Improve suggestions when multiples tuples implement the same trait by rperier · Pull Request #159672 · rust-lang/rust

rperier · 2026-07-21T17:02:18Z

rustbot · 2026-07-21T17:02:23Z

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rperier · 2026-07-21T17:04:05Z

Perhaps a ui test dedicated to this use case, specifically might be helpful, imho. It was convered by any tests.

mejrs · 2026-07-21T18:33:09Z

Idea: can we style the type like rustdoc does: https://doc.rust-lang.org/nightly/std/fmt/trait.Debug.html#impl-Debug-for-(T,) , like this

(T₁, T₂, …, Tₙ)

I'm a bit worried that it's going to look like shit in a terminal, though...

rperier · 2026-07-22T09:00:01Z

Idea: can we style the type like rustdoc does: https://doc.rust-lang.org/nightly/std/fmt/trait.Debug.html#impl-Debug-for-(T,) , like this
(T₁, T₂, …, Tₙ)
I'm a bit worried that it's going to look like shit in a terminal, though...

I like this idea, the output would be more concise and simpler. Plus, I would not have to count the max number of tuples args, so the code would be simpler.

However, I agree with you, how is it about to be rendered in a terminal ? I am going to investigate

rperier · 2026-07-22T09:15:28Z

Idea: can we style the type like rustdoc does: https://doc.rust-lang.org/nightly/std/fmt/trait.Debug.html#impl-Debug-for-(T,) , like this
(T₁, T₂, …, Tₙ)
I'm a bit worried that it's going to look like shit in a terminal, though...
I like this idea, the output would be more concise and simpler. Plus, I would not have to count the max number of tuples args, so the code would be simpler.
However, I agree with you, how is it about to be rendered in a terminal ? I am going to investigate

Simply by using UTF8 ? UTF8 can handle these kind of notation, normally (exponent, indices, etc...)

rperier · 2026-07-22T09:40:29Z

(T₁, T₂, …, Tₙ)

https://play.rust-lang.org/?version=stable&mode=debug&edition=2024&gist=b5b574df5b35a52a002eca066d9b4ba4 ;)

rperier · 2026-07-22T12:31:06Z

What about something like this ? The rendering in a terminal is quiet good.
I have left n as indice of T but I could also display 12 , which is more correct.

mejrs · 2026-07-22T12:39:21Z

I have left n as indice of T but I could also display 12 , which is more correct.

I do think it would be nice to say "up to tuples of length 12" or something.

rperier · 2026-07-22T13:52:24Z

I have left n as indice of T but I could also display 12 , which is more correct.
I do think it would be nice to say "up to tuples of length 12" or something.

Like :

error[E0277]: `Foo` doesn't implement `Debug`
--> tests/ui/suggestions/multiple_tuples_implement_same_trait.rs:8:17
|
8 | testing((1, Foo));
| ------- ^^^ the trait `Debug` is not implemented for `Foo`
| |
| required by a bound introduced by this call
|
= help: the following other types implement trait `Debug`: ()
(T₁, T₂, …, Tₙ) // up to tuples of length 12
// Other relevant impls here
and 5 others
= note: required for `({integer}, Foo)` to implement `Debug`

?

rperier · 2026-07-22T14:06:46Z

@rustbot ready

mejrs

r? me

Thanks, great work. I love this message specifically being more concise.

How does this diagnostic compose with #[splat]? Can you add a test documenting what that looks like? If it's weird or doesn't work then no need to fix that necessarily, feel free to punt it towards the splat people :)

Also cc @estebank I know you care deeply about how errors show up in the terminal, is use of subscript acceptable to you?

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rperier · 2026-07-23T07:34:20Z

r? me
Thanks, great work. I love this message specifically being more concise.
How does this diagnostic compose with #[splat]? Can you add a test documenting what that looks like? If it's weird or doesn't work then no need to fix that necessarily, feel free to punt it towards the splat people :)
Also cc @estebank I know you care deeply about how errors show up in the terminal, is use of subscript acceptable to you?
View changes since this review

Sorry, I don't know what #[splat] is . It's a community crate or as part of the compiler ?

mejrs · 2026-07-23T09:38:55Z

Sorry, I don't know what #[splat] is . It's a community crate or as part of the compiler ?

It's an experiment, see https://rust-lang.github.io/rust-project-goals/2026/overloading-for-ffi.html and #153629

rperier · 2026-07-29T10:08:04Z

There are two branches actually, the case when all types implements the same traits , with less than 5 candidates and the case where there are more than 5 candidates. I did not changes anything to the case with less than 5 candidates, I have added a "concise output" for continuous arities (ranges from 0 to N or from K to N) where there are more than 5 candidates.

