warning: trait objects without an explicit `dyn` are deprecated --> /tmp/icemaker_global_tempdir.yPYGjh9iJjgj/rustc_testrunner_tmpdir_reporting.YjRXwTSsOKW4/mvce.rs:8:13 | 8 | fn g(b: B) -> B; | ^ | = 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: `B` it is not object safe, so it can't be `dyn` = note: `#[warn(bare_trait_objects)]` on by default help: use a new generic type parameter, constrained by `B` | 8 | fn g<T: B>(b: T) -> B; | ++++++ ~ help: you can also use an opaque type, but users won't be able to specify the type parameter when calling the `fn`, having to rely exclusively on type inference | 8 | fn g(b: impl B) -> B; | ++++ warning: trait objects without an explicit `dyn` are deprecated --> /tmp/icemaker_global_tempdir.yPYGjh9iJjgj/rustc_testrunner_tmpdir_reporting.YjRXwTSsOKW4/mvce.rs:8:19 | 8 | fn g(b: B) -> B; | ^ | = 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: `B` is not object safe, use `impl B` to return an opaque type, as long as you return a single underlying type | 8 | fn g(b: B) -> impl B; | ++++ warning: trait objects without an explicit `dyn` are deprecated --> /tmp/icemaker_global_tempdir.yPYGjh9iJjgj/rustc_testrunner_tmpdir_reporting.YjRXwTSsOKW4/mvce.rs:4:13 | 4 | fn f(a: A) -> A; | ^ | = 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: `A` it is not object safe, so it can't be `dyn` help: use a new generic type parameter, constrained by `A` | 4 | fn f<T: A>(a: T) -> A; | ++++++ ~ help: you can also use an opaque type, but users won't be able to specify the type parameter when calling the `fn`, having to rely exclusively on type inference | 4 | fn f(a: impl A) -> A; | ++++ warning: trait objects without an explicit `dyn` are deprecated --> /tmp/icemaker_global_tempdir.yPYGjh9iJjgj/rustc_testrunner_tmpdir_reporting.YjRXwTSsOKW4/mvce.rs:4:19 | 4 | fn f(a: A) -> A; | ^ | = 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: `A` is not object safe, use `impl A` to return an opaque type, as long as you return a single underlying type | 4 | fn f(a: A) -> impl A; | ++++ note: no errors encountered even though `span_delayed_bug` issued note: those delayed bugs will now be shown as internal compiler errors error: internal compiler error[E0391]: cycle detected when computing function signature of `B::f` --> /tmp/icemaker_global_tempdir.yPYGjh9iJjgj/rustc_testrunner_tmpdir_reporting.YjRXwTSsOKW4/mvce.rs:4:5 | 4 | fn f(a: A) -> A; | ^^^^^^^^^^^^^^^^ | note: ...which requires checking if trait `A` is object safe... --> /tmp/icemaker_global_tempdir.yPYGjh9iJjgj/rustc_testrunner_tmpdir_reporting.YjRXwTSsOKW4/mvce.rs:7:1 | 7 | trait A { | ^^^^^^^ note: ...which requires determining object safety of trait `A`... --> /tmp/icemaker_global_tempdir.yPYGjh9iJjgj/rustc_testrunner_tmpdir_reporting.YjRXwTSsOKW4/mvce.rs:7:1 | 7 | trait A { | ^^^^^^^ note: ...which requires computing function signature of `A::g`... --> /tmp/icemaker_global_tempdir.yPYGjh9iJjgj/rustc_testrunner_tmpdir_reporting.YjRXwTSsOKW4/mvce.rs:8:5 | 8 | fn g(b: B) -> B; | ^^^^^^^^^^^^^^^^ note: ...which requires checking if trait `B` is object safe... --> /tmp/icemaker_global_tempdir.yPYGjh9iJjgj/rustc_testrunner_tmpdir_reporting.YjRXwTSsOKW4/mvce.rs:3:1 | 3 | trait B { | ^^^^^^^ note: ...which requires determining object safety of trait `B`... --> /tmp/icemaker_global_tempdir.yPYGjh9iJjgj/rustc_testrunner_tmpdir_reporting.YjRXwTSsOKW4/mvce.rs:3:1 | 3 | trait B { | ^^^^^^^ = note: ...which again requires