ICE: resolution failed during building vtable representation

[alexjg]

Code

#![feature(associated_type_bounds)]

use std::convert::Infallible;

pub trait SuperTrait {
    type Error;

    fn do_thing(&self, data: &[u8]) -> Result<(), Self::Error>;
}

pub trait Trait:
    SuperTrait<Error: std::error::Error + Send + Sync + 'static>
    + Send
    + Sync
    + 'static
{
    fn do_extended_thing(&self) -> Result<(), Self::Error> {
        Ok(())
    }
}

impl<T> Trait for T
where
    T: SuperTrait + Send + Sync + Clone + 'static,
    <T as SuperTrait>::Error: std::error::Error + Send + Sync + 'static,
{
}

#[derive(Clone)]
pub struct SomeTrait<S> {
    pub member: S,
}

pub struct BoxedTrait {
    pub the_trait: Box<dyn Trait<Error = BoxedError>>,
}

pub struct BoxedError {
    error: Box<dyn std::error::Error + Send + Sync + 'static>,
}

impl std::fmt::Debug for BoxedError {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        write!(f, "{:?}", self.error)
    }
}

impl std::fmt::Display for BoxedError {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        write!(f, "{}", self.error)
    }
}

impl std::error::Error for BoxedError {
    fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
        Some(self)
    }

    fn cause(&self) -> Option<&dyn std::error::Error> {
        Some(self)
    }
}

impl BoxedTrait {
    pub fn new<S>(s: S) -> Self
    where
        S: Trait<Error = BoxedError>,
    {
        BoxedTrait {
            the_trait: Box::new(s),
        }
    }
}

impl<S> From<SomeTrait<S>> for BoxedTrait
where
    S: SuperTrait + Clone + Send + Sync + 'static,
    S::Error: std::error::Error + Send + Sync + 'static,
{
    fn from(other: SomeTrait<S>) -> Self {
        // Compilation succeeds if you replace this line with an `unimplemented!()`
        BoxedTrait::new(other)
    }
}

impl<S> SuperTrait for SomeTrait<S>
where
    S: SuperTrait + Clone + Send + Sync + 'static,
    S::Error: std::error::Error + Send + Sync + 'static,
{
    type Error = BoxedError;

    fn do_thing(&self, _data: &[u8]) -> Result<(), Self::Error> {
        Ok(())
    }
}

#[derive(Clone)]
struct Concrete {}

impl SuperTrait for Concrete {
    type Error = Infallible;

    fn do_thing(&self, _data: &[u8]) -> Result<(), Self::Error> {
        Ok(())
    }
}

impl From<Concrete> for BoxedTrait {
    fn from(c: Concrete) -> Self {
        Self::from(SomeTrait { member: c })
    }
}

Meta

rustc --version --verbose:

rustc 1.58.0-nightly (4961b107f 2021-11-04)
binary: rustc
commit-hash: 4961b107f204e15b26961eab0685df6be3ab03c6
commit-date: 2021-11-04
host: x86_64-unknown-linux-gnu
release: 1.58.0-nightly
LLVM version: 13.0.0