@rustbot ready

EDIT: in order to be sure that all tuples and continuous by step of 1, I had to sort the candidates. That's why I have updated the output of some tests, only the ordering output of these test have changed.

mejrs

It looks good to me, just a few nits

View changes since this review

rustbot · 2026-07-30T22:33:05Z

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

Instead of displaying all kind of tuples that implement a given trait, which might flood the user, it displays a concise message only when all the involved types are tuples.

rustbot · 2026-07-31T16:37:08Z

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.

rperier · 2026-07-31T16:37:23Z

@rustbot ready

mejrs

@bors r+ rollup

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rust-bors · 2026-07-31T17:50:54Z

📌 Commit 507283d has been approved by mejrs

It is now in the queue for this repository.

…it_impls_tuples, r=mejrs Improve suggestions when multiples tuples implement the same trait Fixesrust-lang#152903

Rollup of 14 pull requests Successful merges: - #159245 (Emit retags in codegen to support BorrowSanitizer (part 5)) - #159864 (Report "capacity overflow" for oversized Rc<[T]>/Arc<[T]>) - #160079 (make atomic operations const) - #160124 (Structurally prevent zero-count `BackendRepr::SimdVector`s) - #160162 (Make `#[fundamental]` only apply to the first argument of `Box`) - #160210 (Remove an outdated FIXME) - #160282 (Improve diagnostic for patterns in function pointer types) - #157928 (Eagerly fetch typeck results when linting) - #159672 (Improve suggestions when multiples tuples implement the same trait) - #159861 (Add documentation for the `non_exhaustive` attribute) - #159907 (Fix `hidden_glob_reexports` in `rustc_ast`) - #159998 (Align expect messages with guidance) - #160145 (Expand checks for register_tool) - #160307 (Update `minifier` version to `0.4.0`)

Rollup merge of #159672 - rperier:better_suggestions_for_trait_impls_tuples, r=mejrs Improve suggestions when multiples tuples implement the same trait Fixes#152903

Rollup of 14 pull requests Successful merges: - rust-lang/rust#159245 (Emit retags in codegen to support BorrowSanitizer (part 5)) - rust-lang/rust#159864 (Report "capacity overflow" for oversized Rc<[T]>/Arc<[T]>) - rust-lang/rust#160079 (make atomic operations const) - rust-lang/rust#160124 (Structurally prevent zero-count `BackendRepr::SimdVector`s) - rust-lang/rust#160162 (Make `#[fundamental]` only apply to the first argument of `Box`) - rust-lang/rust#160210 (Remove an outdated FIXME) - rust-lang/rust#160282 (Improve diagnostic for patterns in function pointer types) - rust-lang/rust#157928 (Eagerly fetch typeck results when linting) - rust-lang/rust#159672 (Improve suggestions when multiples tuples implement the same trait) - rust-lang/rust#159861 (Add documentation for the `non_exhaustive` attribute) - rust-lang/rust#159907 (Fix `hidden_glob_reexports` in `rustc_ast`) - rust-lang/rust#159998 (Align expect messages with guidance) - rust-lang/rust#160145 (Expand checks for register_tool) - rust-lang/rust#160307 (Update `minifier` version to `0.4.0`)

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rperier force-pushed the better_suggestions_for_trait_impls_tuples branch from 114f1a4 to f9303a9Compare July 21, 2026 18:11

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Emit better diagnostic suggestions for trait implementations on tuples
507283d
Instead of displaying all kind of tuples that implement a given trait, which might flood the user, it displays a concise message only when all the involved types are tuples.

rperier force-pushed the better_suggestions_for_trait_impls_tuples branch from a16ffa9 to 507283dCompare July 31, 2026 16:37

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 Jul 31, 2026

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rust-borsBot 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 31, 2026

jhpratt added a commit to jhpratt/rust that referenced this pull request Aug 1, 2026
Rollup merge ofrust-lang#159672- rperier:better_suggestions_for_tra…
d1bb492
…it_impls_tuples, r=mejrs Improve suggestions when multiples tuples implement the same trait Fixesrust-lang#152903

jhpratt mentioned this pull request Aug 1, 2026
Rollup of 16 pull requests #160308
Closed

jhpratt added a commit to jhpratt/rust that referenced this pull request Aug 1, 2026
Rollup merge ofrust-lang#159672- rperier:better_suggestions_for_tra…
28e4174
…it_impls_tuples, r=mejrs Improve suggestions when multiples tuples implement the same trait Fixesrust-lang#152903

This was referenced Aug 1, 2026
Rollup of 15 pull requests #160309
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Rollup of 14 pull requests #160310
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rust-borsBot merged commit 3ae0608 into rust-lang:mainAug 1, 2026
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rustbot added this to the 1.99.0 milestone Aug 1, 2026

rust-timer added a commit that referenced this pull request Aug 1, 2026
Unrolled build for#159672
7b9f312
Rollup merge of #159672 - rperier:better_suggestions_for_trait_impls_tuples, r=mejrs Improve suggestions when multiples tuples implement the same trait Fixes#152903

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