On the subject of properties, and possibility of having them in the library

[Simen Kjaeraas]

While the storm raged, I decided to try implementing properties as library  
types. I encountered a few obstacles, which I will outline here.

First, my intended syntax:

   class A {
     int _n;
     Property!(
       () => _n,
       value => _n = value
     ) n;
   }

Property would then be a struct, with operators and functions defined as  
required, copying disabled, and of course alias this.

Now, the obstacle here is I can't refer to _n in those lambdas. Why not?  
I'm guessing the struct has no context member, and the lambdas don't  
because the class is not yet instantiated. Could this be fixed? I think  
so, and I think this is a feature with benefits beyond simple properties.

This library solution would not be able to do everything a language  
solution could. Amongst those, typeof(property) would return  
Property!(..., ...). Just as important, this would not work:

   auto a = foo.property;

, because the struct's postblit is marked @disable. Perhaps alias this  
should be attempted in such a situation?

-- 
Simen