Proposal: JDK-8148917 Enhanced-For Statement Should Allow Streams
Brian Goetz
brian.goetz at oracle.com
Tue Mar 12 16:04:16 UTC 2019
No. You have the LSP backwards (though this is easy to do.)
IterableOnce means "*must throw* on subsequent use"; under this spec, an
arbitrary Iterable is most certainly *not* an IterableOnce, and
therefore an LSP violation.
It sounds like you are suggesting that we instead spec
IterableAtLeastOnce, of which Iterable *would* be a credible subtype --
but due to how Iterable is specified now, the problem is that Iterable
*already is* really "iterable at least once." So there would be no
point in introducing this type; we already have it.
If we were doing this from scratch, we might choose a different path,
but that option is not open to us. As several have already noted, this
proposal is not ideal, but due to the corner we're painted into by
Iterable's current spec, there is not going to be an ideal outcome --
and the current strategy (do nothing) is also not ideal and makes many
people unhappy. So the game here is finding the least-bad solution that
is compatible with the constraints we have, which I think Stuart has
done exactly. (Also, he did a very nice job of writing up all the
alternatives, to avoid (or at least reduce) the torrent of "have you
thought about <thing that has been thought about extensively>".)
On 3/6/2019 10:50 AM, Peter Levart wrote:
>
> In this respect Iterable should be a subtype of IterableOnce and
> foreach loop should be retrofitted to work with IterableOnce.
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