Avoid underflow for splatted rust-call receivers by chenyukang · Pull Request #158850 · rust-lang/rust

chenyukang · 2026-07-06T09:11:42Z

We alreay have proper error for #[splat] self in following code, so here we just need to avoid the overflow.

rustbot · 2026-07-06T09:11:46Z

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teor2345

I think that banning splat on rust-call and closures in PR #158645 will make these fixes obsolete. But there's still some useful changes we can make in this code.

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teor2345 · 2026-07-06T10:27:13Z

@@ -1717,14 +1717,18 @@ fn check_fn_or_method<'tcx>(
        let has_implicit_self = hir_decl.implicit_self().has_implicit_self();
        let mut inputs = sig.inputs().iter().skip(if has_implicit_self { 1 } else { 0 });
        // FIXME(splat): support the rest of closure splatting, or replace this code with an error


Based on the ban in #158645, this splatted closure code should probably become a compiler error (or an ICE bug).

And we can delete the rest of the calculations, so there's no underflow.

teor2345 · 2026-07-06T13:21:10Z

Oh, and thank you for the PR! It's great to have a bunch of people finding bugs and fixing things.

chenyukang · 2026-07-06T13:25:39Z

I think that banning splat on rust-call and closures in PR #158645 will make these fixes obsolete. But there's still some useful changes we can make in this code.

View changes since this review

I will rework on it after #158645 is merged.

teor2345 · 2026-07-06T20:19:04Z

@rustbot author

teor2345 · 2026-07-15T21:42:46Z

I will rework on it after #158645 is merged.

It has been merged 🙂

chenyukang · 2026-07-16T02:31:35Z

I will rework on it after #158645 is merged.

It has been merged 🙂

I have a test after rebasing on main branch.

there will be an extra error message:

error: `#[splat]` is not allowed in the arguments of functions with the `rust-call` ABI
  --> /tmp/ha.rs:12:5
   |
12 |     extern "rust-call" fn call_once(#[splat] self) {}
   |     ^^^^^^^^^^^^^^^^^^              ^^^^^^^^
   |
   = help: remove `#[splat]` or change the ABI

but the ICE will happen without the patch on https://github.com/chenyukang/rust/blob/90933f34fd6570c7b82e9e4a464513e9cd99d591/compiler/rustc_hir_analysis/src/check/wfcheck.rs#L1652-L1671.

you assume the code will not run into this part after #158645?

teor2345 · 2026-07-16T09:03:42Z

you assume the code will not run into this part after #158645?

We should add a test that exercises that code, if it runs we must fix the ICE. If we can't make it run using a test, then it's up to you if you want to fix or delete the code. Usually we would delete code for things that are rejected in earlier stages.

chenyukang · 2026-07-16T12:08:07Z

you assume the code will not run into this part after #158645?

We should add a test that exercises that code, if it runs we must fix the ICE. If we can't make it run using a test, then it's up to you if you want to fix or delete the code. Usually we would delete code for things that are rejected in earlier stages.

aha, got it.
it's better to remove this part, I already updated the code.

teor2345

Thanks for the extra test, this looks good!

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jieyouxu

Thanks
@bors r=teor2345,jieyouxu rollup

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jieyouxu · 2026-07-19T10:41:27Z

r= me and teor with the nit
@bors r-

rustbot · 2026-07-19T11:50:48Z

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.

chenyukang · 2026-07-19T12:55:38Z

@bors r=teor2345,jieyouxu

rust-bors · 2026-07-19T12:55:41Z

📌 Commit c213b5f has been approved by teor2345,jieyouxu

It is now in the queue for this repository.

…uwer Rollup of 6 pull requests Successful merges: - #159524 (Gather PGO profiles in parallel) - #158850 (Avoid underflow for splatted rust-call receivers) - #159215 ([compiletest] Differentiate between LLVM LLDB and Apple LLDB) - #159347 (Document rustc_public lib.rs and update README) - #159469 (Reorganize `tests/ui/issues` [27/N]) - #159512 (Add regression tests for fixed dead-code issues)

@teor2345

Rollup merge of #158850 - chenyukang:yukang-fix-158800-splat-self-wfcheck-overflow, r=teor2345,jieyouxu Avoid underflow for splatted rust-call receivers Fixes #158800 We alreay have proper error for `#[splat] self` in following code, so here we just need to avoid the overflow. cc @teor2345

@rustbot

…nTitor Add more splat rust-call regression tests Tracking issue: rust-lang#153629 This PR provides more test coverage for splat, rust-call, and closure rejection (bugs rust-lang#158800 and rust-lang#158605), after the fixes in PRs rust-lang#158645 and rust-lang#158850. This PR only contains tests. @rustbot +F-splat +T-compiler +C-bug

@rustbot

…nTitor Add more splat rust-call regression tests Tracking issue: rust-lang#153629 This PR provides more test coverage for splat, rust-call, and closure rejection (bugs rust-lang#158800 and rust-lang#158605), after the fixes in PRs rust-lang#158645 and rust-lang#158850. This PR only contains tests. @rustbot +F-splat +T-compiler +C-bug

@rustbot

Rollup merge of #159629 - teor2345:splat-closure-test, r=JohnTitor Add more splat rust-call regression tests Tracking issue: #153629 This PR provides more test coverage for splat, rust-call, and closure rejection (bugs #158800 and #158605), after the fixes in PRs #158645 and #158850. This PR only contains tests. @rustbot +F-splat +T-compiler +C-bug

@rustbot

Add more splat rust-call regression tests Tracking issue: rust-lang/rust#153629 This PR provides more test coverage for splat, rust-call, and closure rejection (bugs rust-lang/rust#158800 and rust-lang/rust#158605), after the fixes in PRs rust-lang/rust#158645 and rust-lang/rust#158850. This PR only contains tests. @rustbot +F-splat +T-compiler +C-bug

rustbot assigned jieyouxu Jul 6, 2026

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 Jul 6, 2026

jieyouxu added the F-splat `#![feature(splat)]` https://github.com/rust-lang/rust/issues/153629 label Jul 6, 2026

teor2345 suggested changes Jul 6, 2026

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rustbot added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Jul 6, 2026

teor2345 mentioned this pull request Jul 15, 2026

[ICE]: attempt to subtract with overflow #158800

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chenyukang force-pushed the yukang-fix-158800-splat-self-wfcheck-overflow branch from ca4c42e to 90933f3 Compare July 16, 2026 02:27

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chenyukang force-pushed the yukang-fix-158800-splat-self-wfcheck-overflow branch from 90933f3 to d1f8053 Compare July 16, 2026 10:25

teor2345 approved these changes Jul 16, 2026

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jieyouxu approved these changes Jul 19, 2026

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Avoid underflow for splatted rust-call receivers

c213b5f

chenyukang force-pushed the yukang-fix-158800-splat-self-wfcheck-overflow branch from d1f8053 to c213b5f Compare July 19, 2026 11:50

rust-bors Bot added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Jul 19, 2026

JonathanBrouwer mentioned this pull request Jul 19, 2026

Rollup of 6 pull requests #159569

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rust-bors Bot merged commit d385755 into rust-lang:main Jul 19, 2026
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rustbot added this to the 1.99.0 milestone Jul 19, 2026

teor2345 mentioned this pull request Jul 21, 2026

Add more splat rust-call regression tests #159629

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