ICU依存云々は僕の記憶がどこかで書き換わっていたぽい。 https://github.com/apple/swift/pull/8769#issuecomment-294310129 から引用。
> @dabrahams Sorry, I didn't read the string manifesto. > Hm, it seems that the string manifesto says "Swift string sorting will not be compatible with > Foundation sort order". > Is that correct with that understanding? Yes, non-localized String sorting will not work the same way in Swift as it does in Foundation. We intend to try very hard to keep localized sorting in sync, though. なんか詳細忘れちゃったな…