I am certain there are some demons lurking, and I am even more certain
that we will be surprised by the interactions of language constructs
within a ctor body that give rise to them.
In fact, I would like to see the JEP spend less time rehearsing JLS
modifications and more time exploring how tools, analyzers, linters, etc
will be impacted by ctor bodies that have a prologue. The Risks &
Assumptions section should be pages long.
And I will pose another question: are there any tricks, idioms, or
'patterns' that have been necessary in Java code to workaround the
super()-comes-first rule? I would like the Motivation or Description (or
both) to complement the currently rather abstract story (about
superclasses, guarantees, and top-down initialization) with some
straightforward code samples of what developers had to write before and
why it was error-prone and why it hurt maintainability.
Now that the JEP is stable as a Candidate, it's legitimate for Archie,
as owner, to enhance the text in these ways.
Given the likelihood of dotting i's and crossing t's in the design/spec,
and in the hope that the JEP can get quite a bit richer, I think at
least one round of preview is the right thing to do.
Alex
On 5/15/2023 10:13 AM, Brian Goetz wrote:
I agree that this one is at the edge of what we would need to preview,
and so I can see going either way here. Since we've never done a
non-preview language feature since the advent of preview, we kind of
have to face the problem here and decide not only for this feature, but
on guidelines going forward. So far, we've been following the implicit
policy of "all language features go through preview" (I could easily
imagine relaxing this to exclude things that are effectively language
bugfixes.)
On the one hand, previewing adds some cost and work. It means extra
code in the compiler, extra tests, and then more work and another JEP to
finalize it. On the other, preview is a valuable mechanism for getting
feedback on a feature before being stuck with it forever.
One notable thing about *this* JEP is that, even when everyone agreed on
the scope and the approach, the spec still required a few rounds of
iteration to get it right. That suggests that even given its narrow
focus, there are still potentially some demons lurking.
On 5/15/2023 12:49 PM, Archie Cobbs wrote:
The following question came up and needs opinions from this list...
JEP 447 Statements before super() is currently not specified as a
preview feature... should it be?
On the one hand, language changes are usually previewed first; on the
other hand, this change is fairly simple and straightforward.
Thanks,
-Archie
--
Archie L. Cobbs
