Loosening requirements for super() invocation

[Archie Cobbs]

On Fri, Dec 30, 2022 at 10:48 AM Brian Goetz <brian.goetz at oracle.com> wrote:

> One thing that makes me a little uncomfortable is that @SW usually is used
> to say “the compiler can’t prove this is safe, but I am asserting it is.”
>  But this is different; the compiler has discovered the class is unsafe,
> and @SW is saying “I know, I know, stop telling me.”  So I think there’s an
> additional documentation opportunity here where, for the classes we had to
> annotate with @SW, we include an additional @apiNote of the form “This
> class behaves badly, oops”, with a link to a common doc page explaining the
> problem.  (While we don’t have to do this necessarily immediately, the
> chance of it falling on the floor if we don’t are higher.). Basically, what
> you’ve identified is that there are a  number of classes in the JDK which
> fail to follow best practices with regard to self-use from constructors.
> We can’t turn back the clock, but we can mark these as “don’t code like my
> brother”, so people see these patterns of coding and realize they are not
> to be emulated.
>

Good point.

I think it's also worth considering which scenarios require such
documentation. We have drawn the "boundary lines" at the compilation unit
boundary, but this means (for example) there are package-private classes
that generate warnings. Because these classes will end up in a module,
which requires special effort to crack open, the warnings only really apply
to JDK developers working in that same package.

Might be worth restricting this to classes that a "normal" person could
"normally" extend, for some suitable definitions of "normal" and "normally".

I also see in the code that there are two separate categories,
> LeakingThisInConstructor and this-escape; what’s the difference?
>

Great question. I was surprised to stumble across existing code with
@SuppressWarnings("LeakingThisInConstructor") annotations.

>From what I can tell, these are leftovers from about 10 years ago when some
developers were using NetBeans, which had just such a warning. I don't
think they are relevant any more but I didn't want to presume anything so I
left them in there.

Thinking about them more, we should probably just replace them because
otherwise they will just continue to confuse...

-Archie

-- 
Archie L. Cobbs
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