Error output

thread 'rustc' panicked at 'resolution failed during building vtable representation', compiler/rustc_trait_selection/src/traits/mod.rs:716:22
stack backtrace:
   0: rust_begin_unwind
             at /rustc/4961b107f204e15b26961eab0685df6be3ab03c6/library/std/src/panicking.rs:498:5
   1: core::panicking::panic_fmt
             at /rustc/4961b107f204e15b26961eab0685df6be3ab03c6/library/core/src/panicking.rs:106:14
   2: core::panicking::panic_display
             at /rustc/4961b107f204e15b26961eab0685df6be3ab03c6/library/core/src/panicking.rs:62:5
   3: core::option::expect_failed
             at /rustc/4961b107f204e15b26961eab0685df6be3ab03c6/library/core/src/option.rs:1637:5
   4: <core::iter::adapters::copied::Copied<core::slice::iter::Iter<rustc_span::def_id::DefId>> as core::iter::traits::iterator::Iterator>::fold::<(), core::iter::adapters::map::map_fold<rustc_span::def_id::DefId, rustc_middle::ty::vtable::VtblEntry, (), rustc_trait_selection::traits::vtable_entries::{closure#0}::{closure#1}, core::iter::traits::iterator::Iterator::for_each::call<rustc_middle::ty::vtable::VtblEntry, <alloc::vec::Vec<rustc_middle::ty::vtable::VtblEntry> as alloc::vec::spec_extend::SpecExtend<rustc_middle::ty::vtable::VtblEntry, core::iter::adapters::map::Map<core::iter::adapters::copied::Copied<core::slice::iter::Iter<rustc_span::def_id::DefId>>, rustc_trait_selection::traits::vtable_entries::{closure#0}::{closure#1}>>>::spec_extend::{closure#0}>::{closure#0}>::{closure#0}>
   5: rustc_trait_selection::traits::vtable_entries::{closure#0}
   6: rustc_trait_selection::traits::vtable_entries
   7: <rustc_query_system::dep_graph::graph::DepGraph<rustc_middle::dep_graph::dep_node::DepKind>>::with_task::<rustc_middle::ty::context::TyCtxt, rustc_middle::ty::sty::Binder<rustc_middle::ty::sty::TraitRef>, &[rustc_middle::ty::vtable::VtblEntry]>
   8: rustc_data_structures::stack::ensure_sufficient_stack::<(&[rustc_middle::ty::vtable::VtblEntry], rustc_query_system::dep_graph::graph::DepNodeIndex), rustc_query_system::query::plumbing::execute_job<rustc_query_impl::plumbing::QueryCtxt, rustc_middle::ty::sty::Binder<rustc_middle::ty::sty::TraitRef>, &[rustc_middle::ty::vtable::VtblEntry]>::{closure#3}>
   9: rustc_query_system::query::plumbing::get_query::<rustc_query_impl::queries::vtable_entries, rustc_query_impl::plumbing::QueryCtxt>
  10: <rustc_query_impl::Queries as rustc_middle::ty::query::QueryEngine>::vtable_entries
  11: rustc_middle::ty::vtable::vtable_allocation_provider
  12: <rustc_query_system::dep_graph::graph::DepGraph<rustc_middle::dep_graph::dep_node::DepKind>>::with_task::<rustc_middle::ty::context::TyCtxt, (&rustc_middle::ty::TyS, core::option::Option<rustc_middle::ty::sty::Binder<rustc_middle::ty::sty::ExistentialTraitRef>>), rustc_middle::mir::interpret::AllocId>
  13: rustc_data_structures::stack::ensure_sufficient_stack::<(rustc_middle::mir::interpret::AllocId, rustc_query_system::dep_graph::graph::DepNodeIndex), rustc_query_system::query::plumbing::execute_job<rustc_query_impl::plumbing::QueryCtxt, (&rustc_middle::ty::TyS, core::option::Option<rustc_middle::ty::sty::Binder<rustc_middle::ty::sty::ExistentialTraitRef>>), rustc_middle::mir::interpret::AllocId>::{closure#3}>
  14: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::plumbing::QueryCtxt, rustc_query_system::query::caches::DefaultCache<(&rustc_middle::ty::TyS, core::option::Option<rustc_middle::ty::sty::Binder<rustc_middle::ty::sty::ExistentialTraitRef>>), rustc_middle::mir::interpret::AllocId>>
  15: rustc_query_system::query::plumbing::get_query::<rustc_query_impl::queries::vtable_allocation, rustc_query_impl::plumbing::QueryCtxt>
