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[ICE]: can't be put into typeck results #159704

Description

@matthiaskrgr

auto-reduced (treereduce-rust):

//@compile-flags: -Znext-solver=globally
#![feature(non_lifetime_binders)]
fn trivial<A: ?Sized>()
where
    for<B> Fn(A, B): Fn(A, A) + 'static,
{
}

fn main() {
    trivial();
}

original:

#![feature(non_lifetime_binders)]
fn trivial<A: ?Sized>()
where
    for<B> Fn(A, B): Fn(A, A) +'static {}

fn main() {  trivial() ; }

Version information

rustc 1.99.0-nightly (b9ee8d8bc 2026-07-21)
binary: rustc
commit-hash: b9ee8d8bcb1e4c7905a183a37e6d984c4b9a8468
commit-date: 2026-07-21
host: x86_64-unknown-linux-gnu
release: 1.99.0-nightly
LLVM version: 22.1.8

Possibly related line of code:

fn tcx(&self) -> TyCtxt<'tcx> {
self.fcx.tcx
}
fn write_ty_to_typeck_results(&mut self, hir_id: HirId, ty: Ty<'tcx>) {
debug!("write_ty_to_typeck_results({:?}, {:?})", hir_id, ty);
assert!(
!ty.has_infer() && !ty.has_placeholders() && !ty.has_free_regions(),
"{ty} can't be put into typeck results"
);
self.typeck_results.node_types_mut().insert(hir_id, ty);
}

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

Program output

warning: the feature `non_lifetime_binders` is incomplete and may not be safe to use and/or cause compiler crashes
 --> /tmp/icemaker_global_tempdir.Wpxb176pTay3/rustc_testrunner_tmpdir_reporting.K4nBQlqFjWXB/mvce.rs:1:12
  |
1 | #![feature(non_lifetime_binders)]
  |            ^^^^^^^^^^^^^^^^^^^^
  |
  = note: see issue #108185 <https://github.com/rust-lang/rust/issues/108185> for more information
  = note: `#[warn(incomplete_features)]` on by default

warning: trait objects without an explicit `dyn` are deprecated
 --> /tmp/icemaker_global_tempdir.Wpxb176pTay3/rustc_testrunner_tmpdir_reporting.K4nBQlqFjWXB/mvce.rs:4:12
  |
4 |     for<B> Fn(A, B): Fn(A, A) + 'static,
  |            ^^^^^^^^
  |
  = warning: this is accepted in the current edition (Rust 2015) but is a hard error in Rust 2021!
  = note: for more information, see <https://doc.rust-lang.org/edition-guide/rust-2021/warnings-promoted-to-error.html>
  = note: `#[warn(bare_trait_objects)]` (part of `#[warn(rust_2021_compatibility)]`) on by default
help: if this is a dyn-compatible trait, use `dyn`
  |
4 |     for<B> dyn Fn(A, B): Fn(A, A) + 'static,
  |            +++

error[E0277]: the size for values of type `A` cannot be known at compilation time
  --> /tmp/icemaker_global_tempdir.Wpxb176pTay3/rustc_testrunner_tmpdir_reporting.K4nBQlqFjWXB/mvce.rs:4:22
   |
 2 | fn trivial<A: ?Sized>()
   |            - this type parameter needs to be `Sized`
 3 | where
 4 |     for<B> Fn(A, B): Fn(A, A) + 'static,
   |                      ^^^^^^^^ doesn't have a size known at compile-time
   |
   = note: required because it appears within the type `(A, A)`
note: required by an implicit `Sized` bound in `Fn`
  --> /home/matthias/.rustup/toolchains/master/lib/rustlib/src/rust/library/core/src/ops/function.rs:76:20
   |
76 | pub const trait Fn<Args: Tuple>: [const] FnMut<Args> {
   |                    ^^^^ required by the implicit `Sized` requirement on this type parameter in `Fn`
help: consider removing the `?Sized` bound to make the type parameter `Sized`
   |
 2 - fn trivial<A: ?Sized>()
 2 + fn trivial<A>()
   |

error[E0277]: the size for values of type `A` cannot be known at compilation time
 --> /tmp/icemaker_global_tempdir.Wpxb176pTay3/rustc_testrunner_tmpdir_reporting.K4nBQlqFjWXB/mvce.rs:4:33
  |
2 | fn trivial<A: ?Sized>()
  |            - this type parameter needs to be `Sized`
3 | where
4 |     for<B> Fn(A, B): Fn(A, A) + 'static,
  |                                 ^^^^^^^ doesn't have a size known at compile-time
  |
  = note: only the last element of a tuple may have a dynamically sized type
help: consider removing the `?Sized` bound to make the type parameter `Sized`
  |
2 - fn trivial<A: ?Sized>()
2 + fn trivial<A>()
  |

