ICE: has escaping bound vars, so it cannot be wrapped in a dummy binder

[matthiaskrgr]

auto-reduced (treereduce-rust):

struct QualifiedError<E>(E);

impl<E, T> From<E> for QualifiedError<T>
where
    E:,
    for<'any> &'any mut (): Clone,
{
}

fn infallible() -> Result<(), std::convert::Infallible> {
    Ok(())
}

fn main() {
    let x = || -> Result<_, QualifiedError<_>> {
        infallible()?;
        Ok(())
    };
}

original:

struct QualifiedError<E>(E);

impl<E, T> From<E> for QualifiedError<T>
where
    E: std::error::Error,
    for<'any> &'any mut (): Clone,
{
    fn from(e: E) -> QualifiedError<T> impl TensorOp<Item = ()> + 'a
}

fn infallible() -> Result<(), std::convert::Infallible> {
    Ok(())
}

fn main() {
    let x = || -> Result<_, QualifiedError<_>> {
        infallible()?;
        Ok(())
        //~^ ERROR type annotations needed
    };
}

Version information

rustc 1.88.0-nightly (b8005bff3 2025-04-20)
binary: rustc
commit-hash: b8005bff3248cfc6e327faf4fa631ac49bb49ba9
commit-date: 2025-04-20
host: x86_64-unknown-linux-gnu
release: 1.88.0-nightly
LLVM version: 20.1.2

Possibly related line of code:

rust/compiler/rustc_middle/src/ty/predicate.rs

Lines 504 to 516 in b8005bf

	tcx.mk_predicate(from.map_bound(|clause| PredicateKind::Clause(clause))).expect_clause()
	}
	}
	impl<'tcx> UpcastFrom<TyCtxt<'tcx>, TraitRef<'tcx>> for Predicate<'tcx> {
	fn upcast_from(from: TraitRef<'tcx>, tcx: TyCtxt<'tcx>) -> Self {
	ty::Binder::dummy(from).upcast(tcx)
	}
	}
	impl<'tcx> UpcastFrom<TyCtxt<'tcx>, TraitRef<'tcx>> for Clause<'tcx> {
	fn upcast_from(from: TraitRef<'tcx>, tcx: TyCtxt<'tcx>) -> Self {
	let p: Predicate<'tcx> = from.upcast(tcx);

Command:
/home/matthias/.rustup/toolchains/master/bin/rustc

Program output

error[E0119]: conflicting implementations of trait `From<QualifiedError<_>>` for type `QualifiedError<_>`
 --> /tmp/icemaker_global_tempdir.fJzGYJtIgRNC/rustc_testrunner_tmpdir_reporting.kWZMAN4HkmBg/mvce.rs:3:1
  |
3 | / impl<E, T> From<E> for QualifiedError<T>
4 | | where
5 | |     E:,
6 | |     for<'any> &'any mut (): Clone,
  | |__________________________________^
  |
  = note: conflicting implementation in crate `core`:
          - impl<T> From<T> for T;
  = note: upstream crates may add a new impl of trait `std::clone::Clone` for type `&'any mut ()` in future versions


