int foo(ref x)
  a = 5
end

foo( 3 )
-- -- --
s(:expressions, 
  s(:function,  :int, 
    s(:name,  :foo), 
    s(:parameters, 
      s(:field,  :ref,  :x)), 
    s(:expressions, 
      s(:assign, 
        s(:name,  :a), 
        s(:int,  5)))), 
  s(:call, 
    s(:name,  :foo), 
    s(:arguments, 
      s(:int,  3))))