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Add regression test for mono item collection ICE with generic_const_exprs #154547

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Add regression test for mono item collection ICE with generic_const_exprs #154547

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20 changes: 20 additions & 0 deletions tests/ui/const-generics/generic_const_exprs/generic-const-exprs-mono-collect-ice-149035.rs
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//! Ensure `-Clink-dead-code=true` with `generic_const_exprs` and
//! `min_generic_const_args` doesn't ICE in mono item collection.
//!
//! Regression test for <https://github.com/rust-lang/rust/issues/149035>.

//@ build-pass
//@ compile-flags: -Clink-dead-code=true

#![feature(min_generic_const_args, generic_const_exprs)]

type const L: usize = 4;
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@TaKO8Ki TaKO8Ki Apr 1, 2026 •
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Do you have any reason why this line is different from one in provided code in the issue? #149035 (comment)

Ideally, we need to verify with that test that the ICE occurs without the fix in #152129.

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@jeanibarz jeanibarz Apr 1, 2026 •
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The original const L doesn't compile on current main, as #152129 both fixed the ICE and introduced type const syntax for free consts, so I had to adapt the reproducer.

I verified with rustup:

  • nightly-2025-11-17 (same as the issue): const L ICEs in mono item collection
  • nightly-2026-02-05 (day before MGCA: require #[type_const] on free consts too #152129 merged): const L still ICEs, type const is a parse error
  • current nightly: const L gets a hard error, type const L compiles cleanly

So there's no nightly where type const exists and the ICE is still present, as the syntax was introduced by the same PR that fixed the bug. That means this test can't directly catch a revert of #152129 (the syntax would vanish too). It's more of a smoke test for the const-in-generic-arg + -Clink-dead-code=true path in mono item collection.

Happy to drop it if you don't think that's useful enough, or adjust the approach if you have something else in mind.

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@reddevilmidzy reddevilmidzy Apr 2, 2026

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I don't think we need to test with type const

So I think it would have been more appropriate to close the issue with obsolete instead of adding E-needs-test labels.

I'll close the issue and PR, thanks for your contribution :)

trait Print<const N: usize> {
fn print() -> usize {
N
}
}
struct Printer;
impl Print<L> for Printer {}

fn main() {}
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