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ICE upvar_tys called before capture types are inferred #162440

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#162595
Closed
ICE upvar_tys called before capture types are inferred#162440
#162595
Labels
A-diagnosticsArea: Messages for errors, warnings, and lintsC-bugCategory: This is a bug.I-ICEIssue: The compiler panicked, giving an Internal Compilation Error (ICE) ❄️P-mediumMedium priorityT-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)regression-untriagedUntriaged performance or correctness regression.

Description

@matthiaskrgr
matthiaskrgr
opened on Sep 7, 2026

snippet:

fn main() {
    Some([0]).map(|s| s[..]);
}

Version information

rustc 1.100.0-nightly (752b9bf87 2026-09-07)
binary: rustc
commit-hash: 752b9bf8798c2ffc1d3fe2b804c04454366fc6d6
commit-date: 2026-09-07
host: x86_64-unknown-linux-gnu
release: 1.100.0-nightly
LLVM version: 23.1.1

Possibly related line of code:

rust/compiler/rustc_middle/src/ty/sty.rs

Lines 194 to 206 in 752b9bf

UpvarArgs::CoroutineClosure(args) => args.as_coroutine_closure().tupled_upvars_ty(),
};
match tupled_tys.kind() {
TyKind::Error(_) => ty::List::empty(),
TyKind::Tuple(..) => self.tupled_upvars_ty().tuple_fields(),
TyKind::Infer(_) => bug!("upvar_tys called before capture types are inferred"),
ty => bug!("Unexpected representation of upvar types tuple {:?}", ty),
}
}
#[inline]
pub fn tupled_upvars_ty(self) -> Ty<'tcx> {

Command:
/home/matthias/.rustup/toolchains/master/bin/rustc

Program output 

error[E0277]: the size for values of type `[{integer}]` cannot be known at compilation time
    --> /tmp/icemaker_global_tempdir.y4oxhmSBkaRU/rustc_testrunner_tmpdir_reporting.4aRXUhCYUxEe/mvce.rs:2:15
     |
   2 |     Some([0]).map(|s| s[..]);
     |               ^^^ doesn't have a size known at compile-time
     |
     = help: the trait `Sized` is not implemented for `[{integer}]`
note: required by an implicit `Sized` bound in `Option::<T>::map`
    --> /home/matthias/.rustup/toolchains/master/lib/rustlib/src/rust/library/core/src/option.rs:1160:22
     |
1160 |     pub const fn map<U, F>(self, f: F) -> Option<U>
     |                      ^ required by the implicit `Sized` requirement on this type parameter in `Option::<T>::map`

error[E0277]: the size for values of type `[{integer}]` cannot be known at compilation time
 --> /tmp/icemaker_global_tempdir.y4oxhmSBkaRU/rustc_testrunner_tmpdir_reporting.4aRXUhCYUxEe/mvce.rs:2:23
  |
2 |     Some([0]).map(|s| s[..]);
  |                       ^^^^^ doesn't have a size known at compile-time
  |
  = help: the trait `Sized` is not implemented for `[{integer}]`
  = note: the return type of a function must have a statically known size

error: internal compiler error: /rustc-dev/752b9bf8798c2ffc1d3fe2b804c04454366fc6d6/compiler/rustc_middle/src/ty/sty.rs:200:33: upvar_tys called before capture types are inferred


