SI-5954 Invalidate TypeRef cache when opening package object

I noticed that the pos/5954d was tripping a println "assertion".
This stemmed from an inconsistency between
`TypeRef#{parents, baseTypeSeq}` for a package objects compiled
from source that also has a class file from a previous compilation
run.

I've elevated the println to a devWarning, and changed
`updatePosFlags`, the home of this evil symbol overwriting,
to invalidate the caches in the symbols info. Yuck.

I believe that this symptom is peculiar to package objects because
of the way that the completer for packages calls `parents` during
the Namer phase for package objects, before we switch the symbol
to represent the package-object-from-source. But it seems prudent
to defensively invalidate the caches for any symbol that finds its
way into `updatePosFlags`.

1 files changed, 4 insertions, 0 deletions

diff --git a/src/reflect/scala/reflect/internal/Types.scala b/src/reflect/scala/reflect/internal/Types.scala
index 99e6ae633f..437b962abf 100644
--- a/src/reflect/scala/reflect/internal/Types.scala
+++ b/src/reflect/scala/reflect/internal/Types.scala
@@ -2218,6 +2218,10 @@ trait Types
         trivial = fromBoolean(!sym.isTypeParameter && pre.isTrivial && areTrivialTypes(args))
       toBoolean(trivial)
     }
+    private[scala] def invalidateCaches(): Unit = {
+      parentsPeriod = NoPeriod
+      baseTypeSeqPeriod = NoPeriod
+    }
     private[reflect] var parentsCache: List[Type]      = _
     private[reflect] var parentsPeriod                 = NoPeriod
     private[reflect] var baseTypeSeqCache: BaseTypeSeq = _