??? - A custom optional -> string coalescing operator

CoalescingOperator.swift

// Source: https://oleb.net/blog/2016/12/optionals-string-interpolation

infix operator ???: NilCoalescingPrecedence

/// Provides a String default value for an Optional of any type.
/// Overcomes the problem with the `??` operator whare the default value must be
/// of the same type as the left hand side.
public func ???<T>(optional: T?, defaultValue: @autoclosure () -> String) -> String {
    switch optional {
    case let value?: return String(describing: value)
    case nil: return defaultValue()
    }
}

The source for this code is: https://oleb.net/blog/2016/12/optionals-string-interpolation

I came across the source in Thomas Hanning's Newsletter (11): https://thomashanning.curated.co/issues/11?#start