Implement RFC 3678: Final trait methods by mu001999 · Pull Request #151783 · rust-lang/rust

mu001999 · 2026-01-28T14:54:32Z

This PR is based on #130802, with some minor changes and conflict resolution.

Futhermore, this PR excludes final methods from the vtable of a dyn Trait.

And some excerpt from the original PR description:

Implements the surface part of rust-lang/rfcs#3678.

I'm using the word "method" in the title, but in the diagnostics and the feature gate I used "associated function", since that's more accurate.

cc @joshtriplett

rustbot · 2026-01-28T14:54:37Z

Some changes occurred in compiler/rustc_builtin_macros/src/autodiff.rs

cc @ZuseZ4

Some changes occurred in src/tools/rustfmt

cc @rust-lang/rustfmt

Some changes occurred in src/tools/clippy

cc @rust-lang/clippy

rustbot · 2026-01-28T14:54:40Z

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fmease · 2026-01-28T16:56:45Z

Could you mark errs as a coauthor in all 6 commits, I think that's only fair. Thanks! :)

Namely: Co-authored-by: Michael Goulet <[email protected]>

mu001999 · 2026-01-29T00:09:42Z

@fmease Done. Thanks for the reminder! :)

joshtriplett · 2026-01-29T08:50:18Z

What it doesn't implement are any optimizations that can be done on final trait methods, such as excluding them from the vtable of a dyn Trait.

Does this implement the requirement that final methods don't prevent a trait from being dyn-compatible?

mu001999 · 2026-01-30T14:31:48Z

Does this implement the requirement that final methods don't prevent a trait from being dyn-compatible?

Implemented now :). Also, updated the PR description.

Co-authored-by: Michael Goulet <[email protected]>

compiler/rustc_ast_passes/src/ast_validation.rs

fee1-dead · 2026-02-17T01:13:51Z

LGTM, can iterate on it later
@bors r+

rust-bors · 2026-02-17T01:13:53Z

📌 Commit 8c77b6c has been approved by fee1-dead

It is now in the queue for this repository.

Rollup of 11 pull requests Successful merges: - #152700 (miri subtree update) - #152715 (`rust-analyzer` subtree update) - #151783 (Implement RFC 3678: Final trait methods) - #152512 (core: Implement feature `float_exact_integer_constants`) - #152661 (Avoid ICE in From/TryFrom diagnostic under -Znext-solver) - #152703 (Remove `rustc_query_system`) - #152206 (misc doc improvements) - #152664 (Fix mis-constructed `file_span` when generating scraped examples) - #152698 (Suppress unstable-trait notes under `-Zforce-unstable-if-unmarked`) - #152727 (`probe_op` silence ambiguity errors if tainted) - #152728 (Port #![default_lib_allocator] to the new attribute parser)

@joshtriplett

Rollup merge of #151783 - mu001999-contrib:impl/final-method, r=fee1-dead Implement RFC 3678: Final trait methods Tracking: #131179 This PR is based on #130802, with some minor changes and conflict resolution. Futhermore, this PR excludes final methods from the vtable of a dyn Trait. And some excerpt from the original PR description: > Implements the surface part of rust-lang/rfcs#3678. > > I'm using the word "method" in the title, but in the diagnostics and the feature gate I used "associated function", since that's more accurate. cc @joshtriplett

compiler/rustc_feature/src/unstable.rs

… r=fmease Update tracking issue number for final_associated_functions From rust-lang#151783 (comment)

Rollup of 11 pull requests Successful merges: - rust-lang/rust#152700 (miri subtree update) - rust-lang/rust#152715 (`rust-analyzer` subtree update) - rust-lang/rust#151783 (Implement RFC 3678: Final trait methods) - rust-lang/rust#152512 (core: Implement feature `float_exact_integer_constants`) - rust-lang/rust#152661 (Avoid ICE in From/TryFrom diagnostic under -Znext-solver) - rust-lang/rust#152703 (Remove `rustc_query_system`) - rust-lang/rust#152206 (misc doc improvements) - rust-lang/rust#152664 (Fix mis-constructed `file_span` when generating scraped examples) - rust-lang/rust#152698 (Suppress unstable-trait notes under `-Zforce-unstable-if-unmarked`) - rust-lang/rust#152727 (`probe_op` silence ambiguity errors if tainted) - rust-lang/rust#152728 (Port #![default_lib_allocator] to the new attribute parser)

… r=fmease Update tracking issue number for final_associated_functions From rust-lang#151783 (comment)

Rollup merge of #152778 - mu001999-contrib:fix/final-method, r=fmease Update tracking issue number for final_associated_functions From #151783 (comment)

Update tracking issue number for final_associated_functions From rust-lang/rust#151783 (comment)

