RCR 275: Allow instance variables as method parameters

Allow syntax like...

  class Foo
    def current_style( a, b, c)
      @a = somefunc( a, b)
      @b = b
      @@c = c
    end
    def proposed_style( a, @b, @@c)
       @a = somefunc(a, @b)
    end
  end
  foo = Foo.new
  foo.proposed_style( 1, 2, 3)
  Results in foo.b == 2 and Foo.c == 3

Very often method parameters (especially those of "def initialize" are assigned to @instance variables. As a short cut, you should be able to put the @instance variable as an argument name meaning that it is instantly assigned on entry.

If a variable name with an instance '@' or class variable '@@' sigil appears in the formal arguments of a method, the semantics equivalent to assignment to that @instance of @@class variable.

It would require a syntax change.