error[E0277]: expected an `Fn(B, B)` closure, found `(dyn Fn(B, B) + 'static)`
 --> /tmp/icemaker_global_tempdir.Wpxb176pTay3/rustc_testrunner_tmpdir_reporting.K4nBQlqFjWXB/mvce.rs:9:5
  |
9 |     trivial();
  |     ^^^^^^^^^ expected an `Fn(B, B)` closure, found `(dyn Fn(B, B) + 'static)`
  |
  = help: the trait `Fn(B, B)` is not implemented for `(dyn Fn(B, B) + 'static)`
note: required by a bound in `trivial`
 --> /tmp/icemaker_global_tempdir.Wpxb176pTay3/rustc_testrunner_tmpdir_reporting.K4nBQlqFjWXB/mvce.rs:4:22
  |
2 | fn trivial<A: ?Sized>()
  |    ------- required by a bound in this function
3 | where
4 |     for<B> Fn(A, B): Fn(A, A) + 'static,
  |                      ^^^^^^^^ required by this bound in `trivial`

error[E0277]: the size for values of type `B` cannot be known
 --> /tmp/icemaker_global_tempdir.Wpxb176pTay3/rustc_testrunner_tmpdir_reporting.K4nBQlqFjWXB/mvce.rs:9:5
  |
9 |     trivial();
  |     ^^^^^^^^^ doesn't have a known size
  |
  = help: the nightly-only, unstable trait `MetaSized` is not implemented for `B`
note: required by a bound in `trivial`
 --> /tmp/icemaker_global_tempdir.Wpxb176pTay3/rustc_testrunner_tmpdir_reporting.K4nBQlqFjWXB/mvce.rs:2:15
  |
2 | fn trivial<A: ?Sized>()
  |               ^^^^^^ required by this bound in `trivial`


