error: internal compiler error: compiler/rustc_infer/src/infer/lexical_region_resolve/mod.rs:486:17: cannot relate region: LUB('{erased}, '{erased})

[fredrik-jansson-se]

I wasn't able to reduce this more

Code

#[derive(serde::Serialize, serde::Deserialize)]
pub struct MyRequest {}

#[derive(serde::Serialize, serde::Deserialize)]
pub struct MyResp {}
openraft::declare_raft_types!(
    pub MyTypeConfig:
        D = MyRequest,
        R = MyResp,
        NodeId = u64,
        Node = openraft::BasicNode,
        Entry = openraft::Entry<MyTypeConfig>,
        SnapshotData = std::io::Cursor<Vec<u8>>,
        AsyncRuntime = openraft::TokioRuntime,
);

pub struct MyLogReader {}

impl<C: openraft::RaftTypeConfig> openraft::storage::RaftLogReader<C> for MyLogReader {
    fn try_get_log_entries<RB: std::ops::RangeBounds<u64>>(
        &mut self,
        range: RB,
    ) -> impl std::future::Future<Output = Result<Vec<C::Entry>, openraft::StorageError<C::NodeId>>>
    {
        std::future::pending()
    }
}

use openraft::RaftTypeConfig;

pub struct MyLogStorage {
    node_id: <MyTypeConfig as RaftTypeConfig>::NodeId,
}

impl MyLogStorage {
    pub fn new(node_id: <MyTypeConfig as RaftTypeConfig>::NodeId) -> Self {
        Self { node_id }
    }
}

impl<C: openraft::RaftTypeConfig<NodeId = u64>> openraft::storage::RaftLogReader<C>
    for MyLogStorage
{
    fn try_get_log_entries<RB: std::ops::RangeBounds<u64> + std::fmt::Debug>(
        &mut self,
        range: RB,
    ) -> impl std::future::Future<Output = Result<Vec<C::Entry>, openraft::StorageError<C::NodeId>>>
    {
        std::future::pending()
    }
}

impl<C: openraft::RaftTypeConfig<NodeId = u64>> openraft::storage::RaftLogStorage<C>
    for MyLogStorage
{
    type LogReader = MyLogReader;

    fn get_log_state(
        &mut self,
    ) -> impl std::future::Future<
        Output = Result<openraft::LogState<C>, openraft::StorageError<C::NodeId>>,
    > {
        std::future::pending()
    }

    fn get_log_reader(&mut self) -> impl std::future::Future<Output = Self::LogReader> {
        std::future::pending()
    }

    fn save_vote(
        &mut self,
        vote: &openraft::Vote<C::NodeId>,
    ) -> impl std::future::Future<Output = Result<(), openraft::StorageError<C::NodeId>>> {
        todo!();
        async move {
            let vote = serde_json::to_vec(vote).unwrap();
            tokio::fs::write(&format!("{}.vote", self.node_id), vote).await;
            Ok(())
        }
    }

    fn read_vote(
        &mut self,
    ) -> impl std::future::Future<
        Output = Result<Option<openraft::Vote<C::NodeId>>, openraft::StorageError<C::NodeId>>,
    > {
        std::future::pending()
    }

    fn append<I: IntoIterator<Item = C::Entry> + Send>(
        &mut self,
        entries: I,
        callback: openraft::storage::LogFlushed<C>,
    ) -> impl std::future::Future<Output = Result<(), openraft::StorageError<C::NodeId>>> {
        std::future::pending()
    }

    fn truncate(
        &mut self,
        log_id: openraft::LogId<C::NodeId>,
    ) -> impl std::future::Future<Output = Result<(), openraft::StorageError<C::NodeId>>> {
        std::future::pending()
    }

    fn purge(
        &mut self,
        log_id: openraft::LogId<C::NodeId>,
    ) -> impl std::future::Future<Output = Result<(), openraft::StorageError<C::NodeId>>> {
        std::future::pending()
    }
}

[package]
name = "crash"
version = "0.1.0"
edition = "2021"

[lib]

[dependencies]
anyhow = "1.0.86"
openraft = { version = "0.9.11", features = ["tracing-log", "storage-v2", "serde"] }
serde = { version = "1.0.203", features = ["derive"] }
serde_json = "1.0.117"
tokio = { version = "1.38.0", features = ["full"] }