thread 'rustc' (2995014) panicked at /rustc-dev/752b9bf8798c2ffc1d3fe2b804c04454366fc6d6/compiler/rustc_middle/src/ty/sty.rs:200:33:
Box<dyn Any>
stack backtrace:
   0:     0x7f6b7ead5b46 - <<std[7799338267317a1]::sys::backtrace::BacktraceLock>::print::DisplayBacktrace as core[feb819e0aab98535]::fmt::Display>::fmt
   1:     0x7f6b7f2081cf - core[feb819e0aab98535]::fmt::write
   2:     0x7f6b7eaeac0c - <std[7799338267317a1]::sys::stdio::unix::Stderr as core[feb819e0aab98535]::io::write::Write>::write_fmt
   3:     0x7f6b7eaa83ea - std[7799338267317a1]::panicking::default_hook::{closure#0}
   4:     0x7f6b7eac9e43 - std[7799338267317a1]::panicking::default_hook
   5:     0x7f6b7da1338f - std[7799338267317a1]::panicking::update_hook::<alloc[eddc929262330b86]::boxed::Box<rustc_driver_impl[93e22c4ae85d6128]::install_ice_hook::{closure#1}>>::{closure#0}
   6:     0x7f6b7eaca2e2 - std[7799338267317a1]::panicking::panic_with_hook
   7:     0x7f6b7da41c44 - std[7799338267317a1]::panicking::begin_panic::<rustc_errors[ccb98f0a5bff281a]::ExplicitBug>::{closure#0}
   8:     0x7f6b7da3a71e - std[7799338267317a1]::sys::backtrace::__rust_end_short_backtrace::<std[7799338267317a1]::panicking::begin_panic<rustc_errors[ccb98f0a5bff281a]::ExplicitBug>::{closure#0}, !>
   9:     0x7f6b7da387be - std[7799338267317a1]::panicking::begin_panic::<rustc_errors[ccb98f0a5bff281a]::ExplicitBug>
  10:     0x7f6b7da4d511 - <rustc_errors[ccb98f0a5bff281a]::diagnostic::BugAbort as rustc_errors[ccb98f0a5bff281a]::diagnostic::EmissionGuarantee>::emit_producing_guarantee
  11:     0x7f6b7dff4cb9 - rustc_middle[95f7c36db503aa5c]::util::bug::opt_span_bug_fmt::<rustc_span[aab65db9cf037f3]::span_encoding::Span>::{closure#0}
  12:     0x7f6b7dff50f2 - rustc_middle[95f7c36db503aa5c]::ty::context::tls::with_opt::<rustc_middle[95f7c36db503aa5c]::util::bug::opt_span_bug_fmt<rustc_span[aab65db9cf037f3]::span_encoding::Span>::{closure#0}, !>::{closure#0}
  13:     0x7f6b7dfdfeb0 - rustc_middle[95f7c36db503aa5c]::ty::context::tls::with_context_opt::<rustc_middle[95f7c36db503aa5c]::ty::context::tls::with_opt<rustc_middle[95f7c36db503aa5c]::util::bug::opt_span_bug_fmt<rustc_span[aab65db9cf037f3]::span_encoding::Span>::{closure#0}, !>::{closure#0}, !>
  14:     0x7f6b7aca83d4 - rustc_middle[95f7c36db503aa5c]::util::bug::bug_fmt
  15:     0x7f6b7e7e4b70 - <rustc_trait_selection[b2c49a93e168dccb]::error_reporting::TypeErrCtxt>::note_closure_capture::<rustc_span[aab65db9cf037f3]::ErrorGuaranteed>
  16:     0x7f6b7e7f9e1f - <rustc_trait_selection[b2c49a93e168dccb]::error_reporting::TypeErrCtxt>::note_obligation_cause_code_inner::<rustc_span[aab65db9cf037f3]::ErrorGuaranteed, rustc_middle[95f7c36db503aa5c]::ty::predicate::Predicate>
  17:     0x7f6b7e7e4c36 - <rustc_trait_selection[b2c49a93e168dccb]::error_reporting::TypeErrCtxt>::note_obligation_cause_code::<rustc_span[aab65db9cf037f3]::ErrorGuaranteed, rustc_middle[95f7c36db503aa5c]::ty::predicate::Predicate>
  18:     0x7f6b7e8f1d1c - <rustc_trait_selection[b2c49a93e168dccb]::error_reporting::TypeErrCtxt>::note_obligation_cause
  19:     0x7f6b7e8de797 - <rustc_trait_selection[b2c49a93e168dccb]::error_reporting::TypeErrCtxt>::report_selection_error
  20:     0x7f6b7e905fc9 - <rustc_trait_selection[b2c49a93e168dccb]::error_reporting::TypeErrCtxt>::report_fulfillment_error
