Swift 5 propertyWrapper that wraps a value with a semaphore to prevent overlapping access.

Semaphored propertyWrapper.swift

/// Wraps a value with a DispatchSemaphore(value: 1) to prevent overlapping access.
@propertyWrapper public struct Semaphored<T> {
    
    private var value: T
    private var semaphore = DispatchSemaphore(value: 1)
    
    public var wrappedValue: T {
        get {
            defer { semaphore.signal() }
            semaphore.wait()
            return value
        }
        _modify {
            semaphore.wait()
            yield &value
            semaphore.signal()
        }
    }
    
    public init(wrappedValue: T) {
        self.value = wrappedValue
    }
    
}