thread 'rustc' (1132679) panicked at /rustc-dev/b9ee8d8bcb1e4c7905a183a37e6d984c4b9a8468/compiler/rustc_hir_typeck/src/writeback.rs:139:9:
fn() {trivial::<B>} can't be put into typeck results
stack backtrace:
   0:     0x7f6c80a29516 - <<std[e7e31dd881df98bb]::sys::backtrace::BacktraceLock>::print::DisplayBacktrace as core[c88a0a802f7ea8d1]::fmt::Display>::fmt
   1:     0x7f6c8100d912 - core[c88a0a802f7ea8d1]::fmt::write
   2:     0x7f6c80a3e66c - <std[e7e31dd881df98bb]::sys::stdio::unix::Stderr as core[c88a0a802f7ea8d1]::io::write::Write>::write_fmt
   3:     0x7f6c809fb14a - std[e7e31dd881df98bb]::panicking::default_hook::{closure#0}
   4:     0x7f6c80a1bbb3 - std[e7e31dd881df98bb]::panicking::default_hook
   5:     0x7f6c7f9a090b - std[e7e31dd881df98bb]::panicking::update_hook::<alloc[ec3dd5f39d329b4e]::boxed::Box<rustc_driver_impl[383cde084ff42635]::install_ice_hook::{closure#1}>>::{closure#0}
   6:     0x7f6c80a1c052 - std[e7e31dd881df98bb]::panicking::panic_with_hook
   7:     0x7f6c809fb202 - std[e7e31dd881df98bb]::panicking::panic_handler::{closure#0}
   8:     0x7f6c809f2df9 - std[e7e31dd881df98bb]::sys::backtrace::__rust_end_short_backtrace::<std[e7e31dd881df98bb]::panicking::panic_handler::{closure#0}, !>
   9:     0x7f6c809fcb5d - __rustc[db4185f8d0a68659]::rust_begin_unwind
  10:     0x7f6c7d58dd0c - core[c88a0a802f7ea8d1]::panicking::panic_fmt
  11:     0x7f6c81935a79 - <rustc_hir_typeck[f17462d0efe89a72]::writeback::WritebackCx>::visit_node_id
  12:     0x7f6c81922f04 - <rustc_hir_typeck[f17462d0efe89a72]::writeback::WritebackCx as rustc_hir[d1845a14e12e6fd2]::intravisit::Visitor>::visit_expr
  13:     0x7f6c81922fca - <rustc_hir_typeck[f17462d0efe89a72]::writeback::WritebackCx as rustc_hir[d1845a14e12e6fd2]::intravisit::Visitor>::visit_expr
  14:     0x7f6c81923033 - <rustc_hir_typeck[f17462d0efe89a72]::writeback::WritebackCx as rustc_hir[d1845a14e12e6fd2]::intravisit::Visitor>::visit_expr
  15:     0x7f6c819428bf - <rustc_hir_typeck[f17462d0efe89a72]::fn_ctxt::FnCtxt>::resolve_type_vars_in_body
  16:     0x7f6c822e13bc - rustc_hir_typeck[f17462d0efe89a72]::typeck_with_inspect::{closure#0}
  17:     0x7f6c822dd8b0 - rustc_query_impl[9a9b2dbab4aa42cf]::query_impl::typeck_root::invoke_provider_fn::__rust_begin_short_backtrace
  18:     0x7f6c816b4629 - rustc_query_impl[9a9b2dbab4aa42cf]::execution::try_execute_query::<rustc_data_structures[b573e1ebd6629dca]::vec_cache::VecCache<rustc_span[5e0315be33f6440b]::def_id::LocalDefId, rustc_middle[c436af0429e6724f]::query::erase::ErasedData<[u8; 8usize]>, rustc_middle[c436af0429e6724f]::dep_graph::graph::DepNodeIndex>, false>
  19:     0x7f6c816b4083 - rustc_query_impl[9a9b2dbab4aa42cf]::query_impl::typeck_root::execute_query_non_incr::__rust_end_short_backtrace
  20:     0x7f6c816b6f7e - rustc_hir_analysis[18680bb4726cf8e]::check_crate
  21:     0x7f6c816b0a4b - rustc_interface[1cdecb41dc13d5b0]::passes::analysis
  22:     0x7f6c8222c9c7 - rustc_query_impl[9a9b2dbab4aa42cf]::execution::try_execute_query::<rustc_middle[c436af0429e6724f]::query::caches::SingleCache<rustc_middle[c436af0429e6724f]::query::erase::ErasedData<[u8; 0usize]>>, false>
  23:     0x7f6c8222c6a9 - rustc_query_impl[9a9b2dbab4aa42cf]::query_impl::analysis::execute_query_non_incr::__rust_end_short_backtrace
  24:     0x7f6c82202ecd - rustc_interface[1cdecb41dc13d5b0]::interface::run_compiler::<(), rustc_driver_impl[383cde084ff42635]::run_compiler::{closure#0}>::{closure#2}
  25:     0x7f6c8223a8a4 - std[e7e31dd881df98bb]::sys::backtrace::__rust_begin_short_backtrace::<rustc_interface[1cdecb41dc13d5b0]::util::run_in_thread_with_globals<rustc_interface[1cdecb41dc13d5b0]::util::run_in_thread_pool_with_globals<rustc_interface[1cdecb41dc13d5b0]::interface::run_compiler<(), rustc_driver_impl[383cde084ff42635]::run_compiler::{closure#0}>::{closure#2}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>
  26:     0x7f6c8223a673 - <std[e7e31dd881df98bb]::thread::lifecycle::spawn_unchecked<rustc_interface[1cdecb41dc13d5b0]::util::run_in_thread_with_globals<rustc_interface[1cdecb41dc13d5b0]::util::run_in_thread_pool_with_globals<rustc_interface[1cdecb41dc13d5b0]::interface::run_compiler<(), rustc_driver_impl[383cde084ff42635]::run_compiler::{closure#0}>::{closure#2}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>::{closure#1} as core[c88a0a802f7ea8d1]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  27:     0x7f6c8224547a - <std[e7e31dd881df98bb]::sys::thread::unix::Thread>::new::thread_start
  28:     0x7f6c7b897739 - <unknown>
  29:     0x7f6c7b91bedc - <unknown>
  30:                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 1.99.0-nightly (b9ee8d8bc 2026-07-21) running on x86_64-unknown-linux-gnu

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

query stack during panic:
#0 [typeck_root] type-checking `main`
#1 [analysis] running analysis passes on crate `mvce`
end of query stack
error: aborting due to 4 previous errors; 2 warnings emitted

For more information about this error, try `rustc --explain E0277`.

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

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    C-bugCategory: This is a bug.F-non_lifetime_binders`#![feature(non_lifetime_binders)]`I-ICEIssue: The compiler panicked, giving an Internal Compilation Error (ICE) ❄️T-compilerRelevant to the compiler team, which will review and decide on the PR/issue.WG-trait-system-refactorThe Rustc Trait System Refactor Initiative (-Znext-solver)needs-triageThis issue may need triage. Remove it if it has been sufficiently triaged.

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