gistfile1.txt

scala> def addToFirst[T<:Int](x:Array[T]) = x(0) 
addToFirst: [T <: Int](x: Array[T])T

scala> addToFirst(Array(19))
res32: Int = 19
-------------------------------------------------------

scala> def addToFirst(x : Array[T] forSome {type T <: Integer}) = x(0)
addToFirst: (x: Array[_ <: Integer])Int

scala> addToFirst(Array(19))
res33: Int = 19
-----------------------------------

scala> def addToFirst[T<:Integer](x:Array[T]) = x(0) 
addToFirst: [T <: Integer](x: Array[T])T

scala> addToFirst(Array(19))
<console>:9: error: inferred type arguments [Int] do not conform to method addToFirst's type parameter bounds [T <: Integer]
              addToFirst(Array(19))
              ^
<console>:9: error: type mismatch;
 found   : Array[Int]
 required: Array[T]
              addToFirst(Array(19))
                              ^