ICE: slices are not scalars

[Sky9x]

Code

Playground

trait Clone {
    fn clone(&self) -> Self where Self: Sized;
}

impl<T: Clone> Clone for [T] {
    fn clone(&self) -> Self where Self: Sized {
        unreachable!()
    }
}

Meta

works on stable but not nightly

rustc --version --verbose:

rustc 1.78.0-nightly (3246e7951 2024-02-19)
binary: rustc
commit-hash: 3246e79513cb89ddbfc0f21cb5a877e5b321dcc5
commit-date: 2024-02-19
host: x86_64-unknown-linux-gnu
release: 1.78.0-nightly
LLVM version: 18.1.0

Error output

Backtrace

thread 'rustc' panicked at compiler/rustc_mir_dataflow/src/value_analysis.rs:849:13:
slices are not scalars
stack backtrace:
   0:     0x7f2a0e060f4f - std::backtrace_rs::backtrace::libunwind::trace::h8ae4267cbff78cba
                               at /rustc/3246e79513cb89ddbfc0f21cb5a877e5b321dcc5/library/std/src/../../backtrace/src/backtrace/libunwind.rs:104:5
   1:     0x7f2a0e060f4f - std::backtrace_rs::backtrace::trace_unsynchronized::h51c412dced35f1df
                               at /rustc/3246e79513cb89ddbfc0f21cb5a877e5b321dcc5/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5
   2:     0x7f2a0e060f4f - std::backtrace::Backtrace::create::hb5363bc6fe03a147
                               at /rustc/3246e79513cb89ddbfc0f21cb5a877e5b321dcc5/library/std/src/backtrace.rs:331:13
   3:     0x7f2a0e060e90 - std::backtrace::Backtrace::force_capture::h09cde0b1d72ee122
                               at /rustc/3246e79513cb89ddbfc0f21cb5a877e5b321dcc5/library/std/src/backtrace.rs:312:9
   4:     0x7f2a0ae2fbd7 - std[88cc13ac5e46237b]::panicking::update_hook::<alloc[c36677dfd055d4b5]::boxed::Box<rustc_driver_impl[43e8f7cc04ab8702]::install_ice_hook::{closure#0}>>::{closure#0}
   5:     0x7f2a0e07bd20 - <alloc::boxed::Box<F,A> as core::ops::function::Fn<Args>>::call::h16d70f2ac15ce073
                               at /rustc/3246e79513cb89ddbfc0f21cb5a877e5b321dcc5/library/alloc/src/boxed.rs:2030:9
   6:     0x7f2a0e07bd20 - std::panicking::rust_panic_with_hook::hfcc097815365b485
                               at /rustc/3246e79513cb89ddbfc0f21cb5a877e5b321dcc5/library/std/src/panicking.rs:786:13
   7:     0x7f2a0e07ba29 - std::panicking::begin_panic_handler::{{closure}}::h8dac30e50803d6dd
                               at /rustc/3246e79513cb89ddbfc0f21cb5a877e5b321dcc5/library/std/src/panicking.rs:652:13
   8:     0x7f2a0e078fa6 - std::sys_common::backtrace::__rust_end_short_backtrace::h9fe6177cef6e17f8
                               at /rustc/3246e79513cb89ddbfc0f21cb5a877e5b321dcc5/library/std/src/sys_common/backtrace.rs:171:18
   9:     0x7f2a0e07b794 - rust_begin_unwind
                               at /rustc/3246e79513cb89ddbfc0f21cb5a877e5b321dcc5/library/std/src/panicking.rs:648:5
  10:     0x7f2a0e0c5f65 - core::panicking::panic_fmt::h9ecf1705441f8b1b
                               at /rustc/3246e79513cb89ddbfc0f21cb5a877e5b321dcc5/library/core/src/panicking.rs:72:14
  11:     0x7f2a0ccc0b14 - <rustc_mir_dataflow[eb74de6dd7f7f940]::value_analysis::Map>::new
  12:     0x7f2a0c990e56 - <rustc_mir_transform[1ddaf0ad40506e62]::jump_threading::JumpThreading as rustc_middle[27e5e81444fa3f89]::mir::MirPass>::run_pass
  13:     0x7f2a0c012a8f - rustc_mir_transform[1ddaf0ad40506e62]::pass_manager::run_passes_inner
  14:     0x7f2a0c4e7f7f - rustc_mir_transform[1ddaf0ad40506e62]::optimized_mir
  15:     0x7f2a0c0919b5 - rustc_query_impl[8e5c8e12319352c5]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[8e5c8e12319352c5]::query_impl::optimized_mir::dynamic_query::{closure#2}::{closure#0}, rustc_middle[27e5e81444fa3f89]::query::erase::Erased<[u8; 8usize]>>
  16:     0x7f2a0c092061 - rustc_query_system[bfc5cdf7ae7702b8]::query::plumbing::try_execute_query::<rustc_query_impl[8e5c8e12319352c5]::DynamicConfig<rustc_query_system[bfc5cdf7ae7702b8]::query::caches::DefIdCache<rustc_middle[27e5e81444fa3f89]::query::erase::Erased<[u8; 8usize]>>, false, false, false>, rustc_query_impl[8e5c8e12319352c5]::plumbing::QueryCtxt, false>
  17:     0x7f2a0c0917de - rustc_query_impl[8e5c8e12319352c5]::query_impl::optimized_mir::get_query_non_incr::__rust_end_short_backtrace
  18:     0x7f2a0cedb295 - rustc_middle[27e5e81444fa3f89]::query::plumbing::query_get_at::<rustc_query_system[bfc5cdf7ae7702b8]::query::caches::DefIdCache<rustc_middle[27e5e81444fa3f89]::query::erase::Erased<[u8; 8usize]>>>
