Any.Def.Contains

trait Contains[-CONTAINER, A]

A given Any.Def.Contains instance for a specific type determines if universal method "in" can be applied.

 val range = 1 <> 10

 if(5 in range) "is in".tp

 if("CD" in "ABCDEF") ()
 // same as
 if("ABCDEF".contains("CD")) ()

Any.Def.Contains is defined for most known types and can be defined for new ones.

Source
Contains.scala
class java.lang.Object
trait scala.Matchable
class Any

Def

def contains(c: Any.Def.Contains.CONTAINER, v: A): Boolean