ICE: could not resolve upvar: LocalVarId(HirId(DefId))

[cushionbadak]

Code

#![feature(unsafe_binders)]
#![allow(incomplete_features)]

use std::unsafe_binder::unwrap_binder;

pub struct S([usize; 8]);

pub fn outer_function(x: unsafe<'a> &'a S) -> usize {
    (|| unwrap_binder!(x).0[0])()
}

fn main() {}

A mutant from tests/ui/attributes/no-mangle-closure.rs

Meta

rustc --version --verbose:

rustc 1.89.0-nightly (2eef47813 2025-05-22)
binary: rustc
commit-hash: 2eef47813f25df637026ce3288880e5c587abd92
commit-date: 2025-05-22
host: x86_64-apple-darwin
release: 1.89.0-nightly
LLVM version: 20.1.5

Error output

command: rustc --edition=2021

error: internal compiler error: compiler/rustc_mir_build/src/builder/expr/as_place.rs:260:67: could not resolve upvar: LocalVarId(HirId(DefId(0:8 ~ asplace_r[e01a]::outer_function).2)) + [UnwrapUnsafeBinder(&'{erased} S), Deref, Field(0, [usize; 8_usize])]
 --> asplace_r.rs:8:23
  |
8 | pub fn outer_function(x: unsafe<'a> &'a S) -> usize {
  |                       ^


thread 'rustc' panicked at compiler/rustc_mir_build/src/builder/expr/as_place.rs:260:67:
Box<dyn Any>

Backtrace

stack backtrace:
   0: std::panicking::begin_panic::<rustc_errors::ExplicitBug>
   1: <rustc_errors::diagnostic::BugAbort as rustc_errors::diagnostic::EmissionGuarantee>::emit_producing_guarantee
   2: <rustc_errors::DiagCtxtHandle>::span_bug::<rustc_span::span_encoding::Span, alloc::string::String>
   3: rustc_middle::util::bug::opt_span_bug_fmt::<rustc_span::span_encoding::Span>::{closure#0}
   4: rustc_middle::ty::context::tls::with_opt::<rustc_middle::util::bug::opt_span_bug_fmt<rustc_span::span_encoding::Span>::{closure#0}, !>::{closure#0}
   5: rustc_middle::ty::context::tls::with_context_opt::<rustc_middle::ty::context::tls::with_opt<rustc_middle::util::bug::opt_span_bug_fmt<rustc_span::span_encoding::Span>::{closure#0}, !>::{closure#0}, !>
   6: rustc_middle::util::bug::span_bug_fmt::<rustc_span::span_encoding::Span>
   7: <rustc_mir_build::builder::expr::as_place::PlaceBuilder>::to_place::{closure#0}
   8: <rustc_mir_build::builder::Builder>::bounds_check
   9: <rustc_mir_build::builder::Builder>::expr_as_place
  10: <rustc_mir_build::builder::Builder>::expr_into_dest
  11: <rustc_mir_build::builder::Builder>::expr_into_dest::{closure#0}
  12: <rustc_mir_build::builder::Builder>::expr_into_dest
  13: rustc_mir_build::builder::construct_fn
  14: rustc_mir_build::builder::build_mir
  15: rustc_mir_transform::mir_built
      [... omitted 1 frame ...]
  16: <rustc_mir_build::check_unsafety::UnsafetyVisitor>::visit_inner_body
  17: <rustc_mir_build::check_unsafety::UnsafetyVisitor as rustc_middle::thir::visit::Visitor>::visit_expr
  18: <rustc_mir_build::check_unsafety::UnsafetyVisitor as rustc_middle::thir::visit::Visitor>::visit_expr
  19: <rustc_mir_build::check_unsafety::UnsafetyVisitor as rustc_middle::thir::visit::Visitor>::visit_expr
  20: rustc_middle::thir::visit::walk_expr::<rustc_mir_build::check_unsafety::UnsafetyVisitor>
  21: <rustc_mir_build::check_unsafety::UnsafetyVisitor as rustc_middle::thir::visit::Visitor>::visit_expr
  22: <rustc_mir_build::check_unsafety::UnsafetyVisitor as rustc_middle::thir::visit::Visitor>::visit_expr
  23: <rustc_mir_build::check_unsafety::UnsafetyVisitor as rustc_middle::thir::visit::Visitor>::visit_expr
  24: <rustc_mir_build::check_unsafety::UnsafetyVisitor as rustc_middle::thir::visit::Visitor>::visit_expr
  25: rustc_mir_build::check_unsafety::check_unsafety
      [... omitted 1 frame ...]
  26: <rustc_middle::ty::context::TyCtxt>::par_hir_body_owners::<rustc_interface::passes::run_required_analyses::{closure#2}::{closure#0}>::{closure#0}
  27: rustc_interface::passes::run_required_analyses
  28: rustc_interface::passes::analysis
      [... omitted 1 frame ...]
  29: rustc_interface::passes::create_and_enter_global_ctxt::<core::option::Option<rustc_interface::queries::Linker>, rustc_driver_impl::run_compiler::{closure#0}::{closure#2}>
  30: rustc_interface::interface::run_compiler::<(), rustc_driver_impl::run_compiler::{closure#0}>::{closure#1}
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.

