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Suggest #[derive(PartialEq)] on E0369 #85845

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estebank opened this issue May 31, 2021 · 2 comments
Closed

Suggest #[derive(PartialEq)] on E0369 #85845

estebank opened this issue May 31, 2021 · 2 comments
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A-diagnostics Area: Messages for errors, warnings, and lints A-suggestion-diagnostics Area: Suggestions generated by the compiler applied by `cargo fix` 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. D-terse Diagnostics: An error or lint that doesn't give enough information about the problem at hand. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue.

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@estebank
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When PartialEq isn't implemented for a type, like this

error[E0369]: binary operation `==` cannot be applied to type `&Group`
  --> src/tests/a.rs:19:5
   |
19 |     assert_eq!(result.unwrap(), &group);
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |     |
   |     &Group
   |     &Group
   |
   = note: an implementation of `std::cmp::PartialEq` might be missing for `&Group`
   = note: this error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)

We should suggest #[derive(PartialEq)] on the appropriate type if possible.

Taken from https://blog.frankel.ch/start-rust/1/
@estebank estebank added A-diagnostics Area: Messages for errors, warnings, and lints T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. A-suggestion-diagnostics Area: Suggestions generated by the compiler applied by `cargo fix` D-papercut Diagnostics: An error or lint that needs small tweaks. D-newcomer-roadblock Diagnostics: Confusing error or lint; hard to understand for new users. D-terse Diagnostics: An error or lint that doesn't give enough information about the problem at hand. labels May 31, 2021
@ccgauche
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ccgauche commented Jun 2, 2021

I'm going to try to fix that as my first contribution!

@ccgauche ccgauche mentioned this issue Jun 2, 2021
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ccgauche added a commit to ccgauche/rust that referenced this issue Aug 1, 2021
@ccgauche
Updated the fix for rust-lang#85845
01996be 
 - Made the check stricter.
**Note: I've checked and there is no other trait that can be possibly passed than std ones. (BinOps) so there is no need for a `can_derive` or something similar. Furthermore, this mean we can't pass another thing than a str.**
@jonas-schievink jonas-schievink mentioned this issue Aug 5, 2021
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@jackh726
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Fixed in #86943

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A-diagnostics Area: Messages for errors, warnings, and lints A-suggestion-diagnostics Area: Suggestions generated by the compiler applied by `cargo fix` 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. D-terse Diagnostics: An error or lint that doesn't give enough information about the problem at hand. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue.
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Fixed #85845: Added a note in E0369 if the missing trait is PartialEq ccgauche/rust
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@estebank @ccgauche @jackh726