[records] updates for Preview 9. hashCode

[Kevin Bourrillion]

On Thu, Jan 9, 2020 at 8:46 PM John Rose <john.r.rose at oracle.com> wrote:

All we need to do is promise
> that a record type’s hashCode fulfills the Object contract, especially
> relative to the record’s equals method.


Yes! This, exactly. Thank you.

(It doesn't even matter if the words in the spec technically admit the
possibility it's implemented as `return 0`, because that's just a bad
implementation, and specs shouldn't have the burden of saying "by the way
this isn't/shouldn't be a bad implementation".)

As for toString() it doesn't have the same "Object already says it all"
situation, but I would question whether all the guarantees I currently see
in the patch are really necessary. How do users benefit from those
guarantees?  I do like the "equal values -> equal strings" one (perhaps
noting that the inverse doesn't quite hold?).

$.02

-- 
Kevin Bourrillion | Java Librarian | Google, Inc. | kevinb at google.com
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