Meta

rustc --version --verbose:

rustc 1.79.0 (129f3b996 2024-06-10)
binary: rustc
commit-hash: 129f3b9964af4d4a709d1383930ade12dfe7c081
commit-date: 2024-06-10
host: aarch64-apple-darwin
release: 1.79.0
LLVM version: 18.1.7

Error output

[<output>](error: internal compiler error: compiler/rustc_infer/src/infer/lexical_region_resolve/mod.rs:486:17: cannot relate region: LUB('{erased}, '{erased}))

Backtrace

RUST_BACKTRACE=1 cargo b
   Compiling crash v0.1.0 (/Users/frja/dev/rust/rustc-crash)
warning: unused variable: `range`
  --> src/lib.rs:22:9
   |
22 |         range: RB,
   |         ^^^^^ help: if this is intentional, prefix it with an underscore: `_range`
   |
   = note: `#[warn(unused_variables)]` on by default

warning: unused variable: `range`
  --> src/lib.rs:46:9
   |
46 |         range: RB,
   |         ^^^^^ help: if this is intentional, prefix it with an underscore: `_range`

warning: unreachable expression
  --> src/lib.rs:75:9
   |
74 |           todo!();
   |           ------- any code following this expression is unreachable
75 | /         async move {
76 | |             let vote = serde_json::to_vec(vote).unwrap();
77 | |             tokio::fs::write(&format!("{}.vote", self.node_id), vote).await;
78 | |             Ok(())
79 | |         }
   | |_________^ unreachable expression
   |
   = note: `#[warn(unreachable_code)]` on by default

warning: unused variable: `vote`
  --> src/lib.rs:72:9
   |
72 |         vote: &openraft::Vote<C::NodeId>,
   |         ^^^^ help: if this is intentional, prefix it with an underscore: `_vote`

error: internal compiler error: compiler/rustc_infer/src/infer/lexical_region_resolve/mod.rs:486:17: cannot relate region: LUB('{erased}, '{erased})

