Avoid comparing RefinementClassSymbols with isSubClass in RefChecks

RefinementClassSymbols are created ad hoc for types in asSeenFrom, two
symbols with the same parents don't compare `isSubClass`.

Author: lrytz

src/compiler/scala/tools/nsc/typechecker/RefChecks.scala

@@ -97,11 +97,17 @@ abstract class RefChecks extends Transform {
     private val checkedCombinations = mutable.Map[List[Symbol], (Symbol, Type)]()
     private def notYetCheckedOrAdd(rt: RefinedType, currentBase: Symbol) = {
       val seen = checkedCombinations.get(rt.parents.map(_.typeSymbol)).exists {
-        case (prevBase, prevTp) => currentBase.isSubClass(prevBase) && rt =:= prevTp.asSeenFrom(currentBase.thisType, prevBase)
+        case (prevBase, prevTp) =>
+          val isSub = (currentBase, prevBase) match {
+            case (cRef: RefinementClassSymbol, pRef: RefinementClassSymbol) =>
+              cRef.info.parents.map(_.typeSymbol) == pRef.info.parents.map(_.typeSymbol)
+            case _ =>
+              currentBase.isSubClass(prevBase)
+          }
+          val sameTp = rt =:= prevTp.asSeenFrom(currentBase.thisType, prevBase)
+          isSub && sameTp
       }
-
       if (!seen) checkedCombinations.addOne((rt.parents.map(_.typeSymbol), (currentBase, rt)))
-
       !seen
     }
 

test/files/pos/t13013.scala

@@ -0,0 +1,9 @@
+object Node {
+  trait Root { self: Node =>
+    val root = this
+  }
+}
+trait Node {
+  def root: Node
+}
+final class RootNode extends Node with Node.Root