$ cat non-any.swift protocol Animal {} struct Cat: Animal {} let animal: Animal = Cat() print(animal) $ $ swift -swift-version 5 non-any.swift Cat() $ $ swift -swift-version 6 non-any.swift <unknown>:0: error: invalid value '6' in '-swift-version 6' <unknown>:0: note: valid arguments to '-swift-version' are '4', '4.2', '5'

3:36 PM

この "Swift 6 language mode" はまだ存在しない架空のモードなのか。

this syntax should be required for existential types under the Swift 6 language mode

https://github.com/apple/swift-evolution/blob/main/proposals/0335-existential-any.md