  16: <rustc_query_impl::Queries as rustc_middle::ty::query::QueryEngine>::vtable_allocation
  17: rustc_middle::ty::vtable::vtable_allocation_provider
  18: <rustc_query_system::dep_graph::graph::DepGraph<rustc_middle::dep_graph::dep_node::DepKind>>::with_task::<rustc_middle::ty::context::TyCtxt, (&rustc_middle::ty::TyS, core::option::Option<rustc_middle::ty::sty::Binder<rustc_middle::ty::sty::ExistentialTraitRef>>), rustc_middle::mir::interpret::AllocId>
  19: rustc_data_structures::stack::ensure_sufficient_stack::<(rustc_middle::mir::interpret::AllocId, rustc_query_system::dep_graph::graph::DepNodeIndex), rustc_query_system::query::plumbing::execute_job<rustc_query_impl::plumbing::QueryCtxt, (&rustc_middle::ty::TyS, core::option::Option<rustc_middle::ty::sty::Binder<rustc_middle::ty::sty::ExistentialTraitRef>>), rustc_middle::mir::interpret::AllocId>::{closure#3}>
  20: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::plumbing::QueryCtxt, rustc_query_system::query::caches::DefaultCache<(&rustc_middle::ty::TyS, core::option::Option<rustc_middle::ty::sty::Binder<rustc_middle::ty::sty::ExistentialTraitRef>>), rustc_middle::mir::interpret::AllocId>>
  21: rustc_query_system::query::plumbing::get_query::<rustc_query_impl::queries::vtable_allocation, rustc_query_impl::plumbing::QueryCtxt>
  22: <rustc_query_impl::Queries as rustc_middle::ty::query::QueryEngine>::vtable_allocation
  23: rustc_codegen_ssa::meth::get_vtable::<rustc_codegen_llvm::context::CodegenCx>
  24: rustc_codegen_ssa::base::unsize_ptr::<rustc_codegen_llvm::builder::Builder>
  25: rustc_codegen_ssa::base::unsize_ptr::<rustc_codegen_llvm::builder::Builder>
  26: rustc_codegen_ssa::base::unsize_ptr::<rustc_codegen_llvm::builder::Builder>
  27: <rustc_codegen_ssa::mir::FunctionCx<rustc_codegen_llvm::builder::Builder>>::codegen_rvalue_operand
  28: rustc_codegen_ssa::mir::codegen_mir::<rustc_codegen_llvm::builder::Builder>
  29: rustc_codegen_llvm::base::compile_codegen_unit::module_codegen
  30: <rustc_query_system::dep_graph::graph::DepGraph<rustc_middle::dep_graph::dep_node::DepKind>>::with_task::<rustc_middle::ty::context::TyCtxt, rustc_span::symbol::Symbol, rustc_codegen_ssa::ModuleCodegen<rustc_codegen_llvm::ModuleLlvm>>
  31: rustc_codegen_llvm::base::compile_codegen_unit
  32: rustc_codegen_ssa::base::codegen_crate::<rustc_codegen_llvm::LlvmCodegenBackend>
  33: <rustc_codegen_llvm::LlvmCodegenBackend as rustc_codegen_ssa::traits::backend::CodegenBackend>::codegen_crate
  34: <rustc_session::session::Session>::time::<alloc::boxed::Box<dyn core::any::Any>, rustc_interface::passes::start_codegen::{closure#0}>
  35: <rustc_interface::passes::QueryContext>::enter::<<rustc_interface::queries::Queries>::ongoing_codegen::{closure#0}::{closure#0}, core::result::Result<alloc::boxed::Box<dyn core::any::Any>, rustc_errors::ErrorReported>>
  36: <rustc_interface::queries::Queries>::ongoing_codegen
  37: <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::ErrorReported>>
  38: rustc_span::with_source_map::<core::result::Result<(), rustc_errors::ErrorReported>, rustc_interface::interface::create_compiler_and_run<core::result::Result<(), rustc_errors::ErrorReported>, rustc_driver::run_compiler::{closure#1}>::{closure#0}>
  39: <scoped_tls::ScopedKey<rustc_span::SessionGlobals>>::set::<rustc_interface::util::setup_callbacks_and_run_in_thread_pool_with_globals<rustc_interface::interface::run_compiler<core::result::Result<(), rustc_errors::ErrorReported>, rustc_driver::run_compiler::{closure#1}>::{closure#0}, core::result::Result<(), rustc_errors::ErrorReported>>::{closure#0}::{closure#0}, core::result::Result<(), rustc_errors::ErrorReported>>
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.

