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[ICE]: "Reborrow expression in match" #156304

Closed
#156368
Closed
[ICE]: "Reborrow expression in match"#156304
#156368
Labels
C-bugCategory: This is a bug.F-reborrow`#![feature(reborrow)]`; see #145612I-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.

Description

@theemathas
theemathas
opened on May 8, 2026

Code

#![feature(reborrow)]

use std::marker::Reborrow;

struct Thing<'a>(&'a ());

impl<'a> Reborrow for Thing<'a> {}

fn main() {
    let x = Thing(&());
    let y: Thing<'_> = x;
}

Meta

rustc --version --verbose:

rustc 1.97.0-dev
binary: rustc
commit-hash: unknown
commit-date: unknown
host: aarch64-apple-darwin
release: 1.97.0-dev
LLVM version: 22.1.4

Compiled from the main branch at commit 63b1dfc.

Error output

thread 'rustc' (282284) panicked at compiler/rustc_mir_build/src/thir/pattern/check_match.rs:371:17:
internal error: entered unreachable code: Reborrow expression in match
Backtrace 

stack backtrace:
   0: __rustc::rust_begin_unwind
             at /rustc/ef0fb8a2563200e322fa4419f09f65a63742038c/library/std/src/panicking.rs:689:5
   1: core::panicking::panic_fmt
             at /rustc/ef0fb8a2563200e322fa4419f09f65a63742038c/library/core/src/panicking.rs:80:14
   2: is_known_valid_scrutinee
             at /Users/timch/rust/compiler/rustc_mir_build/src/thir/pattern/check_match.rs:371:17
   3: {closure#0}
             at /Users/timch/rust/compiler/rustc_mir_build/src/thir/pattern/check_match.rs:390:40
   4: map<&rustc_middle::thir::Expr, bool, rustc_mir_build::thir::pattern::check_match::{impl#1}::new_cx::{closure_env#0}>
             at /rustc/ef0fb8a2563200e322fa4419f09f65a63742038c/library/core/src/option.rs:1165:29
   5: new_cx
             at /Users/timch/rust/compiler/rustc_mir_build/src/thir/pattern/check_match.rs:390:23
   6: analyze_binding
             at /Users/timch/rust/compiler/rustc_mir_build/src/thir/pattern/check_match.rs:629:23
   7: check_binding_is_irrefutable
             at /Users/timch/rust/compiler/rustc_mir_build/src/thir/pattern/check_match.rs:659:37
   8: check_let
             at /Users/timch/rust/compiler/rustc_mir_build/src/thir/pattern/check_match.rs:445:18
   9: {closure#1}
             at /Users/timch/rust/compiler/rustc_mir_build/src/thir/pattern/check_match.rs:188:30
  10: {closure#0}<rustc_mir_build::thir::pattern::check_match::{impl#0}::visit_stmt::{closure#0}::{closure_env#1}>
             at /Users/timch/rust/compiler/rustc_mir_build/src/thir/pattern/check_match.rs:205:36
  11: maybe_grow<(), rustc_mir_build::thir::pattern::check_match::{impl#1}::with_let_source::{closure_env#0}<rustc_mir_build::thir::pattern::check_match::{impl#0}::visit_stmt::{closure#0}::{closure_env#1}>>
             at /Users/timch/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/stacker-0.1.21/src/lib.rs:57:9
  12: ensure_sufficient_stack<(), rustc_mir_build::thir::pattern::check_match::{impl#1}::with_let_source::{closure_env#0}<rustc_mir_build::thir::pattern::check_match::{impl#0}::visit_stmt::{closure#0}::{closure_env#1}>>
             at /Users/timch/rust/compiler/rustc_data_structures/src/stack.rs:21:5
  13: with_let_source<rustc_mir_build::thir::pattern::check_match::{impl#0}::visit_stmt::{closure#0}::{closure_env#1}>
             at /Users/timch/rust/compiler/rustc_mir_build/src/thir/pattern/check_match.rs:205:9
  14: {closure#0}
             at /Users/timch/rust/compiler/rustc_mir_build/src/thir/pattern/check_match.rs:187:26
