mgca: Don't ICE when evaluating ValTrees that contain error constants by lapla-cogito · Pull Request #158401 · rust-lang/rust

lapla-cogito · 2026-06-25T14:30:18Z

mir::Const::eval now checks error_reported() and returns Err instead of converting such values to ConstValue.

rustbot · 2026-06-25T14:30:22Z

HIR ty lowering was modified

rustbot · 2026-06-25T14:30:25Z

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lapla-cogito · 2026-06-25T14:31:10Z

The case reported in the original issue goes through lower_const_arg_struct(). I found that a similar ICE can also occur through lower_const_arg_tuple_call(), and this serves as a regression test for that case.

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Is it a similar ICE or literally the same ICE? I'm not sure if it makes sense to have multiple tests for it since they all have the same root cause.

Ah, indeed. When I was investigating using the old fix approach, they appeared to be different paths causing ICE, but now I see these are indeed the same issue. Thanks.

camelid

I'm not sure if this is the right place to be fixing the problem. Given that ValTrees can have arbitrary ty::Const, it feels like they should be able to have error constants in them.

@BoxyUwU do you have thoughts about the best way to handle this?

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camelid · 2026-07-01T21:36:07Z

+        branches: impl IntoIterator<Item = ty::Const<'tcx>>,
+        ty: Ty<'tcx>,
+    ) -> Const<'tcx> {
+        let branches: Vec<_> = branches.into_iter().collect();


Hmm I don't love that this requires collecting the iterator, looking through all the branches, and then passing it on.

I just saw this discussion. Please let me think about it for a while... https://rust-lang.zulipchat.com/#narrow/channel/260443-project-const-generics/topic/const.20generics.20talkies.2013.20jul.202026.201600pm/with/609875464

No worries. The TLDR is that we should probably instead make other parts of the compiler handle errors inside valtrees gracefully, rather than avoiding creating valtrees that contain errors in an ad hoc way like this PR does.

Thanks for waiting! A recent change required additional #![feature(macroless_generic_const_args)] to reproduce ICE in the added tests, so I added it and made the fix.

lapla-cogito · 2026-08-09T09:33:02Z

@rustbot ready

rustbot · 2026-08-09T10:20:26Z

This PR changes a file inside tests/crashes. If a crash was fixed, please move into the corresponding ui subdir and add 'Fixes #' to the PR description to autoclose the issue upon merge.

camelid

Sorry for my delay with this. Looks good overall, but I have a question.

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camelid · 2026-08-27T19:29:52Z

Is it a similar ICE or literally the same ICE? I'm not sure if it makes sense to have multiple tests for it since they all have the same root cause.

rustbot · 2026-08-27T20:26:34Z

This PR was rebased onto a different main commit. Here's a range-diff highlighting what actually changed.

Rebasing is a normal part of keeping PRs up to date, so no action is needed—this note is just to help reviewers.

lapla-cogito · 2026-08-27T20:29:25Z

@rustbot ready

camelid

Thanks!

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camelid · 2026-09-02T16:37:51Z

@bors r+ rollup

rust-bors · 2026-09-02T16:37:54Z

📌 Commit db8797e has been approved by camelid

It is now in the queue for this repository.

mgca: Don't ICE when evaluating ValTrees that contain error constants Fixes rust-lang#154632 Fixes rust-lang#150969 `mir::Const::eval` now checks `error_reported()` and returns `Err` instead of converting such values to `ConstValue`.

…uwer Rollup of 23 pull requests Successful merges: - #162164 (Revert "Implement Debug for C-like enums with a concatenated string") - #160564 (volatile: allow accesses to non-AM memory to trap) - #161579 (suggest calling a fn item used as the iterator of a `for` loop) - #162044 (coverage: Resolve spans to file-coordinates in a separate step) - #162120 (Introduce `PerOwnerLoweringState`) - #162151 (Test itanium mangling of `f16` and `f128`) - #162162 (Don't special-case `!` in stability checks anymore) - #162181 (Remove wrong UnusedBraces lint for iterator loop in edition 2024 ) - #162187 (Rename `thir::ExprKind::Use` to `ValueExpr`) - #158401 (mgca: Don't ICE when evaluating ValTrees that contain error constants) - #159873 (fuchsia: Add safestack as a supported sanitizer for x86_64 fuchsia) - #161847 (Preserve visibility in nested macro import suggestions) - #161972 (Improve tests for `#[track_caller]` in async) - #162008 (Render the `box` pattern removal diagnostic more actionable & remove `box` expression recovery) - #162065 (std: don't reference `libc::O_NOFOLLOW` on VxWorks in `set_perm_nofollow`) - #162076 (docs(num): clarify conditions under which error occurs in `impl TryFrom<int> for int`) - #162152 (Revert "retrieve supported GCC targets from the sysroot") - #162153 (Prefer `LLVMGetVersion` for runtime info) - #162168 (fix ICE in project_goals/inherent) - #162171 (Explain LoongArch f16 NaN-boxing in inline asm) - #162173 (fix supposedly unreachable `bug!` being reachable) - #162191 (core: mark float `ClampBounds` methods as `#[inline]`) - #162199 (docs(time): clarify exact seconds for hour and minute)

