ICE: sty: `range end index 18446744073709551615 out of range for slice of length 0`

[matthiaskrgr]

auto-reduced (treereduce-rust):

#![feature(generic_nonzero, never_type)]

use std::mem::{self};

use std::num::NonZero;

struct Wrap<T> {
    wrapped: T,
}

fn main() {
    unsafe {
        let _val: Wrap<char> = <ext::S as ext::X>::hoy();

        let _val: NonZero<u32> = mem::transmute(0);
    }
}

original code

original:

// This test checks that calling `mem::{uninitialized,zeroed}` with certain types results
// in a lint.
#![allow(deprecated)]
#![deny(invalid_value)]
#![feature(generic_nonzero, never_type, rustc_attrs)]

use std::mem::{self, MaybeUninit};
use std::ptr::NonNull;
use std::num::NonZero;

enum Void {}

struct Ref(&'static i32);
struct RefPair((&'static i32, i32));

struct Wrap<T> { wrapped: T }
enum WrapEnum<T> { Wrapped(T) }

#[rustc_layout_scalar_valid_range_start(0)]
#[rustc_layout_scalar_valid_range_end(128)]
#[repr(transparent)]
pub(crate) struct NonBig(u64);

/// A two-variant enum, thus needs a tag and may not remain uninitialized.
enum Fruit {
    Apple,
    Banana,
}

/// Looks like two variants but really only has one.
enum OneFruit {
    Apple(!),
    Banana,
}

enum OneFruitNonZero {
    Apple(!),
    Banana(NonZero<u32>),
}

enum TwoUninhabited {
    A(!),
    B(Void),
}

#[rustc_layout_scalar_valid_range_start(254)]
#[rustc_layout_scalar_valid_range_end(1)]
pub(crate) struct WrapAroundRange(u8);

#[allow(unused)]
fn generic<T: 'static>() {
    unsafe {
        let _val: &'static T = mem::zeroed(); //~ ERROR: does not permit zero-initialization
        let _val: &'static T = mem::uninitialized(); //~ ERROR: does not permit being left uninitialized

        let _val: Wrap<&'static T> = mem::zeroed(); //~ ERROR: does not permit zero-initialization
        let _val: Wrap<&'static T> = mem::uninitialized(); //~ ERROR: does not permit being left uninitialized
    }
}

fn main() {
    unsafe {
        // Things that cannot even be zero.
        let _val: ! = mem::zeroed(); //~ ERROR: does not permit zero-initialization
        let _val: ! = mem::uninitialized(); //~ ERROR: does not permit being left uninitialized

        let _val: (i32, !) = mem::zeroed(); //~ ERROR: does not permit zero-initialization
        let _val: (i32, !) = mem::uninitialized(); //~ ERROR: does not permit being left uninitialized

        let _val: Void = mem::zeroed(); //~ ERROR: does not permit zero-initialization
        let _val: Void = mem::uninitialized(); //~ ERROR: does not permit being left uninitialized

        let _val: &'static i32 = mem::zeroed(); //~ ERROR: does not permit zero-initialization
        let _val: &'static i32 = mem::uninitialized(); //~ ERROR: does not permit being left uninitialized

        let _val: Ref = mem::zeroed(); //~ ERROR: does not permit zero-initialization
        let _val: Ref = mem::uninitialized(); //~ ERROR: does not permit being left uninitialized

        let _val: fn() = mem::zeroed(); //~ ERROR: does not permit zero-initialization
        let _val: fn() = mem::uninitialized(); //~ ERROR: does not permit being left uninitialized

        let _val: Wrap<fn()> = mem::zeroed(); //~ ERROR: does not permit zero-initialization
        let _val: Wrap<fn()> = mem::uninitialized(); //~ ERROR: does not permit being left uninitialized

        let _val: WrapEnum<fn()> = mem::zeroed(); //~ ERROR: does not permit zero-initialization
        let _val: WrapEnum<fn()> = mem::uninitialized(); //~ ERROR: does not permit being left uninitialized

        let _val: Wrap<(RefPair, i32)> = mem::zeroed(); //~ ERROR: does not permit zero-initialization
        let _val: Wrap<(RefPair, i32)> = mem::uninitialized(); //~ ERROR: does not permit being left uninitialized

