Re: nested class inheritance

[Steven Schveighoffer]

On Fri, 13 Jul 2012 13:59:54 -0400, Gor Gyolchanyan  
<gor.f.gyolchan...@gmail.com> wrote:

Doesn't this make sense?
class Fruit
{
    class Seed { }
}

class Apple: Fruit
{
     class AppleSeed: Fruit.Seed { }
}

This means, that as Fruit.Seed needs access to enclosing Fruit,  
AppleSeed,
being a Fruit.Seed will also have access to enclosing Fruit, which is  
Apple.
DMD 0.259 has this to say:

Error: class main.Apple.AppleSeed is nested within Apple, but super class
Seed is nested within Fruit

Which doesn't make sense, IMO. What do you guys think about this? Who  
makes
more sense me or DMD 2.059?



This is what you are asking for:

class A {}

class B : A {}

class C
{
   A member;
}

class D : C
{
   override B member;
}

You can mimic it via:

class C
{
   protected A _member;
   @property inout(A) member() inout { return _member; }
}

class C : B
{
   override @property inout(B) member() inout { return  
cast(inout(B))_member; }
}

I have had many times where I had to do this workaround (with casting), or  
store extra references, but it would be nice to have this simply work  
depending on the type.  I don't think anyone considered doing this with  
outer, it certainly would be a valid feature.  I'd like to have the  
general feature as well.  Covariant fields...

-Steve