[ICE]: upvar_tys called before capture types are inferred

[matthiaskrgr]

auto-reduced (treereduce-rust):

//@compile-flags: --edition=2024 -Znext-solver=globally
trait NodeImpl {}
struct Wrap<F, P>(F, P);
impl<F, P> Wrap<F, P> {
    fn new(_: F) -> Self {
        loop {}
    }
}

impl<F, A> NodeImpl for Wrap<F, (A,)> where F: std::mem::TransmuteFrom<()> {}
fn trigger_ice() {
    let _: &dyn NodeImpl = &Wrap::<_, (i128,)>::new(async |_: &(), i128| 0);
}

original:

#![feature(transmutability)]
//@compile-flags: --edition=2024 -Znext-solver=globally
trait NodeImpl {}
struct Wrap<F, P>(F, P);
impl<F, P> Wrap<F, P> {
    fn new(_: F) -> Self {
        loop {}
    }
}

impl<F, A> NodeImpl for Wrap<F, (A,)> where F: std::mem::TransmuteFrom<()> {}
fn trigger_ice() {
    let _: &dyn NodeImpl = &Wrap::<_, (i128,)>::new(async |_: &(), i128| 0);
}

fn main() {}

Version information

rustc 1.96.0-nightly (d2218f5f5 2026-03-03)
binary: rustc
commit-hash: d2218f5f5ca3f502772ec4cb69fc2ee44e096512
commit-date: 2026-03-03
host: x86_64-unknown-linux-gnu
release: 1.96.0-nightly
LLVM version: 22.1.0

Possibly related line of code:

rust/compiler/rustc_type_ir/src/ty_kind/closure.rs

Lines 268 to 280 in d2218f5

	#[inline]
	pub fn upvar_tys(self) -> I::Tys {
	match self.tupled_upvars_ty().kind() {
	ty::Error(_) => Default::default(),
	ty::Tuple(..) => self.tupled_upvars_ty().tuple_fields(),
	ty::Infer(_) => panic!("upvar_tys called before capture types are inferred"),
	ty => panic!("Unexpected representation of upvar types tuple {:?}", ty),
	}
	}
	#[inline]
	pub fn tupled_upvars_ty(self) -> I::Ty {

Command:
/home/matthias/.rustup/toolchains/master/bin/rustc --edition=2024 -Znext-solver=globally

Program output

error[E0601]: `main` function not found in crate `mvce`
  --> /tmp/icemaker_global_tempdir.mc5ONQjhTIgY/rustc_testrunner_tmpdir_reporting.h8jdz2dsuD50/mvce.rs:12:2
   |
12 | }
   |  ^ consider adding a `main` function to `/tmp/icemaker_global_tempdir.mc5ONQjhTIgY/rustc_testrunner_tmpdir_reporting.h8jdz2dsuD50/mvce.rs`

error[E0658]: use of unstable library feature `transmutability`
 --> /tmp/icemaker_global_tempdir.mc5ONQjhTIgY/rustc_testrunner_tmpdir_reporting.h8jdz2dsuD50/mvce.rs:9:48
  |
9 | impl<F, A> NodeImpl for Wrap<F, (A,)> where F: std::mem::TransmuteFrom<()> {}
  |                                                ^^^^^^^^^^^^^^^^^^^^^^^^^^^
  |
  = note: see issue #99571 <https://github.com/rust-lang/rust/issues/99571> for more information
  = help: add `#![feature(transmutability)]` to the crate attributes to enable
  = note: this compiler was built on 2026-03-03; consider upgrading it if it is out of date

error[E0658]: use of unstable library feature `transmutability`
  --> /tmp/icemaker_global_tempdir.mc5ONQjhTIgY/rustc_testrunner_tmpdir_reporting.h8jdz2dsuD50/mvce.rs:9:48
   |
 9 | impl<F, A> NodeImpl for Wrap<F, (A,)> where F: std::mem::TransmuteFrom<()> {}
   |                                                ^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = help: add `#![feature(transmutability)]` to the crate attributes to enable
   = note: this compiler was built on 2026-03-03; consider upgrading it if it is out of date
note: required by a bound in `TransmuteFrom`
  --> /home/matthias/.rustup/toolchains/master/lib/rustlib/src/rust/library/core/src/mem/transmutability.rs:86:1
   |
86 | #[unstable_feature_bound(transmutability)]
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `TransmuteFrom`
...
91 | pub unsafe trait TransmuteFrom<Src, const ASSUME: Assume = { Assume::NOTHING }>
   |                  ------------- required by a bound in this trait