  15: with_hir_source<(), rustc_mir_build::thir::pattern::check_match::{impl#0}::visit_stmt::{closure_env#0}>
             at /Users/timch/rust/compiler/rustc_mir_build/src/thir/pattern/check_match.rs:212:19
  16: visit_stmt
             at /Users/timch/rust/compiler/rustc_mir_build/src/thir/pattern/check_match.rs:183:22
  17: walk_block<rustc_mir_build::thir::pattern::check_match::MatchVisitor>
             at /Users/timch/rust/compiler/rustc_middle/src/thir/visit.rs:228:17
  18: {closure#4}
             at /Users/timch/rust/compiler/rustc_mir_build/src/thir/pattern/check_match.rs:177:54
  19: {closure#0}<rustc_mir_build::thir::pattern::check_match::{impl#0}::visit_expr::{closure_env#4}>
             at /Users/timch/rust/compiler/rustc_mir_build/src/thir/pattern/check_match.rs:205:36
  20: maybe_grow<(), rustc_mir_build::thir::pattern::check_match::{impl#1}::with_let_source::{closure_env#0}<rustc_mir_build::thir::pattern::check_match::{impl#0}::visit_expr::{closure_env#4}>>
             at /Users/timch/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/stacker-0.1.21/src/lib.rs:57:9
  21: ensure_sufficient_stack<(), rustc_mir_build::thir::pattern::check_match::{impl#1}::with_let_source::{closure_env#0}<rustc_mir_build::thir::pattern::check_match::{impl#0}::visit_expr::{closure_env#4}>>
             at /Users/timch/rust/compiler/rustc_data_structures/src/stack.rs:21:5
  22: with_let_source<rustc_mir_build::thir::pattern::check_match::{impl#0}::visit_expr::{closure_env#4}>
             at /Users/timch/rust/compiler/rustc_mir_build/src/thir/pattern/check_match.rs:205:9
  23: visit_expr
             at /Users/timch/rust/compiler/rustc_mir_build/src/thir/pattern/check_match.rs:177:14
  24: {closure#0}
             at /Users/timch/rust/compiler/rustc_mir_build/src/thir/pattern/check_match.rs:128:26
  25: with_hir_source<(), rustc_mir_build::thir::pattern::check_match::{impl#0}::visit_expr::{closure_env#0}>
             at /Users/timch/rust/compiler/rustc_mir_build/src/thir/pattern/check_match.rs:212:19
  26: visit_expr
             at /Users/timch/rust/compiler/rustc_mir_build/src/thir/pattern/check_match.rs:127:22
  27: check_match
             at /Users/timch/rust/compiler/rustc_mir_build/src/thir/pattern/check_match.rs:51:13
      [... omitted 42 frames ...]
  28: query_ensure_ok_or_done<rustc_data_structures::vec_cache::VecCache<rustc_span::def_id::LocalDefId, rustc_middle::query::erase::ErasedData<[u8; 8]>, rustc_middle::dep_graph::graph::DepNodeIndex>>
             at /Users/timch/rust/compiler/rustc_middle/src/query/inner.rs:63:13
  29: mir_built<rustc_span::def_id::LocalDefId>
             at /Users/timch/rust/compiler/rustc_middle/src/query/plumbing.rs:623:21
  30: check_unsafety
             at /Users/timch/rust/compiler/rustc_mir_build/src/check_unsafety.rs:1052:23
      [... omitted 28 frames ...]
  31: check_unsafety<rustc_span::def_id::LocalDefId>
             at /Users/timch/rust/compiler/rustc_middle/src/query/plumbing.rs:589:21
  32: {closure#0}
             at /Users/timch/rust/compiler/rustc_interface/src/passes.rs:1159:33
  33: {closure#0}<rustc_interface::passes::run_required_analyses::{closure#2}::{closure_env#0}>
             at /Users/timch/rust/compiler/rustc_middle/src/hir/map.rs:338:79
  34: {closure#0}<&rustc_span::def_id::LocalDefId, &[rustc_span::def_id::LocalDefId], rustc_middle::hir::map::{impl#3}::par_hir_body_owners::{closure_env#0}<rustc_interface::passes::run_required_analyses::{closure#2}::{closure_env#0}>>
             at /Users/timch/rust/compiler/rustc_data_structures/src/sync/parallel.rs:182:30