  21:     0x7f6b7d298d3c - <rustc_trait_selection[b2c49a93e168dccb]::error_reporting::TypeErrCtxt>::report_fulfillment_errors
  22:     0x7f6b7f2f3426 - <rustc_hir_typeck[74465e21f53f1374]::fn_ctxt::FnCtxt>::resolve_vars_with_obligations::<rustc_middle[95f7c36db503aa5c]::ty::Ty>
  23:     0x7f6b7fd33cde - <rustc_hir_typeck[74465e21f53f1374]::fn_ctxt::FnCtxt>::check_expr_with_expectation_and_args
  24:     0x7f6b7fd28105 - <rustc_hir_typeck[74465e21f53f1374]::fn_ctxt::FnCtxt>::check_expr_block
  25:     0x7f6b7fd2f155 - <rustc_hir_typeck[74465e21f53f1374]::fn_ctxt::FnCtxt>::check_expr_with_expectation_and_args
  26:     0x7f6b7fd13258 - rustc_hir_typeck[74465e21f53f1374]::check::check_fn
  27:     0x7f6b8067a55b - rustc_hir_typeck[74465e21f53f1374]::typeck_with_inspect::{closure#0}
  28:     0x7f6b80678b7a - rustc_query_impl[bdd1a1285068393]::query_vtables::typeck_root::invoke_provider_fn::__rust_begin_short_backtrace
  29:     0x7f6b7f879535 - rustc_query_impl[bdd1a1285068393]::execution::try_execute_query::<rustc_data_structures[b3e0016b95cb4620]::vec_cache::VecCache<rustc_span[aab65db9cf037f3]::def_id::LocalDefId, rustc_middle[95f7c36db503aa5c]::query::erase::ErasedData<[u8; 8usize]>, rustc_middle[95f7c36db503aa5c]::dep_graph::graph::DepNodeIndex>, false>
  30:     0x7f6b7f879167 - rustc_query_impl[bdd1a1285068393]::query_vtables::typeck_root::execute_query_non_incr::__rust_end_short_backtrace
  31:     0x7f6b7f93566f - <rustc_middle[95f7c36db503aa5c]::ty::context::TyCtxt>::par_hir_body_owners::<rustc_hir_analysis[3f6e10ab2280337c]::check_crate::{closure#1}>::{closure#0}
  32:     0x7f6b7f93492e - rustc_hir_analysis[3f6e10ab2280337c]::check_crate
  33:     0x7f6b7f87aaf3 - rustc_interface[1845d939591a8dca]::passes::analysis
  34:     0x7f6b8049d7ca - rustc_query_impl[bdd1a1285068393]::execution::try_execute_query::<rustc_middle[95f7c36db503aa5c]::query::caches::SingleCache<rustc_middle[95f7c36db503aa5c]::query::erase::ErasedData<[u8; 0usize]>>, false>
  35:     0x7f6b8049d56b - rustc_query_impl[bdd1a1285068393]::query_vtables::analysis::execute_query_non_incr::__rust_end_short_backtrace
  36:     0x7f6b8054bb4c - rustc_interface[1845d939591a8dca]::interface::run_compiler::<(), rustc_driver_impl[93e22c4ae85d6128]::run_compiler::{closure#0}>::{closure#2}
  37:     0x7f6b80628f42 - std[7799338267317a1]::sys::backtrace::__rust_begin_short_backtrace::<rustc_interface[1845d939591a8dca]::util::run_in_thread_with_globals<rustc_interface[1845d939591a8dca]::util::run_in_thread_pool_with_globals<rustc_interface[1845d939591a8dca]::interface::run_compiler<(), rustc_driver_impl[93e22c4ae85d6128]::run_compiler::{closure#0}>::{closure#2}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>
  38:     0x7f6b80628ced - <std[7799338267317a1]::thread::lifecycle::spawn_unchecked<rustc_interface[1845d939591a8dca]::util::run_in_thread_with_globals<rustc_interface[1845d939591a8dca]::util::run_in_thread_pool_with_globals<rustc_interface[1845d939591a8dca]::interface::run_compiler<(), rustc_driver_impl[93e22c4ae85d6128]::run_compiler::{closure#0}>::{closure#2}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>::{closure#1} as core[feb819e0aab98535]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  39:     0x7f6b80631607 - <std[7799338267317a1]::sys::thread::unix::Thread>::new::thread_start
  40:     0x7f6b796980a2 - <unknown>
  41:     0x7f6b7972080c - <unknown>
  42:                0x0 - <unknown>

