ICE: `tuple pattern not applied to a tuple`

[matthiaskrgr]

auto-reduced (treereduce-rust):

fn test_missing_unsafe_warning_on_repr_packed() {
    struct Foo {
        x: String,
    }

    let foo = Foo {};

    let c = || {
        let (_, t2) = foo.x;
    };

    c();
}

original code

original:

//@ edition:2021

// Given how the closure desugaring is implemented (at least at the time of writing this test),
// we don't need to truncate the captured path to a reference into a packed-struct if the field
// being referenced will be moved into the closure, since it's safe to move out a field from a
// packed-struct.
//
// However to avoid surprises for the user, or issues when the closure is
// inlined we will truncate the capture to access just the struct regardless of if the field
// might get moved into the closure.
//
// It is possible for someone to try writing the code that relies on the desugaring to create a ref
// into a packed-struct. Here we test that the compiler still detects that case.
fn test_missing_unsafe_warning_on_repr_packed() {
    #[derive(Debug, PartialEq, Eq)]
    struct Foo { x: String }

    let foo = Foo { x: String::new() };

    let c = || {
        println!(unused_must_use);
        //~^ ERROR: reference to packed field is unaligned
        let (_, t2) = foo.x;
    };

    c();
}

fn main() {
    test_missing_unsafe_warning_on_repr_packed();
}

Version information

rustc 1.78.0-nightly (f8131a48a 2024-02-21)
binary: rustc
commit-hash: f8131a48a46ac3bc8a3d0fe0477055b132cffdc3
commit-date: 2024-02-21
host: x86_64-unknown-linux-gnu
release: 1.78.0-nightly
LLVM version: 18.1.0

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

Program output

error[E0601]: `main` function not found in crate `mvce`
  --> /tmp/icemaker_global_tempdir.d70TvpvoHEvu/rustc_testrunner_tmpdir_reporting.gabpX6WsInFl/mvce.rs:17:2
   |
17 | }
   |  ^ consider adding a `main` function to `/tmp/icemaker_global_tempdir.d70TvpvoHEvu/rustc_testrunner_tmpdir_reporting.gabpX6WsInFl/mvce.rs`

error[E0063]: missing field `x` in initializer of `Foo`
  --> /tmp/icemaker_global_tempdir.d70TvpvoHEvu/rustc_testrunner_tmpdir_reporting.gabpX6WsInFl/mvce.rs:10:15
   |
10 |     let foo = Foo {};
   |               ^^^ missing `x`

error[E0308]: mismatched types
  --> /tmp/icemaker_global_tempdir.d70TvpvoHEvu/rustc_testrunner_tmpdir_reporting.gabpX6WsInFl/mvce.rs:13:13
   |
13 |         let (_, t2) = foo.x;
   |             ^^^^^^^   ----- this expression has type `String`
   |             |
   |             expected `String`, found `(_, _)`
   |
   = note: expected struct `String`
               found tuple `(_, _)`

error: internal compiler error: tuple pattern not applied to a tuple
  --> /tmp/icemaker_global_tempdir.d70TvpvoHEvu/rustc_testrunner_tmpdir_reporting.gabpX6WsInFl/mvce.rs:13:13
   |
13 |         let (_, t2) = foo.x;
   |             ^^^^^^^