thread 'rustc' panicked at compiler/rustc_infer/src/infer/lexical_region_resolve/mod.rs:486:17:
Box<dyn Any>
stack backtrace:
   0: std::panicking::begin_panic::<rustc_errors::ExplicitBug>
   1: <rustc_errors::diagnostic::BugAbort as rustc_errors::diagnostic::EmissionGuarantee>::emit_producing_guarantee
   2: rustc_middle::util::bug::opt_span_bug_fmt::<rustc_span::span_encoding::Span>::{closure#0}
   3: rustc_middle::ty::context::tls::with_opt::<rustc_middle::util::bug::opt_span_bug_fmt<rustc_span::span_encoding::Span>::{closure#0}, !>::{closure#0}
   4: rustc_middle::ty::context::tls::with_context_opt::<rustc_middle::ty::context::tls::with_opt<rustc_middle::util::bug::opt_span_bug_fmt<rustc_span::span_encoding::Span>::{closure#0}, !>::{closure#0}, !>
   5: rustc_middle::util::bug::bug_fmt
   6: <rustc_infer::infer::lexical_region_resolve::LexicalResolver>::lub_concrete_regions
   7: rustc_infer::infer::lexical_region_resolve::resolve
   8: <rustc_infer::infer::InferCtxt as rustc_trait_selection::regions::InferCtxtRegionExt>::resolve_regions
   9: <rustc_trait_selection::traits::engine::ObligationCtxt>::resolve_regions_and_report_errors
  10: rustc_hir_analysis::check::compare_impl_item::collect_return_position_impl_trait_in_trait_tys
      [... omitted 2 frames ...]
  11: rustc_middle::query::plumbing::query_get_at::<rustc_query_system::query::caches::DefIdCache<rustc_middle::query::erase::Erased<[u8; 8]>>>
  12: rustc_hir_analysis::collect::type_of::type_of
      [... omitted 2 frames ...]
  13: rustc_middle::query::plumbing::query_get_at::<rustc_query_system::query::caches::DefIdCache<rustc_middle::query::erase::Erased<[u8; 8]>>>
  14: <core::iter::adapters::map::Map<core::iter::adapters::flatten::FlatMap<core::slice::iter::Iter<rustc_span::def_id::DefId>, alloc::vec::Vec<rustc_hir_analysis::constrained_generic_params::Parameter>, rustc_hir_analysis::impl_wf_check::enforce_impl_params_are_constrained::{closure#0}>, <hashbrown::set::HashSet<rustc_hir_analysis::constrained_generic_params::Parameter, core::hash::BuildHasherDefault<rustc_hash::FxHasher>> as core::iter::traits::collect::Extend<rustc_hir_analysis::constrained_generic_params::Parameter>>::extend<core::iter::adapters::flatten::FlatMap<core::slice::iter::Iter<rustc_span::def_id::DefId>, alloc::vec::Vec<rustc_hir_analysis::constrained_generic_params::Parameter>, rustc_hir_analysis::impl_wf_check::enforce_impl_params_are_constrained::{closure#0}>>::{closure#0}> as core::iter::traits::iterator::Iterator>::fold::<(), core::iter::traits::iterator::Iterator::for_each::call<(rustc_hir_analysis::constrained_generic_params::Parameter, ()), <hashbrown::map::HashMap<rustc_hir_analysis::constrained_generic_params::Parameter, (), core::hash::BuildHasherDefault<rustc_hash::FxHasher>> as core::iter::traits::collect::Extend<(rustc_hir_analysis::constrained_generic_params::Parameter, ())>>::extend<core::iter::adapters::map::Map<core::iter::adapters::flatten::FlatMap<core::slice::iter::Iter<rustc_span::def_id::DefId>, alloc::vec::Vec<rustc_hir_analysis::constrained_generic_params::Parameter>, rustc_hir_analysis::impl_wf_check::enforce_impl_params_are_constrained::{closure#0}>, <hashbrown::set::HashSet<rustc_hir_analysis::constrained_generic_params::Parameter, core::hash::BuildHasherDefault<rustc_hash::FxHasher>> as core::iter::traits::collect::Extend<rustc_hir_analysis::constrained_generic_params::Parameter>>::extend<core::iter::adapters::flatten::FlatMap<core::slice::iter::Iter<rustc_span::def_id::DefId>, alloc::vec::Vec<rustc_hir_analysis::constrained_generic_params::Parameter>, rustc_hir_analysis::impl_wf_check::enforce_impl_params_are_constrained::{closure#0}>>::{closure#0}>>::{closure#0}>::{closure#0}>
  15: <hashbrown::map::HashMap<rustc_hir_analysis::constrained_generic_params::Parameter, (), core::hash::BuildHasherDefault<rustc_hash::FxHasher>> as core::iter::traits::collect::Extend<(rustc_hir_analysis::constrained_generic_params::Parameter, ())>>::extend::<core::iter::adapters::map::Map<core::iter::adapters::flatten::FlatMap<core::slice::iter::Iter<rustc_span::def_id::DefId>, alloc::vec::Vec<rustc_hir_analysis::constrained_generic_params::Parameter>, rustc_hir_analysis::impl_wf_check::enforce_impl_params_are_constrained::{closure#0}>, <hashbrown::set::HashSet<rustc_hir_analysis::constrained_generic_params::Parameter, core::hash::BuildHasherDefault<rustc_hash::FxHasher>> as core::iter::traits::collect::Extend<rustc_hir_analysis::constrained_generic_params::Parameter>>::extend<core::iter::adapters::flatten::FlatMap<core::slice::iter::Iter<rustc_span::def_id::DefId>, alloc::vec::Vec<rustc_hir_analysis::constrained_generic_params::Parameter>, rustc_hir_analysis::impl_wf_check::enforce_impl_params_are_constrained::{closure#0}>>::{closure#0}>>
  16: rustc_hir_analysis::impl_wf_check::check_impl_wf
  17: rustc_hir_analysis::check::wfcheck::check_well_formed
      [... omitted 2 frames ...]
  18: std::panicking::try::<core::result::Result<(), rustc_span::ErrorGuaranteed>, core::panic::unwind_safe::AssertUnwindSafe<rustc_data_structures::sync::parallel::disabled::try_par_for_each_in<&[rustc_hir::hir::ForeignItemId], rustc_span::ErrorGuaranteed, <rustc_middle::hir::ModuleItems>::par_foreign_items<rustc_hir_analysis::check::wfcheck::check_mod_type_wf::{closure#3}>::{closure#0}>::{closure#0}::{closure#0}::{closure#0}>>
  19: rustc_data_structures::sync::parallel::disabled::try_par_for_each_in::<&[rustc_hir::hir::ItemId], rustc_span::ErrorGuaranteed, <rustc_middle::hir::ModuleItems>::par_items<rustc_hir_analysis::check::wfcheck::check_mod_type_wf::{closure#0}>::{closure#0}>
  20: rustc_hir_analysis::check::wfcheck::check_mod_type_wf
      [... omitted 2 frames ...]
  21: std::panicking::try::<(), core::panic::unwind_safe::AssertUnwindSafe<rustc_data_structures::sync::parallel::disabled::par_for_each_in<&[rustc_hir::hir_id::OwnerId], <rustc_middle::hir::map::Map>::par_for_each_module<rustc_hir_analysis::check_crate::{closure#1}::{closure#0}>::{closure#0}>::{closure#0}::{closure#0}::{closure#0}>>
  22: rustc_data_structures::sync::parallel::disabled::par_for_each_in::<&[rustc_hir::hir_id::OwnerId], <rustc_middle::hir::map::Map>::par_for_each_module<rustc_hir_analysis::check_crate::{closure#1}::{closure#0}>::{closure#0}>
  23: rustc_hir_analysis::check_crate
  24: rustc_interface::passes::analysis
      [... omitted 2 frames ...]
  25: <rustc_middle::ty::context::GlobalCtxt>::enter::<rustc_driver_impl::run_compiler::{closure#0}::{closure#1}::{closure#3}, core::result::Result<(), rustc_span::ErrorGuaranteed>>
  26: <rustc_interface::interface::Compiler>::enter::<rustc_driver_impl::run_compiler::{closure#0}::{closure#1}, core::result::Result<core::option::Option<rustc_interface::queries::Linker>, rustc_span::ErrorGuaranteed>>
  27: <scoped_tls::ScopedKey<rustc_span::SessionGlobals>>::set::<rustc_interface::util::run_in_thread_with_globals<rustc_interface::interface::run_compiler<core::result::Result<(), rustc_span::ErrorGuaranteed>, rustc_driver_impl::run_compiler::{closure#0}>::{closure#1}, core::result::Result<(), rustc_span::ErrorGuaranteed>>::{closure#0}::{closure#0}::{closure#0}, core::result::Result<(), rustc_span::ErrorGuaranteed>>
  28: rustc_span::create_session_globals_then::<core::result::Result<(), rustc_span::ErrorGuaranteed>, rustc_interface::util::run_in_thread_with_globals<rustc_interface::interface::run_compiler<core::result::Result<(), rustc_span::ErrorGuaranteed>, rustc_driver_impl::run_compiler::{closure#0}>::{closure#1}, core::result::Result<(), rustc_span::ErrorGuaranteed>>::{closure#0}::{closure#0}::{closure#0}>
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.

