Better doc comment

Author: odersky

src/dotty/annotation/internal/Child.scala

@@ -2,5 +2,14 @@ package dotty.annotation.internal
 
 import scala.annotation.Annotation
 
-/** An annotation to indicate a child class or object of the annotated class. */
+/** An annotation to indicate a child class or object of the annotated class.
+ *  E.g. if we have
+ *
+ *    sealed class A
+ *    case class B() extends A
+ *    case class C() extends A
+ *
+ *  Then `A` would carry the annotations `@Child[B] @Child[C]` where
+ *  `B`, `C` are TypeRefs.
+ */
 class Child[T] extends Annotation