@joshtriplett

…, r=fee1-dead Implement RFC 3678: Final trait methods Tracking: rust-lang#131179 This PR is based on rust-lang#130802, with some minor changes and conflict resolution. Futhermore, this PR excludes final methods from the vtable of a dyn Trait. And some excerpt from the original PR description: > Implements the surface part of rust-lang/rfcs#3678. > > I'm using the word "method" in the title, but in the diagnostics and the feature gate I used "associated function", since that's more accurate. cc @joshtriplett

Rollup of 11 pull requests Successful merges: - rust-lang/rust#152700 (miri subtree update) - rust-lang/rust#152715 (`rust-analyzer` subtree update) - rust-lang/rust#151783 (Implement RFC 3678: Final trait methods) - rust-lang/rust#152512 (core: Implement feature `float_exact_integer_constants`) - rust-lang/rust#152661 (Avoid ICE in From/TryFrom diagnostic under -Znext-solver) - rust-lang/rust#152703 (Remove `rustc_query_system`) - rust-lang/rust#152206 (misc doc improvements) - rust-lang/rust#152664 (Fix mis-constructed `file_span` when generating scraped examples) - rust-lang/rust#152698 (Suppress unstable-trait notes under `-Zforce-unstable-if-unmarked`) - rust-lang/rust#152727 (`probe_op` silence ambiguity errors if tainted) - rust-lang/rust#152728 (Port #![default_lib_allocator] to the new attribute parser)

rustbot assigned fee1-dead Jan 28, 2026

mu001999 force-pushed the impl/final-method branch from fe8e71f to f0df197 Compare January 29, 2026 00:03

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mu001999 force-pushed the impl/final-method branch from ca5e458 to a0707ab Compare January 30, 2026 12:30

mu001999 marked this pull request as draft January 30, 2026 12:48

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 Jan 30, 2026

mu001999 force-pushed the impl/final-method branch from a0707ab to 5c978e5 Compare January 30, 2026 14:21

mu001999 marked this pull request as ready for review January 30, 2026 14:31

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mu001999 force-pushed the impl/final-method branch from 5c978e5 to 05c342d Compare January 30, 2026 15:40

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mu001999 force-pushed the impl/final-method branch from 05c342d to a630df6 Compare February 5, 2026 16:04

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mu001999 and others added 4 commits February 12, 2026 15:18

Fix rustfmt

f0e1c8f

Co-authored-by: Michael Goulet <[email protected]>

Render final associated functions correctly in rustdoc

f0a019b

Co-authored-by: Michael Goulet <[email protected]>

Fix clippy ast utils

2e0ff1f

Co-authored-by: Michael Goulet <[email protected]>

Exclude final methods from dyn-compat check and vtable

8c77b6c

mu001999 force-pushed the impl/final-method branch from 526d9ed to 8c77b6c Compare February 12, 2026 07:18

nik-rev reviewed Feb 15, 2026

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fee1-dead approved these changes Feb 17, 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 Feb 17, 2026

Zalathar mentioned this pull request Feb 17, 2026

Rollup of 11 pull requests #152739

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rust-bors bot merged commit 1367126 into rust-lang:main Feb 17, 2026
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rustbot added this to the 1.95.0 milestone Feb 17, 2026

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fmease mentioned this pull request Feb 17, 2026

Tracking issue for RFC 3678: Trait method impl restrictions (final methods) #131179

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7 tasks

mu001999 mentioned this pull request Feb 18, 2026

Update tracking issue number for final_associated_functions #152778

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jhpratt added a commit to jhpratt/rust that referenced this pull request Feb 18, 2026

Rollup merge of rust-lang#152778 - mu001999-contrib:fix/final-method,…

44d9f42

… r=fmease Update tracking issue number for final_associated_functions From rust-lang#151783 (comment)

jhpratt added a commit to jhpratt/rust that referenced this pull request Feb 18, 2026

Rollup merge of rust-lang#152778 - mu001999-contrib:fix/final-method,…

a3bb32f

… r=fmease Update tracking issue number for final_associated_functions From rust-lang#151783 (comment)

Zalathar added a commit to Zalathar/rust that referenced this pull request Feb 18, 2026

Rollup merge of rust-lang#152778 - mu001999-contrib:fix/final-method,…

8a2c6ea

… r=fmease Update tracking issue number for final_associated_functions From rust-lang#151783 (comment)

rust-timer added a commit that referenced this pull request Feb 18, 2026

Unrolled build for #152778

f08fc67

Rollup merge of #152778 - mu001999-contrib:fix/final-method, r=fmease Update tracking issue number for final_associated_functions From #151783 (comment)

fmease mentioned this pull request Feb 18, 2026

Under FAF we now wrongly accept final $($expr)? in stmt position parsing it as $($expr)? #152820

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github-actions bot pushed a commit to rust-lang/miri that referenced this pull request Feb 19, 2026

Rollup merge of #152778 - mu001999-contrib:fix/final-method, r=fmease

118610f

Update tracking issue number for final_associated_functions From rust-lang/rust#151783 (comment)

mu001999 deleted the impl/final-method branch February 20, 2026 09:10

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