~~プロトコル準拠って、デフォルトパラメータの有無も含むのか。~~ @swift-5.0.3

protocol X { func say(sentence: String) func say() } struct A: X { // error: Type 'A' does not conform to protocol 'X' func say(sentence: String = "I'm fine, you ?") { print("A : \(sentence)") } }

(edited)