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Misleading description of PartialEq derived implementation for enums in docs #97945

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nirvana-msu opened this issue Jun 10, 2022 · 2 comments · Fixed by #97950
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Misleading description of PartialEq derived implementation for enums in docs #97945

nirvana-msu opened this issue Jun 10, 2022 · 2 comments · Fixed by #97950
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@eggyal
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A-docs Area: documentation for any part of the project, including the compiler, standard library, and tools C-cleanup Category: PRs that clean code up or issues documenting cleanup. E-easy Call for participation: Easy difficulty. Experience needed to fix: Not much. Good first issue. T-libs-api Relevant to the library API team, which will review and decide on the PR/issue.

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@nirvana-msu
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nirvana-msu commented Jun 10, 2022 •
edited by rustbot
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Current docs on PartialEq derive state:

When derived on enums, each variant is equal to itself and not equal to the other variants.

I interpret the above statement as "PartialEq compares enum discriminants", which is not the case.

This is true for enums variants with no data, however for enum variants that are struct-like or tuple struct-like, derived PartialEq actually compares the fields (which is expected) and not just discriminants:
https://play.rust-lang.org/?version=stable&mode=debug&edition=2021&gist=64530ce03a4506d1e82a1df4d78765ff
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eggyal commented Jun 10, 2022

@rustbot label: +A-docs +C-cleanup +E-easy +T-libs-api

@rustbot rustbot added A-docs Area: documentation for any part of the project, including the compiler, standard library, and tools C-cleanup Category: PRs that clean code up or issues documenting cleanup. E-easy Call for participation: Easy difficulty. Experience needed to fix: Not much. Good first issue. T-libs-api Relevant to the library API team, which will review and decide on the PR/issue. labels Jun 10, 2022
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eggyal commented Jun 10, 2022

@rustbot claim

@eggyal eggyal mentioned this issue Jun 10, 2022
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Dylan-DPC added a commit to Dylan-DPC/rust that referenced this issue Jun 12, 2022
@Dylan-DPC
Rollup merge of rust-lang#97950 - eggyal:issue-97945, r=Dylan-DPC
84b5909 
Clarify `#[derive(PartialEq)]` on enums

Fixes rust-lang#97945
compiler-errors added a commit to compiler-errors/rust that referenced this issue Jun 13, 2022
@compiler-errors
Rollup merge of rust-lang#97950 - eggyal:issue-97945, r=Dylan-DPC
5dccf4e 
Clarify `#[derive(PartialEq)]` on enums

Fixes rust-lang#97945
@bors bors closed this as completed in 7bbf914 Jun 13, 2022
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A-docs Area: documentation for any part of the project, including the compiler, standard library, and tools C-cleanup Category: PRs that clean code up or issues documenting cleanup. E-easy Call for participation: Easy difficulty. Experience needed to fix: Not much. Good first issue. T-libs-api Relevant to the library API team, which will review and decide on the PR/issue.
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Clarify #[derive(PartialEq)] on enums eggyal/rust
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@eggyal @nirvana-msu @rustbot