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 1.79.0 (129f3b996 2024-06-10) running on aarch64-apple-darwin

note: compiler flags: --crate-type lib -C embed-bitcode=no -C debuginfo=2 -C split-debuginfo=unpacked -C incremental=[REDACTED]

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

query stack during panic:
#0 [collect_return_position_impl_trait_in_trait_tys] comparing an impl and trait method signature, inferring any hidden `impl Trait` types in the process
#1 [type_of] computing type of `<impl at src/lib.rs:53:1: 54:21>::{synthetic#2}`
#2 [check_well_formed] checking that `<impl at src/lib.rs:53:1: 54:21>` is well-formed
#3 [check_mod_type_wf] checking that types are well-formed in top-level module
#4 [analysis] running analysis passes on this crate
end of query stack
warning: unused variable: `entries`
  --> src/lib.rs:92:9
   |
92 |         entries: I,
   |         ^^^^^^^ help: if this is intentional, prefix it with an underscore: `_entries`

warning: unused variable: `callback`
  --> src/lib.rs:93:9
   |
93 |         callback: openraft::storage::LogFlushed<C>,
   |         ^^^^^^^^ help: if this is intentional, prefix it with an underscore: `_callback`

warning: unused variable: `log_id`
   --> src/lib.rs:100:9
    |
100 |         log_id: openraft::LogId<C::NodeId>,
    |         ^^^^^^ help: if this is intentional, prefix it with an underscore: `_log_id`

warning: unused variable: `log_id`
   --> src/lib.rs:107:9
    |
107 |         log_id: openraft::LogId<C::NodeId>,
    |         ^^^^^^ help: if this is intentional, prefix it with an underscore: `_log_id`

warning: `crash` (lib) generated 8 warnings
error: could not compile `crash` (lib); 8 warnings emitted

[lqd]

Looks like an RPITIT/ async fn ICE from nightly-2023-09-24 or something, could be involving drop tracking MIR as that's when it landed.

