Passing a parameterized function in scala [duplicate]

I am writing a parameterized merge sort functionality and passing the less checker as a function. However, the compiler is throwing following error.

type mismatch;
 found   : y.type (with underlying type T)
 required: T

Here is my full code

def mergeSort[T] (list:List[T], pred:(T,T) =>Boolean):List[T]={
  def merge[T](left:List[T], right:List[T], acc:List[T]):List[T] = (left,right) match{
    case (Nil,_) => acc ++ right
    case (_,Nil) => acc ++ left
    case (x::xs, y::ys) => if(pred(y,x)) merge(left,ys,acc :+ y) else merge(xs,right,acc :+ x)
  }
  val m = list.length/2
  if (m == 0) list
  else {
   val (l,r) = list splitAt m
   merge(mergeSort(l,pred), mergeSort(r,pred), List())
  }
}

The problem is at line

if(pred(y,x))

Everything seems logically correct, can't figure out why this is happening? help appreciated.