thread 'rustc' (910046) panicked at /rustc-dev/d2218f5f5ca3f502772ec4cb69fc2ee44e096512/compiler/rustc_type_ir/src/ty_kind/closure.rs:274:29:
upvar_tys called before capture types are inferred
stack backtrace:
   0:     0x7fc826962aab - <<std[76599d2169901dc8]::sys::backtrace::BacktraceLock>::print::DisplayBacktrace as core[d5ffb84325ed5c2a]::fmt::Display>::fmt
   1:     0x7fc8270228c8 - core[d5ffb84325ed5c2a]::fmt::write
   2:     0x7fc826979ab6 - <std[76599d2169901dc8]::sys::stdio::unix::Stderr as std[76599d2169901dc8]::io::Write>::write_fmt
   3:     0x7fc826938b88 - std[76599d2169901dc8]::panicking::default_hook::{closure#0}
   4:     0x7fc826955f13 - std[76599d2169901dc8]::panicking::default_hook
   5:     0x7fc8259424cc - std[76599d2169901dc8]::panicking::update_hook::<alloc[f847baa7d3d2ac55]::boxed::Box<rustc_driver_impl[ffd722fd6c32666a]::install_ice_hook::{closure#1}>>::{closure#0}
   6:     0x7fc8269561f2 - std[76599d2169901dc8]::panicking::panic_with_hook
   7:     0x7fc826938c7a - std[76599d2169901dc8]::panicking::panic_handler::{closure#0}
   8:     0x7fc82692f979 - std[76599d2169901dc8]::sys::backtrace::__rust_end_short_backtrace::<std[76599d2169901dc8]::panicking::panic_handler::{closure#0}, !>
   9:     0x7fc82693a6ad - __rustc[7dea9537d06e225e]::rust_begin_unwind
  10:     0x7fc82351975c - core[d5ffb84325ed5c2a]::panicking::panic_fmt
  11:     0x7fc827951cdd - rustc_ty_utils[23782f25fc8ac972]::layout::layout_of_uncached
  12:     0x7fc8279451c9 - rustc_ty_utils[23782f25fc8ac972]::layout::layout_of
  13:     0x7fc82794512f - rustc_query_impl[89f9236b2ac04da0]::query_impl::layout_of::invoke_provider_fn::__rust_begin_short_backtrace
  14:     0x7fc82794402a - rustc_query_impl[89f9236b2ac04da0]::execution::try_execute_query::<rustc_middle[7c9cbe436035c5a4]::query::caches::DefaultCache<rustc_middle[7c9cbe436035c5a4]::ty::PseudoCanonicalInput<rustc_middle[7c9cbe436035c5a4]::ty::Ty>, rustc_middle[7c9cbe436035c5a4]::query::erase::ErasedData<[u8; 16usize]>>, false>
  15:     0x7fc827943c5e - rustc_query_impl[89f9236b2ac04da0]::query_impl::layout_of::execute_query_non_incr::__rust_end_short_backtrace
  16:     0x7fc826885dac - rustc_transmute[a3106bcd6ed1d712]::layout::rustc::layout_of
  17:     0x7fc826883e52 - <rustc_transmute[a3106bcd6ed1d712]::layout::tree::Tree<rustc_transmute[a3106bcd6ed1d712]::layout::rustc::Def, rustc_middle[7c9cbe436035c5a4]::ty::region::Region, rustc_middle[7c9cbe436035c5a4]::ty::Ty>>::from_ty
  18:     0x7fc82687d754 - <rustc_transmute[a3106bcd6ed1d712]::rustc::TransmuteTypeEnv>::is_transmutable
  19:     0x7fc8267b6415 - <rustc_trait_selection[502c21a12406236f]::solve::delegate::SolverDelegate as rustc_next_trait_solver[beb9dc5464000fde]::delegate::SolverDelegate>::is_transmutable
  20:     0x7fc8267a8051 - <rustc_type_ir[6a4b9ee69e1ff834]::predicate::TraitPredicate<rustc_middle[7c9cbe436035c5a4]::ty::context::TyCtxt> as rustc_next_trait_solver[beb9dc5464000fde]::solve::assembly::GoalKind<rustc_trait_selection[502c21a12406236f]::solve::delegate::SolverDelegate, rustc_middle[7c9cbe436035c5a4]::ty::context::TyCtxt>>::consider_builtin_transmute_candidate
  21:     0x7fc827f3c349 - <rustc_next_trait_solver[beb9dc5464000fde]::solve::eval_ctxt::EvalCtxt<rustc_trait_selection[502c21a12406236f]::solve::delegate::SolverDelegate, rustc_middle[7c9cbe436035c5a4]::ty::context::TyCtxt>>::assemble_builtin_impl_candidates::<rustc_type_ir[6a4b9ee69e1ff834]::predicate::TraitPredicate<rustc_middle[7c9cbe436035c5a4]::ty::context::TyCtxt>>
