc5ff115d]::option::Option<rustc_interface[21031aeca52a62ab]::queries::Linker>, rustc_driver_impl[5cdc508988eda417]::run_compiler::{closure#0}::{closure#2}>::{closure#2}::{closure#0}
35: 0x7d5490d4389e - rustc_interface[21031aeca52a62ab]::interface::run_compiler::<(), rustc_driver_impl[5cdc508988eda417]::run_compiler::{closure#0}>::{closure#1}
36: 0x7d5490c0e4b8 - std[c460a2864e85620a]::sys::backtrace::__rust_begin_short_backtrace::<rustc_interface[21031aeca52a62ab]::util::run_in_thread_with_globals<rustc_interface[21031aeca52a62ab]::util::run_in_thread_pool_with_globals<rustc_interface[21031aeca52a62ab]::interface::run_compiler<(), rustc_driver_impl[5cdc508988eda417]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>
37: 0x7d5490c0e196 - <<std[c460a2864e85620a]::thread::Builder>::spawn_unchecked_<rustc_interface[21031aeca52a62ab]::util::run_in_thread_with_globals<rustc_interface[21031aeca52a62ab]::util::run_in_thread_pool_with_globals<rustc_interface[21031aeca52a62ab]::interface::run_compiler<(), rustc_driver_impl[5cdc508988eda417]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>::{closure#1} as core[66948c5bc5ff115d]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
38: 0x7d5490c1413d - std::sys::pal::unix::thread::Thread::new::thread_start::h2841d6229de09b0b
39: 0x7d548a4a57eb - <unknown>
40: 0x7d548a52918c - <unknown>
41: 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 1.90.0-nightly (e05ab47e6 2025-07-21) running on x86_64-unknown-linux-gnu
note: compiler flags: -Z dump-mir-dir=dir
query stack during panic:
#0 [type_of] expanding type alias `_0`
#1 [check_well_formed] checking that `_0` is well-formed
#2 [check_type_wf] checking that types are well-formed
#3 [analysis] running analysis passes on this crate
end of query stack
error: aborting due to 2 previous errors
For more information about this error, try `rustc --explain E0601`.
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A-dyn-traitArea: trait objects, vtable layoutArea: trait objects, vtable layoutC-bugCategory: This is a bug.Category: This is a bug.F-negative_bounds`#![feature(negative_bounds)]``#![feature(negative_bounds)]`I-ICEIssue: The compiler panicked, giving an Internal Compilation Error (ICE) ❄️Issue: The compiler panicked, giving an Internal Compilation Error (ICE) ❄️P-lowLow priorityLow priorityT-compilerRelevant to the compiler team, which will review and decide on the PR/issue.Relevant to the compiler team, which will review and decide on the PR/issue.