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 1.100.0-nightly (752b9bf87 2026-09-07) running on x86_64-unknown-linux-gnu

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 3 previous errors

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

Activity

matthiaskrgr
added
C-bugCategory: This is a bug.
on Sep 7, 2026
rustbot
added
needs-triageThis issue may need triage. Remove when done. See docs forge.rust-lang.org/release/issue-triaging
on Sep 7, 2026

matthiaskrgr commented on Sep 7, 2026

@matthiaskrgr
matthiaskrgr
on Sep 7, 2026
MemberAuthor

yesterday:


error[E0277]: the size for values of type `[{integer}]` cannot be known at compilation time
    --> a.rs:2:15
     |
   2 |     Some([0]).map(|s| s[..]);
     |               ^^^ doesn't have a size known at compile-time
     |
     = help: the trait `Sized` is not implemented for `[{integer}]`
note: required by an implicit `Sized` bound in `Option::<T>::map`
    --> /home/matthias/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/option.rs:1160:22
     |
1160 |     pub const fn map<U, F>(self, f: F) -> Option<U>
     |                      ^ required by the implicit `Sized` requirement on this type parameter in `Option::<T>::map`

error[E0277]: the size for values of type `[{integer}]` cannot be known at compilation time
 --> a.rs:2:23
  |
2 |     Some([0]).map(|s| s[..]);
  |                       ^^^^^ doesn't have a size known at compile-time
  |
  = help: the trait `Sized` is not implemented for `[{integer}]`
  = note: the return type of a function must have a statically known size

error[E0277]: the size for values of type `[{integer}]` cannot be known at compilation time
    --> a.rs:2:19
     |
   2 |     Some([0]).map(|s| s[..]);
     |               --- ---^^^^^^
     |               |   |
     |               |   doesn't have a size known at compile-time
     |               |   within this `{closure@a.rs:2:19: 2:22}`
     |               required by a bound introduced by this call
     |
     = help: within `{closure@a.rs:2:19: 2:22}`, the trait `Sized` is not implemented for `[{integer}]`
note: required because it's used within this closure
    --> a.rs:2:19
     |
   2 |     Some([0]).map(|s| s[..]);
     |                   ^^^
note: required by a bound in `Option::<T>::map`
    --> /home/matthias/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/option.rs:1162:12
     |
1160 |     pub const fn map<U, F>(self, f: F) -> Option<U>
     |                  --- required by a bound in this associated function
1161 |     where
1162 |         F: [const] FnOnce(T) -> U + [const] Destruct,
     |            ^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `Option::<T>::map`

error: aborting due to 3 previous errors

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

today:

error[E0277]: the size for values of type `[{integer}]` cannot be known at compilation time
    --> a.rs:2:15
     |
   2 |     Some([0]).map(|s| s[..]);
     |               ^^^ doesn't have a size known at compile-time
     |
     = help: the trait `Sized` is not implemented for `[{integer}]`
note: required by an implicit `Sized` bound in `Option::<T>::map`
    --> /home/matthias/.rustup/toolchains/master/lib/rustlib/src/rust/library/core/src/option.rs:1160:22
     |
1160 |     pub const fn map<U, F>(self, f: F) -> Option<U>
     |                      ^ required by the implicit `Sized` requirement on this type parameter in `Option::<T>::map`

