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Avoid ICE in known_panics_lint for mismatched type const literals#156463

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Avoid ICE in known_panics_lint for mismatched type const literals#156463
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@reddevilmidzy reddevilmidzy commented May 11, 2026

close: #154748
close: #154750

@rustbot rustbot added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels May 11, 2026
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reddevilmidzy commented May 11, 2026

I first tried fixing this during literal-to-const lowering, but that either changed the existing diagnostics or introduced additional delayed-bug ICEs.

The type mismatch is already diagnosed earlier, so this instead makes known_panics_lint bail out on incompatible layouts during const propagation to avoid the ICE while preserving the current errors.

@reddevilmidzy reddevilmidzy changed the title Avoid ICE in known_panics_lint for mismatched type const literals Avoid ICE in known_panics_lint for mismatched type const literals May 11, 2026
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reddevilmidzy commented May 12, 2026

r? @BoxyUwU

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rustbot commented May 12, 2026

BoxyUwU is currently at their maximum review capacity.
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@reddevilmidzy reddevilmidzy marked this pull request as ready for review May 12, 2026 02:38
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rustbot commented May 12, 2026

Some changes occurred to MIR optimizations

cc @rust-lang/wg-mir-opt

@rustbot rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels May 12, 2026
oli-obk
oli-obk reviewed May 12, 2026
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Comment thread compiler/rustc_mir_transform/src/known_panics_lint.rs
_ => return None,
}

if value.layout.size != to.size {
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@oli-obk oli-obk May 12, 2026 •
edited by rustbot
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This fixes the symptom, not the issue itself. Why do we even get here after the error is reported?

Oh I think I may have found it: https://github.com/rust-lang/rust/pull/152001/changes#r3224335944

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[ICE]: attempting to project to field at offset 0 with size 8 into immediate with layout TyAndLayout [ICE]: invalid field access on immediate

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