Out of bounds, case crash.

[orangeince]

Problem

App crashed when the text of UILabel is come from network data parse.May be caused by
string encoding. I simulated the scene with SwiftPlayground.

let key = "天"
let text = String(data: "明天开始".data(using: .unicode)!, encoding: .unicode)!
let ranges = text.lowercased().ranges(of: key)
print("matchedRanges: \(ranges)")
// matchedRanges: [Range(Swift.String.Index(_rawBits: 196608)..<Swift.String.Index(_rawBits: 393216))]

print("originText.endIndex: \(text.endIndex)")
// originText.endIndex: Index(_rawBits: 262144)

print("lowercased.endIndex: \(text.lowercased().endIndex)")
// lowercased.endIndex: Index(_rawBits: 786432)

The upperBound of matched range is greater than the originText.endIndex.

Solution

Remove the lowercased option before match range and use CompareOptions.caseInsensitive as the default value of ranges method.

I am happy to submit PR if you allow it.