error[E0277]: the size for values of type `[{integer}]` cannot be known at compilation time
 --> a.rs:2:23
  |
2 |     Some([0]).map(|s| s[..]);
  |                       ^^^^^ doesn't have a size known at compile-time
  |
  = help: the trait `Sized` is not implemented for `[{integer}]`
  = note: the return type of a function must have a statically known size

error: internal compiler error: /rustc-dev/752b9bf8798c2ffc1d3fe2b804c04454366fc6d6/compiler/rustc_middle/src/ty/sty.rs:200:33: upvar_tys called before capture types are inferred


thread 'rustc' (2995917) panicked at /rustc-dev/752b9bf8798c2ffc1d3fe2b804c04454366fc6d6/compiler/rustc_middle/src/ty/sty.rs:200:33:
Box<dyn Any>
stack backtrace:
   0:     0x7fd8440d5b46 - <<std[7799338267317a1]::sys::backtrace::BacktraceLock>::print::DisplayBacktrace as core[feb819e0aab98535]::fmt::Display>::fmt
   1:     0x7fd8448081cf - core[feb819e0aab98535]::fmt::write
   2:     0x7fd8440eac0c - <std[7799338267317a1]::sys::stdio::unix::Stderr as core[feb819e0aab98535]::io::write::Write>::write_fmt
   3:     0x7fd8440a83ea - std[7799338267317a1]::panicking::default_hook::{closure#0}
   4:     0x7fd8440c9e43 - std[7799338267317a1]::panicking::default_hook
   5:     0x7fd84301338f - std[7799338267317a1]::panicking::update_hook::<alloc[eddc929262330b86]::boxed::Box<rustc_driver_impl[93e22c4ae85d6128]::install_ice_hook::{closure#1}>>::{closure#0}
   6:     0x7fd8440ca2e2 - std[7799338267317a1]::panicking::panic_with_hook
   7:     0x7fd843041c44 - std[7799338267317a1]::panicking::begin_panic::<rustc_errors[ccb98f0a5bff281a]::ExplicitBug>::{closure#0}
   8:     0x7fd84303a71e - std[7799338267317a1]::sys::backtrace::__rust_end_short_backtrace::<std[7799338267317a1]::panicking::begin_panic<rustc_errors[ccb98f0a5bff281a]::ExplicitBug>::{closure#0}, !>
   9:     0x7fd8430387be - std[7799338267317a1]::panicking::begin_panic::<rustc_errors[ccb98f0a5bff281a]::ExplicitBug>
  10:     0x7fd84304d511 - <rustc_errors[ccb98f0a5bff281a]::diagnostic::BugAbort as rustc_errors[ccb98f0a5bff281a]::diagnostic::EmissionGuarantee>::emit_producing_guarantee
  11:     0x7fd8435f4cb9 - rustc_middle[95f7c36db503aa5c]::util::bug::opt_span_bug_fmt::<rustc_span[aab65db9cf037f3]::span_encoding::Span>::{closure#0}
  12:     0x7fd8435f50f2 - rustc_middle[95f7c36db503aa5c]::ty::context::tls::with_opt::<rustc_middle[95f7c36db503aa5c]::util::bug::opt_span_bug_fmt<rustc_span[aab65db9cf037f3]::span_encoding::Span>::{closure#0}, !>::{closure#0}
  13:     0x7fd8435dfeb0 - rustc_middle[95f7c36db503aa5c]::ty::context::tls::with_context_opt::<rustc_middle[95f7c36db503aa5c]::ty::context::tls::with_opt<rustc_middle[95f7c36db503aa5c]::util::bug::opt_span_bug_fmt<rustc_span[aab65db9cf037f3]::span_encoding::Span>::{closure#0}, !>::{closure#0}, !>
  14:     0x7fd8402a83d4 - rustc_middle[95f7c36db503aa5c]::util::bug::bug_fmt
  15:     0x7fd843de4b70 - <rustc_trait_selection[b2c49a93e168dccb]::error_reporting::TypeErrCtxt>::note_closure_capture::<rustc_span[aab65db9cf037f3]::ErrorGuaranteed>
  16:     0x7fd843df9e1f - <rustc_trait_selection[b2c49a93e168dccb]::error_reporting::TypeErrCtxt>::note_obligation_cause_code_inner::<rustc_span[aab65db9cf037f3]::ErrorGuaranteed, rustc_middle[95f7c36db503aa5c]::ty::predicate::Predicate>
  17:     0x7fd843de4c36 - <rustc_trait_selection[b2c49a93e168dccb]::error_reporting::TypeErrCtxt>::note_obligation_cause_code::<rustc_span[aab65db9cf037f3]::ErrorGuaranteed, rustc_middle[95f7c36db503aa5c]::ty::predicate::Predicate>
  18:     0x7fd843ef1d1c - <rustc_trait_selection[b2c49a93e168dccb]::error_reporting::TypeErrCtxt>::note_obligation_cause