thread 'rustc' panicked at compiler/rustc_middle/src/ty/predicate.rs:510:9:
`<&'any mut () as std::convert::From<std::convert::Infallible>>` has escaping bound vars, so it cannot be wrapped in a dummy binder.
stack backtrace:
   0:     0x7b8c086bfa13 - <std::sys::backtrace::BacktraceLock::print::DisplayBacktrace as core::fmt::Display>::fmt::hd3d6a01c34b68e33
   1:     0x7b8c08e05b07 - core::fmt::write::hc8609d2830ea7209
   2:     0x7b8c0a2a2b11 - std::io::Write::write_fmt::h5803b161d154e6bb
   3:     0x7b8c086bf872 - std::sys::backtrace::BacktraceLock::print::h7d1ba71c4ac8a197
   4:     0x7b8c086c31ea - std::panicking::default_hook::{{closure}}::h81636b35691bb80d
   5:     0x7b8c086c2d6f - std::panicking::default_hook::h3d6df3ec9a366961
   6:     0x7b8c077439a3 - std[a4b1c5db45b5369]::panicking::update_hook::<alloc[a753183b20116edd]::boxed::Box<rustc_driver_impl[64822a3bbb8e5a99]::install_ice_hook::{closure#1}>>::{closure#0}
   7:     0x7b8c086c3a63 - std::panicking::rust_panic_with_hook::hc0072f606cfb3c45
   8:     0x7b8c086c375a - std::panicking::begin_panic_handler::{{closure}}::h9dfbf037bfb6d7d4
   9:     0x7b8c086bfee9 - std::sys::backtrace::__rust_end_short_backtrace::hdeb7489c831217fd
  10:     0x7b8c086c341d - __rustc[d3657d69ef8eb27f]::rust_begin_unwind
  11:     0x7b8c05086440 - core::panicking::panic_fmt::h3cd888558dd93878
  12:     0x7b8c0abff2ef - <rustc_middle[105e55ff3e6629a7]::ty::predicate::Predicate as rustc_type_ir[4f792327c2094bfd]::upcast::UpcastFrom<rustc_middle[105e55ff3e6629a7]::ty::context::TyCtxt, rustc_type_ir[4f792327c2094bfd]::predicate::TraitRef<rustc_middle[105e55ff3e6629a7]::ty::context::TyCtxt>>>::upcast_from.cold
  13:     0x7b8c0858bd4b - <rustc_infer[bae4521fee5667b7]::infer::InferCtxt as rustc_trait_selection[b7ee8536d1549794]::infer::InferCtxtExt>::type_implements_trait::<[rustc_middle[105e55ff3e6629a7]::ty::Ty; 2usize]>
  14:     0x7b8c084ed23c - <rustc_trait_selection[b7ee8536d1549794]::error_reporting::TypeErrCtxt>::try_conversion_context
  15:     0x7b8c084e7670 - <rustc_trait_selection[b7ee8536d1549794]::error_reporting::TypeErrCtxt>::report_selection_error
  16:     0x7b8c085484fe - <rustc_trait_selection[b7ee8536d1549794]::error_reporting::TypeErrCtxt>::report_fulfillment_errors
  17:     0x7b8c08f26b48 - <rustc_hir_typeck[d228e38d1a961d74]::fn_ctxt::FnCtxt>::try_structurally_resolve_type
  18:     0x7b8c08f3bbf8 - <rustc_hir_typeck[d228e38d1a961d74]::coercion::CoerceMany<rustc_hir[409be6f9bedee7de]::hir::Arm>>::coerce_inner::<<rustc_hir_typeck[d228e38d1a961d74]::fn_ctxt::FnCtxt>::check_expr_match::{closure#0}::{closure#1}>
  19:     0x7b8c09ba9934 - <rustc_hir_typeck[d228e38d1a961d74]::fn_ctxt::FnCtxt>::check_expr_with_expectation_and_args
  20:     0x7b8c09b9b17c - <rustc_hir_typeck[d228e38d1a961d74]::fn_ctxt::FnCtxt>::check_expr_block
  21:     0x7b8c09ba5f7f - <rustc_hir_typeck[d228e38d1a961d74]::fn_ctxt::FnCtxt>::check_expr_with_expectation_and_args
  22:     0x7b8c09401f84 - rustc_hir_typeck[d228e38d1a961d74]::check::check_fn
  23:     0x7b8c09a9b0c3 - <rustc_hir_typeck[d228e38d1a961d74]::fn_ctxt::FnCtxt>::check_expr_closure
  24:     0x7b8c09baad0e - <rustc_hir_typeck[d228e38d1a961d74]::fn_ctxt::FnCtxt>::check_expr_with_expectation_and_args
  25:     0x7b8c08efbbc9 - <rustc_hir_typeck[d228e38d1a961d74]::fn_ctxt::FnCtxt>::check_decl
  26:     0x7b8c09b9c255 - <rustc_hir_typeck[d228e38d1a961d74]::fn_ctxt::FnCtxt>::check_expr_block
  27:     0x7b8c09ba5f7f - <rustc_hir_typeck[d228e38d1a961d74]::fn_ctxt::FnCtxt>::check_expr_with_expectation_and_args
  28:     0x7b8c09401f84 - rustc_hir_typeck[d228e38d1a961d74]::check::check_fn
  29:     0x7b8c093ef49a - rustc_hir_typeck[d228e38d1a961d74]::typeck_with_inspect::{closure#0}
