Switch-case made less buggy, now with PATCH!

[Chad J]

Don wrote:
> Chad J wrote:
>> Don wrote:
>>> I think you've just created the strongest argument AGAINST this feature:
>>> that it makes it too hard for machine-generated code.  Forget the !:
>>> hack. No chance.
>>>
>>
>> If that's the strongest argument, then this is cake.  I'll go through
>> Phobos and insert goto case's by hand if that's what needs to happen.
>>
>> Most of the fallthrough I saw was stuff like this:
>>
>> case '1': case '2': case '3':
>> case '4': case '5': case '6':
>> case '7': case '8': case '9':
>> ...etc...
>> break;
> 
> You didn't read my post. That is NOT bug-prone. I don't think anyone
> EVER makes bugs in that form.
> It's actually got very little in common with a true fall-through. Real
> fallthrough involves a 'goto' by stealth: the case introduces an entry
> point in the middle of a code block.
> 

I DID read your post.  I'm not saying that it is bug prone.  I was just
demonstrating how it is not very hard to fix code that is broken by
forbidding fallthrough.  I'm explaining why I don't understand how the
"machine-generated" code thing is such a big issue.

>>
>>> The argument for it comes down to this: "fallthrough is very rare and
>>> therefore, most uses of fallthrough are bugs".  
>>
>> Not as I remember.
>>
>> "inline assembly is very rare and therefore, most uses of inline
>> assembly are bugs."
>> Such reasoning wouldn't get inline asm removed either.  Fallthrough is
>> not bad because it is rare.  I think that's only mentioned because the
>> rarity makes it easier to let go of fallthrough altogether.
> 
> Not at all. Requiring changes to existing code is a very big negative to
> any proposal. If the number of changes required is small,
> 

continue...

>>
>> But I think you've just gone about
>>> this wrong way. 
>>
>> Perhaps.  I'll find out for myself.
> 
> I doubt it.
> 

Ow.

> 
> You've missed the point. Andrei made a proposal for eliminating
> accidental fallthrough bugs. It didn't involve any new syntax, and
> changed very little existing code. Anything which violates either of
> those things has very little chance of acceptance. You've done a patch
> which completely ignores his proposal, and which violates both.
> 

Sorry I didn't know about Andrei's proposal.  Buried in the NG.

Why didn't you just say that Andrei made another proposal and that
you're peeved I didn't use it?

> The comment about the auto-generated code raises an aspect which hadn't
> been considered in the original proposal.

I also don't get this argument against requiring code changes.  D2 will
break your code and is allowed to do so for the sake of progress and
long term good.  Everyone knows this.