mgca: Don't ICE when evaluating ValTrees that contain error constants Fixes rust-lang#154632 Fixes rust-lang#150969 `mir::Const::eval` now checks `error_reported()` and returns `Err` instead of converting such values to `ConstValue`.

Rollup of 23 pull requests Successful merges: - #157808 (sanitizers: Implement support for the sanitize ignorelist) - #160564 (volatile: allow accesses to non-AM memory to trap) - #161579 (suggest calling a fn item used as the iterator of a `for` loop) - #162044 (coverage: Resolve spans to file-coordinates in a separate step) - #162120 (Introduce `PerOwnerLoweringState`) - #162151 (Test itanium mangling of `f16` and `f128`) - #162162 (Don't special-case `!` in stability checks anymore) - #162181 (Remove wrong UnusedBraces lint for iterator loop in edition 2024 ) - #162187 (Rename `thir::ExprKind::Use` to `ValueExpr`) - #158401 (mgca: Don't ICE when evaluating ValTrees that contain error constants) - #159873 (fuchsia: Add safestack as a supported sanitizer for x86_64 fuchsia) - #161847 (Preserve visibility in nested macro import suggestions) - #161972 (Improve tests for `#[track_caller]` in async) - #162008 (Render the `box` pattern removal diagnostic more actionable & remove `box` expression recovery) - #162065 (std: don't reference `libc::O_NOFOLLOW` on VxWorks in `set_perm_nofollow`) - #162076 (docs(num): clarify conditions under which error occurs in `impl TryFrom<int> for int`) - #162152 (Revert "retrieve supported GCC targets from the sysroot") - #162153 (Prefer `LLVMGetVersion` for runtime info) - #162168 (fix ICE in project_goals/inherent) - #162171 (Explain LoongArch f16 NaN-boxing in inline asm) - #162173 (fix supposedly unreachable `bug!` being reachable) - #162191 (core: mark float `ClampBounds` methods as `#[inline]`) - #162199 (docs(time): clarify exact seconds for hour and minute)

mgca: Don't ICE when evaluating ValTrees that contain error constants Fixes rust-lang#154632 Fixes rust-lang#150969 `mir::Const::eval` now checks `error_reported()` and returns `Err` instead of converting such values to `ConstValue`.

Rollup of 29 pull requests Successful merges: - #161694 (add `Complex` ABI run-make test) - #162014 (Move more `rustdoc-html` tests using `--test` into the right folder) - #162164 (Revert "Implement Debug for C-like enums with a concatenated string") - #160564 (volatile: allow accesses to non-AM memory to trap) - #161579 (suggest calling a fn item used as the iterator of a `for` loop) - #162044 (coverage: Resolve spans to file-coordinates in a separate step) - #162120 (Introduce `PerOwnerLoweringState`) - #162132 (std: improve safety documentation in UNIX stack overflow code) - #162151 (Test itanium mangling of `f16` and `f128`) - #162162 (Don't special-case `!` in stability checks anymore) - #162181 (Remove wrong UnusedBraces lint for iterator loop in edition 2024 ) - #162187 (Rename `thir::ExprKind::Use` to `ValueExpr`) - #158401 (mgca: Don't ICE when evaluating ValTrees that contain error constants) - #159873 (fuchsia: Add safestack as a supported sanitizer for x86_64 fuchsia) - #161847 (Preserve visibility in nested macro import suggestions) - #161951 (Windows: add fallback if `canonicalize` fails) - #161972 (Improve tests for `#[track_caller]` in async) - #162008 (Render the `box` pattern removal diagnostic more actionable & remove `box` expression recovery) - #162065 (std: don't reference `libc::O_NOFOLLOW` on VxWorks in `set_perm_nofollow`) - #162076 (docs(num): clarify conditions under which error occurs in `impl TryFrom<int> for int`) - #162152 (Revert "retrieve supported GCC targets from the sysroot") - #162153 (Prefer `LLVMGetVersion` for runtime info) - #162168 (fix ICE in project_goals/inherent) - #162171 (Explain LoongArch f16 NaN-boxing in inline asm) - #162173 (fix supposedly unreachable `bug!` being reachable) - #162180 (remove outdated next-solver FIXMEs) - #162191 (core: mark float `ClampBounds` methods as `#[inline]`) - #162195 (docs(time): clarify exact seconds for week and day) - #162199 (docs(time): clarify exact seconds for hour and minute)

