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, 1 insertions, 1 deletions

diff --git a/src/compiler/scala/tools/nsc/typechecker/RefChecks.scala b/src/compiler/scala/tools/nsc/typechecker/RefChecks.scala
index 95f2620061..f5893172e8 100644
--- a/src/compiler/scala/tools/nsc/typechecker/RefChecks.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/RefChecks.scala
@@ -857,7 +857,7 @@ abstract class RefChecks extends InfoTransform with scala.reflect.internal.trans
         val baseClass = clazz.info.baseTypeSeq(i).typeSymbol
         seenTypes(i) match {
           case Nil =>
-            println("??? base "+baseClass+" not found in basetypes of "+clazz)
+            devWarning(s"base $baseClass not found in basetypes of $clazz. This might indicate incorrect caching of TypeRef#parents.")
           case _ :: Nil =>
             ;// OK
           case tp1 :: tp2 :: _ =>