  19:     0x7fd843ede797 - <rustc_trait_selection[b2c49a93e168dccb]::error_reporting::TypeErrCtxt>::report_selection_error
  20:     0x7fd843f05fc9 - <rustc_trait_selection[b2c49a93e168dccb]::error_reporting::TypeErrCtxt>::report_fulfillment_error
  21:     0x7fd842898d3c - <rustc_trait_selection[b2c49a93e168dccb]::error_reporting::TypeErrCtxt>::report_fulfillment_errors
  22:     0x7fd8448f3426 - <rustc_hir_typeck[74465e21f53f1374]::fn_ctxt::FnCtxt>::resolve_vars_with_obligations::<rustc_middle[95f7c36db503aa5c]::ty::Ty>
  23:     0x7fd845333cde - <rustc_hir_typeck[74465e21f53f1374]::fn_ctxt::FnCtxt>::check_expr_with_expectation_and_args
  24:     0x7fd845328105 - <rustc_hir_typeck[74465e21f53f1374]::fn_ctxt::FnCtxt>::check_expr_block
  25:     0x7fd84532f155 - <rustc_hir_typeck[74465e21f53f1374]::fn_ctxt::FnCtxt>::check_expr_with_expectation_and_args
  26:     0x7fd845313258 - rustc_hir_typeck[74465e21f53f1374]::check::check_fn
  27:     0x7fd845c7a55b - rustc_hir_typeck[74465e21f53f1374]::typeck_with_inspect::{closure#0}
  28:     0x7fd845c78b7a - rustc_query_impl[bdd1a1285068393]::query_vtables::typeck_root::invoke_provider_fn::__rust_begin_short_backtrace
  29:     0x7fd844e79535 - rustc_query_impl[bdd1a1285068393]::execution::try_execute_query::<rustc_data_structures[b3e0016b95cb4620]::vec_cache::VecCache<rustc_span[aab65db9cf037f3]::def_id::LocalDefId, rustc_middle[95f7c36db503aa5c]::query::erase::ErasedData<[u8; 8usize]>, rustc_middle[95f7c36db503aa5c]::dep_graph::graph::DepNodeIndex>, false>
  30:     0x7fd844e79167 - rustc_query_impl[bdd1a1285068393]::query_vtables::typeck_root::execute_query_non_incr::__rust_end_short_backtrace
  31:     0x7fd844f3566f - <rustc_middle[95f7c36db503aa5c]::ty::context::TyCtxt>::par_hir_body_owners::<rustc_hir_analysis[3f6e10ab2280337c]::check_crate::{closure#1}>::{closure#0}
  32:     0x7fd844f3492e - rustc_hir_analysis[3f6e10ab2280337c]::check_crate
  33:     0x7fd844e7aaf3 - rustc_interface[1845d939591a8dca]::passes::analysis
  34:     0x7fd845a9d7ca - rustc_query_impl[bdd1a1285068393]::execution::try_execute_query::<rustc_middle[95f7c36db503aa5c]::query::caches::SingleCache<rustc_middle[95f7c36db503aa5c]::query::erase::ErasedData<[u8; 0usize]>>, false>
  35:     0x7fd845a9d56b - rustc_query_impl[bdd1a1285068393]::query_vtables::analysis::execute_query_non_incr::__rust_end_short_backtrace
  36:     0x7fd845b4bb4c - rustc_interface[1845d939591a8dca]::interface::run_compiler::<(), rustc_driver_impl[93e22c4ae85d6128]::run_compiler::{closure#0}>::{closure#2}
  37:     0x7fd845c28f42 - std[7799338267317a1]::sys::backtrace::__rust_begin_short_backtrace::<rustc_interface[1845d939591a8dca]::util::run_in_thread_with_globals<rustc_interface[1845d939591a8dca]::util::run_in_thread_pool_with_globals<rustc_interface[1845d939591a8dca]::interface::run_compiler<(), rustc_driver_impl[93e22c4ae85d6128]::run_compiler::{closure#0}>::{closure#2}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>
  38:     0x7fd845c28ced - <std[7799338267317a1]::thread::lifecycle::spawn_unchecked<rustc_interface[1845d939591a8dca]::util::run_in_thread_with_globals<rustc_interface[1845d939591a8dca]::util::run_in_thread_pool_with_globals<rustc_interface[1845d939591a8dca]::interface::run_compiler<(), rustc_driver_impl[93e22c4ae85d6128]::run_compiler::{closure#0}>::{closure#2}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>::{closure#1} as core[feb819e0aab98535]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  39:     0x7fd845c31607 - <std[7799338267317a1]::sys::thread::unix::Thread>::new::thread_start
  40:     0x7fd83ec980a2 - <unknown>
  41:     0x7fd83ed2080c - <unknown>
  42:                0x0 - <unknown>