        let _val: NonNull<i32> = mem::zeroed(); //~ ERROR: does not permit zero-initialization
        let _val: NonNull<i32> = mem::uninitialized(); //~ ERROR: does not permit being left uninitialized

        let _val: (NonZero<u32>, i32) = mem::zeroed(); //~ ERROR: does not permit zero-initialization
        let _val: (NonZero<u32>, i32) = mem::uninitialized(); //~ ERROR: does not permit being left uninitialized

        let _val: *const dyn Send = mem::zeroed(); //~ ERROR: does not permit zero-initialization
        let _val: *const dyn Send = mem::uninitialized(); //~ ERROR: does not permit being left uninitialized

        let _val: [fn(); 2] = mem::zeroed(); //~ ERROR: does not permit zero-initialization
        let _val: [fn(); 2] = mem::uninitialized(); //~ ERROR: does not permit being left uninitialized

        let _val: TwoUninhabited = mem::zeroed(); //~ ERROR: does not permit zero-initialization
        let _val: TwoUninhabited = mem::uninitialized(); //~ ERROR: does not permit being left uninitialized

        let _val: OneFruitNonZero = mem::zeroed(); //~ ERROR: does not permit zero-initialization
        let _val: OneFruitNonZero = mem::uninitialized(); //~ ERROR: does not permit being left uninitialized

        // Things that can be zero, but not uninit.
        let _val: bool = mem::zeroed();
        let _val: bool = mem::uninitialized(); //~ ERROR: does not permit being left uninitialized

        let _val: Wrap<char> = mem::zeroed();
        let _val: Wrap<char> = <ext::S as ext::X>::hoy(); //~ ERROR: does not permit being left uninitialized

        let _val: NonBig = mem::zeroed();
        let _val: NonBig = mem::uninitialized(); //~ ERROR: does not permit being left uninitialized

        let _val: Fruit = mem::zeroed();
        let _val: Fruit = mem::uninitialized(); //~ ERROR: does not permit being left uninitialized

        let _val: [bool; 2] = mem::zeroed();
        let _val: [i8; 2] = mem::uninitialized(); //~ ERROR: does not permit being left uninitialized

        let _val: i32 = mem::zeroed();
        let _val: i32 = mem::uninitialized(); //~ ERROR: does not permit being left uninitialized

        let _val: f32 = mem::zeroed();
        let _val: f32 = mem::uninitialized(); //~ ERROR: does not permit being left uninitialized

        let _val: *const () = mem::zeroed();
        let _val: *const () = mem::uninitialized(); //~ ERROR: does not permit being left uninitialized

        let _val: *const [()] = mem::zeroed();
        let _val: *const [()] = mem::uninitialized(); //~ ERROR: does not permit being left uninitialized

        let _val: WrapAroundRange = mem::zeroed();
        let _val: WrapAroundRange = mem::uninitialized(); //~ ERROR: does not permit being left uninitialized

        // Things where 0 is okay due to rustc implementation details,
        // but that are not guaranteed to keep working.
        let _val: Result<i32, i32> = mem::zeroed();
        let _val: Result<i32, i32> = mem::uninitialized(); //~ ERROR: does not permit being left uninitialized

        // Some things that happen to be UB-free due to rustc implementation details,
        // but are not guaranteed to keep working.
        let _val: OneFruit = mem::zeroed();
        let _val: OneFruit = mem::uninitialized();

        // Transmute-from-0
        let _val: &'static i32 = mem::transmute(0usize); //~ ERROR: does not permit zero-initialization
        let _val: &'static [i32] = mem::transmute((0usize, 0usize)); //~ ERROR: does not permit zero-initialization
        let _val: NonZero<u32> = mem::transmute(0); //~ ERROR: does not permit zero-initialization

        // `MaybeUninit` cases
        let _val: NonNull<i32> = MaybeUninit::zeroed().assume_init(); //~ ERROR: does not permit zero-initialization
        let _val: NonNull<i32> = MaybeUninit::uninit().assume_init(); //~ ERROR: does not permit being left uninitialized
        let _val: bool = MaybeUninit::uninit().assume_init(); //~ ERROR: does not permit being left uninitialized