error: internal compiler error: unexpected panic

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 1.58.0-nightly (4961b107f 2021-11-04) running on x86_64-unknown-linux-gnu

note: compiler flags: -C embed-bitcode=no -C debuginfo=2 -C linker=/usr/bin/clang -C incremental -C link-arg=-fuse-ld=lld --crate-type lib

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

query stack during panic:
#0 [vtable_entries] finding all vtable entries for trait core::fmt::Debug
#1 [vtable_allocation] vtable const allocation for <SomeTrait<Concrete> as core::fmt::Debug>
#2 [vtable_allocation] vtable const allocation for <SomeTrait<Concrete> as Trait>
end of query stack
error: internal compiler error: Encountered error `Unimplemented` selecting `Binder(<SomeTrait<Concrete> as std::fmt::Debug>, [])` during codegen
  |
  = note: delayed at compiler/rustc_trait_selection/src/traits/codegen.rs:68:32

thread 'rustc' panicked at 'no errors encountered even though `delay_span_bug` issued', compiler/rustc_errors/src/lib.rs:1166:13
stack backtrace:
   0:     0x7f79394be80c - std::backtrace_rs::backtrace::libunwind::trace::h793e05efd273d0f4
                               at /rustc/4961b107f204e15b26961eab0685df6be3ab03c6/library/std/src/../../backtrace/src/backtrace/libunwind.rs:93:5
   1:     0x7f79394be80c - std::backtrace_rs::backtrace::trace_unsynchronized::h640b7b86ff610c77
                               at /rustc/4961b107f204e15b26961eab0685df6be3ab03c6/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5
   2:     0x7f79394be80c - std::sys_common::backtrace::_print_fmt::h362fa2a4f354f877
                               at /rustc/4961b107f204e15b26961eab0685df6be3ab03c6/library/std/src/sys_common/backtrace.rs:67:5
   3:     0x7f79394be80c - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::hf439e5ed84c74abd
                               at /rustc/4961b107f204e15b26961eab0685df6be3ab03c6/library/std/src/sys_common/backtrace.rs:46:22
   4:     0x7f793951ba4c - core::fmt::write::h72801a82c94e6ff1
                               at /rustc/4961b107f204e15b26961eab0685df6be3ab03c6/library/core/src/fmt/mod.rs:1149:17
   5:     0x7f79394af035 - std::io::Write::write_fmt::h5562a8b6da0f0339
                               at /rustc/4961b107f204e15b26961eab0685df6be3ab03c6/library/std/src/io/mod.rs:1697:15
   6:     0x7f79394c1a60 - std::sys_common::backtrace::_print::hb29ddd998d02631c
                               at /rustc/4961b107f204e15b26961eab0685df6be3ab03c6/library/std/src/sys_common/backtrace.rs:49:5
   7:     0x7f79394c1a60 - std::sys_common::backtrace::print::h81965e3d7c90fbb6
                               at /rustc/4961b107f204e15b26961eab0685df6be3ab03c6/library/std/src/sys_common/backtrace.rs:36:9
   8:     0x7f79394c1a60 - std::panicking::default_hook::{{closure}}::h84db205ab6674b38
                               at /rustc/4961b107f204e15b26961eab0685df6be3ab03c6/library/std/src/panicking.rs:211:50
   9:     0x7f79394c160b - std::panicking::default_hook::h1bf8bb4159936bca
                               at /rustc/4961b107f204e15b26961eab0685df6be3ab03c6/library/std/src/panicking.rs:228:9
  10:     0x7f7939c56491 - rustc_driver[e620c7401644acc4]::DEFAULT_HOOK::{closure#0}::{closure#0}
  11:     0x7f79394c2279 - std::panicking::rust_panic_with_hook::hf8e86850fbbd03b1
                               at /rustc/4961b107f204e15b26961eab0685df6be3ab03c6/library/std/src/panicking.rs:610:17
  12:     0x7f79394c1d30 - std::panicking::begin_panic_handler::{{closure}}::h590a0d6060ff866e
                               at /rustc/4961b107f204e15b26961eab0685df6be3ab03c6/library/std/src/panicking.rs:502:13
  13:     0x7f79394becc4 - std::sys_common::backtrace::__rust_end_short_backtrace::h260b8bd1c848a03c
                               at /rustc/4961b107f204e15b26961eab0685df6be3ab03c6/library/std/src/sys_common/backtrace.rs:139:18
  14:     0x7f79394c1c99 - rust_begin_unwind
                               at /rustc/4961b107f204e15b26961eab0685df6be3ab03c6/library/std/src/panicking.rs:498:5
