WTFString.swift

import Foundation

let okString = "WTF\r\nHELLO"
let wtfString = AttributedString(okString)

if let lineRange = okString.range(of: "\n") {
	let lineSubstring = okString[okString.startIndex..<lineRange.lowerBound]
	type(of: lineSubstring)
	lineSubstring.count
}

if let lineRange = wtfString.range(of: "\n") {
	let lineSubstring = wtfString[wtfString.startIndex..<lineRange.lowerBound]
	type(of: lineSubstring.characters)
	lineSubstring.characters.first!
	lineSubstring.characters.last!
	lineSubstring.characters.count // BOOM
	// same with lineSubstring.characters.underestimatedCount
}