Broken?

[Paulo Pinto]

On Wednesday, 12 March 2014 at 11:40:39 UTC, Manu wrote:
> On 12 March 2014 20:40, monarch_dodra <monarchdodra at gmail.com> 
> wrote:
>
>> On Wednesday, 12 March 2014 at 03:05:00 UTC, Manu wrote:
>>
>>> I'm really trying to keep my lid on here...
>>>
>>> I'll just remind that in regard to this particular point 
>>> which sounds
>>> reasonable, it's easy to forgot that *all library code where 
>>> the author
>>> didn't care* is now unusable by anybody who does. The 
>>> converse would not
>>> be
>>> true if the situation was reversed.
>>>
>>> virtual-by-default is incompatible with optimisation, and 
>>> it's reliable to
>>> assume that anybody who doesn't explicitly care about this 
>>> will stick with
>>> the default, which means many potentially useful libraries 
>>> may be
>>> eliminated for use by many customers.
>>> Also, as discussed at length, revoking virtual from a 
>>> function is a
>>> breaking change, adding virtual is not. Which means that, 
>>> instead of
>>> making
>>> a controlled breaking change with a clear migration path here 
>>> and now, we
>>> are committing every single instance of any user's intent to 
>>> 'optimise'
>>> their libraries (by finalising unnecessarily virtuals) to 
>>> breaking changes
>>> in their ABI - which *will* occur, since virtual is the 
>>> default.
>>> According to semantic versioning, this requires bumping the 
>>> major version
>>> number... that's horrible!
>>>
>>> What's better; implementing a controlled deprecation path 
>>> now, or leaving
>>> it up to any project that ever uses the 'class' keyword to 
>>> eventually
>>> confront breaking changes in their API when they encounter a 
>>> performance
>>> oriented customer?
>>>
>>
>> Case in point:
>> https://github.com/D-Programming-Language/phobos/pull/1771
>> "mark std.zip classes as final"
>>
>> Long story short: MartinNowak decided to make the Zip classes 
>> final, since
>> it made no sense to have any of the functions virtual, or to 
>> have anybody
>> derive from them anyways.
>>
>> https://github.com/D-Programming-Language/phobos/pull/1771#issuecomment-
>> 36524041
>> Comment from Dav1dde:
>> "Just to let you know, it broke my code"
>>
>
> Thank you.
> There you go, it's not even hypothetical.

It can also happen the other way if I mark a method virtual that 
used to be final, which was overloaded in a subclass, right?

--
Paulo