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matthiaskrgr opened this issue May 9, 2025 · 2 comments
Closed

ICE: broken mir with let_chains #140866

matthiaskrgr opened this issue May 9, 2025 · 2 comments
Labels
C-bug Category: This is a bug. F-let_chains `#![feature(let_chains)]` I-ICE Issue: The compiler panicked, giving an Internal Compilation Error (ICE) ❄️ T-compiler Relevant to the compiler team, which will review and decide on the PR/issue.

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@matthiaskrgr
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auto-reduced (treereduce-rust):

//@compile-flags: -Zlint-mir
#![feature(let_chains)]
struct TupleIter<T, I: Iterator<Item = T>> {
    inner: I,
}

impl<T, I: Iterator<Item = T>> Iterator for TupleIter<T, I> {
    type Item = (T, T, T);

    fn next(&mut self) -> Option<Self::Item> {
        let inner = &mut self.inner;

        if let Some(first) = inner.next()
            && let Some(second) = inner.next()
            && let Some(third) = inner.next()
        {
            Some((first, second, third))
        } else {
            None
        }
    }
}

fn main() {}

original:

//@ compile-flags: -Zvalidate-mir -C opt-level=3
//@ build-pass
//@ edition: 2024

struct TupleIter<T, I: Iterator<Item = T>> {
    inner: I,
}

impl<T, I: Iterator<Item = T>> Iterator for TupleIter<T, I> {
    type Item = (T, T, T);

    fn next(&mut self) -> Option<Self::Item> {
        let inner = &mut self.inner;

        if let Some(first) = inner.next()
            && let Some(second) = inner.next()
            && let Some(third) = inner.next()
        {
            Some((first, second, third))
        } else {
            None
        }
    }
}

fn main() {
    let vec: Vec<u8> = Vec::new();
    let mut tup_iter = TupleIter {
        inner: vec.into_iter(),
    };
    tup_iter.next();
}

Version information

rustc 1.89.0-nightly (dcecb9917 2025-05-09)
binary: rustc
commit-hash: dcecb99176edf2eec51613730937d21cdd5c8f6e
commit-date: 2025-05-09
host: x86_64-unknown-linux-gnu
release: 1.89.0-nightly
LLVM version: 20.1.4

Command:
/home/matthias/.rustup/toolchains/master/bin/rustc -Zlint-mir -Zcrate-attr=feature(let_chains)

Program output 

warning: struct `TupleIter` is never constructed
 --> /tmp/icemaker_global_tempdir.8Nvh3CQXZMXY/rustc_testrunner_tmpdir_reporting.LQqC63yDbYhH/mvce.rs:1:8
  |
1 | struct TupleIter<T, I: Iterator<Item = T>> {
  |        ^^^^^^^^^
  |
  = note: `#[warn(dead_code)]` on by default

