Assume supertraits in stdlib

The idea is that some traits the 2.13 standard library should get annotated
with @superTrait. I added the annotations to our version in the community build.
Until that is done, we assume that the annotated traits are super traits by
adding them to the assumedSuperTraits set.

Author: odersky

compiler/src/dotty/tools/dotc/core/Definitions.scala

@@ -1306,7 +1306,17 @@ class Definitions {
     (sym eq Object_eq) || (sym eq Object_ne)
 
   @tu lazy val assumedSuperTraits =
-    Set(ComparableClass, ProductClass, SerializableClass)
+    Set(ComparableClass, ProductClass, SerializableClass,
+      ctx.requiredClass("scala.collection.SortedOps"),
+      ctx.requiredClass("scala.collection.StrictOptimizedSortedSetOps"),
+      ctx.requiredClass("scala.collection.generic.DefaultSerializable"),
+      ctx.requiredClass("scala.collection.generic.IsIterable"),
+      ctx.requiredClass("scala.collection.generic.IsIterableOnce"),
+      ctx.requiredClass("scala.collection.generic.IsMap"),
+      ctx.requiredClass("scala.collection.generic.IsSeq"),
+      ctx.requiredClass("scala.collection.generic.Subtractable"),
+      ctx.requiredClass("scala.collection.immutable.StrictOptimizedSeqOps")
+    )
 
   // ----- primitive value class machinery ------------------------------------------
 

tests/pos/listAndVector.scala

@@ -0,0 +1,3 @@
+var xs = Set(List(0), Vector(0))
+var ys: Set[collection.immutable.AbstractSeq[Int]] = xs
+