Fix splat v0 mangling by teor2345 · Pull Request #158890 · rust-lang/rust

teor2345 · 2026-07-07T01:25:32Z

Tracking issue: #153629

Typecheck considers a splatted and non-splatted function as distinct types, so mangling has to include splatting. If it doesn't, we get symbol clashes. See the ticket and the tests in this PR for details.

Demangling PR: rust-lang/rustc-demangle#90
Demangling in rust-lang/rust PR: #159202

@rustbot label +C-bug +F-splat +T-compiler +A-name-mangling

Fixes #158644

This PR was based on #159202, so we waited for that PR to merge first, then rebased this one.

rustbot · 2026-07-07T01:25:36Z

r? @hanna-kruppe

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wesleywiser

Just so you know, changes to the mangling scheme typically also have a corresponding PR to https://github.com/rust-lang/rustc-demangle 🙂

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rustbot · 2026-07-08T06:14:57Z

Reminder, once the PR becomes ready for a review, use @rustbot ready.

hanna-kruppe · 2026-07-11T12:28:26Z

r? wesleywiser

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rustbot · 2026-07-13T04:32:07Z

These commits modify the Cargo.lock file. Unintentional changes to Cargo.lock can be introduced when switching branches and rebasing PRs.

If this was unintentional then you should revert the changes before this PR is merged.
Otherwise, you can ignore this comment.

stdarch is developed in its own repository. If possible, consider making this change to rust-lang/stdarch instead.

cc @Amanieu, @folkertdev, @sayantn

These commits modify the library/Cargo.lock file. Unintentional changes to library/Cargo.lock can be introduced when switching branches and rebasing PRs.

If this was unintentional then you should revert the changes before this PR is merged.
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clippy is developed in its own repository. If possible, consider making this change to rust-lang/rust-clippy instead.

cc @rust-lang/clippy

teor2345 · 2026-07-13T04:33:39Z

The rustc-demangle version bump is in #159202, this PR starts with the commits from that PR, then has the working splat mangling and tests on top of them.

~~This PR should wait to merge until after #159202 merges, just in case we drop some of the version bumps from that PR.~~

rustbot · 2026-07-18T00:32:06Z

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.

teor2345

I squashed most commits, but I left one of the symbol clash tests in a separate commit, because it depends on incremental compilation state.

(I found the issue without incremental compilation, but it involved a race condition or local state that would only trigger the linker error some of the time. The test seems stable in CI and locally now, but I want to leave it in a separate commit, just in case it becomes flaky.)

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teor2345 · 2026-07-17T23:22:48Z

+           //[legacy]~^ ERROR symbol-name(_ZN14splat_mangling4main66Type$LT$fn$LP$$C$$u20$$u23$$u5b$splat$u5d$$LP$u8$C$u32$RP$$RP$$GT
+           //[legacy]~| ERROR demangling(splat_mangling::main::Type<fn(, #[splat](u8,u32))>::
+           //[legacy]~| ERROR demangling-alt(splat_mangling::main::Type<fn(, #[splat](u8,u32))>)
+    //[v0,default]~^^^^ ERROR symbol-name(_RMNvCsCRATE_HASH_14splat_mangling4mainINtB<REF>_4TypeFwThmEEuE)
+       //[v0,default]~| ERROR demangling(<splat_mangling[
+       //[v0,default]~| ERROR demangling-alt(<splat_mangling::main::Type<fn(#[splat] (u8, u32))>>)


It's based on the existing mangling tests, so that the ERROR and symbol names line up across different variants, making them easier to compare.

Edit: this was extremely useful when comparing the splatted and non-splatted mangling.

rust/tests/ui/symbol-names/basic.rs

Lines 8 to 14 in b6839f4

#[rustc_dump_symbol_name]

//[legacy]~^ ERROR symbol-name(_ZN5basic4main

//[legacy]~| ERROR demangling(basic::main

//[legacy]~| ERROR demangling-alt(basic::main)

//[v0]~^^^^ ERROR symbol-name(_RNv

//[v0]~| ERROR demangling(basic[

//[v0]~| ERROR demangling-alt(basic::main)

teor2345 · 2026-07-20T23:46:55Z

@rustbot ready

wesleywiser · 2026-07-21T17:46:47Z

@bors r+

rust-bors · 2026-07-21T17:46:50Z

📌 Commit a34aad0 has been approved by wesleywiser

It is now in the queue for this repository.