  22:     0x7fc827f2e073 - <rustc_next_trait_solver[beb9dc5464000fde]::solve::eval_ctxt::EvalCtxt<rustc_trait_selection[502c21a12406236f]::solve::delegate::SolverDelegate, rustc_middle[7c9cbe436035c5a4]::ty::context::TyCtxt>>::compute_trait_goal
  23:     0x7fc827a423a9 - <rustc_next_trait_solver[beb9dc5464000fde]::solve::search_graph::SearchGraphDelegate<rustc_trait_selection[502c21a12406236f]::solve::delegate::SolverDelegate> as rustc_type_ir[6a4b9ee69e1ff834]::search_graph::Delegate>::compute_goal::{closure#0}
  24:     0x7fc827a5fe89 - <rustc_next_trait_solver[beb9dc5464000fde]::solve::eval_ctxt::EvalCtxt<rustc_trait_selection[502c21a12406236f]::solve::delegate::SolverDelegate, rustc_middle[7c9cbe436035c5a4]::ty::context::TyCtxt>>::evaluate_goal_raw
  25:     0x7fc827a4920a - <rustc_next_trait_solver[beb9dc5464000fde]::solve::eval_ctxt::EvalCtxt<rustc_trait_selection[502c21a12406236f]::solve::delegate::SolverDelegate, rustc_middle[7c9cbe436035c5a4]::ty::context::TyCtxt>>::try_evaluate_added_goals
  26:     0x7fc827db9488 - <rustc_next_trait_solver[beb9dc5464000fde]::solve::eval_ctxt::EvalCtxt<rustc_trait_selection[502c21a12406236f]::solve::delegate::SolverDelegate, rustc_middle[7c9cbe436035c5a4]::ty::context::TyCtxt>>::evaluate_added_goals_and_make_canonical_response
  27:     0x7fc827f29740 - <rustc_next_trait_solver[beb9dc5464000fde]::solve::eval_ctxt::EvalCtxt<rustc_trait_selection[502c21a12406236f]::solve::delegate::SolverDelegate, rustc_middle[7c9cbe436035c5a4]::ty::context::TyCtxt>>::assemble_impl_candidates::<rustc_type_ir[6a4b9ee69e1ff834]::predicate::TraitPredicate<rustc_middle[7c9cbe436035c5a4]::ty::context::TyCtxt>>::{closure#0}
  28:     0x7fc827f2ed6b - <rustc_next_trait_solver[beb9dc5464000fde]::solve::eval_ctxt::EvalCtxt<rustc_trait_selection[502c21a12406236f]::solve::delegate::SolverDelegate, rustc_middle[7c9cbe436035c5a4]::ty::context::TyCtxt>>::compute_trait_goal
  29:     0x7fc827a423a9 - <rustc_next_trait_solver[beb9dc5464000fde]::solve::search_graph::SearchGraphDelegate<rustc_trait_selection[502c21a12406236f]::solve::delegate::SolverDelegate> as rustc_type_ir[6a4b9ee69e1ff834]::search_graph::Delegate>::compute_goal::{closure#0}
  30:     0x7fc827a5fe89 - <rustc_next_trait_solver[beb9dc5464000fde]::solve::eval_ctxt::EvalCtxt<rustc_trait_selection[502c21a12406236f]::solve::delegate::SolverDelegate, rustc_middle[7c9cbe436035c5a4]::ty::context::TyCtxt>>::evaluate_goal_raw
  31:     0x7fc827a4920a - <rustc_next_trait_solver[beb9dc5464000fde]::solve::eval_ctxt::EvalCtxt<rustc_trait_selection[502c21a12406236f]::solve::delegate::SolverDelegate, rustc_middle[7c9cbe436035c5a4]::ty::context::TyCtxt>>::try_evaluate_added_goals
  32:     0x7fc827db9488 - <rustc_next_trait_solver[beb9dc5464000fde]::solve::eval_ctxt::EvalCtxt<rustc_trait_selection[502c21a12406236f]::solve::delegate::SolverDelegate, rustc_middle[7c9cbe436035c5a4]::ty::context::TyCtxt>>::evaluate_added_goals_and_make_canonical_response
  33:     0x7fc827f39de7 - <rustc_next_trait_solver[beb9dc5464000fde]::solve::eval_ctxt::EvalCtxt<rustc_trait_selection[502c21a12406236f]::solve::delegate::SolverDelegate, rustc_middle[7c9cbe436035c5a4]::ty::context::TyCtxt>>::assemble_builtin_impl_candidates::<rustc_type_ir[6a4b9ee69e1ff834]::predicate::TraitPredicate<rustc_middle[7c9cbe436035c5a4]::ty::context::TyCtxt>>
  34:     0x7fc827f2e073 - <rustc_next_trait_solver[beb9dc5464000fde]::solve::eval_ctxt::EvalCtxt<rustc_trait_selection[502c21a12406236f]::solve::delegate::SolverDelegate, rustc_middle[7c9cbe436035c5a4]::ty::context::TyCtxt>>::compute_trait_goal
