Fxing cyclic references during findMember

1) Classes and alias type now take precedence over abstract types.
2) When computing members, parents are visited right to left, which corresponds to existing taking precedence
    over new in mergeDenot.

1 files changed, 10 insertions, 12 deletions

diff --git a/src/dotty/tools/dotc/core/SymDenotations.scala b/src/dotty/tools/dotc/core/SymDenotations.scala
index 3f0ad171a..1d806edc1 100644
--- a/src/dotty/tools/dotc/core/SymDenotations.scala
+++ b/src/dotty/tools/dotc/core/SymDenotations.scala
@@ -825,24 +825,22 @@ object SymDenotations {
           println(s"$this.member($name), ownDenots = $ownDenots")
         def collect(denots: PreDenotation, parents: List[TypeRef]): PreDenotation = parents match {
           case p :: ps =>
-            val denots1 = p.symbol.denot match {
+            val denots1 = collect(denots, ps)
+            p.symbol.denot match {
               case parentd: ClassDenotation =>
                 if (debugTrace) {  // DEBUG
                   val s1 = parentd.membersNamed(name)
                   val s2 = s1.filterExcluded(Private)
-                  val s3 = s2.asSeenFrom(thisType)
-                  val s4 = s3.filterDisjoint(ownDenots)
-                  println(s"$this.member($name) $s1 $s2 $s3 $s4")
+                  val s3 = s2.disjointAsSeenFrom(ownDenots, thisType)
+                  println(s"$this.member($name) $s1 $s2 $s3")
                 }
-                denots union
+                denots1 union
                   parentd.membersNamed(name)
                     .filterExcluded(Private)
-                    .asSeenFrom(thisType)
-                    .filterDisjoint(ownDenots)
+                    .disjointAsSeenFrom(ownDenots, thisType)
               case _ =>
-                denots
+                denots1
             }
-            collect(denots1, ps)
           case _ =>
             denots
         }
@@ -895,7 +893,7 @@ object SymDenotations {
           NoType
       }
 
-      ctx.traceIndented(s"$tp.baseType($this)") {
+      ctx.traceIndented(s"$tp.baseType($this) ${tp.typeSymbol.fullName} ${this.fullName}") {
         if (symbol.isStatic) symbol.typeConstructor
         else tp match {
           case tp: CachedType =>
@@ -905,10 +903,10 @@ object SymDenotations {
             }
             var basetp = baseTypeCache get tp
             if (basetp == null) {
-              baseTypeCache.put(tp, NoType)
+              baseTypeCache.put(tp, NoPrefix)
               basetp = computeBaseTypeOf(tp)
               baseTypeCache.put(tp, basetp)
-            } else if (basetp == NoType) {
+            } else if (basetp == NoPrefix) {
               throw new CyclicReference(symbol)
             }
             basetp