[ICE]: `explicit deref of non-derefable type`

[matthiaskrgr]

auto-reduced (treereduce-rust):

//@compile-flags: --edition=2024 --cap-lints=warn
#![feature(min_generic_const_args)]
#![feature(adt_const_params)]
#![feature(pin_ergonomics)]
async fn other() {}

pub async fn uhoh() {
    other().await;
}

fn main() {}

original:

//@ edition:2018
#![feature(must_not_suspend)]
#![deny(must_not_suspend)]

#[must_not_suspend]
trait Wow {}

impl Wow for i32 {}

fn r#impl() -> impl Wow {
    1
}

fn r#dyn() -> Box<dyn Wow> {
    Box::new(1)
}

async fn other() {}

pub async fn uhoh() {
    let _guard1 = r#impl(); //~ ERROR implementer of `Wow` held across
    let _guard2 = r#dyn(); // Trying to access the data in a vtable does not work, either.

    other().await;
}

fn main() {
}

Version information

rustc 1.96.0-nightly (d1c79458b 2026-03-11)
binary: rustc
commit-hash: d1c79458b5d13bd0179d7dbafd5ca4ea9ae3e6aa
commit-date: 2026-03-11
host: x86_64-unknown-linux-gnu
release: 1.96.0-nightly
LLVM version: 22.1.0

Command:
/home/matthias/.rustup/toolchains/master/bin/rustc --edition=2024 --cap-lints=warn -Zcrate-attr=feature(min_generic_const_args) -Zcrate-attr=feature(adt_const_params) -Zcrate-attr=feature(pin_ergonomics)

Program output

warning: the feature `min_generic_const_args` is incomplete and may not be safe to use and/or cause compiler crashes
 --> <crate attribute>:1:12
  |
1 | #![feature(min_generic_const_args)]
  |            ^^^^^^^^^^^^^^^^^^^^^^
  |
  = note: see issue #132980 <https://github.com/rust-lang/rust/issues/132980> for more information
  = note: `#[warn(incomplete_features)]` on by default

warning: the feature `pin_ergonomics` is incomplete and may not be safe to use and/or cause compiler crashes
 --> <crate attribute>:1:12
  |
1 | #![feature(pin_ergonomics)]
  |            ^^^^^^^^^^^^^^
  |
  = note: see issue #130494 <https://github.com/rust-lang/rust/issues/130494> for more information