        // Some more types that should work just fine.
        let _val: Option<&'static i32> = mem::zeroed();
        let _val: Option<fn()> = mem::zeroed();
        let _val: MaybeUninit<&'static i32> = mem::zeroed();
        let _val: bool = MaybeUninit::zeroed().assume_init();
        let _val: [bool; 0] = MaybeUninit::uninit().assume_init();
        let _val: [!; 0] = MaybeUninit::zeroed().assume_init();
    }
}

Version information

rustc 1.78.0-nightly (bf9c7a64a 2024-02-28)
binary: rustc
commit-hash: bf9c7a64ad222b85397573668b39e6d1ab9f4a72
commit-date: 2024-02-28
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

warning: field `wrapped` is never read
 --> /tmp/icemaker_global_tempdir.dM6dFsZiiTG5/rustc_testrunner_tmpdir_reporting.yGlXFnjDuyZG/mvce.rs:8:5
  |
7 | struct Wrap<T> {
  |        ---- field in this struct
8 |     wrapped: T,
  |     ^^^^^^^
  |
  = note: `#[warn(dead_code)]` on by default

warning: the type `NonZero<u32>` does not permit zero-initialization
  --> /tmp/icemaker_global_tempdir.dM6dFsZiiTG5/rustc_testrunner_tmpdir_reporting.yGlXFnjDuyZG/mvce.rs:15:34
   |
15 |         let _val: NonZero<u32> = mem::transmute(0);
   |                                  ^^^^^^^^^^^^^^^^^
   |                                  |
   |                                  this code causes undefined behavior when executed
   |                                  help: use `MaybeUninit<T>` instead, and only call `assume_init` after initialization is done
   |
   = note: `std::num::NonZero<u32>` must be non-null
   = note: `#[warn(invalid_value)]` on by default

