Erasure: scala.Array survives erasure.

[odersky]

Compiling

./scala-scala/src/library/scala/collection/immutable/TrieIterator.scala

gives a crash in the backend. Everything -Ychecks OK before.

java.lang.AssertionError: assertion failed: class Array
at scala.Predef$.assert(Predef.scala:165)
at dotty.tools.backend.jvm.DottyBackendInterface$$anon$10.primitiveOrClassToBType$1(DottyBackendInterface.scala:814)
at dotty.tools.backend.jvm.DottyBackendInterface$$anon$10.toTypeKind(DottyBackendInterface.scala:835)
at scala.tools.nsc.backend.jvm.BCodeHelpers$BCInnerClassGen$class.toTypeKind(BCodeHelpers.scala:272)
at scala.tools.nsc.backend.jvm.BCodeSkelBuilder$PlainSkelBuilder.toTypeKind(BCodeSkelBuilder.scala:51)
at scala.tools.nsc.backend.jvm.BCodeSkelBuilder$PlainSkelBuilder.tpeTK(BCodeSkelBuilder.scala:84)
at scala.tools.nsc.backend.jvm.BCodeBodyBuilder$PlainBodyBuilder.genTypeApply(BCodeBodyBuilder.scala:582)
at scala.tools.nsc.backend.jvm.BCodeBodyBuilder$PlainBodyBuilder.genLoad(BCodeBodyBuilder.scala:429)

[odersky]

You need to pull the updated dotty-library, otherwise the file is rejected by Typer.

[DarkDimius]

@odersky, could you please help me reproduce the issue?
If I have dotty on c864e11 and library on lampepfl/scala@7f048c4

than I get error from typer:

./scala-scala/src/library/scala/collection/immutable/TrieIterator.scala:69: error: covariant type T occurs in invariant position in type Array[scala.collection.immutable.Iterable[T]] of value xs
  final class DupIterator(xs: Array[Iterable[T]]) extends TrieIterator[T](xs,
                            ^

[odersky]

@DarkDimius You need to compile with -language:Scala2. Then it passes the typer for me.

[DarkDimius]

Was able to reproduce.

[DarkDimius]

@odersky I traced this down to scala.Array surviving erasure.
I've improved post-condition in erasure to check this: #1005

[DarkDimius]

fixed in #1005