computing function signature of `B::f`, completing the cycle note: cycle used when collecting item types in top-level module --> /tmp/icemaker_global_tempdir.yPYGjh9iJjgj/rustc_testrunner_tmpdir_reporting.YjRXwTSsOKW4/mvce.rs:1:1 | 1 | / #![feature(object_safe_for_dispatch)] 2 | | 3 | | trait B { 4 | | fn f(a: A) -> A; ... | 10 | | 11 | | fn main() {} | |____________^ = note: see https://rustc-dev-guide.rust-lang.org/overview.html#queries and https://rustc-dev-guide.rust-lang.org/query.html for more information note: delayed at compiler/rustc_query_system/src/query/job.rs:605:16 0: <rustc_errors::DiagCtxtInner>::emit_diagnostic 1: <rustc_errors::DiagCtxt>::emit_diagnostic 2: <rustc_span::ErrorGuaranteed as rustc_errors::diagnostic_builder::EmissionGuarantee>::emit_producing_guarantee 3: rustc_query_system::query::plumbing::mk_cycle::<rustc_query_impl::DynamicConfig<rustc_query_system::query::caches::DefIdCache<rustc_middle::query::erase::Erased<[u8; 24]>>, false, false, false>, rustc_query_impl::plumbing::QueryCtxt> 4: rustc_query_system::query::plumbing::cycle_error::<rustc_query_impl::DynamicConfig<rustc_query_system::query::caches::DefIdCache<rustc_middle::query::erase::Erased<[u8; 24]>>, false, false, false>, rustc_query_impl::plumbing::QueryCtxt> 5: rustc_query_impl::query_impl::fn_sig::get_query_non_incr::__rust_end_short_backtrace 6: rustc_middle::query::plumbing::query_get_at::<rustc_query_system::query::caches::DefIdCache<rustc_middle::query::erase::Erased<[u8; 24]>>> 7: rustc_trait_selection::traits::object_safety::virtual_call_violations_for_method 8: rustc_trait_selection::traits::object_safety::object_safety_violations_for_assoc_item 9: <core::iter::adapters::flatten::FlatMap<core::iter::adapters::map::Map<core::iter::adapters::map::Map<core::slice::iter::Iter<(rustc_span::symbol::Symbol, rustc_middle::ty::assoc::AssocItem)>, <rustc_data_structures::sorted_map::index_map::SortedIndexMultiMap<u32, rustc_span::symbol::Symbol, rustc_middle::ty::assoc::AssocItem>>::iter::{closure#0}>, <rustc_middle::ty::assoc::AssocItems>::in_definition_order::{closure#0}>, alloc::vec::Vec<rustc_middle::traits::ObjectSafetyViolation>, rustc_trait_selection::traits::object_safety::object_safety_violations_for_trait::{closure#0}> as core::iter::traits::iterator::Iterator>::next 10: <core::iter::adapters::flatten::FlatMap<rustc_trait_selection::traits::util::SupertraitDefIds, alloc::vec::Vec<rustc_middle::traits::ObjectSafetyViolation>, rustc_trait_selection::traits::object_safety::object_safety_violations::{closure#0}> as core::iter::traits::iterator::Iterator>::next 11: rustc_trait_selection::traits::object_safety::object_safety_violations 12: rustc_query_impl::plumbing::__rust_begin_short_backtrace::<rustc_query_impl::query_impl::object_safety_violations::dynamic_query::{closure#2}::{closure#0}, rustc_middle::query::erase::Erased<[u8; 16]>> 13: <rustc_query_impl::query_impl::object_safety_violations::dynamic_query::{closure#2} as core::ops::function::FnOnce<(rustc_middle::ty::context::TyCtxt, rustc_span::def_id::DefId)>>::call_once 14: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::DynamicConfig<rustc_query_system::query::caches::DefIdCache<rustc_middle::query::erase::Erased<[u8; 16]>>, false, false, false>, rustc_query_impl::plumbing::QueryCtxt, false> 15: rustc_query_impl::query_impl::object_safety_violations::get_query_non_incr::__rust_end_short_backtrace 16: rustc_middle::query::plumbing::query_get_at::<rustc_query_system::query::caches::DefIdCache<rustc_middle::query::erase::Erased<[u8; 16]>>> 17: rustc_trait_selection::traits::object_safety::check_is_object_safe 18: rustc_query_impl::plumbing::__rust_begin_short_backtrace::<rustc_query_impl::query_impl::check_is_object_safe::dynamic_query::{closure#2}::{closure#0}, rustc_middle::query::erase::Erased<[u8; 1]>> 19: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::DynamicConfig<rustc_query_system::query::caches::DefIdCache<rustc_middle::query::erase::Erased<[u8; 1]>>, false, false, false>, rustc_query_impl::plumbing::QueryCtxt, false> 20: rustc_query_impl::query_impl::check_is_object_safe::get_query_non_incr::__rust_end_short_backtrace 21: rustc_middle::query::plumbing::query_get_at::<rustc_query_system::query::caches::DefIdCache<rustc_middle::query::erase::Erased<[u8; 1]>>> 22: <dyn rustc_hir_analysis::astconv::AstConv>::maybe_lint_impl_trait 23: <<dyn rustc_hir_analysis::astconv::AstConv>::maybe_lint_bare_trait::{closure#1} as core::ops::function::FnOnce<(&mut rustc_errors::diagnostic_builder::DiagnosticBuilder<()>,)>>::call_once::{shim:vtable#0} 24: <alloc::boxed::Box<dyn for<'a, 'b> core::ops::function::FnOnce<(&'a mut rustc_errors::diagnostic_builder::DiagnosticBuilder<'b, ()>,), Output = ()>> as core::ops::function::FnOnce<(&mut rustc_errors::diagnostic_builder::DiagnosticBuilder<()>,)>>::call_once 25: rustc_middle::lint::struct_lint_level::struct_lint_level_impl::<&str> 26: <dyn rustc_hir_analysis::astconv::AstConv>::maybe_lint_bare_trait 27: <dyn rustc_hir_analysis::astconv::AstConv>::ast_ty_to_ty_inner 28: <dyn rustc_hir_analysis::astconv::AstConv>::ty_of_fn 29: rustc_hir_analysis::collect::fn_sig 30: rustc_query_impl::plumbing::__rust_begin_short_backtrace::<rustc_query_impl::query_impl::fn_sig::dynamic_query::{closure#2}::{closure#0}, rustc_middle::query::erase::Erased<[u8; 24]>> 31: <rustc_query_impl::query_impl::fn_sig::dynamic_query::{closure#2} as core::ops::function::FnOnce<(rustc_middle::ty::context::TyCtxt, rustc_span::def_id::DefId)>>::call_once 32: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::DynamicConfig<rustc_query_system::query::caches::DefIdCache<rustc_middle::query::erase::Erased<[u8; 24]>>, false, false, false>, rustc_query_impl::plumbing::QueryCtxt, false> 33: rustc_query_impl::query_impl::fn_sig::get_query_non_incr::__rust_end_short_backtrace 34: rustc_middle::query::plumbing::query_get_at::<rustc_query_system::query::caches::DefIdCache<rustc_middle::query::erase::Erased<[u8; 24]>>> 35: rustc_trait_selection::traits::object_safety::virtual_call_violations_for_method 36: rustc_trait_selection::traits::object_safety::object_safety_violations_for_assoc_item 37: <core::iter::adapters::flatten::FlatMap<core::iter::adapters::map::Map<core::iter::adapters::map::Map<core::slice::iter::Iter<(rustc_span::symbol::Symbol, rustc_middle::ty::assoc::AssocItem)>, <rustc_data_structures::sorted_map::index_map::SortedIndexMultiMap<u32, rustc_span::symbol::Symbol, rustc_middle::ty::assoc::AssocItem>>::iter::{closure#0}>, <rustc_middle::ty::assoc::AssocItems>::in_definition_order::{closure#0}>, alloc::vec::Vec<rustc_middle::traits::ObjectSafetyViolation>, rustc_trait_selection::traits::object_safety::object_safety_violations_for_trait::{closure#0}> as core::iter::traits::iterator::Iterator>::next 38: <core::iter::adapters::flatten::FlatMap<rustc_trait_selection::traits::util::SupertraitDefIds, alloc::vec::Vec<rustc_middle::traits::ObjectSafetyViolation>, rustc_trait_selection::traits::object_safety::object_safety_violations::{closure#0}> as