warning: 1 warning 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: broken MIR in Item(DefId(0:11 ~ mvce[eae9]::{impl#0}::next)) (after pass CheckForceInline) at bb28[1]:
                                use of local _11, which has no storage here
  --> /tmp/icemaker_global_tempdir.8Nvh3CQXZMXY/rustc_testrunner_tmpdir_reporting.LQqC63yDbYhH/mvce.rs:19:5
   |
19 |     }
   |     ^
   |
note: delayed at compiler/rustc_mir_transform/src/lint.rs:74:22
         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_mir_transform::lint::Lint>::fail::<alloc::string::String>
         5: <rustc_mir_transform::lint::Lint as rustc_middle::mir::visit::Visitor>::visit_local
         6: <rustc_mir_transform::lint::Lint as rustc_middle::mir::visit::Visitor>::visit_place
         7: <rustc_mir_transform::lint::Lint as rustc_middle::mir::visit::Visitor>::visit_terminator
         8: rustc_mir_transform::lint::lint_body
         9: rustc_mir_transform::mir_built
        10: rustc_query_impl::plumbing::__rust_begin_short_backtrace::<rustc_query_impl::query_impl::mir_built::dynamic_query::{closure#2}::{closure#0}, rustc_middle::query::erase::Erased<[u8; 8]>>
        11: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::DynamicConfig<rustc_data_structures::vec_cache::VecCache<rustc_span::def_id::LocalDefId, rustc_middle::query::erase::Erased<[u8; 8]>, rustc_query_system::dep_graph::graph::DepNodeIndex>, false, false, false>, rustc_query_impl::plumbing::QueryCtxt, false>
        12: rustc_query_impl::query_impl::mir_built::get_query_non_incr::__rust_end_short_backtrace
        13: rustc_mir_build::check_unsafety::check_unsafety
        14: rustc_query_impl::plumbing::__rust_begin_short_backtrace::<rustc_query_impl::query_impl::check_unsafety::dynamic_query::{closure#2}::{closure#0}, rustc_middle::query::erase::Erased<[u8; 0]>>
        15: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::DynamicConfig<rustc_data_structures::vec_cache::VecCache<rustc_span::def_id::LocalDefId, rustc_middle::query::erase::Erased<[u8; 0]>, rustc_query_system::dep_graph::graph::DepNodeIndex>, false, false, false>, rustc_query_impl::plumbing::QueryCtxt, false>
        16: rustc_query_impl::query_impl::check_unsafety::get_query_non_incr::__rust_end_short_backtrace
        17: rustc_interface::passes::run_required_analyses
        18: rustc_interface::passes::analysis
        19: rustc_query_impl::plumbing::__rust_begin_short_backtrace::<rustc_query_impl::query_impl::analysis::dynamic_query::{closure#2}::{closure#0}, rustc_middle::query::erase::Erased<[u8; 0]>>
        20: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::DynamicConfig<rustc_query_system::query::caches::SingleCache<rustc_middle::query::erase::Erased<[u8; 0]>>, false, false, false>, rustc_query_impl::plumbing::QueryCtxt, false>
        21: rustc_query_impl::query_impl::analysis::get_query_non_incr::__rust_end_short_backtrace
        22: rustc_interface::passes::create_and_enter_global_ctxt::<core::option::Option<rustc_interface::queries::Linker>, rustc_driver_impl::run_compiler::{closure#0}::{closure#2}>::{closure#2}::{closure#0}
        23: rustc_interface::interface::run_compiler::<(), rustc_driver_impl::run_compiler::{closure#0}>::{closure#1}
        24: 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}, ()>
        25: <<std::thread::Builder>::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}
        26: std::sys::pal::unix::thread::Thread::new::thread_start
        27: <unknown>
        28: <unknown>
  --> /tmp/icemaker_global_tempdir.8Nvh3CQXZMXY/rustc_testrunner_tmpdir_reporting.LQqC63yDbYhH/mvce.rs:19:5
   |
19 |     }
   |     ^

