4.1でconditional conformanceちゃんとリリースされそうな流れですね。標準ライブラリ側も込みで。 https://github.com/apple/swift-evolution/pull/769

[SE-0143] Amend to include adoption of conditional conformances to Equatable by DougGregor · Pull Request #769 · apple/swift-evolution

As discussed in this thread, amend SE-0143: Conditional conformances to include the adoption of conditional conformances for Equatable by Optional, Array, and Dictionary. Implementation available a...