How to display all types of an object (in Scala)?

Question

With the isInstanceOf method, one can check the type of an object. For example:

scala> val i: Int = 5
i: Int = 5

scala> val a: Any = i
a: Any = 5

scala> a.isInstanceOf[Any]
res0: Boolean = true

scala> a.isInstanceOf[Int]
res1: Boolean = true

scala> a.isInstanceOf[String]
res2: Boolean = false

How can one display all types of an object (if it is possible at all ?) ?

Answer 1

You can do this pretty easily in 2.10 (M4 or later):

import scala.reflect.runtime.universe._

def superTypes(t: Type): Set[Type] =
  (t.parents ++ t.parents.flatMap(superTypes)).toSet

def allTypes[A](a: A)(implicit tag: TypeTag[A]) = superTypes(tag.tpe) + tag.tpe

Which gives us the following:

scala> allTypes(1).foreach(println)
AnyVal
Any
NotNull
Int

scala> allTypes("1").foreach(println)
String
Any
Object
Comparable[String]
CharSequence
java.io.Serializable

scala> allTypes(List("1")).foreach(println)
scala.collection.LinearSeq[String]
scala.collection.GenSeq[String]
scala.collection.IterableLike[String,List[String]]
scala.collection.GenIterable[String]
scala.collection.GenTraversableLike[String,Iterable[String]]
...

You'll have a much harder time trying to do anything like this pre-2.10.

Answer 2

Here's another solution, which makes use of the baseType method to reify the type parameter.

import scala.reflect.runtime.universe._

def typesOf[T : TypeTag](v: T): List[Type] =
  typeOf[T].baseClasses.map(typeOf[T].baseType)

Example:

scala> typesOf("1") foreach println
String
CharSequence
Comparable[String]
java.io.Serializable
Object
Any