Generate the alphabet quickly [Swift]

QuickAlphabet.swift

let asciiChars = Character("A")...Character("z")

let allCharsAsString = String(asciiChars)

extension Character: Strideable {
    public func distance(to other: Character) -> Int {
        guard let value = self.asciiValue, let otherValue = other.asciiValue else {
            fatalError("ASCII values are nil")
        }
        return abs(Int(value) - Int(otherValue))
    }
    
    public func advanced(by n: Int) -> Character {
        guard let value = self.asciiValue else {
            fatalError("Could not get ASCII value")
        }
        return Character(UnicodeScalar(value + UInt8(truncatingIfNeeded: n)))
    }
}