unused_enumerate_index.rs: index out of bounds

[matthiaskrgr]

Summary

#![warn(clippy::explicit_into_iter_loop)]

fn main() {
    // Issue #4958
    fn _takes_iterator<T>(iterator: &T)
    where
        for<'a> &'a T: IntoIterator<Item = &'a String>,
    {
        for _ in iterator {}
    }

    struct T;
    impl IntoIterator for &T {
        type Item = ();
        type IntoIter = std::vec::IntoIter<Self::Item>;
        fn into_iter(self) -> Self::IntoIter {
            unimplemented!()
        }
    }

    let mut t = T;

    // No suggestion for this.
    // We'd have to suggest `for _ in *rr {}` which is less clear.
    let rr = &&t;
    for () in rr.into_iter() {}
}

Version

rustc 1.75.0-nightly (9c20ddd95 2023-11-03)
binary: rustc
commit-hash: 9c20ddd956426d577d77cb3f57a7db2227a3c6e9
commit-date: 2023-11-03
host: x86_64-unknown-linux-gnu
release: 1.75.0-nightly
LLVM version: 17.0.4

Error output

Backtrace

warning: variable does not need to be mutable
--> src/main.rs:21:9
 |
21 |     let mut t = T;
 |         ----^
 |         |
 |         help: remove this `mut`
 |
 = note: `#[warn(unused_mut)]` on by default

