ICE: underef: index out of bounds

[matthiaskrgr]

auto-reduced (treereduce-rust):

trait T {}

type Alias<'a> = impl T;

struct S;
impl<'a> T for &'a S {}

fn with_positive(fun: impl Fn(Alias<'_>)) {}

fn main() {
    with_positive(|&n| ());
}

original:

#![feature(type_alias_impl_trait)]

//@ build-pass

trait T { type Item; }

type Alias<'a> = impl T<Item = &'a ()>;

struct S;
impl<'a> T for &'a S {
    type Item = &'a ();
}

fn filter_positive<'a>() -> Alias<'a> {
    &S
}

fn with_positive(fun: impl Fn(Alias<'_>)) {
    fun(filter_positive());
}

fn main() {
    with_positive(|&n| ());
}

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[E0658]: `impl Trait` in type aliases is unstable
 --> /tmp/icemaker_global_tempdir.F5838RU6DQwp/rustc_testrunner_tmpdir_reporting.lgnzWyLkPTPL/mvce.rs:3:18
  |
3 | type Alias<'a> = impl T;
  |                  ^^^^^^
  |
  = note: see issue #63063 <https://github.com/rust-lang/rust/issues/63063> for more information
  = help: add `#![feature(type_alias_impl_trait)]` to the crate attributes to enable
  = note: this compiler was built on 2024-02-21; consider upgrading it if it is out of date

error: item constrains opaque type that is not in its signature
  --> /tmp/icemaker_global_tempdir.F5838RU6DQwp/rustc_testrunner_tmpdir_reporting.lgnzWyLkPTPL/mvce.rs:11:20
   |
11 |     with_positive(|&n| ());
   |                    ^^
   |
   = note: this item must mention the opaque type in its signature in order to be able to register hidden types
note: this item must mention the opaque type in its signature in order to be able to register hidden types
  --> /tmp/icemaker_global_tempdir.F5838RU6DQwp/rustc_testrunner_tmpdir_reporting.lgnzWyLkPTPL/mvce.rs:10:4
   |
10 | fn main() {
   |    ^^^^

warning: unused variable: `n`
  --> /tmp/icemaker_global_tempdir.F5838RU6DQwp/rustc_testrunner_tmpdir_reporting.lgnzWyLkPTPL/mvce.rs:11:21
   |
11 |     with_positive(|&n| ());
   |                     ^ help: if this is intentional, prefix it with an underscore: `_n`
   |
   = note: `#[warn(unused_variables)]` on by default

error[E0507]: cannot move out of a shared reference
  --> /tmp/icemaker_global_tempdir.F5838RU6DQwp/rustc_testrunner_tmpdir_reporting.lgnzWyLkPTPL/mvce.rs:11:20
   |
11 |     with_positive(|&n| ());
   |                    ^-
   |                     |
   |                     data moved here
   |                     move occurs because `n` has type `S`, which does not implement the `Copy` trait
   |
help: consider removing the borrow
   |
11 -     with_positive(|&n| ());
11 +     with_positive(|n| ());
   |

error: item constrains opaque type that is not in its signature
  --> /tmp/icemaker_global_tempdir.F5838RU6DQwp/rustc_testrunner_tmpdir_reporting.lgnzWyLkPTPL/mvce.rs:11:20
   |
11 |     with_positive(|&n| ());
   |                    ^^
   |
   = note: this item must mention the opaque type in its signature in order to be able to register hidden types
note: this item must mention the opaque type in its signature in order to be able to register hidden types
  --> /tmp/icemaker_global_tempdir.F5838RU6DQwp/rustc_testrunner_tmpdir_reporting.lgnzWyLkPTPL/mvce.rs:11:19
   |
11 |     with_positive(|&n| ());
   |                   ^^^^

warning: unused variable: `fun`
 --> /tmp/icemaker_global_tempdir.F5838RU6DQwp/rustc_testrunner_tmpdir_reporting.lgnzWyLkPTPL/mvce.rs:8:18
  |
8 | fn with_positive(fun: impl Fn(Alias<'_>)) {}
  |                  ^^^ help: if this is intentional, prefix it with an underscore: `_fun`