error: internal compiler error: broken MIR in Item(DefId(0:11 ~ mvce[eae9]::{impl#0}::next)) (after pass CheckForceInline) at bb41[0]:
                                use of local _7, which has no storage here
  --> /tmp/icemaker_global_tempdir.8Nvh3CQXZMXY/rustc_testrunner_tmpdir_reporting.LQqC63yDbYhH/mvce.rs:19:5
   |
19 |     }
   |     ^
   |
note: delayed at compiler/rustc_mir_transform/src/lint.rs:74:22
         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_mir_transform::lint::Lint>::fail::<alloc::string::String>
         5: <rustc_mir_transform::lint::Lint as rustc_middle::mir::visit::Visitor>::visit_local
         6: <rustc_mir_transform::lint::Lint as rustc_middle::mir::visit::Visitor>::visit_place
         7: <rustc_mir_transform::lint::Lint as rustc_middle::mir::visit::Visitor>::visit_terminator
         8: rustc_mir_transform::lint::lint_body
         9: rustc_mir_transform::mir_built
        10: rustc_query_impl::plumbing::__rust_begin_short_backtrace::<rustc_query_impl::query_impl::mir_built::dynamic_query::{closure#2}::{closure#0}, rustc_middle::query::erase::Erased<[u8; 8]>>
        11: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::DynamicConfig<rustc_data_structures::vec_cache::VecCache<rustc_span::def_id::LocalDefId, rustc_middle::query::erase::Erased<[u8; 8]>, rustc_query_system::dep_graph::graph::DepNodeIndex>, false, false, false>, rustc_query_impl::plumbing::QueryCtxt, false>
        12: rustc_query_impl::query_impl::mir_built::get_query_non_incr::__rust_end_short_backtrace
        13: rustc_mir_build::check_unsafety::check_unsafety
        14: rustc_query_impl::plumbing::__rust_begin_short_backtrace::<rustc_query_impl::query_impl::check_unsafety::dynamic_query::{closure#2}::{closure#0}, rustc_middle::query::erase::Erased<[u8; 0]>>
        15: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::DynamicConfig<rustc_data_structures::vec_cache::VecCache<rustc_span::def_id::LocalDefId, rustc_middle::query::erase::Erased<[u8; 0]>, rustc_query_system::dep_graph::graph::DepNodeIndex>, false, false, false>, rustc_query_impl::plumbing::QueryCtxt, false>
        16: rustc_query_impl::query_impl::check_unsafety::get_query_non_incr::__rust_end_short_backtrace
        17: rustc_interface::passes::run_required_analyses
        18: rustc_interface::passes::analysis
        19: rustc_query_impl::plumbing::__rust_begin_short_backtrace::<rustc_query_impl::query_impl::analysis::dynamic_query::{closure#2}::{closure#0}, rustc_middle::query::erase::Erased<[u8; 0]>>
        20: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::DynamicConfig<rustc_query_system::query::caches::SingleCache<rustc_middle::query::erase::Erased<[u8; 0]>>, false, false, false>, rustc_query_impl::plumbing::QueryCtxt, false>
        21: rustc_query_impl::query_impl::analysis::get_query_non_incr::__rust_end_short_backtrace
        22: rustc_interface::passes::create_and_enter_global_ctxt::<core::option::Option<rustc_interface::queries::Linker>, rustc_driver_impl::run_compiler::{closure#0}::{closure#2}>::{closure#2}::{closure#0}
        23: rustc_interface::interface::run_compiler::<(), rustc_driver_impl::run_compiler::{closure#0}>::{closure#1}
        24: 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}, ()>
        25: <<std::thread::Builder>::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}
        26: std::sys::pal::unix::thread::Thread::new::thread_start
        27: <unknown>
        28: <unknown>
  --> /tmp/icemaker_global_tempdir.8Nvh3CQXZMXY/rustc_testrunner_tmpdir_reporting.LQqC63yDbYhH/mvce.rs:19:5
   |
19 |     }
   |     ^
<snip>
error: internal compiler error: broken MIR in Item(DefId(0:11 ~ mvce[eae9]::{impl#0}::next)) (after phase change to runtime-post-cleanup) at bb30[0]:
                                use of local _11, which has no storage here
  --> /tmp/icemaker_global_tempdir.8Nvh3CQXZMXY/rustc_testrunner_tmpdir_reporting.LQqC63yDbYhH/mvce.rs:19:5
   |
19 |     }
   |     ^
   |
note: delayed at compiler/rustc_mir_transform/src/lint.rs:74:22
         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_mir_transform::lint::Lint>::fail::<alloc::string::String>
         5: <rustc_mir_transform::lint::Lint as rustc_middle::mir::visit::Visitor>::visit_local
         6: <rustc_mir_transform::lint::Lint as rustc_middle::mir::visit::Visitor>::visit_place
         7: <rustc_mir_transform::lint::Lint as rustc_middle::mir::visit::Visitor>::visit_terminator
         8: rustc_mir_transform::lint::lint_body
         9: rustc_mir_transform::run_analysis_to_runtime_passes
        10: rustc_mir_transform::mir_drops_elaborated_and_const_checked
        11: rustc_query_impl::plumbing::__rust_begin_short_backtrace::<rustc_query_impl::query_impl::mir_drops_elaborated_and_const_checked::dynamic_query::{closure#2}::{closure#0}, rustc_middle::query::erase::Erased<[u8; 8]>>
        12: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::DynamicConfig<rustc_data_structures::vec_cache::VecCache<rustc_span::def_id::LocalDefId, rustc_middle::query::erase::Erased<[u8; 8]>, rustc_query_system::dep_graph::graph::DepNodeIndex>, false, false, false>, rustc_query_impl::plumbing::QueryCtxt, false>
        13: rustc_query_impl::query_impl::mir_drops_elaborated_and_const_checked::get_query_non_incr::__rust_end_short_backtrace
        14: rustc_interface::passes::run_required_analyses
        15: rustc_interface::passes::analysis
        16: rustc_query_impl::plumbing::__rust_begin_short_backtrace::<rustc_query_impl::query_impl::analysis::dynamic_query::{closure#2}::{closure#0}, rustc_middle::query::erase::Erased<[u8; 0]>>
        17: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::DynamicConfig<rustc_query_system::query::caches::SingleCache<rustc_middle::query::erase::Erased<[u8; 0]>>, false, false, false>, rustc_query_impl::plumbing::QueryCtxt, false>
        18: rustc_query_impl::query_impl::analysis::get_query_non_incr::__rust_end_short_backtrace
        19: rustc_interface::passes::create_and_enter_global_ctxt::<core::option::Option<rustc_interface::queries::Linker>, rustc_driver_impl::run_compiler::{closure#0}::{closure#2}>::{closure#2}::{closure#0}
        20: rustc_interface::interface::run_compiler::<(), rustc_driver_impl::run_compiler::{closure#0}>::{closure#1}
        21: 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}, ()>
        22: <<std::thread::Builder>::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}
        23: std::sys::pal::unix::thread::Thread::new::thread_start
        24: <unknown>
        25: <unknown>
  --> /tmp/icemaker_global_tempdir.8Nvh3CQXZMXY/rustc_testrunner_tmpdir_reporting.LQqC63yDbYhH/mvce.rs:19:5
   |
19 |     }
   |     ^