  19:     0x7f2a0cfa0089 - <rustc_metadata[72646f08ecd30116]::rmeta::encoder::EncodeContext>::encode_crate_root
  20:     0x7f2a0cff2756 - rustc_metadata[72646f08ecd30116]::rmeta::encoder::encode_metadata
  21:     0x7f2a0cff08f8 - rustc_metadata[72646f08ecd30116]::fs::encode_and_write_metadata
  22:     0x7f2a0cfefc9d - rustc_interface[6b23f56c014e7e]::passes::start_codegen
  23:     0x7f2a0cfef518 - <rustc_interface[6b23f56c014e7e]::queries::Queries>::codegen_and_build_linker
  24:     0x7f2a0cd4a72a - rustc_interface[6b23f56c014e7e]::interface::run_compiler::<core[9135d4f27aa7f376]::result::Result<(), rustc_span[c3b4d1cce1296ff1]::ErrorGuaranteed>, rustc_driver_impl[43e8f7cc04ab8702]::run_compiler::{closure#0}>::{closure#0}
  25:     0x7f2a0cfd2b05 - std[88cc13ac5e46237b]::sys_common::backtrace::__rust_begin_short_backtrace::<rustc_interface[6b23f56c014e7e]::util::run_in_thread_with_globals<rustc_interface[6b23f56c014e7e]::util::run_in_thread_pool_with_globals<rustc_interface[6b23f56c014e7e]::interface::run_compiler<core[9135d4f27aa7f376]::result::Result<(), rustc_span[c3b4d1cce1296ff1]::ErrorGuaranteed>, rustc_driver_impl[43e8f7cc04ab8702]::run_compiler::{closure#0}>::{closure#0}, core[9135d4f27aa7f376]::result::Result<(), rustc_span[c3b4d1cce1296ff1]::ErrorGuaranteed>>::{closure#0}, core[9135d4f27aa7f376]::result::Result<(), rustc_span[c3b4d1cce1296ff1]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[9135d4f27aa7f376]::result::Result<(), rustc_span[c3b4d1cce1296ff1]::ErrorGuaranteed>>
  26:     0x7f2a0cfd2932 - <<std[88cc13ac5e46237b]::thread::Builder>::spawn_unchecked_<rustc_interface[6b23f56c014e7e]::util::run_in_thread_with_globals<rustc_interface[6b23f56c014e7e]::util::run_in_thread_pool_with_globals<rustc_interface[6b23f56c014e7e]::interface::run_compiler<core[9135d4f27aa7f376]::result::Result<(), rustc_span[c3b4d1cce1296ff1]::ErrorGuaranteed>, rustc_driver_impl[43e8f7cc04ab8702]::run_compiler::{closure#0}>::{closure#0}, core[9135d4f27aa7f376]::result::Result<(), rustc_span[c3b4d1cce1296ff1]::ErrorGuaranteed>>::{closure#0}, core[9135d4f27aa7f376]::result::Result<(), rustc_span[c3b4d1cce1296ff1]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[9135d4f27aa7f376]::result::Result<(), rustc_span[c3b4d1cce1296ff1]::ErrorGuaranteed>>::{closure#1} as core[9135d4f27aa7f376]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  27:     0x7f2a0e0856f5 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::h8884f59d39766bcc
                               at /rustc/3246e79513cb89ddbfc0f21cb5a877e5b321dcc5/library/alloc/src/boxed.rs:2016:9
  28:     0x7f2a0e0856f5 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::hd3cff0ddac56346e
                               at /rustc/3246e79513cb89ddbfc0f21cb5a877e5b321dcc5/library/alloc/src/boxed.rs:2016:9
  29:     0x7f2a0e0856f5 - std::sys::pal::unix::thread::Thread::new::thread_start::h1990c77eff82b16c
                               at /rustc/3246e79513cb89ddbfc0f21cb5a877e5b321dcc5/library/std/src/sys/pal/unix/thread.rs:108:17
  30:     0x7f2a07c94ac3 - start_thread
                               at ./nptl/pthread_create.c:442:8
  31:     0x7f2a07d26850 - __GI___clone3
                               at ./misc/../sysdeps/unix/sysv/linux/x86_64/clone3.S:81
  32:                0x0 - <unknown>


rustc version: 1.78.0-nightly (3246e7951 2024-02-19)
platform: x86_64-unknown-linux-gnu

query stack during panic:
#0 [optimized_mir] optimizing MIR for `<impl at unsized_clone.rs:7:1: 7:29>::clone`
end of query stack

[matthiaskrgr]

This is probably a duplicate of #116721

[Sky9x]

searched nightlies: from nightly-2024-02-05 to nightly-2024-02-20
regressed nightly: nightly-2024-02-12
searched commit range: 6cc4843...1a648b3
regressed commit: 42752cb

bisected with cargo-bisect-rustc v0.6.8

Host triple: x86_64-unknown-linux-gnu
Reproduce with:

cargo bisect-rustc --regress ice -- build --release 

regresses in earlier nightlies with -Zmir-opt-level=3, the regressed commit only seems to have made it show up in -Zmir-opt-level=2 and thus in release mode

[Noratrieb]

some MIR opt stuff that only regressed it incorrectly, as expected
so it probably is a duplicate of the existing bug