thread 'rustc' panicked at /rustc/f8131a48a46ac3bc8a3d0fe0477055b132cffdc3/compiler/rustc_mir_dataflow/src/un_derefer.rs:67:20:
index out of bounds: the len is 0 but the index is 0
stack backtrace:
   0:     0x7f603d823af6 - std::backtrace_rs::backtrace::libunwind::trace::hbec2edc838b433e2
                               at /rustc/f8131a48a46ac3bc8a3d0fe0477055b132cffdc3/library/std/src/../../backtrace/src/backtrace/libunwind.rs:104:5
   1:     0x7f603d823af6 - std::backtrace_rs::backtrace::trace_unsynchronized::h88c30257ee0dd166
                               at /rustc/f8131a48a46ac3bc8a3d0fe0477055b132cffdc3/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5
   2:     0x7f603d823af6 - std::sys_common::backtrace::_print_fmt::h9176654d509e3088
                               at /rustc/f8131a48a46ac3bc8a3d0fe0477055b132cffdc3/library/std/src/sys_common/backtrace.rs:68:5
   3:     0x7f603d823af6 - <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:     0x7f603d874a7c - core::fmt::rt::Argument::fmt::h59605c83ae32d935
                               at /rustc/f8131a48a46ac3bc8a3d0fe0477055b132cffdc3/library/core/src/fmt/rt.rs:142:9
   5:     0x7f603d874a7c - core::fmt::write::hf7af8dfcfd20db5b
                               at /rustc/f8131a48a46ac3bc8a3d0fe0477055b132cffdc3/library/core/src/fmt/mod.rs:1120:17
   6:     0x7f603d8184bf - std::io::Write::write_fmt::h92a5dbf489025e71
                               at /rustc/f8131a48a46ac3bc8a3d0fe0477055b132cffdc3/library/std/src/io/mod.rs:1846:15
   7:     0x7f603d8238a4 - std::sys_common::backtrace::_print::h00080302d23998ae
                               at /rustc/f8131a48a46ac3bc8a3d0fe0477055b132cffdc3/library/std/src/sys_common/backtrace.rs:47:5
   8:     0x7f603d8238a4 - std::sys_common::backtrace::print::h6b23124445400245
                               at /rustc/f8131a48a46ac3bc8a3d0fe0477055b132cffdc3/library/std/src/sys_common/backtrace.rs:34:9
   9:     0x7f603d8265eb - std::panicking::default_hook::{{closure}}::hd67b2f9d36675a28
  10:     0x7f603d826339 - std::panicking::default_hook::h10a39ef11c714e42
                               at /rustc/f8131a48a46ac3bc8a3d0fe0477055b132cffdc3/library/std/src/panicking.rs:292:9
  11:     0x7f603a47a94c - std[5a8e7f94216a9138]::panicking::update_hook::<alloc[e14ab1f516d287ab]::boxed::Box<rustc_driver_impl[e279e4f1fedd9109]::install_ice_hook::{closure#0}>>::{closure#0}
  12:     0x7f603d826d50 - <alloc::boxed::Box<F,A> as core::ops::function::Fn<Args>>::call::h37ba37dc48823c1d
                               at /rustc/f8131a48a46ac3bc8a3d0fe0477055b132cffdc3/library/alloc/src/boxed.rs:2030:9
  13:     0x7f603d826d50 - std::panicking::rust_panic_with_hook::he3e3bc7c345bf54b
                               at /rustc/f8131a48a46ac3bc8a3d0fe0477055b132cffdc3/library/std/src/panicking.rs:786:13
  14:     0x7f603d826a92 - std::panicking::begin_panic_handler::{{closure}}::h4bfbc62f377d59e6
                               at /rustc/f8131a48a46ac3bc8a3d0fe0477055b132cffdc3/library/std/src/panicking.rs:660:13
  15:     0x7f603d823fd6 - std::sys_common::backtrace::__rust_end_short_backtrace::hc8487cf1bc04a693
                               at /rustc/f8131a48a46ac3bc8a3d0fe0477055b132cffdc3/library/std/src/sys_common/backtrace.rs:171:18
  16:     0x7f603d8267c4 - rust_begin_unwind
                               at /rustc/f8131a48a46ac3bc8a3d0fe0477055b132cffdc3/library/std/src/panicking.rs:648:5
  17:     0x7f603d870f95 - core::panicking::panic_fmt::h88277cce839da186
