Hi all,
We’re having a bit of a debate <https://github.com/apple/swift/pull/12910> over
the question of whether SE-0143 “Conditional Conformances”
<https://github.com/apple/swift-evolution/blob/master/proposals/0143-conditional-conformances.md>
actually proposes any standard library changes at all, or whether they should
all be brought up separately. So, I’ll pitch the pieces that I’d love to put
into 4.1 to see if they’re as obvious as I think they should be :)
Proposal: make Optional, Array, ArraySlice, ContiguousArray, and Dictionary
conform to Equatable when their type parameters are Equatable (and Set always
conform to Equatable). Specifically, add to the standard library:
extension Optional: Equatable where Wrapped: Equatable { /*== already
exists */ }
extension Array: Equatable where Element: Equatable { /*== already
exists */ }
extension ArraySlice: Equatable where Element: Equatable { /*== already
exists */ }
extension ContiguousArray: Equatable where Element: Equatable { /*==
already exists */ }
extension Dictionary: Equatable where Value: Equatable { /*== already
exists */ }
extension Set: Equatable { /*== already exists */ }
Motivation: we need these for ==/!= to properly compose. It’s a
highly-requested feature and an obvious “first use” of conditional conformances
for the standard library that is unlikely to break any code.
Implementation: https://github.com/apple/swift/pull/13046
Thoughts?
- Doug
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