Make TypeAccumulators follow LazyRefs

TypeMaps do the same, so it is logical, and helps
prevent subtle errors as when we mispredicted whether
a RecType contains references that point to it.

Author: odersky

src/dotty/tools/dotc/core/Types.scala

@@ -3708,6 +3708,9 @@ object Types {
       case tp: JavaArrayType =>
         this(x, tp.elemType)
 
+      case tp: LazyRef =>
+        this(x, tp.ref)
+
       case tp: ProtoType =>
         tp.fold(x, this)