SI-8576 Minimal changes for `-Xcheckinit` compatibility

As explained in https://issues.scala-lang.org/browse/SI-8576, I expect
serialization compatibility between builds with and without
`-Xcheckinit` to be unattainable. This commit contains some minor fixes
for issues discovered while running builds with `-Xcheckinit`:

- Add `@SerialVersionUID` to `scala.collection.immutable.Vector`, as
  requested in SI-8576. Note that this does not make `Vector`
  serialization compatible.

- Use lazy initialization for `global` in `PresentationCompilation`. It
  used to access the uninitialized `self` variable (which seems to be
  inconsequential in practice and only fails under `-Xcheckinit`).

We should consider using `Externalizable` instead of `Serializable` for
collections in 2.13 to make collection classes serialization compatible.

1 files changed, 1 insertions, 0 deletions

diff --git a/src/library/scala/collection/immutable/Vector.scala b/src/library/scala/collection/immutable/Vector.scala
index 539ae9c387..d8c422c700 100644
--- a/src/library/scala/collection/immutable/Vector.scala
+++ b/src/library/scala/collection/immutable/Vector.scala
@@ -59,6 +59,7 @@ object Vector extends IndexedSeqFactory[Vector] {
  *  @define mayNotTerminateInf
  *  @define willNotTerminateInf
  */
+@SerialVersionUID(-1334388273712300479L)
 final class Vector[+A] private[immutable] (private[collection] val startIndex: Int, private[collection] val endIndex: Int, focus: Int)
 extends AbstractSeq[A]
    with IndexedSeq[A]