thread 'rustc' panicked at compiler/rustc_middle/src/ty/sty.rs:1293:32:
range end index 18446744073709551615 out of range for slice of length 0
stack backtrace:
   0:     0x7f72c8874db6 - std::backtrace_rs::backtrace::libunwind::trace::he457b7c2e954e7cb
                               at /rustc/bf9c7a64ad222b85397573668b39e6d1ab9f4a72/library/std/src/../../backtrace/src/backtrace/libunwind.rs:104:5
   1:     0x7f72c8874db6 - std::backtrace_rs::backtrace::trace_unsynchronized::h2a45be351b5d4141
                               at /rustc/bf9c7a64ad222b85397573668b39e6d1ab9f4a72/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5
   2:     0x7f72c8874db6 - std::sys_common::backtrace::_print_fmt::h254e2aa93776cf56
                               at /rustc/bf9c7a64ad222b85397573668b39e6d1ab9f4a72/library/std/src/sys_common/backtrace.rs:68:5
   3:     0x7f72c8874db6 - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::h23f87d31c4a532b3
                               at /rustc/bf9c7a64ad222b85397573668b39e6d1ab9f4a72/library/std/src/sys_common/backtrace.rs:44:22
   4:     0x7f72c88c5d3c - core::fmt::rt::Argument::fmt::h70ae5cf40e1b3a9c
                               at /rustc/bf9c7a64ad222b85397573668b39e6d1ab9f4a72/library/core/src/fmt/rt.rs:142:9
   5:     0x7f72c88c5d3c - core::fmt::write::h1f9b4f3016092efe
                               at /rustc/bf9c7a64ad222b85397573668b39e6d1ab9f4a72/library/core/src/fmt/mod.rs:1120:17
   6:     0x7f72c88696cf - std::io::Write::write_fmt::ha5bad477c78ce031
                               at /rustc/bf9c7a64ad222b85397573668b39e6d1ab9f4a72/library/std/src/io/mod.rs:1846:15
   7:     0x7f72c8874b64 - std::sys_common::backtrace::_print::h390dc9acd71fecbd
                               at /rustc/bf9c7a64ad222b85397573668b39e6d1ab9f4a72/library/std/src/sys_common/backtrace.rs:47:5
   8:     0x7f72c8874b64 - std::sys_common::backtrace::print::hc3a43bb3ca42dd1a
                               at /rustc/bf9c7a64ad222b85397573668b39e6d1ab9f4a72/library/std/src/sys_common/backtrace.rs:34:9
   9:     0x7f72c88778ab - std::panicking::default_hook::{{closure}}::h54889b789689d8e2
  10:     0x7f72c88775f9 - std::panicking::default_hook::hc6795fcf5c686a1c
                               at /rustc/bf9c7a64ad222b85397573668b39e6d1ab9f4a72/library/std/src/panicking.rs:292:9
  11:     0x7f72c54a364c - std[6a867b114883c3c6]::panicking::update_hook::<alloc[f73d663d2b2ff203]::boxed::Box<rustc_driver_impl[9619562741c0c3f7]::install_ice_hook::{closure#0}>>::{closure#0}
  12:     0x7f72c8878010 - <alloc::boxed::Box<F,A> as core::ops::function::Fn<Args>>::call::h7f2babd05d8d24e0
                               at /rustc/bf9c7a64ad222b85397573668b39e6d1ab9f4a72/library/alloc/src/boxed.rs:2030:9
  13:     0x7f72c8878010 - std::panicking::rust_panic_with_hook::hbcbaaf53a9baed5d
                               at /rustc/bf9c7a64ad222b85397573668b39e6d1ab9f4a72/library/std/src/panicking.rs:783:13
  14:     0x7f72c8877d52 - std::panicking::begin_panic_handler::{{closure}}::h820c2a5e7c045958
                               at /rustc/bf9c7a64ad222b85397573668b39e6d1ab9f4a72/library/std/src/panicking.rs:657:13
  15:     0x7f72c8875296 - std::sys_common::backtrace::__rust_end_short_backtrace::ha7a9f3d2e3615f51
                               at /rustc/bf9c7a64ad222b85397573668b39e6d1ab9f4a72/library/std/src/sys_common/backtrace.rs:171:18
  16:     0x7f72c8877a84 - rust_begin_unwind
                               at /rustc/bf9c7a64ad222b85397573668b39e6d1ab9f4a72/library/std/src/panicking.rs:645:5
  17:     0x7f72c88c2255 - core::panicking::panic_fmt::h2c39cf2986b33eb5
                               at /rustc/bf9c7a64ad222b85397573668b39e6d1ab9f4a72/library/core/src/panicking.rs:72:14
  18:     0x7f72c88c85f2 - core::slice::index::slice_end_index_len_fail_rt::h5c90c9c2c1f6c19f
                               at /rustc/bf9c7a64ad222b85397573668b39e6d1ab9f4a72/library/core/src/slice/index.rs:76:5
  19:     0x7f72c88c8576 - core::slice::index::slice_end_index_len_fail::h43960563f86cf51e
                               at /rustc/bf9c7a64ad222b85397573668b39e6d1ab9f4a72/library/core/src/slice/index.rs:68:9
  20:     0x7f72c6a09c89 - <rustc_lint[8f247e7d87c5413e]::BuiltinCombinedModuleLateLintPass as rustc_lint[8f247e7d87c5413e]::passes::LateLintPass>::check_expr
  21:     0x7f72c69fd81e - <rustc_lint[8f247e7d87c5413e]::late::LateContextAndPass<rustc_lint[8f247e7d87c5413e]::BuiltinCombinedModuleLateLintPass> as rustc_hir[746b3c41ee825a99]::intravisit::Visitor>::visit_expr
  22:     0x7f72c69fd915 - <rustc_lint[8f247e7d87c5413e]::late::LateContextAndPass<rustc_lint[8f247e7d87c5413e]::BuiltinCombinedModuleLateLintPass> as rustc_hir[746b3c41ee825a99]::intravisit::Visitor>::visit_expr
  23:     0x7f72c69fc496 - <rustc_lint[8f247e7d87c5413e]::late::LateContextAndPass<rustc_lint[8f247e7d87c5413e]::BuiltinCombinedModuleLateLintPass> as rustc_hir[746b3c41ee825a99]::intravisit::Visitor>::visit_block
  24:     0x7f72c69fd8e7 - <rustc_lint[8f247e7d87c5413e]::late::LateContextAndPass<rustc_lint[8f247e7d87c5413e]::BuiltinCombinedModuleLateLintPass> as rustc_hir[746b3c41ee825a99]::intravisit::Visitor>::visit_expr
  25:     0x7f72c69fc307 - <rustc_lint[8f247e7d87c5413e]::late::LateContextAndPass<rustc_lint[8f247e7d87c5413e]::BuiltinCombinedModuleLateLintPass> as rustc_hir[746b3c41ee825a99]::intravisit::Visitor>::visit_block