  35:     0x7fc827a423a9 - <rustc_next_trait_solver[beb9dc5464000fde]::solve::search_graph::SearchGraphDelegate<rustc_trait_selection[502c21a12406236f]::solve::delegate::SolverDelegate> as rustc_type_ir[6a4b9ee69e1ff834]::search_graph::Delegate>::compute_goal::{closure#0}
  36:     0x7fc827a5fe89 - <rustc_next_trait_solver[beb9dc5464000fde]::solve::eval_ctxt::EvalCtxt<rustc_trait_selection[502c21a12406236f]::solve::delegate::SolverDelegate, rustc_middle[7c9cbe436035c5a4]::ty::context::TyCtxt>>::evaluate_goal_raw
  37:     0x7fc827a4920a - <rustc_next_trait_solver[beb9dc5464000fde]::solve::eval_ctxt::EvalCtxt<rustc_trait_selection[502c21a12406236f]::solve::delegate::SolverDelegate, rustc_middle[7c9cbe436035c5a4]::ty::context::TyCtxt>>::try_evaluate_added_goals
  38:     0x7fc827db9488 - <rustc_next_trait_solver[beb9dc5464000fde]::solve::eval_ctxt::EvalCtxt<rustc_trait_selection[502c21a12406236f]::solve::delegate::SolverDelegate, rustc_middle[7c9cbe436035c5a4]::ty::context::TyCtxt>>::evaluate_added_goals_and_make_canonical_response
  39:     0x7fc827f29740 - <rustc_next_trait_solver[beb9dc5464000fde]::solve::eval_ctxt::EvalCtxt<rustc_trait_selection[502c21a12406236f]::solve::delegate::SolverDelegate, rustc_middle[7c9cbe436035c5a4]::ty::context::TyCtxt>>::assemble_impl_candidates::<rustc_type_ir[6a4b9ee69e1ff834]::predicate::TraitPredicate<rustc_middle[7c9cbe436035c5a4]::ty::context::TyCtxt>>::{closure#0}
  40:     0x7fc827f2ed6b - <rustc_next_trait_solver[beb9dc5464000fde]::solve::eval_ctxt::EvalCtxt<rustc_trait_selection[502c21a12406236f]::solve::delegate::SolverDelegate, rustc_middle[7c9cbe436035c5a4]::ty::context::TyCtxt>>::compute_trait_goal
  41:     0x7fc827a423a9 - <rustc_next_trait_solver[beb9dc5464000fde]::solve::search_graph::SearchGraphDelegate<rustc_trait_selection[502c21a12406236f]::solve::delegate::SolverDelegate> as rustc_type_ir[6a4b9ee69e1ff834]::search_graph::Delegate>::compute_goal::{closure#0}
  42:     0x7fc827a40b97 - <rustc_type_ir[6a4b9ee69e1ff834]::search_graph::SearchGraph<rustc_next_trait_solver[beb9dc5464000fde]::solve::search_graph::SearchGraphDelegate<rustc_trait_selection[502c21a12406236f]::solve::delegate::SolverDelegate>, rustc_middle[7c9cbe436035c5a4]::ty::context::TyCtxt>>::evaluate_goal_in_task
  43:     0x7fc827a40691 - rustc_trait_selection[502c21a12406236f]::solve::evaluate_root_goal_for_proof_tree_raw
  44:     0x7fc827a404d8 - rustc_query_impl[89f9236b2ac04da0]::query_impl::evaluate_root_goal_for_proof_tree_raw::invoke_provider_fn::__rust_begin_short_backtrace
  45:     0x7fc827a3d2c3 - rustc_query_impl[89f9236b2ac04da0]::execution::try_execute_query::<rustc_middle[7c9cbe436035c5a4]::query::caches::DefaultCache<rustc_type_ir[6a4b9ee69e1ff834]::canonical::CanonicalQueryInput<rustc_middle[7c9cbe436035c5a4]::ty::context::TyCtxt, rustc_type_ir[6a4b9ee69e1ff834]::solve::QueryInput<rustc_middle[7c9cbe436035c5a4]::ty::context::TyCtxt, rustc_middle[7c9cbe436035c5a4]::ty::predicate::Predicate>>, rustc_middle[7c9cbe436035c5a4]::query::erase::ErasedData<[u8; 48usize]>>, false>
  46:     0x7fc827db3bdd - rustc_query_impl[89f9236b2ac04da0]::query_impl::evaluate_root_goal_for_proof_tree_raw::execute_query_non_incr::__rust_end_short_backtrace
  47:     0x7fc827db3b11 - <rustc_middle[7c9cbe436035c5a4]::ty::context::TyCtxt as rustc_type_ir[6a4b9ee69e1ff834]::interner::Interner>::evaluate_root_goal_for_proof_tree_raw