  35: call_once<(), rustc_data_structures::sync::parallel::par_for_each_in::{closure#0}::{closure#1}::{closure_env#0}<&rustc_span::def_id::LocalDefId, &[rustc_span::def_id::LocalDefId], rustc_middle::hir::map::{impl#3}::par_hir_body_owners::{closure_env#0}<rustc_interface::passes::run_required_analyses::{closure#2}::{closure_env#0}>>>
             at /rustc/ef0fb8a2563200e322fa4419f09f65a63742038c/library/core/src/panic/unwind_safe.rs:275:9
  36: do_call<core::panic::unwind_safe::AssertUnwindSafe<rustc_data_structures::sync::parallel::par_for_each_in::{closure#0}::{closure#1}::{closure_env#0}<&rustc_span::def_id::LocalDefId, &[rustc_span::def_id::LocalDefId], rustc_middle::hir::map::{impl#3}::par_hir_body_owners::{closure_env#0}<rustc_interface::passes::run_required_analyses::{closure#2}::{closure_env#0}>>>, ()>
             at /rustc/ef0fb8a2563200e322fa4419f09f65a63742038c/library/std/src/panicking.rs:581:40
  37: catch_unwind<(), core::panic::unwind_safe::AssertUnwindSafe<rustc_data_structures::sync::parallel::par_for_each_in::{closure#0}::{closure#1}::{closure_env#0}<&rustc_span::def_id::LocalDefId, &[rustc_span::def_id::LocalDefId], rustc_middle::hir::map::{impl#3}::par_hir_body_owners::{closure_env#0}<rustc_interface::passes::run_required_analyses::{closure#2}::{closure_env#0}>>>>
             at /rustc/ef0fb8a2563200e322fa4419f09f65a63742038c/library/std/src/panicking.rs:544:19
  38: catch_unwind<core::panic::unwind_safe::AssertUnwindSafe<rustc_data_structures::sync::parallel::par_for_each_in::{closure#0}::{closure#1}::{closure_env#0}<&rustc_span::def_id::LocalDefId, &[rustc_span::def_id::LocalDefId], rustc_middle::hir::map::{impl#3}::par_hir_body_owners::{closure_env#0}<rustc_interface::passes::run_required_analyses::{closure#2}::{closure_env#0}>>>, ()>
             at /rustc/ef0fb8a2563200e322fa4419f09f65a63742038c/library/std/src/panic.rs:359:14
  39: run<(), rustc_data_structures::sync::parallel::par_for_each_in::{closure#0}::{closure#1}::{closure_env#0}<&rustc_span::def_id::LocalDefId, &[rustc_span::def_id::LocalDefId], rustc_middle::hir::map::{impl#3}::par_hir_body_owners::{closure_env#0}<rustc_interface::passes::run_required_analyses::{closure#2}::{closure_env#0}>>>
             at /Users/timch/rust/compiler/rustc_data_structures/src/sync/parallel.rs:23:9
  40: {closure#1}<&rustc_span::def_id::LocalDefId, &[rustc_span::def_id::LocalDefId], rustc_middle::hir::map::{impl#3}::par_hir_body_owners::{closure_env#0}<rustc_interface::passes::run_required_analyses::{closure#2}::{closure_env#0}>>
             at /Users/timch/rust/compiler/rustc_data_structures/src/sync/parallel.rs:182:23
  41: for_each<rustc_span::def_id::LocalDefId, rustc_data_structures::sync::parallel::par_for_each_in::{closure#0}::{closure_env#1}<&rustc_span::def_id::LocalDefId, &[rustc_span::def_id::LocalDefId], rustc_middle::hir::map::{impl#3}::par_hir_body_owners::{closure_env#0}<rustc_interface::passes::run_required_analyses::{closure#2}::{closure_env#0}>>>
             at /rustc/ef0fb8a2563200e322fa4419f09f65a63742038c/library/core/src/slice/iter/macros.rs:301:21
  42: {closure#0}<&rustc_span::def_id::LocalDefId, &[rustc_span::def_id::LocalDefId], rustc_middle::hir::map::{impl#3}::par_hir_body_owners::{closure_env#0}<rustc_interface::passes::run_required_analyses::{closure#2}::{closure_env#0}>>
             at /Users/timch/rust/compiler/rustc_data_structures/src/sync/parallel.rs:181:27
