Buildable protocol Swift

Buildable.swift

protocol Buildable {}
extension Buildable {
    func with(transform: (inout Self) throws -> Void) rethrows -> Self {
        var mutableSelf = self
        try transform(&mutableSelf)
        return mutableSelf
    }
}

func mutating<Type>(_ type: Type, transform: (inout Type) throws -> Void) rethrows -> Type {
    var mutableType = type
    try transform(&mutableType)
    return mutableType
}