On Thu, 3 Nov 2022 00:49:52 GMT, Stuart Marks <sma...@openjdk.org> wrote:
>> @stuart-marks What are examples of cases where it wouldn't be reasonable: >> https://github.com/openjdk/jdk/pull/7387/files#diff-2b261a88d9ed30893d24186a36ef500d284d82e8f345591fc6c44ed5ae15da4fR161 >> ? > > I had to uncomment that line to figure out what broke. :-) Turns out > `TreeSet.reversed().reversed()` doesn't return the original TreeSet. This is > because `descendingSet().descendingSet()` doesn't unwrap, and neither does > TreeMap's `descendingMap().descendingMap()`. I don't know what this wasn't > done in the first place. Nonetheless, since unwrapping isn't done in the > underlying implementation, it doesn't seem reasonable for the specification > to require it be done. Furthermore this enables `reversed()` to be > implemented as a default method that simply delegates to the respective > `descending*()` method. Also, `unmodifiableSequencedCollection(c).reversed().reversed()` does not return the original `unmodifiableSequencedCollection(c)`. And we probably cannot even specify that `x.reversed().reversed().equals(x)`, due to lack of `equals()` specification for all collections (in particular, Deques)... ------------- PR Review Comment: https://git.openjdk.org/jdk/pull/7387#discussion_r1148106570