thread 'rustc' panicked at compiler/rustc_hir_typeck/src/mem_categorization.rs:585:34:
Box<dyn Any>
stack backtrace:
   0:     0x7f82c541daf6 - std::backtrace_rs::backtrace::libunwind::trace::hbec2edc838b433e2
                               at /rustc/f8131a48a46ac3bc8a3d0fe0477055b132cffdc3/library/std/src/../../backtrace/src/backtrace/libunwind.rs:104:5
   1:     0x7f82c541daf6 - std::backtrace_rs::backtrace::trace_unsynchronized::h88c30257ee0dd166
                               at /rustc/f8131a48a46ac3bc8a3d0fe0477055b132cffdc3/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5
   2:     0x7f82c541daf6 - std::sys_common::backtrace::_print_fmt::h9176654d509e3088
                               at /rustc/f8131a48a46ac3bc8a3d0fe0477055b132cffdc3/library/std/src/sys_common/backtrace.rs:68:5
   3:     0x7f82c541daf6 - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::h671feaee1776bf19
                               at /rustc/f8131a48a46ac3bc8a3d0fe0477055b132cffdc3/library/std/src/sys_common/backtrace.rs:44:22
   4:     0x7f82c546ea7c - core::fmt::rt::Argument::fmt::h59605c83ae32d935
                               at /rustc/f8131a48a46ac3bc8a3d0fe0477055b132cffdc3/library/core/src/fmt/rt.rs:142:9
   5:     0x7f82c546ea7c - core::fmt::write::hf7af8dfcfd20db5b
                               at /rustc/f8131a48a46ac3bc8a3d0fe0477055b132cffdc3/library/core/src/fmt/mod.rs:1120:17
   6:     0x7f82c54124bf - std::io::Write::write_fmt::h92a5dbf489025e71
                               at /rustc/f8131a48a46ac3bc8a3d0fe0477055b132cffdc3/library/std/src/io/mod.rs:1846:15
   7:     0x7f82c541d8a4 - std::sys_common::backtrace::_print::h00080302d23998ae
                               at /rustc/f8131a48a46ac3bc8a3d0fe0477055b132cffdc3/library/std/src/sys_common/backtrace.rs:47:5
   8:     0x7f82c541d8a4 - std::sys_common::backtrace::print::h6b23124445400245
                               at /rustc/f8131a48a46ac3bc8a3d0fe0477055b132cffdc3/library/std/src/sys_common/backtrace.rs:34:9
   9:     0x7f82c54205eb - std::panicking::default_hook::{{closure}}::hd67b2f9d36675a28
  10:     0x7f82c5420339 - std::panicking::default_hook::h10a39ef11c714e42
                               at /rustc/f8131a48a46ac3bc8a3d0fe0477055b132cffdc3/library/std/src/panicking.rs:292:9
  11:     0x7f82c207a94c - std[5a8e7f94216a9138]::panicking::update_hook::<alloc[e14ab1f516d287ab]::boxed::Box<rustc_driver_impl[e279e4f1fedd9109]::install_ice_hook::{closure#0}>>::{closure#0}
  12:     0x7f82c5420d50 - <alloc::boxed::Box<F,A> as core::ops::function::Fn<Args>>::call::h37ba37dc48823c1d
                               at /rustc/f8131a48a46ac3bc8a3d0fe0477055b132cffdc3/library/alloc/src/boxed.rs:2030:9
  13:     0x7f82c5420d50 - std::panicking::rust_panic_with_hook::he3e3bc7c345bf54b
                               at /rustc/f8131a48a46ac3bc8a3d0fe0477055b132cffdc3/library/std/src/panicking.rs:786:13
  14:     0x7f82c20a7524 - std[5a8e7f94216a9138]::panicking::begin_panic::<rustc_errors[34364e5c712fab73]::ExplicitBug>::{closure#0}
  15:     0x7f82c20a4176 - std[5a8e7f94216a9138]::sys_common::backtrace::__rust_end_short_backtrace::<std[5a8e7f94216a9138]::panicking::begin_panic<rustc_errors[34364e5c712fab73]::ExplicitBug>::{closure#0}, !>
  16:     0x7f82c209f936 - std[5a8e7f94216a9138]::panicking::begin_panic::<rustc_errors[34364e5c712fab73]::ExplicitBug>
