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Error suggests implementing private trait instead of importing it. #57457

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pierzchalski opened this issue Jan 8, 2019 · 2 comments · Fixed by #116862
Closed

Error suggests implementing private trait instead of importing it. #57457

pierzchalski opened this issue Jan 8, 2019 · 2 comments · Fixed by #116862
Labels
A-diagnostics Area: Messages for errors, warnings, and lints A-traits Area: Trait system A-visibility Area: Visibility / privacy C-enhancement Category: An issue proposing an enhancement or a PR with one. D-newcomer-roadblock Diagnostics: Confusing error or lint; hard to understand for new users. D-papercut Diagnostics: An error or lint that needs small tweaks. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue.

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@pierzchalski
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If I implement a private trait on a public struct, then use a trait method elsewhere, the diagnostic message suggests implementing the already implemented private trait instead of making the trait public and importing it. For example, this code:

mod m {
    trait T {
        fn f(&self);
    }
    
    pub struct S;
    
    impl T for S {
        fn f(&self) {}
    }
}

fn main() {
    let s = m::S;
    s.f();
}

Results in this diagnostic:

error[E0599]: no method named `f` found for type `m::S` in the current scope
  --> src/main.rs:15:7
   |
6  |     pub struct S;
   |     ------------- method `f` not found for this
...
15 |     s.f();
   |       ^
   |
   = help: items from traits can only be used if the trait is implemented and in scope
   = note: the following trait defines an item `f`, perhaps you need to implement it:
           candidate #1: `m::T`

The note should suggest making m::T public and useing it at the top level.

@estebank estebank added the A-diagnostics Area: Messages for errors, warnings, and lints label Jan 9, 2019
@estebank estebank added T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. D-newcomer-roadblock Diagnostics: Confusing error or lint; hard to understand for new users. D-papercut Diagnostics: An error or lint that needs small tweaks. labels Jan 6, 2020
Dylan-DPC-zz pushed a commit to Dylan-DPC-zz/rust that referenced this issue Feb 27, 2020
Dylan-DPC-zz pushed a commit to Dylan-DPC-zz/rust that referenced this issue Feb 28, 2020
bors added a commit that referenced this issue Feb 29, 2020
Add more context to E0599 errors

Point at the intermediary unfulfilled trait bounds.

Fix #52523, fix #61661, cc #36513, fix #68131, fix #64417, fix #61768, cc #57457, cc #9082, fix #57994, cc #64934, cc #65149.
@crlf0710 crlf0710 added the C-enhancement Category: An issue proposing an enhancement or a PR with one. label Jun 11, 2020
@estebank
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Current output:

error[E0599]: no method named `f` found for struct `S` in the current scope
  --> src/main.rs:15:7
   |
6  |     pub struct S;
   |     ------------- method `f` not found for this
...
15 |     s.f();
   |       ^ method not found in `S`
   |
   = help: items from traits can only be used if the trait is implemented and in scope
note: `T` defines an item `f`, perhaps you need to implement it
  --> src/main.rs:2:5
   |
2  |     trait T {
   |     ^^^^^^^

We still don't check for accessibility.

@estebank estebank added A-traits Area: Trait system A-visibility Area: Visibility / privacy labels Sep 10, 2021
@estebank
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Triage: no change

matthiaskrgr added a commit to matthiaskrgr/rust that referenced this issue Oct 30, 2023
Detect when trait is implemented for type and suggest importing it

Fix rust-lang#57457.
@bors bors closed this as completed in 162443b Oct 30, 2023
rust-timer added a commit to rust-lang-ci/rust that referenced this issue Oct 30, 2023
Rollup merge of rust-lang#116862 - estebank:issue-57457, r=oli-obk

Detect when trait is implemented for type and suggest importing it

Fix rust-lang#57457.
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Labels
A-diagnostics Area: Messages for errors, warnings, and lints A-traits Area: Trait system A-visibility Area: Visibility / privacy C-enhancement Category: An issue proposing an enhancement or a PR with one. D-newcomer-roadblock Diagnostics: Confusing error or lint; hard to understand for new users. D-papercut Diagnostics: An error or lint that needs small tweaks. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue.
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3 participants