  43: parallel_guard<(), rustc_data_structures::sync::parallel::par_for_each_in::{closure_env#0}<&rustc_span::def_id::LocalDefId, &[rustc_span::def_id::LocalDefId], rustc_middle::hir::map::{impl#3}::par_hir_body_owners::{closure_env#0}<rustc_interface::passes::run_required_analyses::{closure#2}::{closure_env#0}>>>
             at /Users/timch/rust/compiler/rustc_data_structures/src/sync/parallel.rs:39:15
  44: par_for_each_in<&rustc_span::def_id::LocalDefId, &[rustc_span::def_id::LocalDefId], rustc_middle::hir::map::{impl#3}::par_hir_body_owners::{closure_env#0}<rustc_interface::passes::run_required_analyses::{closure#2}::{closure_env#0}>>
             at /Users/timch/rust/compiler/rustc_data_structures/src/sync/parallel.rs:176:5
  45: par_hir_body_owners<rustc_interface::passes::run_required_analyses::{closure#2}::{closure_env#0}>
             at /Users/timch/rust/compiler/rustc_middle/src/hir/map.rs:338:9
  46: {closure#2}
             at /Users/timch/rust/compiler/rustc_interface/src/passes.rs:1155:13
  47: run<(), rustc_interface::passes::run_required_analyses::{closure_env#2}>
             at /Users/timch/rust/compiler/rustc_data_structures/src/profiling.rs:845:9
  48: time<(), rustc_interface::passes::run_required_analyses::{closure_env#2}>
             at /Users/timch/rust/compiler/rustc_session/src/utils.rs:17:50
  49: run_required_analyses
             at /Users/timch/rust/compiler/rustc_interface/src/passes.rs:1154:10
  50: analysis
             at /Users/timch/rust/compiler/rustc_interface/src/passes.rs:1198:5
      [... omitted 28 frames ...]
  51: query_ensure_ok_or_done<rustc_middle::query::caches::SingleCache<rustc_middle::query::erase::ErasedData<[u8; 0]>>>
             at /Users/timch/rust/compiler/rustc_middle/src/query/inner.rs:63:13
  52: analysis
             at /Users/timch/rust/compiler/rustc_middle/src/query/plumbing.rs:589:21
  53: {closure#2}
             at /Users/timch/rust/compiler/rustc_driver_impl/src/lib.rs:325:29
  54: {closure#0}<core::option::Option<rustc_interface::queries::Linker>, rustc_driver_impl::run_compiler::{closure#0}::{closure_env#2}>
             at /Users/timch/rust/compiler/rustc_interface/src/passes.rs:1026:80
  55: call_once<core::option::Option<rustc_interface::queries::Linker>, rustc_interface::passes::create_and_enter_global_ctxt::{closure#2}::{closure_env#0}<core::option::Option<rustc_interface::queries::Linker>, rustc_driver_impl::run_compiler::{closure#0}::{closure_env#2}>>
             at /rustc/ef0fb8a2563200e322fa4419f09f65a63742038c/library/core/src/panic/unwind_safe.rs:275:9
  56: do_call<core::panic::unwind_safe::AssertUnwindSafe<rustc_interface::passes::create_and_enter_global_ctxt::{closure#2}::{closure_env#0}<core::option::Option<rustc_interface::queries::Linker>, rustc_driver_impl::run_compiler::{closure#0}::{closure_env#2}>>, core::option::Option<rustc_interface::queries::Linker>>
             at /rustc/ef0fb8a2563200e322fa4419f09f65a63742038c/library/std/src/panicking.rs:581:40
  57: catch_unwind<core::option::Option<rustc_interface::queries::Linker>, core::panic::unwind_safe::AssertUnwindSafe<rustc_interface::passes::create_and_enter_global_ctxt::{closure#2}::{closure_env#0}<core::option::Option<rustc_interface::queries::Linker>, rustc_driver_impl::run_compiler::{closure#0}::{closure_env#2}>>>
             at /rustc/ef0fb8a2563200e322fa4419f09f65a63742038c/library/std/src/panicking.rs:544:19
  58: catch_unwind<core::panic::unwind_safe::AssertUnwindSafe<rustc_interface::passes::create_and_enter_global_ctxt::{closure#2}::{closure_env#0}<core::option::Option<rustc_interface::queries::Linker>, rustc_driver_impl::run_compiler::{closure#0}::{closure_env#2}>>, core::option::Option<rustc_interface::queries::Linker>>