  17:     0x7f82c0a17631 - <rustc_errors[34364e5c712fab73]::diagnostic::BugAbort as rustc_errors[34364e5c712fab73]::diagnostic::EmissionGuarantee>::emit_producing_guarantee
  18:     0x7f82c3b1b06c - <rustc_hir_typeck[7492106fe3468815]::mem_categorization::MemCategorizationContext>::cat_pattern_::<<rustc_hir_typeck[7492106fe3468815]::expr_use_visitor::ExprUseVisitor>::walk_pat::{closure#1}>
  19:     0x7f82c3b19e18 - <rustc_hir_typeck[7492106fe3468815]::expr_use_visitor::ExprUseVisitor>::walk_pat
  20:     0x7f82c3a89048 - <rustc_hir_typeck[7492106fe3468815]::expr_use_visitor::ExprUseVisitor>::walk_block
  21:     0x7f82c138fb84 - <rustc_hir_typeck[7492106fe3468815]::expr_use_visitor::ExprUseVisitor>::walk_expr
  22:     0x7f82c3a89c4d - <rustc_hir_typeck[7492106fe3468815]::expr_use_visitor::ExprUseVisitor>::consume_expr
  23:     0x7f82c3a895e4 - <rustc_hir_typeck[7492106fe3468815]::expr_use_visitor::ExprUseVisitor>::consume_body
  24:     0x7f82c3ecb08a - <rustc_hir_typeck[7492106fe3468815]::fn_ctxt::FnCtxt>::analyze_closure
  25:     0x7f82c027c57b - <rustc_hir_typeck[7492106fe3468815]::upvar::InferBorrowKindVisitor as rustc_hir[170b9793d794ea06]::intravisit::Visitor>::visit_expr
  26:     0x7f82c3660659 - <rustc_hir_typeck[7492106fe3468815]::upvar::InferBorrowKindVisitor as rustc_hir[170b9793d794ea06]::intravisit::Visitor>::visit_block
  27:     0x7f82c3653ddd - rustc_hir_typeck[7492106fe3468815]::typeck
  28:     0x7f82c3652d17 - rustc_query_impl[9d4c51777e2bb749]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[9d4c51777e2bb749]::query_impl::typeck::dynamic_query::{closure#2}::{closure#0}, rustc_middle[446dd094ad85939e]::query::erase::Erased<[u8; 8usize]>>
  29:     0x7f82c35098b0 - rustc_query_system[9b2ccfe41ae3bb1b]::query::plumbing::try_execute_query::<rustc_query_impl[9d4c51777e2bb749]::DynamicConfig<rustc_query_system[9b2ccfe41ae3bb1b]::query::caches::VecCache<rustc_span[adb133ac03280fc1]::def_id::LocalDefId, rustc_middle[446dd094ad85939e]::query::erase::Erased<[u8; 8usize]>>, false, false, false>, rustc_query_impl[9d4c51777e2bb749]::plumbing::QueryCtxt, false>
  30:     0x7f82c35093cc - rustc_query_impl[9d4c51777e2bb749]::query_impl::typeck::get_query_non_incr::__rust_end_short_backtrace
  31:     0x7f82c3daf412 - <rustc_middle[446dd094ad85939e]::hir::map::Map>::par_body_owners::<rustc_hir_analysis[71d4294717f7f2b7]::check_crate::{closure#6}>::{closure#0}
  32:     0x7f82c3dadcdd - rustc_hir_analysis[71d4294717f7f2b7]::check_crate
  33:     0x7f82c3ea2dd3 - rustc_interface[7ca501d7f8f3a34f]::passes::analysis
  34:     0x7f82c3ea2a29 - rustc_query_impl[9d4c51777e2bb749]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[9d4c51777e2bb749]::query_impl::analysis::dynamic_query::{closure#2}::{closure#0}, rustc_middle[446dd094ad85939e]::query::erase::Erased<[u8; 1usize]>>
  35:     0x7f82c413d4a5 - rustc_query_system[9b2ccfe41ae3bb1b]::query::plumbing::try_execute_query::<rustc_query_impl[9d4c51777e2bb749]::DynamicConfig<rustc_query_system[9b2ccfe41ae3bb1b]::query::caches::SingleCache<rustc_middle[446dd094ad85939e]::query::erase::Erased<[u8; 1usize]>>, false, false, false>, rustc_query_impl[9d4c51777e2bb749]::plumbing::QueryCtxt, false>
  36:     0x7f82c413d209 - rustc_query_impl[9d4c51777e2bb749]::query_impl::analysis::get_query_non_incr::__rust_end_short_backtrace
