================================================================================
wrong - trailing comma (1)
================================================================================
CREATE FUNCTION FOO (foo bar,) RETURNS void AS 'select' LANGUAGE sql;
--------------------------------------------------------------------------------

(source_file
  (create_function_statement
    (function_signature
      (identifier)
      (function_parameters
        (var_declaration
          (identifier)
          (identifier))
        (ERROR)))
    (function_return
      (identifier))
    (string)
    (identifier)))

================================================================================
wrong - trailing comma (2)
================================================================================
CREATE FUNCTION FOO (foo bar, foo bar,) RETURNS void AS 'select' LANGUAGE sql;
--------------------------------------------------------------------------------

(source_file
  (create_function_statement
    (function_signature
      (identifier)
      (function_parameters
        (var_declaration
          (identifier)
          (identifier))
        (var_declaration
          (identifier)
          (identifier))
        (ERROR)))
    (function_return
      (identifier))
    (string)
    (identifier)))

================================================================================
wrong - missing type
================================================================================
CREATE FUNCTION FOO (foo,) RETURNS void AS 'select' LANGUAGE sql;
--------------------------------------------------------------------------------

(source_file
  (create_function_statement
    (function_signature
      (identifier)
      (function_parameters
        (ERROR
          (identifier))))
    (function_return
      (identifier))
    (string)
    (identifier)))

================================================================================
wrong - many volatilities
================================================================================
CREATE FUNCTION FOO () RETURNS void AS 'select' LANGUAGE sql STABLE VOLATILE;
--------------------------------------------------------------------------------

(source_file
  (create_function_statement
    (function_signature
      (identifier)
      (function_parameters))
    (function_return
      (identifier))
    (string)
    (identifier)
    (function_volatility))
  (ERROR))