             at /rustc/ef0fb8a2563200e322fa4419f09f65a63742038c/library/std/src/panic.rs:359:14
  59: {closure#2}<core::option::Option<rustc_interface::queries::Linker>, rustc_driver_impl::run_compiler::{closure#0}::{closure_env#2}>
             at /Users/timch/rust/compiler/rustc_interface/src/passes.rs:1026:23
  60: {closure#1}<rustc_interface::passes::create_and_enter_global_ctxt::{closure_env#2}<core::option::Option<rustc_interface::queries::Linker>, rustc_driver_impl::run_compiler::{closure#0}::{closure_env#2}>, core::option::Option<rustc_interface::queries::Linker>>
             at /Users/timch/rust/compiler/rustc_middle/src/ty/context.rs:788:37
  61: {closure#0}<rustc_middle::ty::context::{impl#15}::enter::{closure_env#1}<rustc_interface::passes::create_and_enter_global_ctxt::{closure_env#2}<core::option::Option<rustc_interface::queries::Linker>, rustc_driver_impl::run_compiler::{closure#0}::{closure_env#2}>, core::option::Option<rustc_interface::queries::Linker>>, core::option::Option<rustc_interface::queries::Linker>>
             at /Users/timch/rust/compiler/rustc_middle/src/ty/context/tls.rs:56:9
  62: try_with<core::cell::Cell<*const ()>, rustc_middle::ty::context::tls::enter_context::{closure_env#0}<rustc_middle::ty::context::{impl#15}::enter::{closure_env#1}<rustc_interface::passes::create_and_enter_global_ctxt::{closure_env#2}<core::option::Option<rustc_interface::queries::Linker>, rustc_driver_impl::run_compiler::{closure#0}::{closure_env#2}>, core::option::Option<rustc_interface::queries::Linker>>, core::option::Option<rustc_interface::queries::Linker>>, core::option::Option<rustc_interface::queries::Linker>>
             at /rustc/ef0fb8a2563200e322fa4419f09f65a63742038c/library/std/src/thread/local.rs:462:12
  63: with<core::cell::Cell<*const ()>, rustc_middle::ty::context::tls::enter_context::{closure_env#0}<rustc_middle::ty::context::{impl#15}::enter::{closure_env#1}<rustc_interface::passes::create_and_enter_global_ctxt::{closure_env#2}<core::option::Option<rustc_interface::queries::Linker>, rustc_driver_impl::run_compiler::{closure#0}::{closure_env#2}>, core::option::Option<rustc_interface::queries::Linker>>, core::option::Option<rustc_interface::queries::Linker>>, core::option::Option<rustc_interface::queries::Linker>>
             at /rustc/ef0fb8a2563200e322fa4419f09f65a63742038c/library/std/src/thread/local.rs:426:20
  64: enter_context<rustc_middle::ty::context::{impl#15}::enter::{closure_env#1}<rustc_interface::passes::create_and_enter_global_ctxt::{closure_env#2}<core::option::Option<rustc_interface::queries::Linker>, rustc_driver_impl::run_compiler::{closure#0}::{closure_env#2}>, core::option::Option<rustc_interface::queries::Linker>>, core::option::Option<rustc_interface::queries::Linker>>
             at /Users/timch/rust/compiler/rustc_middle/src/ty/context/tls.rs:53:9
  65: enter<rustc_interface::passes::create_and_enter_global_ctxt::{closure_env#2}<core::option::Option<rustc_interface::queries::Linker>, rustc_driver_impl::run_compiler::{closure#0}::{closure_env#2}>, core::option::Option<rustc_interface::queries::Linker>>
             at /Users/timch/rust/compiler/rustc_middle/src/ty/context.rs:788:9
  66: create_global_ctxt<core::option::Option<rustc_interface::queries::Linker>, rustc_interface::passes::create_and_enter_global_ctxt::{closure_env#2}<core::option::Option<rustc_interface::queries::Linker>, rustc_driver_impl::run_compiler::{closure#0}::{closure_env#2}>>