  30:     0x7b8c093ee1b6 - rustc_query_impl[f9677782d554bbe0]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[f9677782d554bbe0]::query_impl::typeck::dynamic_query::{closure#2}::{closure#0}, rustc_middle[105e55ff3e6629a7]::query::erase::Erased<[u8; 8usize]>>
  31:     0x7b8c09085e2c - rustc_query_system[6c94265d9bb07c02]::query::plumbing::try_execute_query::<rustc_query_impl[f9677782d554bbe0]::DynamicConfig<rustc_data_structures[d346d185fbcc034d]::vec_cache::VecCache<rustc_span[f33b24d4c40821a8]::def_id::LocalDefId, rustc_middle[105e55ff3e6629a7]::query::erase::Erased<[u8; 8usize]>, rustc_query_system[6c94265d9bb07c02]::dep_graph::graph::DepNodeIndex>, false, false, false>, rustc_query_impl[f9677782d554bbe0]::plumbing::QueryCtxt, false>
  32:     0x7b8c0908588b - rustc_query_impl[f9677782d554bbe0]::query_impl::typeck::get_query_non_incr::__rust_end_short_backtrace
  33:     0x7b8c09084308 - rustc_hir_analysis[c91f60f1cedeb164]::check_crate
  34:     0x7b8c097ba674 - rustc_interface[87387720858aeda]::passes::run_required_analyses
  35:     0x7b8c09a1e41e - rustc_interface[87387720858aeda]::passes::analysis
  36:     0x7b8c09a1e3ed - rustc_query_impl[f9677782d554bbe0]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[f9677782d554bbe0]::query_impl::analysis::dynamic_query::{closure#2}::{closure#0}, rustc_middle[105e55ff3e6629a7]::query::erase::Erased<[u8; 0usize]>>
  37:     0x7b8c09e0db3d - rustc_query_system[6c94265d9bb07c02]::query::plumbing::try_execute_query::<rustc_query_impl[f9677782d554bbe0]::DynamicConfig<rustc_query_system[6c94265d9bb07c02]::query::caches::SingleCache<rustc_middle[105e55ff3e6629a7]::query::erase::Erased<[u8; 0usize]>>, false, false, false>, rustc_query_impl[f9677782d554bbe0]::plumbing::QueryCtxt, false>
  38:     0x7b8c09e0d838 - rustc_query_impl[f9677782d554bbe0]::query_impl::analysis::get_query_non_incr::__rust_end_short_backtrace
  39:     0x7b8c0a11ee3e - rustc_interface[87387720858aeda]::passes::create_and_enter_global_ctxt::<core[89ea4ceba863dd14]::option::Option<rustc_interface[87387720858aeda]::queries::Linker>, rustc_driver_impl[64822a3bbb8e5a99]::run_compiler::{closure#0}::{closure#2}>::{closure#2}::{closure#0}
  40:     0x7b8c09f55404 - rustc_interface[87387720858aeda]::interface::run_compiler::<(), rustc_driver_impl[64822a3bbb8e5a99]::run_compiler::{closure#0}>::{closure#1}
  41:     0x7b8c09cecd68 - std[a4b1c5db45b5369]::sys::backtrace::__rust_begin_short_backtrace::<rustc_interface[87387720858aeda]::util::run_in_thread_with_globals<rustc_interface[87387720858aeda]::util::run_in_thread_pool_with_globals<rustc_interface[87387720858aeda]::interface::run_compiler<(), rustc_driver_impl[64822a3bbb8e5a99]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>
  42:     0x7b8c09ced1b4 - <<std[a4b1c5db45b5369]::thread::Builder>::spawn_unchecked_<rustc_interface[87387720858aeda]::util::run_in_thread_with_globals<rustc_interface[87387720858aeda]::util::run_in_thread_pool_with_globals<rustc_interface[87387720858aeda]::interface::run_compiler<(), rustc_driver_impl[64822a3bbb8e5a99]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>::{closure#1} as core[89ea4ceba863dd14]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  43:     0x7b8c09cee5b7 - std::sys::pal::unix::thread::Thread::new::thread_start::h763527da6478f178
  44:     0x7b8c03ca370a - <unknown>
  45:     0x7b8c03d27aac - <unknown>
  46:                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 1.88.0-nightly (b8005bff3 2025-04-20) running on x86_64-unknown-linux-gnu

query stack during panic:
#0 [typeck] type-checking `main`
#1 [analysis] running analysis passes on this crate
end of query stack
error: aborting due to 1 previous error

For more information about this error, try `rustc --explain E0119`.

[matthiaskrgr]

struct a;
impl From for a where for<'any> &'any mut (): Clone {}
fn b() -> Result<(), std::convert::Infallible> {
    || -> Result<_, a> { b()? }
}

[matthiaskrgr]

bisects to #137245