                               at /rustc/f8131a48a46ac3bc8a3d0fe0477055b132cffdc3/library/core/src/panicking.rs:72:14
  18:     0x7f603d8711e2 - core::panicking::panic_bounds_check::h7889403d641fd53a
                               at /rustc/f8131a48a46ac3bc8a3d0fe0477055b132cffdc3/library/core/src/panicking.rs:208:5
  19:     0x7f603898e24a - <rustc_mir_dataflow[9dbea5a14cdf9346]::move_paths::builder::Gatherer<<rustc_mir_transform[2f80b166b66099ac]::elaborate_drops::ElaborateDrops as rustc_middle[446dd094ad85939e]::mir::MirPass>::run_pass::{closure#0}>>::gather_move
  20:     0x7f6038973697 - <rustc_mir_transform[2f80b166b66099ac]::elaborate_drops::ElaborateDrops as rustc_middle[446dd094ad85939e]::mir::MirPass>::run_pass
  21:     0x7f603b812689 - rustc_mir_transform[2f80b166b66099ac]::pass_manager::run_passes_inner
  22:     0x7f603ba42806 - rustc_mir_transform[2f80b166b66099ac]::mir_drops_elaborated_and_const_checked
  23:     0x7f603ba4213d - rustc_query_impl[9d4c51777e2bb749]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[9d4c51777e2bb749]::query_impl::mir_drops_elaborated_and_const_checked::dynamic_query::{closure#2}::{closure#0}, rustc_middle[446dd094ad85939e]::query::erase::Erased<[u8; 8usize]>>
  24:     0x7f603b9098b0 - 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>
  25:     0x7f603b90919e - rustc_query_impl[9d4c51777e2bb749]::query_impl::mir_drops_elaborated_and_const_checked::get_query_non_incr::__rust_end_short_backtrace
  26:     0x7f603c2a333f - rustc_interface[7ca501d7f8f3a34f]::passes::analysis
  27:     0x7f603c2a2a29 - 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]>>
  28:     0x7f603c53d4a5 - 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>
  29:     0x7f603c53d209 - rustc_query_impl[9d4c51777e2bb749]::query_impl::analysis::get_query_non_incr::__rust_end_short_backtrace
  30:     0x7f603c54c719 - rustc_interface[7ca501d7f8f3a34f]::interface::run_compiler::<core[85b4fd477ce5bb21]::result::Result<(), rustc_span[adb133ac03280fc1]::ErrorGuaranteed>, rustc_driver_impl[e279e4f1fedd9109]::run_compiler::{closure#0}>::{closure#0}
  31:     0x7f603c7be705 - 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>>
  32:     0x7f603c7be532 - <<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}
  33:     0x7f603d830725 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::h1bff3efb61c3fa6b
                               at /rustc/f8131a48a46ac3bc8a3d0fe0477055b132cffdc3/library/alloc/src/boxed.rs:2016:9
  34:     0x7f603d830725 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::h83141cf549dced8a
                               at /rustc/f8131a48a46ac3bc8a3d0fe0477055b132cffdc3/library/alloc/src/boxed.rs:2016:9
  35:     0x7f603d830725 - std::sys::pal::unix::thread::Thread::new::thread_start::hbe9287fdd7c325bc
                               at /rustc/f8131a48a46ac3bc8a3d0fe0477055b132cffdc3/library/std/src/sys/pal/unix/thread.rs:108:17
  36:     0x7f60374aa9eb - <unknown>
  37:     0x7f603752e7cc - <unknown>
  38:                0x0 - <unknown>

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

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 [mir_drops_elaborated_and_const_checked] elaborating drops for `main::{closure#0}`
#1 [analysis] running analysis passes on this crate
end of query stack
error: aborting due to 4 previous errors; 2 warnings emitted

Some errors have detailed explanations: E0507, E0658.
For more information about an error, try `rustc --explain E0507`.

[matthiaskrgr]

#120550 cc @oli-obk