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update ancient note #113618

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Merged
merged 2 commits into from
Jul 14, 2023
Merged

update ancient note #113618

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5710fca
update ancient note
tshepang Jul 12, 2023
df3f45d
avoid ambiguous word
tshepang Jul 12, 2023
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4 changes: 2 additions & 2 deletions library/std/src/collections/hash/set.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -65,8 +65,8 @@ use super::map::{map_try_reserve_error, RandomState};
/// ```
///
/// The easiest way to use `HashSet` with a custom type is to derive
/// [`Eq`] and [`Hash`]. We must also derive [`PartialEq`], this will in the
/// future be implied by [`Eq`].
/// [`Eq`] and [`Hash`]. We must also derive [`PartialEq`],
/// which is required if [`Eq`] is derived.
///
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i don't think this change is correct. the note is saying "we have to derive PartialEq because Eq without PartialEq will error, and at some point we want to change derive(Eq) to imply derive(PartialEq)". that second half still isn't the case today — it's probably true that it's never going to happen, but i would expect the new comment to look a little different if that's what you meant.

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I suspected that could be the case, but got confused by:

This property cannot be checked by the compiler, and therefore Eq implies PartialEq, and has no extra methods.

from https://doc.rust-lang.org/std/cmp/trait.Eq.html

I guess implies means something else in that example?

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yes, unfortunately. the one here is using it to describe a behavior of the compiler and the one on the trait page is using it to describe a property of the language (that your code won't compile if you have Eq without PartialEq).

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please see if latest wording is acceptable

/// ```
/// use std::collections::HashSet;
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