  48:     0x7fc827db33e7 - <rustc_trait_selection[502c21a12406236f]::solve::delegate::SolverDelegate as rustc_next_trait_solver[beb9dc5464000fde]::solve::eval_ctxt::SolverDelegateEvalExt>::evaluate_root_goal_for_proof_tree
  49:     0x7fc8270ea6c5 - <rustc_hir_typeck[9092ee1b27375cdd]::fn_ctxt::FnCtxt>::coerce
  50:     0x7fc8270e3937 - <rustc_hir_typeck[9092ee1b27375cdd]::fn_ctxt::FnCtxt>::demand_coerce_diag
  51:     0x7fc82742855e - <rustc_hir_typeck[9092ee1b27375cdd]::fn_ctxt::FnCtxt>::check_decl
  52:     0x7fc827446c43 - <rustc_hir_typeck[9092ee1b27375cdd]::fn_ctxt::FnCtxt>::check_expr_block
  53:     0x7fc82744bd17 - <rustc_hir_typeck[9092ee1b27375cdd]::fn_ctxt::FnCtxt>::check_expr_with_expectation_and_args
  54:     0x7fc82741a9f8 - rustc_hir_typeck[9092ee1b27375cdd]::check::check_fn
  55:     0x7fc827e26374 - rustc_hir_typeck[9092ee1b27375cdd]::typeck_with_inspect::{closure#0}
  56:     0x7fc827e24df2 - rustc_query_impl[89f9236b2ac04da0]::query_impl::typeck::invoke_provider_fn::__rust_begin_short_backtrace
  57:     0x7fc82716d18a - rustc_query_impl[89f9236b2ac04da0]::execution::try_execute_query::<rustc_data_structures[79f5f180de225010]::vec_cache::VecCache<rustc_span[8a71b77c74bc13cb]::def_id::LocalDefId, rustc_middle[7c9cbe436035c5a4]::query::erase::ErasedData<[u8; 8usize]>, rustc_middle[7c9cbe436035c5a4]::dep_graph::graph::DepNodeIndex>, false>
  58:     0x7fc82716cb03 - rustc_query_impl[89f9236b2ac04da0]::query_impl::typeck::execute_query_non_incr::__rust_end_short_backtrace
  59:     0x7fc8276a5a96 - <rustc_middle[7c9cbe436035c5a4]::ty::context::TyCtxt>::par_hir_body_owners::<rustc_hir_analysis[7282aa5ba0febab4]::check_crate::{closure#2}>::{closure#0}
  60:     0x7fc8276a54f5 - rustc_hir_analysis[7282aa5ba0febab4]::check_crate
  61:     0x7fc827169b93 - rustc_interface[400bc27e64bfd912]::passes::analysis
  62:     0x7fc82823175c - rustc_query_impl[89f9236b2ac04da0]::execution::try_execute_query::<rustc_middle[7c9cbe436035c5a4]::query::caches::SingleCache<rustc_middle[7c9cbe436035c5a4]::query::erase::ErasedData<[u8; 0usize]>>, false>
  63:     0x7fc8282314bb - rustc_query_impl[89f9236b2ac04da0]::query_impl::analysis::execute_query_non_incr::__rust_end_short_backtrace
  64:     0x7fc8281eda2d - rustc_interface[400bc27e64bfd912]::interface::run_compiler::<(), rustc_driver_impl[ffd722fd6c32666a]::run_compiler::{closure#0}>::{closure#1}
  65:     0x7fc8281d20be - std[76599d2169901dc8]::sys::backtrace::__rust_begin_short_backtrace::<rustc_interface[400bc27e64bfd912]::util::run_in_thread_with_globals<rustc_interface[400bc27e64bfd912]::util::run_in_thread_pool_with_globals<rustc_interface[400bc27e64bfd912]::interface::run_compiler<(), rustc_driver_impl[ffd722fd6c32666a]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>
  66:     0x7fc8281d2720 - <std[76599d2169901dc8]::thread::lifecycle::spawn_unchecked<rustc_interface[400bc27e64bfd912]::util::run_in_thread_with_globals<rustc_interface[400bc27e64bfd912]::util::run_in_thread_pool_with_globals<rustc_interface[400bc27e64bfd912]::interface::run_compiler<(), rustc_driver_impl[ffd722fd6c32666a]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>::{closure#1} as core[d5ffb84325ed5c2a]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  67:     0x7fc8281d35ac - <std[76599d2169901dc8]::sys::thread::unix::Thread>::new::thread_start
  68:     0x7fc821ca598b - <unknown>
  69:     0x7fc821d29a0c - <unknown>
  70:                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 1.96.0-nightly (d2218f5f5 2026-03-03) running on x86_64-unknown-linux-gnu