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: please attach the file at `/Volumes/T7/workspace/scratch_250523/run_250522_250505_feat_unsafe_binder/scratch/rustc-ice-2025-05-23T03_44_48-89849.txt` to your bug report

query stack during panic:
#0 [mir_built] building MIR for `outer_function::{closure#0}`
#1 [check_unsafety] unsafety-checking `outer_function`
#2 [analysis] running analysis passes on this crate
end of query stack
error: aborting due to 1 previous error

Bisects to

searched nightlies: from nightly-2024-05-01 to nightly-2025-05-22
regressed nightly: nightly-2025-02-02
searched commit range: 854f225...8239a37
regressed commit: 8239a37

bisected with cargo-bisect-rustc v0.6.9

Host triple: x86_64-unknown-linux-gnu
Reproduce with:

cargo bisect-rustc --end=2025-05-22 --regress ice --preserve --script rustc -- asplace_r.rs --edition=2021

********************************************************************************
Regression in 8239a37f9c0951a037cfc51763ea52a20e71e6bd
********************************************************************************

Attempting to search unrolled perf builds
Found commits ["be995312", "150da37e", "20325765", "9264389d", "d38d22f1", "590d9bf4"]
installing be995312299b441ca428237a2b2ba69b769d517e
testing...
RESULT: be995312299b441ca428237a2b2ba69b769d517e, ===> Script found ICE

Regression in https://github.com/rust-lang-ci/rust/commit/be995312299b441ca428237a2b2ba69b769d517e
The PR introducing the regression in this rollup is #130514: Implement MIR lowering for unsafe binders

Notes

• ICE location: compiler/rustc_mir_build/src/builder/expr/as_place.rs Line-260
  

  rust/compiler/rustc_mir_build/src/builder/expr/as_place.rs

  Lines 252 to 266 in 2eef478

  	impl<'tcx> PlaceBuilder<'tcx> {
  	pub(in crate::builder) fn to_place(&self, cx: &Builder<'_, 'tcx>) -> Place<'tcx> {
  	self.try_to_place(cx).unwrap_or_else(|| match self.base {
  	PlaceBase::Local(local) => span_bug!(
  	cx.local_decls[local].source_info.span,
  	"could not resolve local: {local:#?} + {:?}",
  	self.projection
  	),
  	PlaceBase::Upvar { var_hir_id, closure_def_id: _ } => span_bug!(
  	cx.tcx.hir_span(var_hir_id.0),
  	"could not resolve upvar: {var_hir_id:?} + {:?}",
  	self.projection
  	),
  	})
  	}

• ICE: could not resolve upvar: LocalVarId(HirId(DefId))) #125553 has identical ICE location and currently open,

  • but issue-125553 requires #![feature(type_alias_impl_trait)] and #![feature(unboxed_closures)],
  • and this one requires #![feature(unsafe_binders)].

@rustbot label +F-unsafe_binders