DIP65: Fixing Exception Handling Syntax

[Justin Whear via Digitalmars-d]

On Thu, 17 Jul 2014 12:28:33 -0700, Andrei Alexandrescu wrote:

> On 7/8/14, 2:31 PM, Brian Schott wrote:
>> http://wiki.dlang.org/DIP65
>>
>> tldr: There are parser and specification bugs and I want to fix them.
>> It will break some poorly-written code, but I think I can automate the
>> upgrade process.
> 
> I vote we reject this DIP. It has clear appeal but there's also the
> issue with putting currently correct code on a deprecation path, with no
> obvious win in quality.
> 
> I think Walter's fix eliminates the problem during the semantic pass
> even though there's a grammar ambiguity. It's a judgment call, and by
> definition someone has to make it.
> 
> 
> Andrei

My understanding (and this is supported by hard numbers from Brian's 
survey of Phobos), is that Walter's proposal will perpetuate a bad design 
choice that is rarely if ever used (never in Phobos) in favor of 
deprecating a better syntax that is used (in Phobos and elsewhere).

That is to say, we have hard numbers to prove that Walter's fix will 
deprecate currently working code while leaving us with the less-desirable 
syntax, while Brian's proposal will transition us to the more desirable 
syntax without breaking code written in the currently used idiom.

And, as Brian pointed out[1], the current idiom of `catch (Throwable)` 
_is described_ in the spec, albeit not in the formal grammar.  Ergo, 
Walter's fix also deprecates currently-working, correct syntax.  Given 
that both are correct, but one is nearly completely unused and error 
prone, I vote yes on this DIP.

[1] http://forum.dlang.org/thread/xmqzrgysgxdmqrnfpxdq@forum.dlang.org?
page=2#post-zsvbxhtbwevsrrflxzyr:40forum.dlang.org