core::iter::traits::iterator::Iterator>::next 39: rustc_trait_selection::traits::object_safety::object_safety_violations 40: rustc_query_impl::plumbing::__rust_begin_short_backtrace::<rustc_query_impl::query_impl::object_safety_violations::dynamic_query::{closure#2}::{closure#0}, rustc_middle::query::erase::Erased<[u8; 16]>> 41: <rustc_query_impl::query_impl::object_safety_violations::dynamic_query::{closure#2} as core::ops::function::FnOnce<(rustc_middle::ty::context::TyCtxt, rustc_span::def_id::DefId)>>::call_once 42: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::DynamicConfig<rustc_query_system::query::caches::DefIdCache<rustc_middle::query::erase::Erased<[u8; 16]>>, false, false, false>, rustc_query_impl::plumbing::QueryCtxt, false> 43: rustc_query_impl::query_impl::object_safety_violations::get_query_non_incr::__rust_end_short_backtrace 44: rustc_middle::query::plumbing::query_get_at::<rustc_query_system::query::caches::DefIdCache<rustc_middle::query::erase::Erased<[u8; 16]>>> 45: rustc_trait_selection::traits::object_safety::check_is_object_safe 46: rustc_query_impl::plumbing::__rust_begin_short_backtrace::<rustc_query_impl::query_impl::check_is_object_safe::dynamic_query::{closure#2}::{closure#0}, rustc_middle::query::erase::Erased<[u8; 1]>> 47: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::DynamicConfig<rustc_query_system::query::caches::DefIdCache<rustc_middle::query::erase::Erased<[u8; 1]>>, false, false, false>, rustc_query_impl::plumbing::QueryCtxt, false> 48: rustc_query_impl::query_impl::check_is_object_safe::get_query_non_incr::__rust_end_short_backtrace 49: rustc_middle::query::plumbing::query_get_at::<rustc_query_system::query::caches::DefIdCache<rustc_middle::query::erase::Erased<[u8; 1]>>> 50: <dyn rustc_hir_analysis::astconv::AstConv>::maybe_lint_impl_trait 51: <<dyn rustc_hir_analysis::astconv::AstConv>::maybe_lint_bare_trait::{closure#1} as core::ops::function::FnOnce<(&mut rustc_errors::diagnostic_builder::DiagnosticBuilder<()>,)>>::call_once::{shim:vtable#0} 52: <alloc::boxed::Box<dyn for<'a, 'b> core::ops::function::FnOnce<(&'a mut rustc_errors::diagnostic_builder::DiagnosticBuilder<'b, ()>,), Output = ()>> as core::ops::function::FnOnce<(&mut rustc_errors::diagnostic_builder::DiagnosticBuilder<()>,)>>::call_once 53: rustc_middle::lint::struct_lint_level::struct_lint_level_impl::<&str> 54: <dyn rustc_hir_analysis::astconv::AstConv>::maybe_lint_bare_trait 55: <dyn rustc_hir_analysis::astconv::AstConv>::ast_ty_to_ty_inner 56: <dyn rustc_hir_analysis::astconv::AstConv>::ty_of_fn 57: rustc_hir_analysis::collect::fn_sig 58: rustc_query_impl::plumbing::__rust_begin_short_backtrace::<rustc_query_impl::query_impl::fn_sig::dynamic_query::{closure#2}::{closure#0}, rustc_middle::query::erase::Erased<[u8; 24]>> 59: <rustc_query_impl::query_impl::fn_sig::dynamic_query::{closure#2} as core::ops::function::FnOnce<(rustc_middle::ty::context::TyCtxt, rustc_span::def_id::DefId)>>::call_once 60: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::DynamicConfig<rustc_query_system::query::caches::DefIdCache<rustc_middle::query::erase::Erased<[u8; 24]>>, false, false, false>, rustc_query_impl::plumbing::QueryCtxt, false> 61: rustc_query_impl::query_impl::fn_sig::get_query_non_incr::__rust_end_short_backtrace 62: <rustc_hir_analysis::collect::CollectItemTypesVisitor as