             at /Users/timch/rust/compiler/rustc_middle/src/ty/context.rs:982:13
  67: create_and_enter_global_ctxt<core::option::Option<rustc_interface::queries::Linker>, rustc_driver_impl::run_compiler::{closure#0}::{closure_env#2}>
             at /Users/timch/rust/compiler/rustc_interface/src/passes.rs:986:5
  68: {closure#0}
             at /Users/timch/rust/compiler/rustc_driver_impl/src/lib.rs:298:22
  69: {closure#0}<(), rustc_driver_impl::run_compiler::{closure_env#0}>
             at /Users/timch/rust/compiler/rustc_interface/src/interface.rs:495:80
  70: call_once<(), rustc_interface::interface::run_compiler::{closure#1}::{closure_env#0}<(), rustc_driver_impl::run_compiler::{closure_env#0}>>
             at /rustc/ef0fb8a2563200e322fa4419f09f65a63742038c/library/core/src/panic/unwind_safe.rs:275:9
  71: do_call<core::panic::unwind_safe::AssertUnwindSafe<rustc_interface::interface::run_compiler::{closure#1}::{closure_env#0}<(), rustc_driver_impl::run_compiler::{closure_env#0}>>, ()>
             at /rustc/ef0fb8a2563200e322fa4419f09f65a63742038c/library/std/src/panicking.rs:581:40
  72: catch_unwind<(), core::panic::unwind_safe::AssertUnwindSafe<rustc_interface::interface::run_compiler::{closure#1}::{closure_env#0}<(), rustc_driver_impl::run_compiler::{closure_env#0}>>>
             at /rustc/ef0fb8a2563200e322fa4419f09f65a63742038c/library/std/src/panicking.rs:544:19
  73: catch_unwind<core::panic::unwind_safe::AssertUnwindSafe<rustc_interface::interface::run_compiler::{closure#1}::{closure_env#0}<(), rustc_driver_impl::run_compiler::{closure_env#0}>>, ()>
             at /rustc/ef0fb8a2563200e322fa4419f09f65a63742038c/library/std/src/panic.rs:359:14
  74: {closure#1}<(), rustc_driver_impl::run_compiler::{closure_env#0}>
             at /Users/timch/rust/compiler/rustc_interface/src/interface.rs:495:23
  75: {closure#0}<rustc_interface::interface::run_compiler::{closure_env#1}<(), rustc_driver_impl::run_compiler::{closure_env#0}>, ()>
             at /Users/timch/rust/compiler/rustc_interface/src/util.rs:205:17
  76: {closure#0}<rustc_interface::util::run_in_thread_pool_with_globals::{closure_env#0}<rustc_interface::interface::run_compiler::{closure_env#1}<(), rustc_driver_impl::run_compiler::{closure_env#0}>, ()>, ()>
             at /Users/timch/rust/compiler/rustc_interface/src/util.rs:161:24
  77: set<rustc_span::SessionGlobals, rustc_interface::util::run_in_thread_with_globals::{closure#0}::{closure#0}::{closure_env#0}<rustc_interface::util::run_in_thread_pool_with_globals::{closure_env#0}<rustc_interface::interface::run_compiler::{closure_env#1}<(), rustc_driver_impl::run_compiler::{closure_env#0}>, ()>, ()>, ()>
             at /Users/timch/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/scoped-tls-1.0.1/src/lib.rs:137:9
  78: create_session_globals_then<(), rustc_interface::util::run_in_thread_with_globals::{closure#0}::{closure#0}::{closure_env#0}<rustc_interface::util::run_in_thread_pool_with_globals::{closure_env#0}<rustc_interface::interface::run_compiler::{closure_env#1}<(), rustc_driver_impl::run_compiler::{closure_env#0}>, ()>, ()>>
             at /Users/timch/rust/compiler/rustc_span/src/lib.rs:154:21
  79: {closure#0}<rustc_interface::util::run_in_thread_pool_with_globals::{closure_env#0}<rustc_interface::interface::run_compiler::{closure_env#1}<(), rustc_driver_impl::run_compiler::{closure_env#0}>, ()>, ()>
             at /Users/timch/rust/compiler/rustc_interface/src/util.rs:157:17
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.

