Arg splat experiment - syntax impl by teor2345 · Pull Request #157605 · rust-lang/rust

teor2345 · 2026-06-08T11:36:51Z

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This PR is part of the argument splatting lang experiment, and FFI overloading / C++ interop project goals:

I've split it from #153697 to make reviewing easier, see that PR for more details.

The PR is the initial implementation of the feature:

splat incomplete feature gate
#[splat] attribute on function arguments
feature gate and UI tests for item type filtering, non-splattable arguments

Once this PR merges, I'll rebase #153697.

rustbot · 2026-06-08T11:36:54Z

Some changes occurred in compiler/rustc_attr_parsing

cc @jdonszelmann, @JonathanBrouwer

Some changes occurred in compiler/rustc_hir/src/attrs

cc @jdonszelmann, @JonathanBrouwer

Some changes occurred in compiler/rustc_passes/src/check_attr.rs

cc @jdonszelmann, @JonathanBrouwer

rustbot · 2026-06-08T11:36:56Z

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rustbot · 2026-06-08T13:01:21Z

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

rustbot · 2026-06-09T07:39:03Z

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 · 2026-06-09T07:42:00Z

Thanks for the reviews! Since they were small changes in a small PR, and I had to rebase anyway, I went ahead and squashed the fixes into the commits.

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JonathanBrouwer

@bors r+ rollup

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rust-bors · 2026-06-09T08:12:02Z

📌 Commit 5a93925 has been approved by JonathanBrouwer

It is now in the queue for this repository.

…r=JonathanBrouwer Arg splat experiment - syntax impl This PR is part of the argument splatting lang experiment, and FFI overloading / C++ interop project goals: - rust-lang#153629 - https://rust-lang.github.io/rust-project-goals/2026/overloading-for-ffi.html - https://rust-lang.github.io/rust-project-goals/2025h2/interop-problem-map.html I've split it from rust-lang#153697 to make reviewing easier, see that PR for more details. The PR is the initial implementation of the feature: - `splat` incomplete feature gate - `#[splat]` attribute on function arguments - feature gate and UI tests for item type filtering, non-splattable arguments Once this PR merges, I'll rebase rust-lang#153697.

Rollup of 3 pull requests Successful merges: - #157503 (Disable `tests/debuginfo/pretty-std.rs` `OsString` cdb check) - #156399 (fix improper ctypes in Znext solver) - #157605 (Arg splat experiment - syntax impl)

…r=JonathanBrouwer Arg splat experiment - syntax impl This PR is part of the argument splatting lang experiment, and FFI overloading / C++ interop project goals: - rust-lang#153629 - https://rust-lang.github.io/rust-project-goals/2026/overloading-for-ffi.html - https://rust-lang.github.io/rust-project-goals/2025h2/interop-problem-map.html I've split it from rust-lang#153697 to make reviewing easier, see that PR for more details. The PR is the initial implementation of the feature: - `splat` incomplete feature gate - `#[splat]` attribute on function arguments - feature gate and UI tests for item type filtering, non-splattable arguments Once this PR merges, I'll rebase rust-lang#153697.

Rollup of 10 pull requests Successful merges: - #157335 (bootstrap: Handle dotted table keys when parsing bootstrap.toml) - #157503 (Disable `tests/debuginfo/pretty-std.rs` `OsString` cdb check) - #148183 (rustdoc: Test & document `test_harness` code block attribute) - #156067 (Fix async drop glue for Box<T>) - #156399 (fix improper ctypes in Znext solver) - #157410 (Implement rustc_public::CrateDef{,Type} for FieldDef) - #157605 (Arg splat experiment - syntax impl) - #157630 (Add multibyte JSON diagnostic regression test) - #157633 (Reorder `impl` restriction rendering and add bottom margin) - #157642 (Report duplicate relaxed bounds during ast lowering)

…r=JonathanBrouwer Arg splat experiment - syntax impl This PR is part of the argument splatting lang experiment, and FFI overloading / C++ interop project goals: - rust-lang#153629 - https://rust-lang.github.io/rust-project-goals/2026/overloading-for-ffi.html - https://rust-lang.github.io/rust-project-goals/2025h2/interop-problem-map.html I've split it from rust-lang#153697 to make reviewing easier, see that PR for more details. The PR is the initial implementation of the feature: - `splat` incomplete feature gate - `#[splat]` attribute on function arguments - feature gate and UI tests for item type filtering, non-splattable arguments Once this PR merges, I'll rebase rust-lang#153697.