[pacak]

A smaller example

pub struct Vote;

pub trait RaftLogStorage {
    fn save_vote(&mut self, vote: &Vote) -> impl std::future::Future + Send;
}

struct X;
impl RaftLogStorage for X {
    fn save_vote(&mut self, vote: &Vote) -> impl std::future::Future<Output = Result<(), String>> {
        loop {}
        async {
            vote;
            Ok(())
        }
    }
}

[pacak]

searched toolchains nightly-2023-01-01 through nightly-2024-06-27


********************************************************************************
Regression in nightly-2023-10-15
********************************************************************************

fetching https://static.rust-lang.org/dist/2023-10-14/channel-rust-nightly-git-commit-hash.txt
nightly manifest 2023-10-14: 40 B / 40 B [================================================================================================================================================================================] 100.00 % 1.69 MB/s converted 2023-10-14 to fcab24817c72ffbd6ffb66d92b7ddc0d3ee4d2f0
fetching https://static.rust-lang.org/dist/2023-10-15/channel-rust-nightly-git-commit-hash.txt
nightly manifest 2023-10-15: 40 B / 40 B [==============================================================================================================================================================================] 100.00 % 461.52 KB/s converted 2023-10-15 to c543b6f3516767150af84d94c14a27b19d4b0291
looking for regression commit between 2023-10-14 and 2023-10-15
fetching (via remote github) commits from max(fcab24817c72ffbd6ffb66d92b7ddc0d3ee4d2f0, 2023-10-12) to c543b6f3516767150af84d94c14a27b19d4b0291
ending github query because we found starting sha: fcab24817c72ffbd6ffb66d92b7ddc0d3ee4d2f0
get_commits_between returning commits, len: 12
  commit[0] 2023-10-13: Auto merge of #116705 - pitaj:android-revert, r=workingjubilee
  commit[1] 2023-10-14: Auto merge of #115524 - RalfJung:misalign, r=wesleywiser
  commit[2] 2023-10-14: Auto merge of #115719 - tgross35:atomic-from-ptr, r=dtolnay
  commit[3] 2023-10-14: Auto merge of #116407 - Mark-Simulacrum:bootstrap-bump, r=onur-ozkan
  commit[4] 2023-10-14: Auto merge of #115822 - compiler-errors:stabilize-rpitit, r=jackh726
  commit[5] 2023-10-14: Auto merge of #116015 - EvanMerlock:master, r=oli-obk
  commit[6] 2023-10-14: Auto merge of #116702 - durin42:compress-debuginfo, r=compiler-errors
  commit[7] 2023-10-14: Auto merge of #116728 - matthiaskrgr:rollup-4xzcsnv, r=matthiaskrgr
  commit[8] 2023-10-14: Auto merge of #116727 - matthiaskrgr:rollup-3qqdrny, r=matthiaskrgr
  commit[9] 2023-10-14: Auto merge of #116264 - reez12g:issue-109728, r=Mark-Simulacrum
  commit[10] 2023-10-14: Auto merge of #116737 - matthiaskrgr:rollup-jftlnmt, r=matthiaskrgr
  commit[11] 2023-10-14: Auto merge of #116352 - Kobzol:rustc-driver-bolt, r=Mark-Simulacrum
ERROR: no CI builds available between fcab24817c72ffbd6ffb66d92b7ddc0d3ee4d2f0 and c543b6f3516767150af84d94c14a27b19d4b0291 within last 167 days

[matthiaskrgr]

