Fix #2396: don't create refernces to packages in ElimStaticThis.

compiler/src/dotty/tools/dotc/transform/ElimStaticThis.scala

@@ -27,10 +27,10 @@ class ElimStaticThis extends MiniPhaseTransform {
   override def transformIdent(tree: tpd.Ident)(implicit ctx: Context, info: TransformerInfo): tpd.Tree = {
     if (ctx.owner.enclosingMethod.is(JavaStatic)) {
       tree.tpe match {
-        case TermRef(thiz: ThisType, _) if thiz.cls.is(ModuleClass) =>
+        case TermRef(thiz: ThisType, _) if thiz.cls.is(ModuleClass, JavaDefined) =>
           ref(thiz.cls.sourceModule).select(tree.symbol)
         case TermRef(thiz: ThisType, _) =>
-          assert(tree.symbol.is(Flags.JavaStatic))
+          assert(tree.symbol.is(Flags.JavaStatic) || thiz.cls.is(JavaDefined))
           tree
         case _ => tree
       }

tests/run/i2396.scala

@@ -0,0 +1,15 @@
+class B {
+  val buzz = Some(Bees.Bee("buzz")).collect {
+    case Bees.Bee(value) => value
+  }
+}
+
+object Test {
+  def main(args: Array[String]): Unit = {
+    new B
+  }
+}
+
+object Bees {
+  case class Bee(value: String)
+}

tests/run/i2396c.scala

@@ -0,0 +1,15 @@
+class Bees {
+  import Test._
+
+  def f: PartialFunction[Bee, Unit] = {
+     case Test.Bee(_) => ""
+ //    case Bee(_) => ""  // This one works
+  }
+
+  f(new Bee("buzz"))
+}
+
+object Test {
+  case class Bee(value: String)
+  def main(args: Array[String]): Unit = new Bees
+}