これは導入されたらうれしいかもしれない。↓が全部いける extension Array where Element == String { ... } extension Array<String> { ... } extension [String] { ... } https://github.com/apple/swift-evolution/blob/main/proposals/0361-bound-generic-extensions.md

swift-evolution/0361-bound-generic-extensions.md at main · apple/sw...

This maintains proposals for changes and user-visible enhancements to the Swift Programming Language. - swift-evolution/0361-bound-generic-extensions.md at main · apple/swift-evolution