Construct immutable member in derived class

[Alex]

On Wednesday, 4 April 2018 at 21:49:08 UTC, Timoses wrote:
> "[...] the construction of the base class can be independent 
> from the derived one."
>
> Hm, the points 7 and 8 don't clearly state what you wrote.

Yes :)

> But it somehow does make sense.. Still I wonder why that is so.
>
> Let's say you have an abstract class with immutable members. 
> Why shouldn't derived class constructors be allowed to 
> initialize these immutable members?

My reason is a semantic one, so it's rather how I'm explaining 
this to me, then a formal one.

Let's assume, we abstract away a member from different derived 
classes to an abstract class, which cannot be handled by this 
abstract class.
Ok, this can happen, so it would be ok, if the base class does 
not handle the var.

But then, we add a qualifier. How can this be? As the abstract 
class cannot handle the abstraction, it also can not add any 
qualifiers.
As the qualifier is there, then, the base class at least has 
knowledge about the immutability. And due this fact, its own 
constructor has to handle this variable in some way.

However, this a minor problem, isn't it? If you argue, that you 
can also abstract the immutability qualifier, then, I would say, 
that a derived class always has a better knowledge how to handle 
its members, and therefore how to call the base class 
constructor, as it knows which class it is derived from.

So, for short:
Either: the immutability belongs to the base class and therefore 
it has to manage the var
Or: it doesn't and the derived classes have the knowledge how to 
serve their base class.