Why are opCall's not implicitely assignable?

[Hasan Aljudy]

Your example demonstrates very well why overriding assignments shouldn't 
be allowed.

# Car mycar;
# mycar = COLOR.RED; //!!!!!!!

How can a car turn to a red color? This is totally meaningless and bogus.

Color is a property of the car:
# mycar.color = COLOR.RED;

roof is a property of the car, but this doesn't justify using
# mycar.roof = COLOR.RED;
because you're not changing the property roof (well, you're changing its 
state) but rather, you're changing the "color" of the roof; so you're 
changing a property of roof, thus:
# mycar.roof.color = COLOR.RED;

What you're trying to do makes code totally unreadable.

Karen Lanrap wrote:
> Mike Parker wrote:
> 
>> Cars have color. These could all be considered object
>> properties. Can you name an object that has the property of
>> opCall?
> 
> Assume we have some colors
> 
>   enum COLOR{ LIGHTBLUE, DARKBLUE, RED};
> 
> and a car with some colorable parts
> 
>   class Car
>   {
>     Roofliner roof;
>     Seat[4] seats;
>     Carpet carpet;
>     this()
>     {
>       roof= new Roofs.Handmade;
>       seats[0]= new Seats.Handicapped(OVERWEIGHT);
>       seats[1]= new Seats.Standard;
>       seats[2]= new Seats.Auxiliar(LEFT, TINY);
>       // ...
> 
> Now I want to assign colors to the colorable parts
>   
>   Car car;
>   void main()
>   {
>     car= new Car;
>     car.roof= COLOR.LIGHTBLUE;
>     seats[0]= COLOR.DARKBLUE;
>     seats[1]= COLOR.RED
>     // ...
> 
> But you say that I am not allowed to do this, because the colorable 
> parts are no properties of the car?
> 
> I have to write
> 
>   Car car;
>   void main()
>   {
>     car= new Car;
>     with(car)
>     {
>       roof.color= COLOR.LIGHTBLUE;
>       seats[0].color= COLOR.DARKBLUE;
>       seats[1].color= COLOR.RED
>     // ...
> 
> instead? Thereby explicitely saying that I mean the color each time? 
> 
> How does this fit with "auto c='c';" implicit type inference? Why do 
> I have to write
> 
>   COLOR col= seats[0].color;
> 
> when it would suffice to write:
> 
>   COLOR col= seats[0];
> 
> because of appropriate opCalls?
> 
>