  37:     0x7f82c414c719 - rustc_interface[7ca501d7f8f3a34f]::interface::run_compiler::<core[85b4fd477ce5bb21]::result::Result<(), rustc_span[adb133ac03280fc1]::ErrorGuaranteed>, rustc_driver_impl[e279e4f1fedd9109]::run_compiler::{closure#0}>::{closure#0}
  38:     0x7f82c43be705 - std[5a8e7f94216a9138]::sys_common::backtrace::__rust_begin_short_backtrace::<rustc_interface[7ca501d7f8f3a34f]::util::run_in_thread_with_globals<rustc_interface[7ca501d7f8f3a34f]::util::run_in_thread_pool_with_globals<rustc_interface[7ca501d7f8f3a34f]::interface::run_compiler<core[85b4fd477ce5bb21]::result::Result<(), rustc_span[adb133ac03280fc1]::ErrorGuaranteed>, rustc_driver_impl[e279e4f1fedd9109]::run_compiler::{closure#0}>::{closure#0}, core[85b4fd477ce5bb21]::result::Result<(), rustc_span[adb133ac03280fc1]::ErrorGuaranteed>>::{closure#0}, core[85b4fd477ce5bb21]::result::Result<(), rustc_span[adb133ac03280fc1]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[85b4fd477ce5bb21]::result::Result<(), rustc_span[adb133ac03280fc1]::ErrorGuaranteed>>
  39:     0x7f82c43be532 - <<std[5a8e7f94216a9138]::thread::Builder>::spawn_unchecked_<rustc_interface[7ca501d7f8f3a34f]::util::run_in_thread_with_globals<rustc_interface[7ca501d7f8f3a34f]::util::run_in_thread_pool_with_globals<rustc_interface[7ca501d7f8f3a34f]::interface::run_compiler<core[85b4fd477ce5bb21]::result::Result<(), rustc_span[adb133ac03280fc1]::ErrorGuaranteed>, rustc_driver_impl[e279e4f1fedd9109]::run_compiler::{closure#0}>::{closure#0}, core[85b4fd477ce5bb21]::result::Result<(), rustc_span[adb133ac03280fc1]::ErrorGuaranteed>>::{closure#0}, core[85b4fd477ce5bb21]::result::Result<(), rustc_span[adb133ac03280fc1]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[85b4fd477ce5bb21]::result::Result<(), rustc_span[adb133ac03280fc1]::ErrorGuaranteed>>::{closure#1} as core[85b4fd477ce5bb21]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  40:     0x7f82c542a725 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::h1bff3efb61c3fa6b
                               at /rustc/f8131a48a46ac3bc8a3d0fe0477055b132cffdc3/library/alloc/src/boxed.rs:2016:9
  41:     0x7f82c542a725 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::h83141cf549dced8a
                               at /rustc/f8131a48a46ac3bc8a3d0fe0477055b132cffdc3/library/alloc/src/boxed.rs:2016:9
  42:     0x7f82c542a725 - std::sys::pal::unix::thread::Thread::new::thread_start::hbe9287fdd7c325bc
                               at /rustc/f8131a48a46ac3bc8a3d0fe0477055b132cffdc3/library/std/src/sys/pal/unix/thread.rs:108:17
  43:     0x7f82bf0aa9eb - <unknown>
  44:     0x7f82bf12e7cc - <unknown>
  45:                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: rustc 1.78.0-nightly (f8131a48a 2024-02-21) running on x86_64-unknown-linux-gnu

query stack during panic:
#0 [typeck] type-checking `test_missing_unsafe_warning_on_repr_packed`
#1 [analysis] running analysis passes on this crate
end of query stack
error: aborting due to 4 previous errors

Some errors have detailed explanations: E0063, E0308, E0601.
For more information about an error, try `rustc --explain E0063`.

[jieyouxu]

• Does not ICE on stable
• Does not ICE on older nightly (rustc 1.78.0-nightly (bb594538f 2024-02-20))

[jieyouxu]

Seems closure is required, moving let (_, t2) = foo.x; out of closure does not ICE.