Regression in nightly-2022-09-10

fetching (via remote github) commits from max(1120c5e, 2022-09-07) to 1d37ed6
ending github query because we found starting sha: 1120c5e
get_commits_between returning commits, len: 7
commit[0] 2022-09-08: Auto merge of #101437 - compiler-errors:erase-normalize-ordering, r=tmandry
commit[1] 2022-09-08: Auto merge of #101592 - compiler-errors:rollup-d2fya7z, r=compiler-errors
commit[2] 2022-09-09: Auto merge of #93873 - Stovent:big-ints, r=m-ou-se
commit[3] 2022-09-09: Auto merge of #101224 - compiler-errors:rpitit, r=oli-obk
commit[4] 2022-09-09: Auto merge of #101603 - matthiaskrgr:rollup-8y6kf20, r=matthiaskrgr
commit[5] 2022-09-09: Auto merge of #101527 - Kobzol:ci-update-llvm, r=Mark-Simulacrum
commit[6] 2022-09-09: Auto merge of #101611 - GuillaumeGomez:rollup-yw3qtug, r=GuillaumeGomez

probably #101224 ? 🤔

[pacak]

probably #101224 ? 🤔

Bisecting with git now. We'll see.

[pacak]

But yeah, #101224 looks sus.

[matthiaskrgr]

@pacak your bisection just points to the stabilization of the feature gate.
To go later, you will need to add the feature gates which allows the ICE again because otherwise rust would just reject the code with "can't do that without activating the feature" right away.

add something like this:

#![feature(return_position_impl_trait_in_trait)]
#![feature(async_fn_in_trait)]

[lqd]

add something like this:

#![feature(return_position_impl_trait_in_trait)]
#![feature(async_fn_in_trait)]

and if you do that you'll hit nightly-2023-09-24 where the ICE turns into regular errors on the OP (or more precisely, on one of its dependencies)

[pacak]

I added missing feature flags and got a new bisect

searched toolchains nightly-2022-01-01 through nightly-2024-06-27


********************************************************************************
Regression in nightly-2022-09-10
********************************************************************************

fetching https://static.rust-lang.org/dist/2022-09-09/channel-rust-nightly-git-commit-hash.txt
nightly manifest 2022-09-09: 40 B / 40 B [==============================================================================================================================================================================] 100.00 % 442.22 KB/s converted 2022-09-09 to 1120c5e01df508de64fe6642f22fadeb574afd6d
fetching https://static.rust-lang.org/dist/2022-09-10/channel-rust-nightly-git-commit-hash.txt
nightly manifest 2022-09-10: 40 B / 40 B [================================================================================================================================================================================] 100.00 % 1.73 MB/s converted 2022-09-10 to 1d37ed661a6922e7a167609b8cd7eb31e972b19b
looking for regression commit between 2022-09-09 and 2022-09-10
fetching (via remote github) commits from max(1120c5e01df508de64fe6642f22fadeb574afd6d, 2022-09-07) to 1d37ed661a6922e7a167609b8cd7eb31e972b19b
ending github query because we found starting sha: 1120c5e01df508de64fe6642f22fadeb574afd6d
get_commits_between returning commits, len: 7

commit[0] 2022-09-08: Auto merge of #101437 - compiler-errors:erase-normalize-ordering, r=tmandry
commit[1] 2022-09-08: Auto merge of #101592 - compiler-errors:rollup-d2fya7z, r=compiler-errors
commit[2] 2022-09-09: Auto merge of #93873 - Stovent:big-ints, r=m-ou-se
commit[3] 2022-09-09: Auto merge of #101224 - compiler-errors:rpitit, r=oli-obk
commit[4] 2022-09-09: Auto merge of #101603 - matthiaskrgr:rollup-8y6kf20, r=matthiaskrgr
commit[5] 2022-09-09: Auto merge of #101527 - Kobzol:ci-update-llvm, r=Mark-Simulacrum
commit[6] 2022-09-09: Auto merge of #101611 - GuillaumeGomez:rollup-yw3qtug, r=GuillaumeGomez
ERROR: no CI builds available between 1120c5e and 1d37ed6 within last 167 days

[pacak]

Hmm... my example starts failing at #101224, did it ever worked?

[lqd]

No, it's not a regression per se 😆

[spastorino]

This issue is duplicate of #112417, this PR #125285 prevents this from happening but as stated in the PR it regresses todo!(), unimplemented!() and panic!().

I'd need to investigate a little bit as I've seen in some tests indicators of some work being done and @lcnr is well aware of this and know better than I for sure.