The Right Approach to Exceptions

[deadalnix]

Le 19/02/2012 02:23, Jonathan M Davis a écrit :
> On Saturday, February 18, 2012 17:20:41 H. S. Teoh wrote:
>> On Sun, Feb 19, 2012 at 01:10:10AM +0000, Ben Davis wrote:
>> [...]
>>
>>> I guess this is a bit off topic, but what you probably want is
>>> syntactic sugar that says "declare constructors matching all super
>>> constructors and calling through to them" and can be used in ANY class
>>> hierarchy (not necessarily exceptions). For example:
>>>
>>> class Subtype : Supertype {
>>>
>>>      super all;
>>>
>>> }
>>>
>>> If you want to expose just specific constructors, then there could
>>> also be a shorthand for "declare a constructor matching a specific
>>> super constructor and calling through to it" - so you don't have to
>>> repeat all the arguments. For example:
>>>
>>> class Subtype : Supertype {
>>>
>>>      super();
>>>      super(string,int);
>>>
>>> }
>>>
>>> That would then make it an entirely separate issue and completely
>>> not Exception-specific.
>>
>> +1.
>>
>> This is definitely something not specific to Exception. Quite often, you
>> want to create a derived class overriding just one or two members of the
>> base class, but end up having to copy-n-paste most of the many ctors in
>> the base class along with their elaborate arguments just so you can pass
>> through the arguments to them.
>>
>> Having a way of simply saying "the ctors in this class default to the
>> base class ctors" will solve this problem in a very nice and logical
>> way. (I.e., you're sortof "inheriting the base class ctors", although
>> not exactly, of course.)
>
> Feel free to open a pull request. It would certainly be a useful feature for
> reducing boilerplate code in some class hierarchies (though in many, the
> constructors in the derived class must be different, in which case it wouldn't
> work).
>
> One potential issue though is that not all base classes necessarily share the
> same constructors. Which ones would be grabbed? The ones from the immediate
> base class? All of them? Only the ones common to all?
>
> - Jonathan M Davis

Well that should be achievable with compile time refexion and CTFE/mixin 
or mixin template. Maybe this should be inserted in phobos.