Fix a splat legacy demangling display bug by teor2345 · Pull Request #160050 · rust-lang/rust

teor2345 · 2026-07-28T06:25:45Z

Tracking issue: #153629

This PR fixes a splat legacy demangling display bug, where the comma is in the wrong place in the argument list.

It also does a cleanup from @folkertdev's PR #159643 review:

move rustfmt::skip to main() and deduplicate it: Add support for splatted function pointers #159643 (comment)

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

Edit: this PR now accepts 8-16 character crate hashes in normalisation regexes, so it no longer depends on rust-lang/rustc-demangle#94 being reviewed, merged, and updated in rustc's deps

Edit 2: this PR only fixes legacy demangling. The v0 splat attribute name is not changed here, because it requires rust-lang/rustc-demangle#93 to be reviewed and merged, a rustc-demangle release, and a version bump in rust-lang/rust to fix. That seems to be better done in another PR.

rustbot · 2026-07-28T06:25:51Z

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teor2345 · 2026-08-29T18:56:47Z

It looks like we're stalled on the rustc-demangle side here, so I might redesign these tests so they're not blocked on it.

teor2345 · 2026-09-04T13:18:49Z

@rustbot ready

I changed this PR to accept 8-16 character crate hashes in normalisation regexes, so it no longer depends on rust-lang/rustc-demangle#94 being reviewed, merged, and updated in rustc's deps. This is consistent with the normalisation approach taken in the UI test framework.

camelid

Sorry for my delay with this. Looks good except for the splat/rustc_splat inconsistency (and the merge conflicts).

View changes since this review

camelid · 2026-09-24T18:33:30Z

+           //[legacy]~| ERROR demangling(splat_mangling::main::Type<*mut fn(u32,i8,#[rustc_splat] (f64,))>::
+           //[legacy]~| ERROR demangling-alt(splat_mangling::main::Type<*mut fn(u32,i8,#[rustc_splat] (f64,))>)
+    //[v0,default]~^^^^ ERROR symbol-name(_RMs6_NvCsCRATE_HASH_14splat_mangling4mainINtB<REF>_4TypeOFmawTdEEuE)
+       //[v0,default]~| ERROR demangling(<splat_mangling[
+       //[v0,default]~| ERROR demangling-alt(<splat_mangling::main::Type<*mut fn(u32, i8, #[splat] (f64,))>>)


Is it intentional that legacy mangling says #[rustc_splat] but v0 says #[splat]? It seems like v0 is wrong.

v0 is not fixed, but also out of scope for this PR. v0 requires rust-lang/rustc-demangle#93 to be reviewed and merged, a rustc-demangle release, and a version bump in rust-lang/rust to fix.

So I think it's best that they're fixed separately.

I'll do a rebase right now.

By accepting 8-16 character crate hashes

rustbot · 2026-09-25T07:01:13Z

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 · 2026-09-25T07:01:41Z

Just a change from ERROR to NOTE on some log lines

@rustbot ready

rustbot assigned camelid Jul 28, 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 28, 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 28, 2026

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teor2345 mentioned this pull request Jul 31, 2026

Rename splat attribute to rustc_splat rust-lang/rustc-demangle#93

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Demangle using fixed-length disambiguators rust-lang/rustc-demangle#94

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camelid added S-blocked Status: Blocked on something else such as an RFC or other implementation work. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Jul 31, 2026

teor2345 mentioned this pull request Aug 18, 2026

Nightly support for function overloading in FFI bindings rust-lang/goals#643

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teor2345 added 4 commits September 25, 2026 08:47

Refactor pretty print comma_sep flag

e3e4fed

Fix a splat legacy demangling bug, add extra tests

48f1386

Move rustfmt::skip to main in one test

5c8074f

Disentangle from rustc-demangle fix

2fb58b9

By accepting 8-16 character crate hashes

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