Fix missing known subtypes

Author: pikinier20

scaladoc/src/dotty/tools/scaladoc/tasty/ClassLikeSupport.scala

@@ -292,7 +292,10 @@ trait ClassLikeSupport:
     def getParentsAsTreeSymbolTuples: List[(Tree, Symbol)] =
       for
         parentTree <- c.parents if isValidPos(parentTree.pos)  // We assume here that order is correct
-        parentSymbol = if parentTree.symbol.isClassConstructor then parentTree.symbol.owner else parentTree.symbol
+        parentSymbol = parentTree match
+          case t: TypeTree => t.tpe.typeSymbol
+          case tree if tree.symbol.isClassConstructor => tree.symbol.owner
+          case tree => tree.symbol
         if parentSymbol != defn.ObjectClass && parentSymbol != defn.AnyClass
       yield (parentTree, parentSymbol)
 

scaladoc/src/dotty/tools/scaladoc/transformers/InheritanceInformationTransformer.scala

@@ -3,7 +3,7 @@ package transformers
 
 class InheritanceInformationTransformer(using DocContext) extends (Module => Module):
   override def apply(original: Module): Module =
-    val subtypes = getSupertypes(original.rootPackage).groupBy(_._1).transform((k, v) => v.map(_._2))
+    val subtypes = getSupertypes(original.rootPackage).groupMap(_(0))(_(1))
     original.updateMembers { m =>
       val edges = getEdges(m.asLink.copy(kind = bareClasslikeKind(m.kind)), subtypes)
       val st: Seq[LinkToType] = edges.map(_._1).distinct