thread 'rustc' panicked at src/tools/clippy/clippy_lints/src/loops/unused_enumerate_index.rs:22:26:
index out of bounds: the len is 0 but the index is 0
stack backtrace:
 0:     0x7fbae6169cfc - std::backtrace_rs::backtrace::libunwind::trace::h758dc582e496f583
                             at /rustc/9c20ddd956426d577d77cb3f57a7db2227a3c6e9/library/std/src/../../backtrace/src/backtrace/libunwind.rs:104:5
 1:     0x7fbae6169cfc - std::backtrace_rs::backtrace::trace_unsynchronized::h8dc222be4ae72b4b
                             at /rustc/9c20ddd956426d577d77cb3f57a7db2227a3c6e9/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5
 2:     0x7fbae6169cfc - std::sys_common::backtrace::_print_fmt::h23e2ea9fbbcd356c
                             at /rustc/9c20ddd956426d577d77cb3f57a7db2227a3c6e9/library/std/src/sys_common/backtrace.rs:67:5
 3:     0x7fbae6169cfc - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::hb940fea53fcb72c6
                             at /rustc/9c20ddd956426d577d77cb3f57a7db2227a3c6e9/library/std/src/sys_common/backtrace.rs:44:22
 4:     0x7fbae61cbef0 - core::fmt::rt::Argument::fmt::h2ec284a6958f856b
                             at /rustc/9c20ddd956426d577d77cb3f57a7db2227a3c6e9/library/core/src/fmt/rt.rs:142:9
 5:     0x7fbae61cbef0 - core::fmt::write::h1a43870c46fc6b6f
                             at /rustc/9c20ddd956426d577d77cb3f57a7db2227a3c6e9/library/core/src/fmt/mod.rs:1117:17
 6:     0x7fbae615dc1f - std::io::Write::write_fmt::he374ab97e1606dfa
                             at /rustc/9c20ddd956426d577d77cb3f57a7db2227a3c6e9/library/std/src/io/mod.rs:1763:15
 7:     0x7fbae6169ae4 - std::sys_common::backtrace::_print::hca7cfc3a03899ad0
                             at /rustc/9c20ddd956426d577d77cb3f57a7db2227a3c6e9/library/std/src/sys_common/backtrace.rs:47:5
 8:     0x7fbae6169ae4 - std::sys_common::backtrace::print::h0dd58cdf92547322
                             at /rustc/9c20ddd956426d577d77cb3f57a7db2227a3c6e9/library/std/src/sys_common/backtrace.rs:34:9
 9:     0x7fbae616c777 - std::panicking::default_hook::{{closure}}::hfc16e8c187950ef4
10:     0x7fbae616c4df - std::panicking::default_hook::h643e9bd7ed7f72e2
                             at /rustc/9c20ddd956426d577d77cb3f57a7db2227a3c6e9/library/std/src/panicking.rs:292:9
11:     0x7fbae8ce8bf0 - std[518c55d442b65d9f]::panicking::update_hook::<alloc[74508e9abee3a8aa]::boxed::Box<rustc_driver_impl[1e399a535c91638]::install_ice_hook::{closure#0}>>::{closure#0}
12:     0x7fbae616ceb8 - <alloc::boxed::Box<F,A> as core::ops::function::Fn<Args>>::call::h36e8952ab2d612b9
                             at /rustc/9c20ddd956426d577d77cb3f57a7db2227a3c6e9/library/alloc/src/boxed.rs:2021:9
13:     0x7fbae616ceb8 - std::panicking::rust_panic_with_hook::h6a54412da87bc2b0
                             at /rustc/9c20ddd956426d577d77cb3f57a7db2227a3c6e9/library/std/src/panicking.rs:783:13
14:     0x7fbae616cc0e - std::panicking::begin_panic_handler::{{closure}}::hc08d2d7ca1705b25
                             at /rustc/9c20ddd956426d577d77cb3f57a7db2227a3c6e9/library/std/src/panicking.rs:657:13
15:     0x7fbae616a1c6 - std::sys_common::backtrace::__rust_end_short_backtrace::h1891b26ea5d933da
                             at /rustc/9c20ddd956426d577d77cb3f57a7db2227a3c6e9/library/std/src/sys_common/backtrace.rs:170:18
16:     0x7fbae616c972 - rust_begin_unwind
                             at /rustc/9c20ddd956426d577d77cb3f57a7db2227a3c6e9/library/std/src/panicking.rs:645:5
17:     0x7fbae61c8615 - core::panicking::panic_fmt::h9daf40465fe34391
                             at /rustc/9c20ddd956426d577d77cb3f57a7db2227a3c6e9/library/core/src/panicking.rs:72:14
18:     0x7fbae61c8832 - core::panicking::panic_bounds_check::h7af9710afaa522af
                             at /rustc/9c20ddd956426d577d77cb3f57a7db2227a3c6e9/library/core/src/panicking.rs:190:5
19:     0x555da51fd074 - <clippy_lints[e56e61f55af512fc]::loops::Loops>::check_for_loop
20:     0x555da51f51b2 - <clippy_lints[e56e61f55af512fc]::loops::Loops as rustc_lint[9b82381af560af5d]::passes::LateLintPass>::check_expr
21:     0x7fbae900daf0 - <rustc_lint[9b82381af560af5d]::late::LateContextAndPass<rustc_lint[9b82381af560af5d]::late::RuntimeCombinedLateLintPass> as rustc_hir[6eb0c9a90e014d38]::intravisit::Visitor>::visit_expr::{closure#0}
22:     0x7fbae900d978 - <rustc_lint[9b82381af560af5d]::late::LateContextAndPass<rustc_lint[9b82381af560af5d]::late::RuntimeCombinedLateLintPass> as rustc_hir[6eb0c9a90e014d38]::intravisit::Visitor>::visit_expr
23:     0x7fbae900ecff - <rustc_lint[9b82381af560af5d]::late::LateContextAndPass<rustc_lint[9b82381af560af5d]::late::RuntimeCombinedLateLintPass> as rustc_hir[6eb0c9a90e014d38]::intravisit::Visitor>::visit_block