note: compiler flags: -Z next-solver=globally -Z dump-mir-dir=dir

query stack during panic:
#0 [layout_of] computing layout of `{async closure@/tmp/icemaker_global_tempdir.mc5ONQjhTIgY/rustc_testrunner_tmpdir_reporting.h8jdz2dsuD50/mvce.rs:11:53: 11:73}`
#1 [evaluate_root_goal_for_proof_tree_raw] computing proof tree for `&Wrap<{async closure@/tmp/icemaker_global_tempdir.mc5ONQjhTIgY/rustc_testrunner_tmpdir_reporting.h8jdz2dsuD50/mvce.rs:11:53: 11:73}, (i128,)>: core::ops::unsize::CoerceUnsized<&dyn NodeImpl>`
#2 [typeck] type-checking `trigger_ice`
#3 [analysis] running analysis passes on crate `mvce`
end of query stack
error: aborting due to 3 previous errors

Some errors have detailed explanations: E0601, E0658.
For more information about an error, try `rustc --explain E0601`.

@rustbot label +F-transmutability +WG-trait-system-refactor

[matthiaskrgr]

old solver:

error[E0283]: type annotations needed
  --> code.rs:13:29
   |
13 |     let _: &dyn NodeImpl = &Wrap::<_, (i128,)>::new(async |_: &(), i128| 0);
   |                             ^^^^^^^^^^^^^^^^^^^^^^^ cannot infer type of the type parameter `F` declared on the struct `Wrap`
   |
   = note: cannot satisfy `{async closure@code.rs:13:53}: TransmuteFrom<(), Assume { alignment: false, lifetimes: false, safety: false, validity: false }>`
note: required for `Wrap<{async closure@code.rs:13:53: 13:73}, (i128,)>` to implement `NodeImpl`
  --> code.rs:11:12
   |
11 | impl<F, A> NodeImpl for Wrap<F, (A,)> where F: std::mem::TransmuteFrom<()> {}
   |            ^^^^^^^^     ^^^^^^^^^^^^^          --------------------------- unsatisfied trait bound introduced here
   = note: required for the cast from `&Wrap<{async closure@code.rs:13:53: 13:73}, (i128,)>` to `&dyn NodeImpl`
   = note: the full name for the type has been written to 'code.long-type-3036478202028696332.txt'
   = note: consider using `--verbose` to print the full type name to the console

error: aborting due to 1 previous error

For more information about this error, try `rustc --explain E0283`.

[matthiaskrgr]

bit smaller

#![feature(transmutability)]
#![feature(unboxed_closures)]
trait NodeImpl {}
struct Wrap<F>;
impl<F> Wrap<F> {
    fn new(_: F) -> Self {}
}
impl<F> NodeImpl for Wrap<F> where F: std::mem::TransmuteFrom() {}
fn main() {
    let _: &dyn NodeImpl = Wrap::new(0);
}