warning: 2 warnings emitted

note: no errors encountered even though delayed bugs were created

note: those delayed bugs will now be shown as internal compiler errors

error: internal compiler error: explicit deref of non-derefable type
 --> /tmp/icemaker_global_tempdir.zSJT70QNghmg/rustc_testrunner_tmpdir_reporting.nyD9Mf6Fn4JA/mvce.rs:4:13
  |
4 |     other().await;
  |             ^^^^^
  |
note: delayed at /rustc-dev/d1c79458b5d13bd0179d7dbafd5ca4ea9ae3e6aa/compiler/rustc_hir_typeck/src/expr_use_visitor.rs:200:20
         0: <rustc_errors::DiagCtxtInner>::emit_diagnostic
         1: <rustc_errors::DiagCtxtHandle>::emit_diagnostic
         2: <rustc_span::ErrorGuaranteed as rustc_errors::diagnostic::EmissionGuarantee>::emit_producing_guarantee
         3: <rustc_errors::DiagCtxtHandle>::span_delayed_bug::<rustc_span::span_encoding::Span, alloc::string::String>
         4: <&rustc_hir_typeck::fn_ctxt::FnCtxt as rustc_hir_typeck::expr_use_visitor::TypeInformationCtxt>::report_bug::<&str>
         5: <rustc_hir_typeck::expr_use_visitor::ExprUseVisitor<&rustc_hir_typeck::fn_ctxt::FnCtxt, &mut rustc_hir_typeck::upvar::InferBorrowKind>>::cat_deref
         6: <rustc_hir_typeck::expr_use_visitor::ExprUseVisitor<&rustc_hir_typeck::fn_ctxt::FnCtxt, &mut rustc_hir_typeck::upvar::InferBorrowKind>>::walk_expr
         7: <rustc_hir_typeck::expr_use_visitor::ExprUseVisitor<&rustc_hir_typeck::fn_ctxt::FnCtxt, &mut rustc_hir_typeck::upvar::InferBorrowKind>>::consume_expr
         8: <rustc_hir_typeck::expr_use_visitor::ExprUseVisitor<&rustc_hir_typeck::fn_ctxt::FnCtxt, &mut rustc_hir_typeck::upvar::InferBorrowKind>>::walk_expr
         9: <rustc_hir_typeck::expr_use_visitor::ExprUseVisitor<&rustc_hir_typeck::fn_ctxt::FnCtxt, &mut rustc_hir_typeck::upvar::InferBorrowKind>>::consume_expr
        10: <rustc_hir_typeck::expr_use_visitor::ExprUseVisitor<&rustc_hir_typeck::fn_ctxt::FnCtxt, &mut rustc_hir_typeck::upvar::InferBorrowKind>>::walk_block
        11: <rustc_hir_typeck::expr_use_visitor::ExprUseVisitor<&rustc_hir_typeck::fn_ctxt::FnCtxt, &mut rustc_hir_typeck::upvar::InferBorrowKind>>::walk_expr
        12: <rustc_hir_typeck::expr_use_visitor::ExprUseVisitor<&rustc_hir_typeck::fn_ctxt::FnCtxt, &mut rustc_hir_typeck::upvar::InferBorrowKind>>::walk_expr
        13: <rustc_hir_typeck::expr_use_visitor::ExprUseVisitor<&rustc_hir_typeck::fn_ctxt::FnCtxt, &mut rustc_hir_typeck::upvar::InferBorrowKind>>::consume_expr
        14: <rustc_hir_typeck::expr_use_visitor::ExprUseVisitor<&rustc_hir_typeck::fn_ctxt::FnCtxt, &mut rustc_hir_typeck::upvar::InferBorrowKind>>::walk_block
        15: <rustc_hir_typeck::expr_use_visitor::ExprUseVisitor<&rustc_hir_typeck::fn_ctxt::FnCtxt, &mut rustc_hir_typeck::upvar::InferBorrowKind>>::walk_expr
        16: <rustc_hir_typeck::expr_use_visitor::ExprUseVisitor<&rustc_hir_typeck::fn_ctxt::FnCtxt, &mut rustc_hir_typeck::upvar::InferBorrowKind>>::consume_expr
        17: <rustc_hir_typeck::expr_use_visitor::ExprUseVisitor<&rustc_hir_typeck::fn_ctxt::FnCtxt, &mut rustc_hir_typeck::upvar::InferBorrowKind>>::walk_expr
        18: <rustc_hir_typeck::expr_use_visitor::ExprUseVisitor<&rustc_hir_typeck::fn_ctxt::FnCtxt, &mut rustc_hir_typeck::upvar::InferBorrowKind>>::consume_expr
        19: <rustc_hir_typeck::expr_use_visitor::ExprUseVisitor<&rustc_hir_typeck::fn_ctxt::FnCtxt, &mut rustc_hir_typeck::upvar::InferBorrowKind>>::walk_block
        20: <rustc_hir_typeck::expr_use_visitor::ExprUseVisitor<&rustc_hir_typeck::fn_ctxt::FnCtxt, &mut rustc_hir_typeck::upvar::InferBorrowKind>>::walk_expr
        21: <rustc_hir_typeck::expr_use_visitor::ExprUseVisitor<&rustc_hir_typeck::fn_ctxt::FnCtxt, &mut rustc_hir_typeck::upvar::InferBorrowKind>>::consume_expr
        22: <rustc_hir_typeck::expr_use_visitor::ExprUseVisitor<&rustc_hir_typeck::fn_ctxt::FnCtxt, &mut rustc_hir_typeck::upvar::InferBorrowKind>>::walk_expr
        23: <rustc_hir_typeck::expr_use_visitor::ExprUseVisitor<&rustc_hir_typeck::fn_ctxt::FnCtxt, &mut rustc_hir_typeck::upvar::InferBorrowKind>>::consume_expr
        24: <rustc_hir_typeck::expr_use_visitor::ExprUseVisitor<&rustc_hir_typeck::fn_ctxt::FnCtxt, &mut rustc_hir_typeck::upvar::InferBorrowKind>>::walk_block
        25: <rustc_hir_typeck::expr_use_visitor::ExprUseVisitor<&rustc_hir_typeck::fn_ctxt::FnCtxt, &mut rustc_hir_typeck::upvar::InferBorrowKind>>::walk_expr
        26: <rustc_hir_typeck::expr_use_visitor::ExprUseVisitor<&rustc_hir_typeck::fn_ctxt::FnCtxt, &mut rustc_hir_typeck::upvar::InferBorrowKind>>::consume_expr
        27: <rustc_hir_typeck::fn_ctxt::FnCtxt>::analyze_closure
        28: <rustc_hir_typeck::upvar::InferBorrowKindVisitor as rustc_hir::intravisit::Visitor>::visit_expr
        29: rustc_hir_typeck::typeck_with_inspect::{closure#0}
        30: rustc_query_impl::query_impl::typeck::invoke_provider_fn::__rust_begin_short_backtrace
        31: rustc_query_impl::execution::try_execute_query::<rustc_data_structures::vec_cache::VecCache<rustc_span::def_id::LocalDefId, rustc_middle::query::erase::ErasedData<[u8; 8]>, rustc_middle::dep_graph::graph::DepNodeIndex>, false>
        32: rustc_query_impl::query_impl::typeck::execute_query_non_incr::__rust_end_short_backtrace
        33: rustc_mir_build::thir::pattern::check_match::check_match
        34: rustc_query_impl::query_impl::check_match::invoke_provider_fn::__rust_begin_short_backtrace