Rollup of 18 pull requests Successful merges: - #152852 (Remove driver_lint_caps) - #157166 (Change type of async context parameter after state transform.) - #157335 (bootstrap: Handle dotted table keys when parsing bootstrap.toml) - #157503 (Disable `tests/debuginfo/pretty-std.rs` `OsString` cdb check) - #157571 (Remove ProcMacro enum from proc macro ABI) - #148183 (rustdoc: Test & document `test_harness` code block attribute) - #153847 (Fix marker trait winnowing depending on impl order) - #156067 (Fix async drop glue for Box<T>) - #156399 (fix improper ctypes in Znext solver) - #157338 (Make `Literal::byte_character_value` work with bytes as well) - #157410 (Implement rustc_public::CrateDef{,Type} for FieldDef) - #157605 (Arg splat experiment - syntax impl) - #157630 (Add multibyte JSON diagnostic regression test) - #157633 (Reorder `impl` restriction rendering and add bottom margin) - #157642 (Report duplicate relaxed bounds during ast lowering) - #157652 (fix doc for unicode normalization faq on `casefold` APIs) - #157661 (Update to ar_archive_writer v0.5.2) - #157668 (Add test for matches in `rustc_must_match_exhaustively`) Failed merges: - #157670 (Rename `errors.rs` file to `diagnostics.rs` (4/N))

Rollup of 17 pull requests Successful merges: - #157166 (Change type of async context parameter after state transform.) - #157335 (bootstrap: Handle dotted table keys when parsing bootstrap.toml) - #157503 (Disable `tests/debuginfo/pretty-std.rs` `OsString` cdb check) - #157571 (Remove ProcMacro enum from proc macro ABI) - #148183 (rustdoc: Test & document `test_harness` code block attribute) - #153847 (Fix marker trait winnowing depending on impl order) - #156067 (Fix async drop glue for Box<T>) - #156399 (fix improper ctypes in Znext solver) - #157338 (Make `Literal::byte_character_value` work with bytes as well) - #157410 (Implement rustc_public::CrateDef{,Type} for FieldDef) - #157605 (Arg splat experiment - syntax impl) - #157630 (Add multibyte JSON diagnostic regression test) - #157633 (Reorder `impl` restriction rendering and add bottom margin) - #157642 (Report duplicate relaxed bounds during ast lowering) - #157652 (fix doc for unicode normalization faq on `casefold` APIs) - #157661 (Update to ar_archive_writer v0.5.2) - #157668 (Add test for matches in `rustc_must_match_exhaustively`) Failed merges: - #157670 (Rename `errors.rs` file to `diagnostics.rs` (4/N))

Rollup merge of #157605 - teor2345:fn-arg-splat-exp-syntax, r=JonathanBrouwer Arg splat experiment - syntax impl This PR is part of the argument splatting lang experiment, and FFI overloading / C++ interop project goals: - #153629 - https://rust-lang.github.io/rust-project-goals/2026/overloading-for-ffi.html - https://rust-lang.github.io/rust-project-goals/2025h2/interop-problem-map.html I've split it from #153697 to make reviewing easier, see that PR for more details. The PR is the initial implementation of the feature: - `splat` incomplete feature gate - `#[splat]` attribute on function arguments - feature gate and UI tests for item type filtering, non-splattable arguments Once this PR merges, I'll rebase #153697.

rustbot added A-attributes Area: Attributes (`#[…]`, `#![…]`) 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 8, 2026

rustbot assigned TaKO8Ki Jun 8, 2026

This was referenced Jun 8, 2026

Add arg splat experiment initial tuple impl #153697

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Tracking Issue for argument splatting lang experiment #153629

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JonathanBrouwer requested changes Jun 8, 2026

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Comment thread compiler/rustc_attr_parsing/src/attributes/splat.rs Outdated

Comment thread compiler/rustc_attr_parsing/src/attributes/splat.rs Outdated

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 Jun 8, 2026

JonathanBrouwer assigned JonathanBrouwer and unassigned TaKO8Ki Jun 8, 2026

Kivooeo reviewed Jun 8, 2026

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Comment thread compiler/rustc_ast_passes/src/ast_validation.rs Outdated

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teor2345 added 2 commits June 9, 2026 09:38

Add splat builtin attribute & feature gate

2a3a8dd

Add AST validation for #[splat]

5a93925

teor2345 force-pushed the fn-arg-splat-exp-syntax branch from 193c83e to 5a93925 Compare June 9, 2026 07:38

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 Jun 9, 2026

JonathanBrouwer approved these changes Jun 9, 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 Jun 9, 2026

jhpratt mentioned this pull request Jun 9, 2026

Rollup of 3 pull requests #157648

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GuillaumeGomez mentioned this pull request Jun 9, 2026

Rollup of 7 pull requests #157656

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GuillaumeGomez mentioned this pull request Jun 9, 2026

Rollup of 10 pull requests #157663

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GuillaumeGomez mentioned this pull request Jun 9, 2026

Rollup of 15 pull requests #157673

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jhpratt mentioned this pull request Jun 9, 2026

Rollup of 18 pull requests #157679

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jhpratt mentioned this pull request Jun 9, 2026

Rollup of 17 pull requests #157683

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rust-bors Bot merged commit 930d870 into rust-lang:main Jun 10, 2026
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Arg splat experiment - syntax impl#157605

Arg splat experiment - syntax impl#157605
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