  15:     0x7f79394871a1 - core::panicking::panic_fmt::h7b8580d81fcbbacd
                               at /rustc/4961b107f204e15b26961eab0685df6be3ab03c6/library/core/src/panicking.rs:106:14
  16:     0x7f793ad527bc - core[cc79c391059f8e46]::panicking::panic_display::<&str>
  17:     0x7f793c3f3446 - <rustc_errors[c8a333c965fedc03]::HandlerInner>::flush_delayed
  18:     0x7f793c3f1b5d - <rustc_errors[c8a333c965fedc03]::HandlerInner as core[cc79c391059f8e46]::ops::drop::Drop>::drop
  19:     0x7f793bace5c6 - core[cc79c391059f8e46]::ptr::drop_in_place::<rustc_session[cec017cef00f19c9]::parse::ParseSess>
  20:     0x7f793bad043a - <alloc[9a4bc13598ff604f]::rc::Rc<rustc_session[cec017cef00f19c9]::session::Session> as core[cc79c391059f8e46]::ops::drop::Drop>::drop
  21:     0x7f793baac43d - core[cc79c391059f8e46]::ptr::drop_in_place::<rustc_interface[f89f8228a4e35bc7]::interface::Compiler>
  22:     0x7f793baac3a5 - rustc_span[2d5555579096f1fe]::with_source_map::<core[cc79c391059f8e46]::result::Result<(), rustc_errors[c8a333c965fedc03]::ErrorReported>, rustc_interface[f89f8228a4e35bc7]::interface::create_compiler_and_run<core[cc79c391059f8e46]::result::Result<(), rustc_errors[c8a333c965fedc03]::ErrorReported>, rustc_driver[e620c7401644acc4]::run_compiler::{closure#1}>::{closure#0}>
  23:     0x7f793babc810 - <scoped_tls[3fea4c3dcac147b1]::ScopedKey<rustc_span[2d5555579096f1fe]::SessionGlobals>>::set::<rustc_interface[f89f8228a4e35bc7]::util::setup_callbacks_and_run_in_thread_pool_with_globals<rustc_interface[f89f8228a4e35bc7]::interface::run_compiler<core[cc79c391059f8e46]::result::Result<(), rustc_errors[c8a333c965fedc03]::ErrorReported>, rustc_driver[e620c7401644acc4]::run_compiler::{closure#1}>::{closure#0}, core[cc79c391059f8e46]::result::Result<(), rustc_errors[c8a333c965fedc03]::ErrorReported>>::{closure#0}::{closure#0}, core[cc79c391059f8e46]::result::Result<(), rustc_errors[c8a333c965fedc03]::ErrorReported>>
  24:     0x7f793baae795 - std[a5529df289459975]::sys_common::backtrace::__rust_begin_short_backtrace::<rustc_interface[f89f8228a4e35bc7]::util::setup_callbacks_and_run_in_thread_pool_with_globals<rustc_interface[f89f8228a4e35bc7]::interface::run_compiler<core[cc79c391059f8e46]::result::Result<(), rustc_errors[c8a333c965fedc03]::ErrorReported>, rustc_driver[e620c7401644acc4]::run_compiler::{closure#1}>::{closure#0}, core[cc79c391059f8e46]::result::Result<(), rustc_errors[c8a333c965fedc03]::ErrorReported>>::{closure#0}, core[cc79c391059f8e46]::result::Result<(), rustc_errors[c8a333c965fedc03]::ErrorReported>>
  25:     0x7f793baaa902 - <<std[a5529df289459975]::thread::Builder>::spawn_unchecked<rustc_interface[f89f8228a4e35bc7]::util::setup_callbacks_and_run_in_thread_pool_with_globals<rustc_interface[f89f8228a4e35bc7]::interface::run_compiler<core[cc79c391059f8e46]::result::Result<(), rustc_errors[c8a333c965fedc03]::ErrorReported>, rustc_driver[e620c7401644acc4]::run_compiler::{closure#1}>::{closure#0}, core[cc79c391059f8e46]::result::Result<(), rustc_errors[c8a333c965fedc03]::ErrorReported>>::{closure#0}, core[cc79c391059f8e46]::result::Result<(), rustc_errors[c8a333c965fedc03]::ErrorReported>>::{closure#1} as core[cc79c391059f8e46]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  26:     0x7f79394cd563 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::h771719d52c343434
                               at /rustc/4961b107f204e15b26961eab0685df6be3ab03c6/library/alloc/src/boxed.rs:1691:9
  27:     0x7f79394cd563 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::hf441746dfa4b0f57
                               at /rustc/4961b107f204e15b26961eab0685df6be3ab03c6/library/alloc/src/boxed.rs:1691:9
  28:     0x7f79394cd563 - std::sys::unix::thread::Thread::new::thread_start::hfd168f9d312b29ca
                               at /rustc/4961b107f204e15b26961eab0685df6be3ab03c6/library/std/src/sys/unix/thread.rs:106:17
  29:     0x7f79393d4259 - start_thread
  30:     0x7f79392e95e3 - __GI___clone
  31:                0x0 - <unknown>