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: please attach the file at `/Users/timch/foo/rustc-ice-2026-05-08T09_28_21-11701.txt` to your bug report

note: rustc 1.97.0-dev running on aarch64-apple-darwin

note: compiler flags: --crate-type bin -C embed-bitcode=no -C debuginfo=2 -C split-debuginfo=unpacked -C incremental=[REDACTED]

note: some of the compiler flags provided by cargo are hidden

query stack during panic:
#0 [check_match] match-checking `main`
#1 [check_unsafety] unsafety-checking `main`
... and 1 other queries... use `env RUST_BACKTRACE=1` to see the full query stack
there was a panic while trying to force a dep node
try_mark_green dep node stack:
#0 mir_built(foo[d3ea]::main)
end of try_mark_green dep node stack
error: could not compile `foo` (bin "foo")

Activity

  1. theemathas
    added
    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.
    C-bugCategory: This is a bug.
    F-reborrow`#![feature(reborrow)]`; see #145612
    on May 8, 2026
  2. rustbot
    added
    needs-triageThis issue may need triage. Remove when done. See docs forge.rust-lang.org/release/issue-triaging
    on May 8, 2026

  3. theemathas commented on May 8, 2026

    @theemathas
    theemathas
    on May 8, 2026
    ContributorAuthor

    Presumably started ICE-ing in #151753. cc @aapoalas

  4. theemathas
    removed
    needs-triageThis issue may need triage. Remove when done. See docs forge.rust-lang.org/release/issue-triaging
    on May 8, 2026

  5. aapoalas commented on May 8, 2026

    @aapoalas
    aapoalas
    on May 8, 2026
    Contributor

    Presumably this came from trying out the feature? Thank you for that! I'll try take a look maybe this weekend.

  6. aapoalas commented on May 8, 2026

    @aapoalas
    aapoalas
    on May 8, 2026
    Contributor

    I believe there's a similar test but it doesn't define the type on the assignment's left hand side, which perhaps is what's making the difference....?

  7. theemathas commented on May 8, 2026

    @theemathas
    theemathas
    on May 8, 2026
    ContributorAuthor

    let statements are a coercion site only if there's a type annotation. https://doc.rust-lang.org/stable/reference/type-coercions.html#r-coerce.site.let

  8. theemathas commented on May 8, 2026

    @theemathas
    theemathas
    on May 8, 2026
    ContributorAuthor

    Another way to trigger the ICE:

    #![feature(reborrow)]

use std::marker::Reborrow;

struct Thing<'a>(&'a ());

impl<'a> Reborrow for Thing<'a> {}

fn main() {
    let x = Thing(&());
    let y = x as Thing<'_>;
}
  9. JonathanBrouwer
    added 2 commits that reference this issue on May 10, 2026

    Rollup merge of rust-lang#156368 - aapoalas:reborrow-in-match-stateme…

    d33589d

    Rollup merge of rust-lang#156368 - aapoalas:reborrow-in-match-stateme…

    cfd0d4c
  10. rust-bors
    closed this as completedin #156368on May 10, 2026
  11. rust-timer
    added a commit that references this issue on May 10, 2026

    Unrolled build for #156368

    ec10a1d
  12. WhySoBad
    added a commit that references this issue on May 13, 2026

    Rollup merge of #156368 - aapoalas:reborrow-in-match-statement, r=Nad…

    5586ae1
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