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 1.89.0-nightly (dcecb9917 2025-05-09) running on x86_64-unknown-linux-gnu

note: compiler flags: -Z lint-mir -Z crate-attr=feature(let_chains) -Z dump-mir-dir=dir

query stack during panic:
end of query stack

@rustbot label +F-let_chains
@matthiaskrgr matthiaskrgr added I-ICE Issue: The compiler panicked, giving an Internal Compilation Error (ICE) ❄️ T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. C-bug Category: This is a bug. labels May 9, 2025
@rustbot rustbot added needs-triage This issue may need triage. Remove it if it has been sufficiently triaged. F-let_chains `#![feature(let_chains)]` labels May 9, 2025
@compiler-errors
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Is this not a known bug and the reason we're stabilizing let chains only in edition 2024? #104843 (comment)

@matthiaskrgr
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matthiaskrgr commented May 9, 2025 •
edited
Loading

ah could be 👍
this bug felt vaguely familiar but I could't find any open ICE tickets about it / other tickets were all fixed

@fmease fmease removed the needs-triage This issue may need triage. Remove it if it has been sufficiently triaged. label May 10, 2025
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C-bug Category: This is a bug. F-let_chains `#![feature(let_chains)]` I-ICE Issue: The compiler panicked, giving an Internal Compilation Error (ICE) ❄️ T-compiler Relevant to the compiler team, which will review and decide on the PR/issue.
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