fs2 upgrade 2.2.0 - ClassCastException

[regis-leray]

After upgrading fs2:2.0.1 to fs2:2.2.0 im getting this stacktrace, it looks there is some optimisation have been done with Chunk

I tried with fs2:2.1.0 and everything work fines

[info] - should readFile *** FAILED ***
[info]   java.lang.ClassCastException: class [Ljava.lang.Object; cannot be cast to class [B ([Ljava.lang.Object; and [B are in module java.base of loader 'bootstrap')
[info]   at fs2.Chunk.toBytes(Chunk.scala:276)
[info]   at fs2.io.file.FileHandle$$anon$1.$anonfun$write$1(FileHandle.scala:148)
[info]   at scala.runtime.java8.JFunction0$mcI$sp.apply(JFunction0$mcI$sp.scala:17)
[info]   at cats.effect.internals.IORunLoop$.cats$effect$internals$IORunLoop$$loop(IORunLoop.scala:87)
[info]   at cats.effect.internals.IORunLoop$.startCancelable(IORunLoop.scala:41)
[info]   at cats.effect.internals.IOBracket$BracketStart.run(IOBracket.scala:86)
[info]   at cats.effect.internals.Trampoline.cats$effect$internals$Trampoline$$immediateLoop(Trampoline.scala:70)
[info]   at cats.effect.internals.Trampoline.startLoop(Trampoline.scala:36)
[info]   at cats.effect.internals.TrampolineEC$JVMTrampoline.super$startLoop(TrampolineEC.scala:93)
[info]   at cats.effect.internals.TrampolineEC$JVMTrampoline.$anonfun$startLoop$1(TrampolineEC.scala:93)

if you want to see the whole code it is here =>
regis-leray/fs2-ftp#11

[mpilquist]

Thanks for the report. This reproduces:

> Chunk(0, 0).map(_.toByte).toArray
java.lang.ClassCastException: class [Ljava.lang.Object; cannot be cast to class [B ([Ljava.lang.Object; and [B are in module java.base of loader 'bootstrap')

[mpilquist]

Introduced by #1715. We could roll that back and release a 2.2.1. @CremboC any thoughts? Problem is that map is creating an Array[Any] but then later when toArray is called, it's cast to an Array[Byte].

[CremboC]

I was worried that this could happen. Hoped that tests would catch this, but obviously was too optimistic! Could just deoptimise map back to what it was before, or just undo the whole PR. Up to you! Sorry about that.

Also could look into how ArraySeq map is implemented - afaik it's a Seq backed by an Array so should be very similar to what we're doing with Chunk

[mpilquist]

Fixed by #1746