@rustbot

…esleywiser Fix splat v0 mangling Tracking issue: rust-lang#153629 Typecheck considers a splatted and non-splatted function as distinct types, so mangling has to include splatting. If it doesn't, we get symbol clashes. See the ticket and the tests in this PR for details. Demangling PR: rust-lang/rustc-demangle#90 Demangling in rust-lang/rust PR: rust-lang#159202 @rustbot label +C-bug +F-splat +T-compiler +A-name-mangling Fixes rust-lang#158644 This PR was based on rust-lang#159202, so we waited for that PR to merge first, then rebased this one.

@rustbot

…esleywiser Fix splat v0 mangling Tracking issue: rust-lang#153629 Typecheck considers a splatted and non-splatted function as distinct types, so mangling has to include splatting. If it doesn't, we get symbol clashes. See the ticket and the tests in this PR for details. Demangling PR: rust-lang/rustc-demangle#90 Demangling in rust-lang/rust PR: rust-lang#159202 @rustbot label +C-bug +F-splat +T-compiler +A-name-mangling Fixes rust-lang#158644 This PR was based on rust-lang#159202, so we waited for that PR to merge first, then rebased this one.

@rustbot

…esleywiser Fix splat v0 mangling Tracking issue: rust-lang#153629 Typecheck considers a splatted and non-splatted function as distinct types, so mangling has to include splatting. If it doesn't, we get symbol clashes. See the ticket and the tests in this PR for details. Demangling PR: rust-lang/rustc-demangle#90 Demangling in rust-lang/rust PR: rust-lang#159202 @rustbot label +C-bug +F-splat +T-compiler +A-name-mangling Fixes rust-lang#158644 This PR was based on rust-lang#159202, so we waited for that PR to merge first, then rebased this one.

Rollup of 12 pull requests Successful merges: - #159582 (Sync from portable simd 2026 07 20) - #158890 (Fix splat v0 mangling) - #159411 ([rustdoc] Correctly handle output options with --show-coverage) - #159647 (Remove `early_exit` closures) - #159656 (define a `Simd` type in `minicore`) - #156474 (Add paths for linked associated items) - #159211 (Fix debuginfo argument when invoking LLBC linker) - #159527 (Bring runtime symbols statics on par with foreign functions) - #159625 (Refactor is_opsem_inhabited) - #159652 (Remove `cfg(not(no_global_oom_handling))` from the `Drop` impl of `UniqueArcUninit`) - #159657 (Remove the blanket `#![cfg_attr(test, allow(unused))]` from bootstrap ) - #159663 (Add layout cycle hang regression test)

@rustbot

…esleywiser Fix splat v0 mangling Tracking issue: rust-lang#153629 Typecheck considers a splatted and non-splatted function as distinct types, so mangling has to include splatting. If it doesn't, we get symbol clashes. See the ticket and the tests in this PR for details. Demangling PR: rust-lang/rustc-demangle#90 Demangling in rust-lang/rust PR: rust-lang#159202 @rustbot label +C-bug +F-splat +T-compiler +A-name-mangling Fixes rust-lang#158644 This PR was based on rust-lang#159202, so we waited for that PR to merge first, then rebased this one.

Rollup of 13 pull requests Successful merges: - #159582 (Sync from portable simd 2026 07 20) - #158890 (Fix splat v0 mangling) - #159614 (debuginfo generation for unsafe binders) - #159647 (Remove `early_exit` closures) - #159656 (define a `Simd` type in `minicore`) - #156474 (Add paths for linked associated items) - #159211 (Fix debuginfo argument when invoking LLBC linker) - #159527 (Bring runtime symbols statics on par with foreign functions) - #159625 (Refactor is_opsem_inhabited) - #159629 (Add more splat rust-call regression tests) - #159652 (Remove `cfg(not(no_global_oom_handling))` from the `Drop` impl of `UniqueArcUninit`) - #159657 (Remove the blanket `#![cfg_attr(test, allow(unused))]` from bootstrap ) - #159663 (Add layout cycle hang regression test)

@rustbot

Rollup merge of #158890 - teor2345:splat-mangling-clash, r=wesleywiser Fix splat v0 mangling Tracking issue: #153629 Typecheck considers a splatted and non-splatted function as distinct types, so mangling has to include splatting. If it doesn't, we get symbol clashes. See the ticket and the tests in this PR for details. Demangling PR: rust-lang/rustc-demangle#90 Demangling in rust-lang/rust PR: #159202 @rustbot label +C-bug +F-splat +T-compiler +A-name-mangling Fixes #158644 This PR was based on #159202, so we waited for that PR to merge first, then rebased this one.

