String length bug

Repro.swift

//
//  Repro.swift
//
//  Created by Stadelman, Stan on 5/10/19.
//

import Foundation

/// Sample bidirectional string, which happens to include neutral characters "(" and ")"
/// String source: [Section #1 #1](https://forum.wordreference.com/threads/important-please-read-before-you-post-الرجاء-القراءة-قبل-المشاركة.53282/)
let string = "انظر في قواميس WordReference (إذا كانت متوفرة) ثم اذهب إلى أدنى الصفحة حيث توجد قائمة بمواضيع المنتدى التي ناقشت الكلمة التى تبحث عنها، أو ابحث في المنتديات مباشرةً.​"
/// Raw attributed string produced from `string`
let attrString = NSAttributedString(string: string)

/// Expection:  `string.count` should match `attrString.length`
print(string.count)             // 165
print(attrString.length)        // 166
print(attrString.string.count)  // 165

/// Observation: iterating through the String.Index of `string`, we encounter
/// an "out of bounds" error, where we would expect a null index as a result of
/// the `limitedBy` parameter, directing the flow to line 28.
for i in 0..<200 {
    if let parIndex = string.index(string.startIndex, offsetBy: i, limitedBy: string.endIndex) {
        print("at index(\(i)): \(string[parIndex])")
    } else {
        print("no index: \(i)")
    }
}