Tweak auto trait errors by estebank · Pull Request #137831 · rust-lang/rust (original) (raw)

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estebank

Make suggestions to remove params and super traits verbose.

error[E0567]: auto traits cannot have generic parameters
  --> $DIR/auto-trait-validation.rs:6:19
   |
LL | auto trait Generic<T> {}
   |            -------^^^
   |            |
   |            auto trait cannot have generic parameters
   |
help: remove the parameters
   |
LL - auto trait Generic<T> {}
LL + auto trait Generic {}
   |

error[E0568]: auto traits cannot have super traits or lifetime bounds
  --> $DIR/auto-trait-validation.rs:8:20
   |
LL | auto trait Bound : Copy {}
   |            -----   ^^^^
   |            |
   |            auto traits cannot have super traits or lifetime bounds
   |
help: remove the super traits or lifetime bounds
   |
LL - auto trait Bound : Copy {}
LL + auto trait Bound {}
   |

Make suggestion to remove associated items hidden.

error[E0380]: auto traits cannot have associated items
  --> $DIR/issue-23080.rs:5:8
   |
LL | unsafe auto trait Trait {
   |                   ----- auto traits cannot have associated items
LL |     fn method(&self) {
   |        ^^^^^^
   |
   = help: remove the associated items

Make spans smaller.

r? @compiler-errors

@rustbot rustbot added S-waiting-on-review

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T-compiler

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Feb 28, 2025

compiler-errors

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I think that all of these removals are clear enough that we should probably make all of them hidden. A suggestion that says "remove the parameters" doesn't need to take 4 extra lines to render the removal of those parameters; it's pretty clear by the name and the span that's being highlighted what the user needs to do here, and really the only thing we want to make sure is that they're still suggestions so they can be applicable.

In general, I think instead of making what I'll call "unambiguous removal" suggestions verbose, it's probably best to make them hidden.

@rustbot 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

Feb 28, 2025

@estebank

Make suggestions to remove params and super traits verbose.

error[E0567]: auto traits cannot have generic parameters
  --> $DIR/auto-trait-validation.rs:6:19
   |
LL | auto trait Generic<T> {}
   |            -------^^^
   |            |
   |            auto trait cannot have generic parameters
   |
help: remove the parameters
   |
LL - auto trait Generic<T> {}
LL + auto trait Generic {}
   |

error[E0568]: auto traits cannot have super traits or lifetime bounds
  --> $DIR/auto-trait-validation.rs:8:20
   |
LL | auto trait Bound : Copy {}
   |            -----   ^^^^
   |            |
   |            auto traits cannot have super traits or lifetime bounds
   |
help: remove the super traits or lifetime bounds
   |
LL - auto trait Bound : Copy {}
LL + auto trait Bound {}
   |

Make suggestion to remove associated items hidden.

error[E0380]: auto traits cannot have associated items
  --> $DIR/issue-23080.rs:5:8
   |
LL | unsafe auto trait Trait {
   |                   ----- auto traits cannot have associated items
LL |     fn method(&self) {
   |        ^^^^^^
   |
   = help: remove the associated items

Make spans smaller.

@estebank

The only caveat that I have is that not everyone is well versed on the jargon we use. For generic parameters, that'd be weird, but for super traits, that can conceivably be true (although what would a person be doing adding super traits without knowing what they are called, but I digress). The other consideration that I have is the likelihood of an error being seen in the first place. A really uncommon diagnostic doesn't need to be as short as necessary. Having said that, I agree: suggestions that are clear from the message only for the vast majority of people should not be rendering the code to make the diagnostic shorter. The only thing we should be super careful about is to make sure that all "hidden" suggestions have a run-rustfix annotation (and maybe add a flag to render suggestions regardless in stderr files so that we can notice mistakes?).

@compiler-errors

The other consideration that I have is the likelihood of an error being seen in the first place. A really uncommon diagnostic doesn't need to be as short as necessary.

I'm not totally sure if I agree with this part. For diagnostics that we expect users to never see (auto traits are almost never likely to be stabilized any time soon), I think we should be optimizing these diagnostics for the people who we do expect to see them (e.g. people working on the type system, or experimenting with the unstable feature).

So I'd still prefer shorter presentations for these, since anyone who's going to be messing with auto traits either knows what a supertrait is, or can and should find out what they are (if anything because without knowing what it is, they'll be in the dark by blindly applying the suggestion).

@estebank

@estebank estebank 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

Mar 1, 2025

@compiler-errors

@rustbot 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

Mar 21, 2025

Labels

S-waiting-on-author

Status: This is awaiting some action (such as code changes or more information) from the author.

T-compiler

Relevant to the compiler team, which will review and decide on the PR/issue.