Rollup of 13 pull requests Successful merges: - rust-lang/rust#159582 (Sync from portable simd 2026 07 20) - rust-lang/rust#158890 (Fix splat v0 mangling) - rust-lang/rust#159614 (debuginfo generation for unsafe binders) - rust-lang/rust#159647 (Remove `early_exit` closures) - rust-lang/rust#159656 (define a `Simd` type in `minicore`) - rust-lang/rust#156474 (Add paths for linked associated items) - rust-lang/rust#159211 (Fix debuginfo argument when invoking LLBC linker) - rust-lang/rust#159527 (Bring runtime symbols statics on par with foreign functions) - rust-lang/rust#159625 (Refactor is_opsem_inhabited) - rust-lang/rust#159629 (Add more splat rust-call regression tests) - rust-lang/rust#159652 (Remove `cfg(not(no_global_oom_handling))` from the `Drop` impl of `UniqueArcUninit`) - rust-lang/rust#159657 (Remove the blanket `#![cfg_attr(test, allow(unused))]` from bootstrap ) - rust-lang/rust#159663 (Add layout cycle hang regression test)

rustbot assigned hanna-kruppe Jul 7, 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 7, 2026

rustbot added A-name-mangling Area: Name mangling / decoration aka symbol mangling C-bug Category: This is a bug. F-splat `#![feature(splat)]` https://github.com/rust-lang/rust/issues/153629 labels Jul 7, 2026

teor2345 mentioned this pull request Jul 7, 2026

Fix splat ICEs and ban it in closures #158645

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wesleywiser reviewed Jul 7, 2026

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Comment thread compiler/rustc_symbol_mangling/src/v0.rs Outdated

teor2345 force-pushed the splat-mangling-clash branch 2 times, most recently from a30c0d8 to afaae5b Compare July 8, 2026 03:16

teor2345 mentioned this pull request Jul 8, 2026

Implement demangling for #[splat] rust-lang/rustc-demangle#90

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teor2345 commented Jul 8, 2026

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Comment thread tests/ui/splat/splat-mangling-issue-158644.rs Outdated

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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 8, 2026

rustbot assigned wesleywiser Jul 11, 2026

rustbot unassigned hanna-kruppe Jul 11, 2026

teor2345 force-pushed the splat-mangling-clash branch from afaae5b to 1c094c4 Compare July 13, 2026 04:32

rustbot added A-LLVM Area: Code generation parts specific to LLVM. Both correctness bugs and optimization-related issues. T-clippy Relevant to the Clippy team. labels Jul 13, 2026

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ada4a closed this Jul 13, 2026

teor2345 added 4 commits July 18, 2026 10:30

Add splat mangling bug tests (flaky?)

da5e0cf

Implement v0 symbol mangling for splat

cbb2169

Doc splat mangling in the reference

553dbd7

Fix typo in symbol-mangling/v0.md

a34aad0

teor2345 force-pushed the splat-mangling-clash branch from 36d0eb8 to a34aad0 Compare July 18, 2026 00:32

teor2345 commented Jul 18, 2026

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wesleywiser approved these changes Jul 21, 2026

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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-review Status: Awaiting review from the assignee but also interested parties. labels Jul 21, 2026

JonathanBrouwer mentioned this pull request Jul 21, 2026

Rollup of 10 pull requests #159684

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GuillaumeGomez mentioned this pull request Jul 21, 2026

Rollup of 11 pull requests #159692

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GuillaumeGomez mentioned this pull request Jul 21, 2026

Rollup of 12 pull requests #159693

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teor2345 mentioned this pull request Jul 21, 2026

1.98 beta regression due to name collision with splat #159428

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This was referenced Jul 22, 2026

Rollup of 13 pull requests #159696

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Rollup of 13 pull requests #159697

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rust-bors Bot merged commit 4609c87 into rust-lang:main Jul 22, 2026
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rustbot added this to the 1.99.0 milestone Jul 22, 2026

	#[rustc_dump_symbol_name]
	//[legacy]~^ ERROR symbol-name(_ZN5basic4main
	//[legacy]~\| ERROR demangling(basic::main
	//[legacy]~\| ERROR demangling-alt(basic::main)
	//[v0]~^^^^ ERROR symbol-name(_RNv
	//[v0]~\| ERROR demangling(basic[
	//[v0]~\| ERROR demangling-alt(basic::main)

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