jrudolph commented on code in PR #1026:
URL: https://github.com/apache/incubator-pekko/pull/1026#discussion_r1469387989
##########
stream/src/main/scala/org/apache/pekko/stream/impl/fusing/CollectWhile.scala:
##########
@@ -43,18 +44,17 @@ private[pekko] final class CollectWhile[In, Out](pf:
PartialFunction[In, Out]) e
private lazy val decider =
inheritedAttributes.mandatoryAttribute[SupervisionStrategy].decider
import Collect.NotApplied
+ @nowarn("msg=Any")
override final def onPush(): Unit =
try {
// 1. `applyOrElse` is faster than (`pf.isDefinedAt` and then
`pf.apply`)
// 2. using reference comparing here instead of pattern matching can
generate less and quicker bytecode,
// eg: just a simple `IF_ACMPNE`, and you can find the same trick
in `Collect` operator.
// If you interest, you can check the associated PR for this
change and the
// current implementation of
`scala.collection.IterableOnceOps.collectFirst`.
- val result = pf.applyOrElse(grab(in), NotApplied)
- if (result.asInstanceOf[AnyRef] eq NotApplied) {
- completeStage()
- } else {
- push(out, result.asInstanceOf[Out])
+ pf.applyOrElse(grab(in), NotApplied) match {
+ case _: NotApplied.type => completeStage()
Review Comment:
TIL, thanks for the explanations. I see how matching on the instance needs
to call `equals`, especially if the scrutinee is of `Any` type (though, this
could be optimized away, if you know that the singleton does not override
`equals`?. Somewhat surprising to see that for this type match the reference
comparison is preferred over a `checkcast` (though, of course, I don't think
any of this matters).
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