24:     0x7fbae900e148 - <rustc_lint[9b82381af560af5d]::late::LateContextAndPass<rustc_lint[9b82381af560af5d]::late::RuntimeCombinedLateLintPass> as rustc_hir[6eb0c9a90e014d38]::intravisit::Visitor>::visit_expr::{closure#0}
25:     0x7fbae900d978 - <rustc_lint[9b82381af560af5d]::late::LateContextAndPass<rustc_lint[9b82381af560af5d]::late::RuntimeCombinedLateLintPass> as rustc_hir[6eb0c9a90e014d38]::intravisit::Visitor>::visit_expr
26:     0x7fbae900c34a - <rustc_lint[9b82381af560af5d]::late::LateContextAndPass<rustc_lint[9b82381af560af5d]::late::RuntimeCombinedLateLintPass> as rustc_hir[6eb0c9a90e014d38]::intravisit::Visitor>::visit_nested_body
27:     0x7fbae900e4e4 - <rustc_lint[9b82381af560af5d]::late::LateContextAndPass<rustc_lint[9b82381af560af5d]::late::RuntimeCombinedLateLintPass> as rustc_hir[6eb0c9a90e014d38]::intravisit::Visitor>::visit_fn
28:     0x7fbae900cb95 - <rustc_lint[9b82381af560af5d]::late::LateContextAndPass<rustc_lint[9b82381af560af5d]::late::RuntimeCombinedLateLintPass> as rustc_hir[6eb0c9a90e014d38]::intravisit::Visitor>::visit_item
29:     0x7fbae900e81a - <rustc_lint[9b82381af560af5d]::late::LateContextAndPass<rustc_lint[9b82381af560af5d]::late::RuntimeCombinedLateLintPass> as rustc_hir[6eb0c9a90e014d38]::intravisit::Visitor>::visit_mod
30:     0x7fbaea6ef3fc - rustc_lint[9b82381af560af5d]::late::check_crate
31:     0x7fbaea39758c - rustc_interface[7f727f1a527a46c]::passes::analysis
32:     0x7fbaea396535 - rustc_query_impl[60decf841e455888]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[60decf841e455888]::query_impl::analysis::dynamic_query::{closure#2}::{closure#0}, rustc_middle[c65a3bd53e6d447a]::query::erase::Erased<[u8; 1usize]>>
33:     0x7fbaea8d0ca6 - rustc_query_system[25ce05dcfae31225]::query::plumbing::try_execute_query::<rustc_query_impl[60decf841e455888]::DynamicConfig<rustc_query_system[25ce05dcfae31225]::query::caches::SingleCache<rustc_middle[c65a3bd53e6d447a]::query::erase::Erased<[u8; 1usize]>>, false, false, false>, rustc_query_impl[60decf841e455888]::plumbing::QueryCtxt, false>
34:     0x7fbaea8d0ad5 - rustc_query_impl[60decf841e455888]::query_impl::analysis::get_query_non_incr::__rust_end_short_backtrace
35:     0x7fbaea9e99c6 - rustc_interface[7f727f1a527a46c]::interface::run_compiler::<core[3fe6d5b66435123e]::result::Result<(), rustc_span[fd77bf372609ae77]::ErrorGuaranteed>, rustc_driver_impl[1e399a535c91638]::run_compiler::{closure#1}>::{closure#0}
36:     0x7fbaead3115b - std[518c55d442b65d9f]::sys_common::backtrace::__rust_begin_short_backtrace::<rustc_interface[7f727f1a527a46c]::util::run_in_thread_with_globals<rustc_interface[7f727f1a527a46c]::interface::run_compiler<core[3fe6d5b66435123e]::result::Result<(), rustc_span[fd77bf372609ae77]::ErrorGuaranteed>, rustc_driver_impl[1e399a535c91638]::run_compiler::{closure#1}>::{closure#0}, core[3fe6d5b66435123e]::result::Result<(), rustc_span[fd77bf372609ae77]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[3fe6d5b66435123e]::result::Result<(), rustc_span[fd77bf372609ae77]::ErrorGuaranteed>>
37:     0x7fbaead30fb3 - <<std[518c55d442b65d9f]::thread::Builder>::spawn_unchecked_<rustc_interface[7f727f1a527a46c]::util::run_in_thread_with_globals<rustc_interface[7f727f1a527a46c]::interface::run_compiler<core[3fe6d5b66435123e]::result::Result<(), rustc_span[fd77bf372609ae77]::ErrorGuaranteed>, rustc_driver_impl[1e399a535c91638]::run_compiler::{closure#1}>::{closure#0}, core[3fe6d5b66435123e]::result::Result<(), rustc_span[fd77bf372609ae77]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[3fe6d5b66435123e]::result::Result<(), rustc_span[fd77bf372609ae77]::ErrorGuaranteed>>::{closure#1} as core[3fe6d5b66435123e]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
38:     0x7fbae6177c25 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::hfcff71f52665e7e6
                             at /rustc/9c20ddd956426d577d77cb3f57a7db2227a3c6e9/library/alloc/src/boxed.rs:2007:9
39:     0x7fbae6177c25 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::h3a2c5ad677d53ad0
                             at /rustc/9c20ddd956426d577d77cb3f57a7db2227a3c6e9/library/alloc/src/boxed.rs:2007:9
40:     0x7fbae6177c25 - std::sys::unix::thread::Thread::new::thread_start::h3d93699ba4bcb9bc
                             at /rustc/9c20ddd956426d577d77cb3f57a7db2227a3c6e9/library/std/src/sys/unix/thread.rs:108:17
41:     0x7fbae5e549eb - <unknown>
42:     0x7fbae5ed87cc - <unknown>
43:                0x0 - <unknown>

error: the compiler unexpectedly panicked. this is a bug.

note: we would appreciate a bug report: https://github.com/rust-lang/rust-clippy/issues/new?template=ice.yml

note: please attach the file at `/tmp/icemaker/rustc-ice-2023-11-03T19_25_55-3361208.txt` to your bug report

query stack during panic:
#0 [analysis] running analysis passes on this crate
end of query stack
note: Clippy version: clippy 0.1.75 (9c20ddd 2023-11-03)

warning: 1 warning emitted