Java flow dsl lower bounds #24575
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Java flow dsl lower bounds #24575
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Test FAILed. |
patriknw
approved these changes
Feb 20, 2018
| * | ||
| * {{{ | ||
| * Source<Apple, NotUsed> apples = null; | ||
| * Source<Orange, NotUsed> oranges = null; |
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perhaps use Source.empty in such examples instead of null
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Ups, yes, indeed, copy pasta from the test.
| @@ -14,7 +14,8 @@ final class BidiFlow[-I1, +O1, -I2, +O2, +Mat]( | |||
| override val shape: BidiShape[I1, O1, I2, O2] | |||
| ) extends Graph[BidiShape[I1, O1, I2, O2], Mat] { | |||
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| def asJava: javadsl.BidiFlow[I1, O1, I2, O2, Mat] = new javadsl.BidiFlow(this) | |||
| def asJava[JI1 <: I1, JO1 >: O1, JI2 <: I2, JO2 >: O2, JMat >: Mat]: javadsl.BidiFlow[JI1, JO1, JI2, JO2, JMat] = | |||
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Test PASSed. |
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jrudolph
reviewed
Mar 5, 2018
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IMO the change is the right way to go, the question is under which conditions we can pull it off.
I also tried things back when @johanandren was working on it to find out whether there are better solutions but it seems that Java doesn't offer anything better. I guess the main reason why there is no better support in Java is that most collections are mutable and therefore must be invariant so the support for covariant data types is just too limited.
I wonder though, if this isn't a bug in the Scala compiler as well because it creates unsafe generic signatures. Shouldn't it create generic signatures that are just not usable from Java instead of bailing out and silently allowing unsafe usage?
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Needs, rebasing/merging btw. |
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2m
approved these changes
Mar 15, 2018
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Fixes #24368
A bit on the fence about this, not source compatible and quite invasive.
However, the current situation is that methods that looks like they have a bound actually do not provide any type safety at all, for example this compiles fine and blows up later: