nightly panic: index out of bounds: the len is 533 but the index is 533

[yyny]

Meta

$ rustc +nightly --version --verbose
rustc 1.33.0-nightly (60e825389 2018-12-28)
binary: rustc
commit-hash: 60e825389db3cb7421afb7015b28cb9436c79bba
commit-date: 2018-12-28
host: x86_64-unknown-linux-gnu
release: 1.33.0-nightly
LLVM version: 8.0

Code Sample

cargo.toml

[package]
name = "bug"

[dependencies]

src/main.rs

trait Scan<T> {
    fn scan(&mut self) -> Option<T>;
}
impl<'a, T> Scan<T> for Iterator<Item=T> {
    fn scan(&mut self) -> Option<T> {
        self.next()
    }
}
fn wrap_scanner<'a, T>(s: &'a mut Scan<T>) -> (impl FnMut() -> Option<T> + 'a) {
    move || { s.scan() }
}
fn main() {
    let scanner = &mut wrap_scanner(&mut "buggy".chars() as &mut Iterator<Item=char>);
}

Compiler flags

RUST_BACKTRACE=full cargo +nightly run --verbose

Backtrace

   Compiling bug v0.1.0 (/home/jonne/bug)
     Running `rustc --crate-name bug src/main.rs --color always --crate-type bin --emit=dep-info,link -C debuginfo=2 -C metadata=f60f04bfbdb5bf06 -C extra-filename=-f60f04bfbdb5bf06 --out-dir /home/jonne/bug/target/debug/deps -C incremental=/home/jonne/bug/target/debug/incremental -L dependency=/home/jonne/bug/target/debug/deps`
thread 'rustc' panicked at 'index out of bounds: the len is 533 but the index is 533', /rustc/60e825389db3cb7421afb7015b28cb9436c79bba/src/libcore/slice/mod.rs:2455:10
stack backtrace:
   0:     0x7fe6ff227663 - std::sys::unix::backtrace::tracing::imp::unwind_backtrace::ha048ab13d89f3a09
                               at src/libstd/sys/unix/backtrace/tracing/gcc_s.rs:39
   1:     0x7fe6ff21fcc8 - std::sys_common::backtrace::_print::hdc3d6ec6d0c40360
                               at src/libstd/sys_common/backtrace.rs:70
   2:     0x7fe6ff2237f2 - std::panicking::default_hook::{{closure}}::h7acca10a85297ad4
                               at src/libstd/sys_common/backtrace.rs:58
                               at src/libstd/panicking.rs:200
   3:     0x7fe6ff223564 - std::panicking::default_hook::h0269753a0683b10e
                               at src/libstd/panicking.rs:215
   4:     0x7fe6fb2c2f2f - rustc::util::common::panic_hook::h1695c95b4d531ed2
   5:     0x7fe6ff223fd9 - std::panicking::rust_panic_with_hook::h9c5e819f879ce50a
                               at src/libstd/panicking.rs:482
   6:     0x7fe6ff223a81 - std::panicking::continue_panic_fmt::hc486db806482bb1d
                               at src/libstd/panicking.rs:385
   7:     0x7fe6ff223965 - rust_begin_unwind
                               at src/libstd/panicking.rs:312
   8:     0x7fe6ff24dc7c - core::panicking::panic_fmt::h47839c417f27461d
                               at src/libcore/panicking.rs:85
   9:     0x7fe6ff24dc30 - core::panicking::panic_bounds_check::h61628935017e404a
                               at src/libcore/panicking.rs:61
  10:     0x7fe6fae4aeb7 - <ena::unify::UnificationTable<S>>::get_root_key::h54b43cd349b1d84c
  11:     0x7fe6fb054318 - rustc::infer::InferCtxt::shallow_resolve::h72d4e24505d52216
  12:     0x7fe6fb49871c - <rustc::infer::resolve::OpportunisticTypeResolver<'a, 'gcx, 'tcx> as rustc::ty::fold::TypeFolder<'gcx, 'tcx>>::fold_ty::h3df340bcefea71c6
  13:     0x7fe6fd74c6d4 - rustc::infer::InferCtxt::probe::haef55bcadde8315d
  14:     0x7fe6fd92b601 - <alloc::vec::Vec<T> as alloc::vec::SpecExtend<T, I>>::from_iter::h4465b21670ac69fc
  15:     0x7fe6fd90037b - rustc_typeck::check::method::probe::ProbeContext::pick_method::h3084489de37473fb
  16:     0x7fe6fd8ff950 - rustc_typeck::check::method::probe::ProbeContext::pick_core::h6bcb6ee844014648
  17:     0x7fe6fd93675e - <core::iter::FilterMap<I, F> as core::iter::iterator::Iterator>::next::h885bd6d0582f6e15
  18:     0x7fe6fd92b2d3 - <alloc::vec::Vec<T> as alloc::vec::SpecExtend<T, I>>::from_iter::h3f9649def844822f
  19:     0x7fe6fd74a473 - rustc::infer::InferCtxt::probe::h69effbf9671f3ad3
  20:     0x7fe6fd8ff31b - rustc_typeck::check::method::probe::ProbeContext::pick::hf4be5658576b8647
  21:     0x7fe6fd74d723 - rustc::infer::InferCtxt::probe::hfc12c7dd9980b78d
  22:     0x7fe6fd7ff882 - rustc_typeck::check::method::probe::<impl rustc_typeck::check::FnCtxt<'a, 'gcx, 'tcx>>::probe_op::hdb7ddbc1ebaa5b1d
  23:     0x7fe6fd92632e - <alloc::vec::Vec<T> as alloc::vec::SpecExtend<T, I>>::from_iter::h1075ce2f37577934
  24:     0x7fe6fd831e28 - rustc_typeck::check::FnCtxt::suggest_ref_or_into::hf3d0404a8be0d11f
  25:     0x7fe6fd7fd948 - rustc_typeck::check::demand::<impl rustc_typeck::check::FnCtxt<'a, 'gcx, 'tcx>>::demand_coerce::h1115fac74c7ebec3