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 `/tmp/upvar/rustc-ice-2026-09-07T17_23_13-2995915.txt` to your bug report

note: rustc 1.100.0-nightly (752b9bf87 2026-09-07) running on x86_64-unknown-linux-gnu

query stack during panic:
#0 [typeck_root] type-checking `main`
#1 [analysis] running analysis passes on crate `a`
end of query stack
error: aborting due to 3 previous errors

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

my guess would be its related to #161624

matthiaskrgr
added
A-diagnosticsArea: Messages for errors, warnings, and lints
I-ICEIssue: The compiler panicked, giving an Internal Compilation Error (ICE) ❄️
regression-untriagedUntriaged performance or correctness regression.
on Sep 7, 2026
rustbot
added
T-compilerRelevant to the compiler team, which will review and decide on the PR/issue.
I-prioritizeIssue needs a team member to assess the impact. Will be replaced by P-{low,medium,high,critical}
on Sep 7, 2026
lcnr
added
WG-trait-system-refactorThe Rustc Trait System Refactor Initiative (-Znext-solver)
P-mediumMedium priority
and removed
I-prioritizeIssue needs a team member to assess the impact. Will be replaced by P-{low,medium,high,critical}
on Sep 8, 2026

lcnr commented on Sep 8, 2026

@lcnr
lcnr
on Sep 8, 2026
Contributor

https://rust-lang.zulipchat.com/#narrow/channel/618216-t-types.2Fcall-for-participation/topic/incorrectly.20accessing.20upvars.20in.20diagnostics.20code/with/622511748

matthiaskrgr commented on Sep 8, 2026

@matthiaskrgr
matthiaskrgr
on Sep 8, 2026
MemberAuthor

Ooh its a next-solver thing! >.<
I was wondering how this could have passed in our testsuite without ICEing but we use coherence there :/