  26:     0x7f72c69fd1ba - <rustc_lint[8f247e7d87c5413e]::late::LateContextAndPass<rustc_lint[8f247e7d87c5413e]::BuiltinCombinedModuleLateLintPass> as rustc_hir[746b3c41ee825a99]::intravisit::Visitor>::visit_expr::{closure#0}
  27:     0x7f72c6baec66 - <rustc_lint[8f247e7d87c5413e]::late::LateContextAndPass<rustc_lint[8f247e7d87c5413e]::BuiltinCombinedModuleLateLintPass> as rustc_hir[746b3c41ee825a99]::intravisit::Visitor>::visit_nested_body
  28:     0x7f72c6d9548d - <rustc_lint[8f247e7d87c5413e]::late::LateContextAndPass<rustc_lint[8f247e7d87c5413e]::BuiltinCombinedModuleLateLintPass> as rustc_hir[746b3c41ee825a99]::intravisit::Visitor>::visit_nested_item
  29:     0x7f72c6d9380e - rustc_lint[8f247e7d87c5413e]::lint_mod
  30:     0x7f72c6d93619 - rustc_query_impl[b823c4807244354d]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[b823c4807244354d]::query_impl::lint_mod::dynamic_query::{closure#2}::{closure#0}, rustc_middle[cb673eed9ea95983]::query::erase::Erased<[u8; 0usize]>>
  31:     0x7f72c73c7b6d - rustc_query_system[22dbc0c5f4018966]::query::plumbing::try_execute_query::<rustc_query_impl[b823c4807244354d]::DynamicConfig<rustc_query_system[22dbc0c5f4018966]::query::caches::DefaultCache<rustc_span[f0f44e44da00740b]::def_id::LocalModDefId, rustc_middle[cb673eed9ea95983]::query::erase::Erased<[u8; 0usize]>>, false, false, false>, rustc_query_impl[b823c4807244354d]::plumbing::QueryCtxt, false>
  32:     0x7f72c73c647f - rustc_query_impl[b823c4807244354d]::query_impl::lint_mod::get_query_non_incr::__rust_end_short_backtrace
  33:     0x7f72c73c601f - rustc_lint[8f247e7d87c5413e]::late::check_crate::{closure#1}
  34:     0x7f72c73c5a1e - rustc_lint[8f247e7d87c5413e]::late::check_crate
  35:     0x7f72c73bf925 - rustc_interface[9dd67852b69825df]::passes::analysis
  36:     0x7f72c73be619 - rustc_query_impl[b823c4807244354d]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[b823c4807244354d]::query_impl::analysis::dynamic_query::{closure#2}::{closure#0}, rustc_middle[cb673eed9ea95983]::query::erase::Erased<[u8; 1usize]>>
  37:     0x7f72c75323e5 - rustc_query_system[22dbc0c5f4018966]::query::plumbing::try_execute_query::<rustc_query_impl[b823c4807244354d]::DynamicConfig<rustc_query_system[22dbc0c5f4018966]::query::caches::SingleCache<rustc_middle[cb673eed9ea95983]::query::erase::Erased<[u8; 1usize]>>, false, false, false>, rustc_query_impl[b823c4807244354d]::plumbing::QueryCtxt, false>
  38:     0x7f72c7532149 - rustc_query_impl[b823c4807244354d]::query_impl::analysis::get_query_non_incr::__rust_end_short_backtrace
  39:     0x7f72c7539c7c - rustc_interface[9dd67852b69825df]::interface::run_compiler::<core[2b2f398b31a1f20f]::result::Result<(), rustc_span[f0f44e44da00740b]::ErrorGuaranteed>, rustc_driver_impl[9619562741c0c3f7]::run_compiler::{closure#0}>::{closure#0}
  40:     0x7f72c77daea3 - std[6a867b114883c3c6]::sys_common::backtrace::__rust_begin_short_backtrace::<rustc_interface[9dd67852b69825df]::util::run_in_thread_with_globals<rustc_interface[9dd67852b69825df]::util::run_in_thread_pool_with_globals<rustc_interface[9dd67852b69825df]::interface::run_compiler<core[2b2f398b31a1f20f]::result::Result<(), rustc_span[f0f44e44da00740b]::ErrorGuaranteed>, rustc_driver_impl[9619562741c0c3f7]::run_compiler::{closure#0}>::{closure#0}, core[2b2f398b31a1f20f]::result::Result<(), rustc_span[f0f44e44da00740b]::ErrorGuaranteed>>::{closure#0}, core[2b2f398b31a1f20f]::result::Result<(), rustc_span[f0f44e44da00740b]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[2b2f398b31a1f20f]::result::Result<(), rustc_span[f0f44e44da00740b]::ErrorGuaranteed>>
  41:     0x7f72c77dacd0 - <<std[6a867b114883c3c6]::thread::Builder>::spawn_unchecked_<rustc_interface[9dd67852b69825df]::util::run_in_thread_with_globals<rustc_interface[9dd67852b69825df]::util::run_in_thread_pool_with_globals<rustc_interface[9dd67852b69825df]::interface::run_compiler<core[2b2f398b31a1f20f]::result::Result<(), rustc_span[f0f44e44da00740b]::ErrorGuaranteed>, rustc_driver_impl[9619562741c0c3f7]::run_compiler::{closure#0}>::{closure#0}, core[2b2f398b31a1f20f]::result::Result<(), rustc_span[f0f44e44da00740b]::ErrorGuaranteed>>::{closure#0}, core[2b2f398b31a1f20f]::result::Result<(), rustc_span[f0f44e44da00740b]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[2b2f398b31a1f20f]::result::Result<(), rustc_span[f0f44e44da00740b]::ErrorGuaranteed>>::{closure#1} as core[2b2f398b31a1f20f]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  42:     0x7f72c88819e5 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::hff43642bea8880be
                               at /rustc/bf9c7a64ad222b85397573668b39e6d1ab9f4a72/library/alloc/src/boxed.rs:2016:9
  43:     0x7f72c88819e5 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::h1fd164abdd6e6853
                               at /rustc/bf9c7a64ad222b85397573668b39e6d1ab9f4a72/library/alloc/src/boxed.rs:2016:9
  44:     0x7f72c88819e5 - std::sys::pal::unix::thread::Thread::new::thread_start::h222e68bb559bca79
                               at /rustc/bf9c7a64ad222b85397573668b39e6d1ab9f4a72/library/std/src/sys/pal/unix/thread.rs:108:17
  45:     0x7f72c24a955a - <unknown>
  46:     0x7f72c2526a3c - <unknown>
  47:                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 (bf9c7a64a 2024-02-28) running on x86_64-unknown-linux-gnu

