Title: The name of the function with its arity increased by one already exists in the module
Goal: Generalize the function `double/1' by selecting the number `2', the new parameter is `N'.
Parameters: [{file,"gen4.erl"},{posrange,{60,60}},{varname,"N"}].
Documentation: The result of the transformation would be a the function `double/2', but it is already declared in the module, so the name collision makes the refactoring invalid.
