Ghosting a language feature
geod24 at gmail.com
Mon Sep 21 09:06:50 UTC 2020
On Monday, 21 September 2020 at 02:43:57 UTC, Walter Bright wrote:
> On 9/20/2020 7:38 PM, Avrina wrote:
>> why not just remove it so no one uses it.
> Because legacy code will use it. Removing features has been a
> constant source of irritation to users, and they're right.
I wish D would stop trying to be this or that, and finally settle
on its identity.
People that use D don't do it because they want a flawless
upgrade path and everything to just be the same 10 years from
now. If you want this, you just stick with one of the big
languages. This is not just an hypothesis out of thin air, look
at the community survey:
Grep for "What is your tolerance for stability vs. breaking
changes". Provided the question is biased, but still, the answers
lean heavily in one direction.
But still, people complain. And many core contributors, myself
included, will heavily weight against breaking change. So why the
apparent disconnect ?
Once again, the person that managed to put it together best was
Don Clugston. He mentioned it in his talk @ DConf 2013.
It's exactly 5 minutes, starting from here:
Now, the example that Don used, implicit fallthru, was a win for
Sociomantic. But what if there was no bug ? If there was only a
handful occurrences, none of them buggy ? Then they would really
pay a cost for nothing. A small cost, but a cost nonetheless.
I hit a similar case a few years ago, when I deprecated using the
return of the comma operator. To my surprise, there were quite a
few users. Even more surprising, after looking at the way this
feature was used, it **made perfect sense**. In the particular
situations, reading the code, using the return of a comma
expression was... Neat. And here I was, asking those people to
change their neat code because I thought it was wrong and led to
issues such as `synchronized(a, b)`.
Well turns out, D has one of the most powerful tool to deal with
Deprecating something, and giving a decent timeframe, allows to
move things forward without destroying the ecosystem. It gives
the weary programmer a way to ignore a few annoying deprecations
in his/her code when all that programmer's want to do is enjoy
the new features in the latest release. It gives times for
everyone, including dependency, to tackle the problem, at the
minor inconvenience of a little message.
We've been refining deprecated for years. When it started, you
could only apply it on functions, and no message was allowed.
Then we added support for string literal. Then one day Vibe.d
broke because of a stray import to an empty Phobos module, and we
added support for deprecated module. Then CTFE-able messages.
Along the way, we made sure that one could access deprecated code
within a deprecated scope, so a library can keep providing the
same functionality to users without breaking compatibility. And
with D's amazing feature set, a library can even use `static if
(__VERSION__ >= 2094)` to deprecated based on the compiler used.
Did you know that `deprecated` is so amazing that it's the
feature that Sociomantic **backported to D1** ? That's right,
this feature is so awesome that Sociomantic decided they needed
it more than any other D2 features, because of how much it
simplified internal libraries updates. And it had amazing ROI.
In conclusion, I simply hope we keep on putting more
consideration into why people come to D, as opposed to why people
say they won't. And people come to D not for a language that has
eternal backwards compatibility, because one simply can use C++
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