Newbie initial comments on D language - scope

[Walter Bright]

Edward Diener wrote:
> In your above, if the c object is 'scope', whether it is because the C 
> class is 'scope' or, as in your example, you specify 'scope' on the 
> object ( which in current D is the same thing as saying that the C class 
> is 'scope' ) then the assignment to another object makes that object 
> 'scope' automatically. This is yet another reason why 'scope' at the 
> compiler should be tracked at the object level, not at the class level. 
> The canonical situation is:
> 
> class C { ... }
> scope class D : C { ... }
> 
> scope ( redundant IMO ) D  d = new D(...);
> C c = d;
> 
> Clearly c, whose polymorphical type is a D, has to be 'scope'.

Let's look at it by analogy to 'const'. Implicitly converting a const D 
to its base class will produce a const C, not a C. A const C cannot be 
assigned to a C.

I think it should work similarly with scope, and that like const, it 
should be part of the type system (a proxy struct would accomplish 
that). Making it a dynamic part of the object would exact a heavy cost 
for most objects which don't need it.