`no warnings or errors encountered even though delayed_good_path_bugs issued` when constructing a `const` never type with warnings disabled

[rMazeiks]

I was working on some perfectly reasonable and definitely not cursed Rust code when Cargo suddenly started crashing for some reason.

Code

Playground link

#![allow(warnings)]
#![feature(never_type)]
#![allow(const_err)]

use std::mem::MaybeUninit;

const fn never() -> ! {
    unsafe { MaybeUninit::uninit().assume_init() }
}

const NEVER: ! = never();

fn main() {}

Meta

This happens on nightly

cargo +nightly --version:

cargo 1.64.0-nightly (85b500cca 2022-07-24)

Error output

error: internal compiler error: no warnings or errors encountered even though `delayed_good_path_bugs` issued

Backtrace

error: internal compiler error: no warnings or errors encountered even though `delayed_good_path_bugs` issued

error: internal compiler error: trimmed_def_paths constructed
  |
  = note: delayed at    0: <rustc_errors::Handler>::delay_good_path_bug::<&str>
             1: rustc_middle::ty::print::pretty::trimmed_def_paths
             2: <rustc_middle::dep_graph::dep_node::DepKind as rustc_query_system::dep_graph::DepKind>::with_deps::<<rustc_query_system::dep_graph::graph::DepGraph<rustc_middle::dep_graph::dep_node::DepKind>>::with_task_impl<rustc_middle::ty::context::TyCtxt, (), std::collections::hash::map::HashMap<rustc_span::def_id::DefId, rustc_span::symbol::Symbol, core::hash::BuildHasherDefault<rustc_hash::FxHasher>>>::{closure#0}, std::collections::hash::map::HashMap<rustc_span::def_id::DefId, rustc_span::symbol::Symbol, core::hash::BuildHasherDefault<rustc_hash::FxHasher>>>
             3: <rustc_query_system::dep_graph::graph::DepGraph<rustc_middle::dep_graph::dep_node::DepKind>>::with_task::<rustc_middle::ty::context::TyCtxt, (), std::collections::hash::map::HashMap<rustc_span::def_id::DefId, rustc_span::symbol::Symbol, core::hash::BuildHasherDefault<rustc_hash::FxHasher>>>
             4: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::plumbing::QueryCtxt, rustc_query_system::query::caches::ArenaCache<(), std::collections::hash::map::HashMap<rustc_span::def_id::DefId, rustc_span::symbol::Symbol, core::hash::BuildHasherDefault<rustc_hash::FxHasher>>>>
             5: rustc_query_system::query::plumbing::force_query::<rustc_query_impl::queries::trimmed_def_paths, rustc_query_impl::plumbing::QueryCtxt>
             6: rustc_query_impl::query_callbacks::trimmed_def_paths::force_from_dep_node
             7: <rustc_middle::ty::context::TyCtxt as rustc_query_system::dep_graph::DepContext>::try_force_from_dep_node
             8: <rustc_query_system::dep_graph::graph::DepGraph<rustc_middle::dep_graph::dep_node::DepKind>>::try_mark_previous_green::<rustc_query_impl::plumbing::QueryCtxt>
             9: <rustc_query_system::dep_graph::graph::DepGraph<rustc_middle::dep_graph::dep_node::DepKind>>::try_mark_previous_green::<rustc_query_impl::plumbing::QueryCtxt>
            10: <rustc_query_system::dep_graph::graph::DepGraph<rustc_middle::dep_graph::dep_node::DepKind>>::try_mark_previous_green::<rustc_query_impl::plumbing::QueryCtxt>
            11: <rustc_query_system::dep_graph::graph::DepGraph<rustc_middle::dep_graph::dep_node::DepKind>>::try_mark_previous_green::<rustc_query_impl::plumbing::QueryCtxt>
            12: rustc_query_system::query::plumbing::ensure_must_run::<rustc_query_impl::plumbing::QueryCtxt, rustc_span::def_id::LocalDefId, ()>
            13: rustc_query_system::query::plumbing::get_query::<rustc_query_impl::queries::lint_mod, rustc_query_impl::plumbing::QueryCtxt>
            14: <rustc_middle::hir::map::Map>::for_each_module::<rustc_lint::late::check_crate<rustc_lint::BuiltinCombinedLateLintPass, rustc_interface::passes::analysis::{closure#5}::{closure#1}::{closure#2}::{closure#0}::{closure#0}>::{closure#1}::{closure#0}::{closure#0}>
            15: <rustc_session::session::Session>::time::<(), rustc_lint::late::check_crate<rustc_lint::BuiltinCombinedLateLintPass, rustc_interface::passes::analysis::{closure#5}::{closure#1}::{closure#2}::{closure#0}::{closure#0}>::{closure#1}::{closure#0}>
            16: <rustc_session::session::Session>::time::<(), rustc_interface::passes::analysis::{closure#5}::{closure#1}::{closure#2}::{closure#0}>
            17: <core::panic::unwind_safe::AssertUnwindSafe<rustc_interface::passes::analysis::{closure#5}::{closure#1}> as core::ops::function::FnOnce<()>>::call_once
            18: <rustc_session::session::Session>::time::<(), rustc_interface::passes::analysis::{closure#5}>
            19: rustc_interface::passes::analysis
            20: <rustc_query_system::dep_graph::graph::DepGraph<rustc_middle::dep_graph::dep_node::DepKind>>::with_task::<rustc_middle::ty::context::TyCtxt, (), core::result::Result<(), rustc_errors::ErrorGuaranteed>>
            21: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::plumbing::QueryCtxt, rustc_query_system::query::caches::DefaultCache<(), core::result::Result<(), rustc_errors::ErrorGuaranteed>>>
            22: rustc_query_system::query::plumbing::get_query::<rustc_query_impl::queries::analysis, rustc_query_impl::plumbing::QueryCtxt>
            23: <rustc_interface::interface::Compiler>::enter::<rustc_driver::run_compiler::{closure#1}::{closure#2}, core::result::Result<core::option::Option<rustc_interface::queries::Linker>, rustc_errors::ErrorGuaranteed>>
            24: rustc_span::with_source_map::<core::result::Result<(), rustc_errors::ErrorGuaranteed>, rustc_interface::interface::create_compiler_and_run<core::result::Result<(), rustc_errors::ErrorGuaranteed>, rustc_driver::run_compiler::{closure#1}>::{closure#1}>
            25: rustc_interface::interface::create_compiler_and_run::<core::result::Result<(), rustc_errors::ErrorGuaranteed>, rustc_driver::run_compiler::{closure#1}>
            26: <scoped_tls::ScopedKey<rustc_span::SessionGlobals>>::set::<rustc_interface::interface::run_compiler<core::result::Result<(), rustc_errors::ErrorGuaranteed>, rustc_driver::run_compiler::{closure#1}>::{closure#0}, core::result::Result<(), rustc_errors::ErrorGuaranteed>>
            27: std::sys_common::backtrace::__rust_begin_short_backtrace::<rustc_interface::util::run_in_thread_pool_with_globals<rustc_interface::interface::run_compiler<core::result::Result<(), rustc_errors::ErrorGuaranteed>, rustc_driver::run_compiler::{closure#1}>::{closure#0}, core::result::Result<(), rustc_errors::ErrorGuaranteed>>::{closure#0}, core::result::Result<(), rustc_errors::ErrorGuaranteed>>
            28: <<std::thread::Builder>::spawn_unchecked_<rustc_interface::util::run_in_thread_pool_with_globals<rustc_interface::interface::run_compiler<core::result::Result<(), rustc_errors::ErrorGuaranteed>, rustc_driver::run_compiler::{closure#1}>::{closure#0}, core::result::Result<(), rustc_errors::ErrorGuaranteed>>::{closure#0}, core::result::Result<(), rustc_errors::ErrorGuaranteed>>::{closure#1} as core::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
            29: <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once
                       at /rustc/4493a0f4724c0bae1436242d76cccc9c0a287b80/library/alloc/src/boxed.rs:1935:9
            30: <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once
                       at /rustc/4493a0f4724c0bae1436242d76cccc9c0a287b80/library/alloc/src/boxed.rs:1935:9
            31: std::sys::unix::thread::Thread::new::thread_start
                       at /rustc/4493a0f4724c0bae1436242d76cccc9c0a287b80/library/std/src/sys/unix/thread.rs:108:17
            32: start_thread
                       at /build/glibc-SzIz7B/glibc-2.31/nptl/pthread_create.c:477:8
            33: clone
                       at /build/glibc-SzIz7B/glibc-2.31/misc/../sysdeps/unix/sysv/linux/x86_64/clone.S:95
          