query stack during panic:
#0 [lint_mod] linting top-level module
#1 [analysis] running analysis passes on this crate
end of query stack
error[E0433]: failed to resolve: use of undeclared crate or module `ext`
  --> /tmp/icemaker_global_tempdir.dM6dFsZiiTG5/rustc_testrunner_tmpdir_reporting.yGlXFnjDuyZG/mvce.rs:13:43
   |
13 |         let _val: Wrap<char> = <ext::S as ext::X>::hoy();
   |                                           ^^^ use of undeclared crate or module `ext`

error[E0433]: failed to resolve: use of undeclared crate or module `ext`
  --> /tmp/icemaker_global_tempdir.dM6dFsZiiTG5/rustc_testrunner_tmpdir_reporting.yGlXFnjDuyZG/mvce.rs:13:33
   |
13 |         let _val: Wrap<char> = <ext::S as ext::X>::hoy();
   |                                 ^^^ use of undeclared crate or module `ext`

error: aborting due to 2 previous errors; 2 warnings emitted

For more information about this error, try `rustc --explain E0433`.

[matthiaskrgr]

#121206 cc @nnethercote found another one :D

[nnethercote]

👍 Hopefully will be fixed by #121669.

[nnethercote]

I just confirmed that #121669 fixes this. I don't think it's worth adding this as a test to the test suite.