        35: rustc_query_impl::execution::try_execute_query::<rustc_data_structures::vec_cache::VecCache<rustc_span::def_id::LocalDefId, rustc_middle::query::erase::ErasedData<[u8; 1]>, rustc_middle::dep_graph::graph::DepNodeIndex>, false>
        36: rustc_query_impl::query_impl::check_match::execute_query_non_incr::__rust_end_short_backtrace
        37: rustc_mir_build::builder::build_mir_inner_impl
        38: rustc_mir_transform::mir_built
        39: rustc_query_impl::execution::try_execute_query::<rustc_data_structures::vec_cache::VecCache<rustc_span::def_id::LocalDefId, rustc_middle::query::erase::ErasedData<[u8; 8]>, rustc_middle::dep_graph::graph::DepNodeIndex>, false>
        40: rustc_query_impl::query_impl::mir_built::execute_query_non_incr::__rust_end_short_backtrace
        41: rustc_mir_transform::ffi_unwind_calls::has_ffi_unwind_calls
        42: rustc_query_impl::query_impl::has_ffi_unwind_calls::invoke_provider_fn::__rust_begin_short_backtrace
        43: rustc_query_impl::execution::try_execute_query::<rustc_data_structures::vec_cache::VecCache<rustc_span::def_id::LocalDefId, rustc_middle::query::erase::ErasedData<[u8; 1]>, rustc_middle::dep_graph::graph::DepNodeIndex>, false>
        44: rustc_query_impl::query_impl::has_ffi_unwind_calls::execute_query_non_incr::__rust_end_short_backtrace
        45: rustc_mir_transform::mir_promoted
        46: rustc_query_impl::query_impl::mir_promoted::invoke_provider_fn::__rust_begin_short_backtrace
        47: rustc_query_impl::execution::try_execute_query::<rustc_data_structures::vec_cache::VecCache<rustc_span::def_id::LocalDefId, rustc_middle::query::erase::ErasedData<[u8; 16]>, rustc_middle::dep_graph::graph::DepNodeIndex>, false>
        48: rustc_query_impl::query_impl::mir_promoted::execute_query_non_incr::__rust_end_short_backtrace
        49: rustc_borrowck::mir_borrowck
        50: rustc_query_impl::query_impl::mir_borrowck::invoke_provider_fn::__rust_begin_short_backtrace
        51: rustc_query_impl::execution::try_execute_query::<rustc_data_structures::vec_cache::VecCache<rustc_span::def_id::LocalDefId, rustc_middle::query::erase::ErasedData<[u8; 8]>, rustc_middle::dep_graph::graph::DepNodeIndex>, false>
        52: rustc_query_impl::query_impl::mir_borrowck::execute_query_non_incr::__rust_end_short_backtrace
        53: rustc_hir_analysis::collect::type_of::opaque::find_opaque_ty_constraints_for_rpit
        54: rustc_hir_analysis::collect::type_of::type_of_opaque
        55: rustc_query_impl::execution::try_execute_query::<rustc_middle::query::caches::DefIdCache<rustc_middle::query::erase::ErasedData<[u8; 8]>>, false>
        56: rustc_query_impl::query_impl::type_of_opaque::execute_query_non_incr::__rust_end_short_backtrace
        57: rustc_hir_analysis::collect::type_of::type_of
        58: rustc_query_impl::query_impl::type_of::invoke_provider_fn::__rust_begin_short_backtrace
        59: rustc_query_impl::execution::try_execute_query::<rustc_middle::query::caches::DefIdCache<rustc_middle::query::erase::ErasedData<[u8; 8]>>, false>
        60: rustc_query_impl::query_impl::type_of::execute_query_non_incr::__rust_end_short_backtrace
        61: rustc_hir_analysis::check::check::check_opaque
        62: rustc_hir_analysis::check::check::check_item_type
        63: rustc_hir_analysis::check::wfcheck::check_well_formed
        64: rustc_query_impl::query_impl::check_well_formed::invoke_provider_fn::__rust_begin_short_backtrace
        65: rustc_query_impl::execution::try_execute_query::<rustc_data_structures::vec_cache::VecCache<rustc_span::def_id::LocalDefId, rustc_middle::query::erase::ErasedData<[u8; 1]>, rustc_middle::dep_graph::graph::DepNodeIndex>, false>
        66: rustc_query_impl::query_impl::check_well_formed::execute_query_non_incr::__rust_end_short_backtrace
        67: rustc_hir_analysis::check::wfcheck::check_type_wf
        68: rustc_query_impl::query_impl::check_type_wf::invoke_provider_fn::__rust_begin_short_backtrace
        69: rustc_query_impl::execution::try_execute_query::<rustc_middle::query::caches::SingleCache<rustc_middle::query::erase::ErasedData<[u8; 1]>>, false>
        70: rustc_query_impl::query_impl::check_type_wf::execute_query_non_incr::__rust_end_short_backtrace
        71: rustc_hir_analysis::check_crate
        72: rustc_interface::passes::analysis
        73: rustc_query_impl::execution::try_execute_query::<rustc_middle::query::caches::SingleCache<rustc_middle::query::erase::ErasedData<[u8; 0]>>, false>
        74: rustc_query_impl::query_impl::analysis::execute_query_non_incr::__rust_end_short_backtrace
        75: rustc_interface::interface::run_compiler::<(), rustc_driver_impl::run_compiler::{closure#0}>::{closure#1}
        76: std::sys::backtrace::__rust_begin_short_backtrace::<rustc_interface::util::run_in_thread_with_globals<rustc_interface::util::run_in_thread_pool_with_globals<rustc_interface::interface::run_compiler<(), rustc_driver_impl::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>
        77: <std::thread::lifecycle::spawn_unchecked<rustc_interface::util::run_in_thread_with_globals<rustc_interface::util::run_in_thread_pool_with_globals<rustc_interface::interface::run_compiler<(), rustc_driver_impl::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>::{closure#1} as core::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
        78: <std::sys::thread::unix::Thread>::new::thread_start
        79: <unknown>
        80: <unknown>
      