rustc_hir::intravisit::Visitor>::visit_trait_item 63: rustc_hir_analysis::collect::collect_mod_item_types 64: rustc_query_impl::plumbing::__rust_begin_short_backtrace::<rustc_query_impl::query_impl::collect_mod_item_types::dynamic_query::{closure#2}::{closure#0}, rustc_middle::query::erase::Erased<[u8; 0]>> 65: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::DynamicConfig<rustc_query_system::query::caches::DefaultCache<rustc_span::def_id::LocalModDefId, rustc_middle::query::erase::Erased<[u8; 0]>>, false, false, false>, rustc_query_impl::plumbing::QueryCtxt, false> 66: rustc_query_impl::query_impl::collect_mod_item_types::get_query_non_incr::__rust_end_short_backtrace 67: rustc_hir_analysis::check_crate 68: rustc_interface::passes::analysis 69: rustc_query_impl::plumbing::__rust_begin_short_backtrace::<rustc_query_impl::query_impl::analysis::dynamic_query::{closure#2}::{closure#0}, rustc_middle::query::erase::Erased<[u8; 1]>> 70: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::DynamicConfig<rustc_query_system::query::caches::SingleCache<rustc_middle::query::erase::Erased<[u8; 1]>>, false, false, false>, rustc_query_impl::plumbing::QueryCtxt, false> 71: rustc_query_impl::query_impl::analysis::get_query_non_incr::__rust_end_short_backtrace 72: rustc_interface::interface::run_compiler::<core::result::Result<(), rustc_span::ErrorGuaranteed>, rustc_driver_impl::run_compiler::{closure#0}>::{closure#0} 73: std::sys_common::backtrace::__rust_begin_short_backtrace::<rustc_interface::util::run_in_thread_with_globals<rustc_interface::util::run_in_thread_pool_with_globals<rustc_interface::interface::run_compiler<core::result::Result<(), rustc_span::ErrorGuaranteed>, rustc_driver_impl::run_compiler::{closure#0}>::{closure#0}, core::result::Result<(), rustc_span::ErrorGuaranteed>>::{closure#0}, core::result::Result<(), rustc_span::ErrorGuaranteed>>::{closure#0}::{closure#0}, core::result::Result<(), rustc_span::ErrorGuaranteed>> 74: <<std::thread::Builder>::spawn_unchecked_<rustc_interface::util::run_in_thread_with_globals<rustc_interface::util::run_in_thread_pool_with_globals<rustc_interface::interface::run_compiler<core::result::Result<(), rustc_span::ErrorGuaranteed>, rustc_driver_impl::run_compiler::{closure#0}>::{closure#0}, core::result::Result<(), rustc_span::ErrorGuaranteed>>::{closure#0}, core::result::Result<(), rustc_span::ErrorGuaranteed>>::{closure#0}::{closure#0}, core::result::Result<(), rustc_span::ErrorGuaranteed>>::{closure#1} as core::ops::function::FnOnce<()>>::call_once::{shim:vtable#0} 75: <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once at /rustc/a58ec8ff03b3269b20104eb7eae407be48ab95a7/library/alloc/src/boxed.rs:2016:9 76: <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once at /rustc/a58ec8ff03b3269b20104eb7eae407be48ab95a7/library/alloc/src/boxed.rs:2016:9 77: std::sys::pal::unix::thread::Thread::new::thread_start at /rustc/a58ec8ff03b3269b20104eb7eae407be48ab95a7/library/std/src/sys/pal/unix/thread.rs:108:17 78: <unknown> 79: <unknown> --> /tmp/icemaker_global_tempdir.yPYGjh9iJjgj/rustc_testrunner_tmpdir_reporting.YjRXwTSsOKW4/mvce.rs:4:5 | 4 | fn f(a: A) -> A; | ^^^^^^^^^^^^^^^^ 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 1.77.0-nightly (a58ec8ff0 2024-01-22) running on x86_64-unknown-linux-gnu query stack during panic: end of query stack error: aborting due to 1 previous error; 4 warnings emitted For more information about this error, try `rustc --explain E0391`.