Scala - strange compile error (multiple overloaded alternatives of a method define default arguments)

Question

In Scala IDE I get the following error about the class I am to compile:

in object MapArea, multiple overloaded alternatives of method addAnim define default arguments.

So yes, They do! So what? I do not understand the philosophy of this...

UPDATE:

It turns out that there could be a situation where compiler can't know which method to choose (as pointed out by Tomasz Nurkiewicz), ok I understand.. but in my situation these two methods can clearly be distinguished. Here is the exact piece of code (with all original names and stuff preserved this time):

  def addAnim (name: String, x: Float, y: Float, tex: Buffer[Texture], fps: Int, percent: Float = 0): TImageSequence =
    addAnim (name, x, y, tex(0).getImage.getWidth, tex(0).getImage.getHeight, tex, fps, percent)

  def addAnim (name: String, x: Float, y: Float, w: Float, h: Float, tex: Buffer[Texture], fps: Int, percent: Float = 0): TImageSequence = {
     // do stuff
  }

Answer 1

It isn't possible to have two methods with default parameters and with the same name. Scala generates methods to obtain default values with names based on target method's name, so some sort of name collision may occur.

scala> object Test {
     |   def m(i: String = "Default value") {}
     | }
defined module Test

scala> Test.`m$default$1`
res0: String = Default value

Answer 2

You are not showing your code, but here is a simple example:

object C {
  def addAnim(x: Int = 42) {}
  def addAnim(y: String = "abc") {}
}

If I now call:

C.addAnim()

which method should be invoked? The object C won't compile because the compiler is not capable of guessing which addAnim method do you mean when not providing any argument.

Answer 3

Why not combine both methods in one by making w and h optional as well, e.g.

def addAnim (name: String, 
    x: Float, y: Float, 
    tex: Buffer[Texture], 
    fps: Int, 
    percent: Float = 0, 
    w: Float = Float.NaN, h:Float = Float.NaN): TImageSequence