  26:     0x7fe6fd81db15 - rustc_typeck::check::FnCtxt::check_argument_types::h8d0262e5ccd1eadb
  27:     0x7fe6fd809c64 - rustc_typeck::check::callee::<impl rustc_typeck::check::FnCtxt<'a, 'gcx, 'tcx>>::confirm_builtin_call::h3559f919d63a244b
  28:     0x7fe6fd82650f - rustc_typeck::check::FnCtxt::check_expr_kind::hd58fd448e44d5764
  29:     0x7fe6fd820520 - rustc_typeck::check::FnCtxt::check_expr_with_expectation_and_needs::h9f2763fcc5139c57
  30:     0x7fe6fd8267cf - rustc_typeck::check::FnCtxt::check_expr_kind::hd58fd448e44d5764
  31:     0x7fe6fd820520 - rustc_typeck::check::FnCtxt::check_expr_with_expectation_and_needs::h9f2763fcc5139c57
  32:     0x7fe6fd82ec19 - rustc_typeck::check::FnCtxt::check_decl_local::h0cf9f8849fb9ea48
  33:     0x7fe6fd82f1b4 - rustc_typeck::check::FnCtxt::check_block_with_expected::h8f701afea4ff4f9d
  34:     0x7fe6fd820e51 - rustc_typeck::check::FnCtxt::check_expr_kind::hd58fd448e44d5764
  35:     0x7fe6fd820520 - rustc_typeck::check::FnCtxt::check_expr_with_expectation_and_needs::h9f2763fcc5139c57
  36:     0x7fe6fd81f729 - rustc_typeck::check::FnCtxt::check_return_expr::hd59b265a860efc30
  37:     0x7fe6fd80fe3c - rustc_typeck::check::check_fn::h76d7437b6ade8cba
  38:     0x7fe6fd8c91c9 - rustc::ty::context::GlobalCtxt::enter_local::hd6501c6e488678af
  39:     0x7fe6fd80eb16 - rustc_typeck::check::typeck_tables_of::h10efc5b3a8f1b01a
  40:     0x7fe6fae3aa3c - rustc::ty::query::<impl rustc::ty::query::config::QueryAccessors<'tcx> for rustc::ty::query::queries::typeck_tables_of<'tcx>>::compute::h435fb0347d553697
  41:     0x7fe6fb450a33 - rustc::dep_graph::graph::DepGraph::with_task_impl::hb4a58a0b2aa1e4e0
  42:     0x7fe6fadfa3e1 - <rustc::ty::query::plumbing::JobOwner<'a, 'tcx, Q>>::start::h554bc5fb05753448
  43:     0x7fe6fb16b590 - rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt<'a, 'gcx, 'tcx>>::force_query_with_job::h0005598c45c306a5
  44:     0x7fe6fb15f533 - rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt<'a, 'gcx, 'tcx>>::try_get_with::hf3c19a1f27a1d380
  45:     0x7fe6fb1a2804 - rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt<'a, 'gcx, 'tcx>>::ensure_query::h5e1d9ab0477d63eb
  46:     0x7fe6fd6b818c - rustc::session::Session::track_errors::h4498f2993bed0651
  47:     0x7fe6fd80e5fe - rustc_typeck::check::typeck_item_bodies::hc8c51eb3fd4f00ec
  48:     0x7fe6fd7730e6 - rustc::ty::query::__query_compute::typeck_item_bodies::h25849d3e9df44c07
  49:     0x7fe6fd771b18 - rustc::ty::query::<impl rustc::ty::query::config::QueryAccessors<'tcx> for rustc::ty::query::queries::typeck_item_bodies<'tcx>>::compute::hc2b47b6e6c3e8533
  50:     0x7fe6fd70f7af - rustc::dep_graph::graph::DepGraph::with_task_impl::h102c01efa786843a
  51:     0x7fe6fd78fc1c - <rustc::ty::query::plumbing::JobOwner<'a, 'tcx, Q>>::start::h54d4ba74bafe6933
  52:     0x7fe6fd8b5977 - rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt<'a, 'gcx, 'tcx>>::force_query_with_job::hd6834514b10be281
  53:     0x7fe6fd86c566 - rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt<'a, 'gcx, 'tcx>>::try_get_with::h11a804961bda941c
  54:     0x7fe6fd6c96c4 - rustc_typeck::check_crate::ha6849350ff284a8d
  55:     0x7fe6ff5cfe96 - <std::thread::local::LocalKey<T>>::with::h5b1d17641d082546
  56:     0x7fe6ff57da60 - rustc::ty::context::TyCtxt::create_and_enter::haf4f12b4da36ea42
  57:     0x7fe6ff59df9a - rustc_driver::driver::compile_input::ha861e86974807b4d
  58:     0x7fe6ff51db30 - rustc_driver::run_compiler_with_pool::h094540acf0a58157
  59:     0x7fe6ff528b35 - <scoped_tls::ScopedKey<T>>::set::haf59a094991db106
  60:     0x7fe6ff51c97a - rustc_driver::run_compiler::h51c542194a1aa7e5
  61:     0x7fe6ff528cea - <scoped_tls::ScopedKey<T>>::set::hcf03caad7f1e4ad3
  62:     0x7fe6ff5dae32 - std::sys_common::backtrace::__rust_begin_short_backtrace::hc15361ac1cb68e6c
  63:     0x7fe6ff235569 - __rust_maybe_catch_panic
                               at src/libpanic_unwind/lib.rs:92
  64:     0x7fe6ff5ee460 - <F as alloc::boxed::FnBox<A>>::call_box::h2da068bc8228d7c0
  65:     0x7fe6ff23434d - std::sys::unix::thread::Thread::new::thread_start::h568fd870028046e0
                               at /rustc/60e825389db3cb7421afb7015b28cb9436c79bba/src/liballoc/boxed.rs:734
                               at src/libstd/sys_common/thread.rs:14
                               at src/libstd/sys/unix/thread.rs:81
  66:     0x7fe6f8f8f6da - start_thread
  67:     0x7fe6feeef88e - __clone
  68:                0x0 - <unknown>
query stack during panic:
#0 [typeck_tables_of] processing `main`
#1 [typeck_item_bodies] type-checking all item bodies
end of query stack

