ICE: `this path really should be doomed`

[matthiaskrgr]

auto-reduced (treereduce-rust):

fn main() {
    struct X;

    let xs = [X, X, X];
    let eq = xs == [panic!("panic evaluated"); 2];
}

original:

fn main() {
    struct X;
    //~^ HELP consider annotating `X` with `#[derive(PartialEq)]`
    let xs = [X, X, X];
    let eq = xs == [panic!("panic evaluated"); 2];
    //~^ ERROR binary operation `==` cannot be applied to type `[X; 3]`
}

Version information

rustc 1.85.0-nightly (33c245b9e 2024-12-10)
binary: rustc
commit-hash: 33c245b9e98bc91e18ea1c5033824f4c6f92766f
commit-date: 2024-12-10
host: x86_64-unknown-linux-gnu
release: 1.85.0-nightly
LLVM version: 19.1.5

Command:
/home/matthias/.rustup/toolchains/master/bin/rustc

Program output

warning: unreachable expression
 --> /tmp/icemaker_global_tempdir.NcZ6cDcOgb7d/rustc_testrunner_tmpdir_reporting.dN0NI0VTaCoG/mvce.rs:5:20
  |
5 |     let eq = xs == [panic!("panic evaluated"); 2];
  |                    ^-------------------------^^^^
  |                    ||
  |                    |any code following this expression is unreachable
  |                    unreachable expression
  |
  = note: `#[warn(unreachable_code)]` on by default

warning: 1 warning emitted

note: no errors encountered even though delayed bugs were created

note: those delayed bugs will now be shown as internal compiler errors

error: internal compiler error: this path really should be doomed...
 --> /tmp/icemaker_global_tempdir.NcZ6cDcOgb7d/rustc_testrunner_tmpdir_reporting.dN0NI0VTaCoG/mvce.rs:5:17
  |
5 |     let eq = xs == [panic!("panic evaluated"); 2];
  |                 ^^
  |
note: delayed at compiler/rustc_hir_typeck/src/op.rs:925:28 - disabled backtrace
 --> /tmp/icemaker_global_tempdir.NcZ6cDcOgb7d/rustc_testrunner_tmpdir_reporting.dN0NI0VTaCoG/mvce.rs:5:17
  |
5 |     let eq = xs == [panic!("panic evaluated"); 2];
  |                 ^^

error: internal compiler error: expression with never type wound up being adjusted
 --> /tmp/icemaker_global_tempdir.NcZ6cDcOgb7d/rustc_testrunner_tmpdir_reporting.dN0NI0VTaCoG/mvce.rs:5:21
  |
5 |     let eq = xs == [panic!("panic evaluated"); 2];
  |                     ^^^^^^^^^^^^^^^^^^^^^^^^^
  |
note: delayed at compiler/rustc_hir_typeck/src/expr.rs:76:43 - disabled backtrace
 --> /tmp/icemaker_global_tempdir.NcZ6cDcOgb7d/rustc_testrunner_tmpdir_reporting.dN0NI0VTaCoG/mvce.rs:5:21
  |
5 |     let eq = xs == [panic!("panic evaluated"); 2];
  |                     ^^^^^^^^^^^^^^^^^^^^^^^^^
  = note: this error: internal compiler error originates in the macro `$crate::panic::panic_2015` which comes from the expansion of the macro `panic` (in Nightly builds, run with -Z macro-backtrace for more info)

error: internal compiler error: TyKind::Error constructed but no error reported
  |
  = note: delayed at compiler/rustc_hir_typeck/src/op.rs:303:17 - disabled backtrace

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: please make sure that you have updated to the latest nightly

note: rustc 1.85.0-nightly (33c245b9e 2024-12-10) running on x86_64-unknown-linux-gnu

query stack during panic:
end of query stack

[jieyouxu]

ICEs on stable too.

[jieyouxu]

********************************************************************************
Regression in nightly-2024-02-22
********************************************************************************

looking for regression commit between 2024-02-21 and 2024-02-22
fetching (via remote github) commits from max(bb594538fc6e84213a6b8d5e165442570aa48923, 2024-02-19) to 3406ada96f8e16e49e947a91db3eba0db45245fa
ending github query because we found starting sha: bb594538fc6e84213a6b8d5e165442570aa48923
get_commits_between returning commits, len: 11
  commit[0] 2024-02-20: Auto merge of #121345 - Nilstrieb:rollup-reb0xge, r=Nilstrieb
  commit[1] 2024-02-20: Auto merge of #121356 - matthiaskrgr:rollup-d80af2s, r=matthiaskrgr
  commit[2] 2024-02-21: Auto merge of #120904 - Nadrieril:match-lowering-intermediate-repr, r=matthewjasper
  commit[3] 2024-02-21: Auto merge of #121172 - Nadrieril:simplify-empty-selection, r=matthewjasper
  commit[4] 2024-02-21: Auto merge of #121380 - weihanglo:update-cargo, r=weihanglo
  commit[5] 2024-02-21: Auto merge of #120588 - alexcrichton:wasm-rmeta-object, r=wesleywiser,bjorn3
  commit[6] 2024-02-21: Auto merge of #120718 - saethlin:reasonable-fast-math, r=nnethercote
  commit[7] 2024-02-21: Auto merge of #121383 - Dylan-DPC:rollup-735p4u4, r=Dylan-DPC
  commit[8] 2024-02-21: Auto merge of #121400 - fmease:rollup-8m29g7a, r=fmease
  commit[9] 2024-02-21: Auto merge of #121321 - compiler-errors:yeet-querytyperelating, r=lcnr
  commit[10] 2024-02-21: Auto merge of #117658 - RalfJung:ptr-dangling, r=m-ou-se
ERROR: no CI builds available between bb594538fc6e84213a6b8d5e165442570aa48923 and 3406ada96f8e16e49e947a91db3eba0db45245fa within last 167 days

[jieyouxu]

I have a feeling this might be a #121208

[jieyouxu]

Indeed: https://github.com/rust-lang/rust/pull/121208/files#r1494187622

[jieyouxu]

fn main() {
    struct X;
    let _ = [X] == [panic!(); 2];
}

[jieyouxu]

Ah: this is also edition sensitive. It ICEs on 2021 and 2024, but not on earlier editions.