scala> implicit val f1: Int => String  = _ => "Int" ; implicit val f2: Long => String = _ => "Long"
f1: Int => String = <function1>
f2: Long => String = <function1>

scala> (5: String)
<console>:15: error: type mismatch;
 found   : Int(5)
 required: String
Note that implicit conversions are not applicable because they are ambiguous:
 both value f1 of type => Int => String
 and value f2 of type => Long => String
 are possible conversion functions from Int(5) to String
              (5: String)
               ^