…uwer Rollup of 25 pull requests Successful merges: - #161694 (add `Complex` ABI run-make test) - #162014 (Move more `rustdoc-html` tests using `--test` into the right folder) - #162164 (Revert "Implement Debug for C-like enums with a concatenated string") - #160564 (volatile: allow accesses to non-AM memory to trap) - #161579 (suggest calling a fn item used as the iterator of a `for` loop) - #162044 (coverage: Resolve spans to file-coordinates in a separate step) - #162120 (Introduce `PerOwnerLoweringState`) - #162132 (std: improve safety documentation in UNIX stack overflow code) - #162151 (Test itanium mangling of `f16` and `f128`) - #162162 (Don't special-case `!` in stability checks anymore) - #162181 (Remove wrong UnusedBraces lint for iterator loop in edition 2024 ) - #162187 (Rename `thir::ExprKind::Use` to `ValueExpr`) - #158401 (mgca: Don't ICE when evaluating ValTrees that contain error constants) - #159873 (fuchsia: Add safestack as a supported sanitizer for x86_64 fuchsia) - #161135 (Add `f16` and `f128` inline ASM support for PowerPC) - #161847 (Preserve visibility in nested macro import suggestions) - #161972 (Improve tests for `#[track_caller]` in async) - #162008 (Render the `box` pattern removal diagnostic more actionable & remove `box` expression recovery) - #162065 (std: don't reference `libc::O_NOFOLLOW` on VxWorks in `set_perm_nofollow`) - #162076 (docs(num): clarify conditions under which error occurs in `impl TryFrom<int> for int`) - #162111 (Update mailmap for Will Crichton and Petr Hosek) - #162152 (Revert "retrieve supported GCC targets from the sysroot") - #162153 (Prefer `LLVMGetVersion` for runtime info) - #162168 (fix ICE in project_goals/inherent) - #162171 (Explain LoongArch f16 NaN-boxing in inline asm)

Rollup merge of #158401 - lapla-cogito:issue_154632, r=camelid mgca: Don't ICE when evaluating ValTrees that contain error constants Fixes #154632 Fixes #150969 `mir::Const::eval` now checks `error_reported()` and returns `Err` instead of converting such values to `ConstValue`.

rust-timer · 2026-09-03T18:50:38Z

Note

This PR was benchmarked as part of triage of its containing rollup: triage URL.

Finished benchmarking commit (3b029aa): comparison URL.

Overall result: no relevant changes - no action needed

@rustbot label: -perf-regression

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Artifact size: 401.86 MiB -> 400.99 MiB (-0.22%)

rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels Jun 25, 2026

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lapla-cogito commented Jun 25, 2026

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lapla-cogito changed the title ~~mgca: Propagate errors in const-to-valtree lowering~~ mgca: Don't ICE when evaluating ValTrees that contain error constants Aug 9, 2026

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lapla-cogito added 2 commits August 28, 2026 05:26

Don't ICE when evaluating ValTrees that contain error constants

e19a834

Move test/crashes/150969 to UI now that it no longer ICEs

db8797e

lapla-cogito force-pushed the issue_154632 branch from bce6199 to db8797e Compare August 27, 2026 20:26

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JonathanBrouwer mentioned this pull request Sep 2, 2026

Rollup of 23 pull requests #162206

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Rollup of 23 pull requests #162211

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Rollup of 23 pull requests #162216

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Rollup of 29 pull requests #162221

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Rollup of 25 pull requests #162229

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rust-bors Bot merged commit 2417275 into rust-lang:main Sep 3, 2026
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