EDIT: to make it even more obvious there's no difference:

    class Fire{}
    class Water {}
    class Grass {}
    class Ice {}
    
    def eff(Fire f, Grass g) { 'burn' }
    def eff(Fire f, Ice ice) { 'melt' }
    def eff(Water w, Grass g) { 'grow' }
    def eff(Water w, Ice ice) { 'freeze' }
    def eff(a, b) { 'undefined' }
    
    // hide compile-time types
    Object fire = new Fire()
    Object grass = new Grass()
    Object ice = new Ice()
    Object water = new Water()
    
    println eff(fire, grass)
    println eff(fire, ice)
    println eff(water, grass)
    println eff(water, ice)
    
    println eff(ice, water)

    burn
    melt
    grow
    freeze
    undefined