JonathanBrouwer
added 2 commits that reference this issue on Sep 8, 2026

Rollup merge of rust-lang#162489 - chenyukang:yukang-refactor-upvar_t…

425d19e

Rollup merge of rust-lang#162489 - chenyukang:yukang-refactor-upvar_t…

588de2e
rust-bors
added a commit that references this issue on Sep 9, 2026

Unrolled build for #162489 in rollup 162503

c144f50
matthiaskrgr
marked [ICE]: upvar_tys called before capture types are inferred #162977 as a duplicate of this issue on Sep 18, 2026

BuilderEd commented on Sep 19, 2026

@BuilderEd
BuilderEd
on Sep 19, 2026

Another reproducer for this ICE, found by an automated compiler-testing
campaign; sharing in case it is a useful extra test case for #162595.

pub trait Sieve {
    fn strain(&self, xs: &[u64], f: &dyn Fn(&u64) -> u64) -> &u64;
    def_sieve!();
}
macro_rules! def_sieve {
    () => {
        fn sift(&self, xs: &[u64]) -> u64 {
            let a = self.strain(xs, &|v: u64| v.wrapping_mul(127));
            0
        }
    };
}
use def_sieve;
pub struct Pan(pub Vec<u64>);
impl Sieve for Pan {
    fn strain(&self, xs: &[u64], f: &dyn Fn(&u64) -> u64) -> &u64 {
        &self.0[0]
    }
}
pub fn temper_fold(t: (u64, Option<u16>, Result<u32, u16>, &[u64])) -> u64 {
    match t {
        (a, None, Err(_), [x, ..]) => x,
        (a, None | Some(_), Ok(_) | Err(_), rest @ ..) if rest.len() == 0 => 5,
        _ => 0,
    }
}

Expected: the two pattern errors (rest @ is not allowed in a tuple,
.. patterns are not allowed here) and a clean rejection. Actual: additionally

error: internal compiler error: compiler/rustc_middle/src/ty/sty.rs:194:33:
upvar_tys called before capture types are inferred

with the same backtrace path as the original report
(note_closure_capture -> note_obligation_cause_code_inner ->
report_selection_error -> report_fulfillment_errors).

Versions tested:

  • nightly-2026-09-07 (5a2be9f): this input is rejected cleanly (E0277
    CoerceUnsized errors on the closures, no ICE). I did not test the
    issue-body snippet on this toolchain; it is reported against a master
    build of the same date (752b9bf)
  • nightly-2026-09-12 (0fc1413): ICE
  • nightly-2026-09-18 (420ed2a): ICE (newest nightly I tested)

The reproducer combines two ingredients: a closure coerced to &dyn Fn
inside a macro-generated trait method, and the invalid tuple pattern
elsewhere in the crate. I did not isolate which ingredient drives error
reporting into note_closure_capture before capture types are inferred
(the issue-body snippet ICEs without any pattern error, so the closure
error path may be the driver here too). Happy to file this as a separate
issue if the trigger turns out to be distinct.

RashingPro
marked [ICE]: rustc panic at rustc_middle/src/ty/sty.rs:194:33 #163072 as a duplicate of this issue on Sep 21, 2026

RashingPro commented on Sep 21, 2026

@RashingPro
RashingPro
on Sep 21, 2026

#163072 contains another code snippet triggering this, just in case

JonathanBrouwer
added a commit that references this issue on Sep 24, 2026

Rollup merge of rust-lang#162595 - amirHdev:uninferred-upvars, r=lcnr

be3bb9f
rust-bors
closed this as completedin be3bb9fon Sep 24, 2026
rust-bors
added a commit that references this issue on Sep 24, 2026

Unrolled build for #162595 in rollup 163265

7b9efef
pull
added a commit that references this issue on Sep 25, 2026

Rollup merge of #162595 - amirHdev:uninferred-upvars, r=lcnr

eb3e475
reddevilmidzy
removed
needs-triageThis issue may need triage. Remove when done. See docs forge.rust-lang.org/release/issue-triaging
on Sep 27, 2026
clarfonthey
added a commit that references this issue on Sep 30, 2026

Rollup merge of #162595 - amirHdev:uninferred-upvars, r=lcnr

27546fb
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