error: internal compiler error: unexpected panic

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 1.58.0-nightly (4961b107f 2021-11-04) running on x86_64-unknown-linux-gnu

note: compiler flags: -C embed-bitcode=no -C debuginfo=2 -C linker=/usr/bin/clang -C incremental -C link-arg=-fuse-ld=lld --crate-type lib

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

query stack during panic:
end of query stack
thread panicked while panicking. aborting.
error: could not compile `compiler-error`

Caused by:
  process didn't exit successfully: `rustc --crate-name compiler_error --edition=2021 src/lib.rs --error-format=json --json=diagnostic-rendered-ansi --crate-type lib --emit=dep-info,metadata,link -C embed-bitcode=no -C debuginfo=2 -C metadata=a7940e4ff600f0e3 -C extra-filename=-a7940e4ff600f0e3 --out-dir /home/alex/Projects/rust/compiler-error/target/debug/deps -C linker=/usr/bin/clang -C incremental=/home/alex/Projects/rust/compiler-error/target/debug/incremental -L dependency=/home/alex/Projects/rust/compiler-error/target/debug/deps --extern async_trait=/home/alex/Projects/rust/compiler-error/target/debug/deps/libasync_trait-4d187e561976744c.so -Clink-arg=-fuse-ld=lld` (signal: 4, SIGILL: illegal instruction)

[sofia-snow]

Can reproduce on the playground, but curiously adding fn main() {} does not trigger the ICE.

[hellow554]

Reduced to:

#![feature(associated_type_bounds)]

trait TError: std::fmt::Debug {}
impl TError for () {}

trait SuperTrait {
    type Error;
}

trait Trait: SuperTrait<Error: TError> {}

impl<T> Trait for T
where
    T: SuperTrait,
    <T as SuperTrait>::Error: TError,
{
}

struct SomeTrait<S>(S);
struct BoxedTrait(Box<dyn Trait<Error = ()>>);

impl<S: 'static> From<SomeTrait<S>> for BoxedTrait {
    fn from(other: SomeTrait<S>) -> Self {
        Self(Box::new(other))
    }
}

impl<S> SuperTrait for SomeTrait<S> {
    type Error = ();
}

impl From<()> for BoxedTrait {
    fn from(c: ()) -> Self {
        Self::from(SomeTrait(c))
    }
}

fn main() {
    let _: BoxedTrait = ().into();
}

regressed commit: f9b95f9

cc #86461 @crlf0710

[JohnTitor]

Triage: This seems to be fixed since today's nightly.
@rustbot labels: +E-needs-test