error: internal compiler error: unexpected panic

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

note: we would appreciate a bug report: https://github.com/rust-lang/rust/blob/master/CONTRIBUTING.md#bug-reports

note: rustc 1.33.0-nightly (60e825389 2018-12-28) running on x86_64-unknown-linux-gnu

note: compiler flags: -C debuginfo=2 -C incremental --crate-type bin

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

error: Could not compile `bug`.

Caused by:
  process didn't exit successfully: `rustc --crate-name bug src/main.rs --color always --crate-type bin --emit=dep-info,link -C debuginfo=2 -C metadata=f60f04bfbdb5bf06 -C extra-filename=-f60f04bfbdb5bf06 --out-dir /home/jonne/bug/target/debug/deps -C incremental=/home/jonne/bug/target/debug/incremental -L dependency=/home/jonne/bug/target/debug/deps` (exit code: 101)

[matprec]

This ICEs on nightly (a2b0f24 2018-12-30), but not in beta.

I've hit this as well, but i'm not sure if it's the same issue, because my project compiles fine in a fresh (cargo clean, cargo run) build, but immediately panics when trying to rebuild after touching (insert newline) the file.

[LukasKalbertodt]

I'm hitting this bug, too. For me, cargo clean doesn't help -- rustc always crashes.

[rosscanning]

I have hit what is probably the same bug, so here's my repro:

struct SomeStruct {}

fn group_by_shifts<'a, I, J, F>(trips: I, mut on_trip: F)
where
    I: Iterator<Item = (&'a SomeStruct)>,
    J: Iterator<Item = (&'a SomeStruct)>,
    F: FnMut(u32, J),
{
    for g in trips {
        on_trip(123, &g as &Iterator<Item = (&'a SomeStruct)>);
    }
}

My platform is x86_64-pc-windows-msvc. "cargo clean" has no effect for me.

[pnkfelix]

PR #57835 fixes the example posted by @rosscanning

I am looking into whether it fixes the broader test case in the description for this bug (#57216).

[pnkfelix]

PR #57835 looks like it fixes this bug too, based on a quick local test.