thread 'rustc' panicked at 'Box<dyn Any>', compiler/rustc_errors/src/lib.rs:1426:13
stack backtrace:
   0: std::panicking::begin_panic::<rustc_errors::ExplicitBug>
   1: std::panic::panic_any::<rustc_errors::ExplicitBug>
   2: <rustc_errors::HandlerInner as core::ops::drop::Drop>::drop
   3: core::ptr::drop_in_place::<rustc_session::parse::ParseSess>
   4: <alloc::rc::Rc<rustc_session::session::Session> as core::ops::drop::Drop>::drop
   5: core::ptr::drop_in_place::<rustc_interface::interface::Compiler>
   6: rustc_span::with_source_map::<core::result::Result<(), rustc_errors::ErrorGuaranteed>, rustc_interface::interface::create_compiler_and_run<core::result::Result<(), rustc_errors::ErrorGuaranteed>, rustc_driver::run_compiler::{closure#1}>::{closure#1}>
   7: rustc_interface::interface::create_compiler_and_run::<core::result::Result<(), rustc_errors::ErrorGuaranteed>, rustc_driver::run_compiler::{closure#1}>
   8: <scoped_tls::ScopedKey<rustc_span::SessionGlobals>>::set::<rustc_interface::interface::run_compiler<core::result::Result<(), rustc_errors::ErrorGuaranteed>, rustc_driver::run_compiler::{closure#1}>::{closure#0}, core::result::Result<(), rustc_errors::ErrorGuaranteed>>
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.

note: 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 1.64.0-nightly (4493a0f47 2022-08-02) running on x86_64-unknown-linux-gnu

note: compiler flags: --crate-type bin -C embed-bitcode=no -C debuginfo=2 -C incremental

note: some of the compiler flags provided by cargo are hidden

query stack during panic:
end of query stack
error: could not compile `rust_playground`; 1 warning emitted

[matthiaskrgr]

This one might also get fixed with #99893

[compiler-errors]

Probably not fixed by #99893, but the fix is very likely quite similar. Let me take a look tonight (and also complete that PR mentioned).

@rustbot claim

[RalfJung]

This will be resolved by #71800 since then you cannot allow(const_err) any more.

Meanwhile I think this might be an instance of #97699, combined with a delay_span_bug somewhere that turns it into an ICE. no the spans are local so this does not make sense

[RalfJung]

I was hoping to make const_err a hard error in ~6 weeks anyway, so the best way forward here might be to just wait for that...