class Opal::Rewriters::DeduplicateArgName

function $$funny_method_name(_, __$2)
compiler result:
leave the first appearance as it is and rename the other ones
funny_method_name(1, 2) => 1
Ruby assigns the value of the first arg given
but JavaScript in strict mode does not allow for args with the same name
end
puts _
def funny_method_name(_, _)
Ruby allows for args with the same name, if the arg starts with a ‘_’, like:

def on_args(node) 

def on_args(node)
  @arg_name_count = Hash.new(0)
  children = node.children.map do |arg|
    rename_arg(arg)
  end
  super(node.updated(nil, children))
end

def rename_arg(arg) 

def rename_arg(arg)
  case arg.type
  when :arg, :restarg, :kwarg, :kwrestarg, :blockarg
    name = arg.children[0]
    name ? arg.updated(nil, [unique_name(name)]) : arg
  when :optarg, :kwoptarg
    name, value = arg.children
    arg.updated(nil, [unique_name(name), value])
  when :mlhs
    new_children = arg.children.map { |child| rename_arg(child) }
    arg.updated(nil, new_children)
  else
    arg
  end
end

def unique_name(name) 

def unique_name(name)
  count = (@arg_name_count[name] += 1)
  count > 1 ? :"#{name}_$#{count}" : name
end