Multiple subtyping with alias this and nested classes
Yigal Chripun
yigal100 at gmail.com
Mon Oct 5 22:45:01 PDT 2009
On 06/10/2009 02:15, Andrei Alexandrescu wrote:
> Yigal Chripun wrote:
>>> I think 'alias this' is a powerful feature.
>>>
>>> Given the constraints like "easy for the compiler writer to implement"
>>> and "we have many other things to do", I doubt traits or something
>>> like that will be or needs to be in the language.
>>
>> Alias this is powerful black magic. being powerful doesn't make it any
>> less dark.
>
> So how does this work? Alias this was meant very clearly for allowing
> subtyping. Conversely, using it for subtyping is precisely how it was
> meant to be used. How exactly did you decide it was a hack or black
> magic or whatever?
>
> Andrei
D already has syntax for sub-typing reference types and alias this
introduces a completely different syntax doing the same for value types
which is bad human interface IMO.
it also mixes two concepts - sub-typing and opImplicitCast (as i recall,
this is done by alias this to a function)
we discussed this in the past already and IIRC you agreed with me about
implementing compile time inheritance for structs which I feel is much
cleaner and more consistent with the existing syntax of interfaces.
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