String methods missing - including replaceRange and advance

Elements Silver
1 
	extension String {
	mutating func replaceCharacterAtIndex(index: Int, withString str: String) {
		replaceRange(Range(start: advance(self.startIndex, index), end: advance(self.startIndex, index+1)), with: str) // Unknown identifier "replaceRange"
																													   // Unknown identifier "advance"
																													   // Unknown identifier "advance"
	}
}

var ab = "abcdefg"
ab.replaceCharacterAtIndex(3, withString: "o")
2

Swift-specific members for String will need to be added to the base library. we haven’t gotten around to that yet (mainly because extension support was finished rathe recently), but i’ll make sure we do. If you send me your gut hub account, i can also give you access to our (currently still private, eventually we’ll open it up) repository for this library so you could directly contribute as well,i if you want to.

bugs://70591: Silver: base library support for String members