 --> /tmp/icemaker_global_tempdir.zSJT70QNghmg/rustc_testrunner_tmpdir_reporting.nyD9Mf6Fn4JA/mvce.rs:4:13
  |
4 |     other().await;
  |             ^^^^^

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 (d1c79458b 2026-03-11) running on x86_64-unknown-linux-gnu

note: compiler flags: -Z crate-attr=feature(min_generic_const_args) -Z crate-attr=feature(adt_const_params) -Z crate-attr=feature(pin_ergonomics) -Z dump-mir-dir=dir

query stack during panic:
end of query stack

@rustbot label +F-min_generic_const_args +F-adt_const_params +F-pin_ergonomics

[rustbot]

Error: Unknown labels: F-must_not_suspend

Please file an issue on GitHub at triagebot if there's a problem with this bot, or reach out on #triagebot on Zulip.

[matthiaskrgr]

since #149130 🤔

edit: minimized without the features (this is a bug in my program which I haven't fixed yet 😅 )

#![feature(pin_ergonomics)]
async fn other() {}
async fn uhoh() {
    other().await
}
fn main() {}

[theemathas]

Another way to cause an ICE:

#![feature(pin_ergonomics)]
#![expect(incomplete_features)]

pub async fn foo() {
    let x: std::pin::Pin<&mut i32> = None.unwrap();
    let _y: std::pin::Pin<&mut i32> = x;
}