================================================================================
Empty
================================================================================
CREATE FUNCTION FOO () AS $$ $$ LANGUAGE sql;
--------------------------------------------------------------------------------

(source_file
  (create_function_statement
    (function_signature
      (identifier)
      (function_parameters))
    (block
      (dollar_quote)
      (dollar_quote))
    (identifier)))

================================================================================
With argument
================================================================================
CREATE FUNCTION FOO (_foo bar.baz) AS $$ $$ LANGUAGE sql;
--------------------------------------------------------------------------------

(source_file
  (create_function_statement
    (function_signature
      (identifier)
      (function_parameters
        (function_parameter
          (identifier)
          (identifier))))
    (block
      (dollar_quote)
      (dollar_quote))
    (identifier)))

================================================================================
With arguments
================================================================================
CREATE FUNCTION FOO (foo bar, foo bar) AS $$ $$ LANGUAGE sql;
--------------------------------------------------------------------------------

(source_file
  (create_function_statement
    (function_signature
      (identifier)
      (function_parameters
        (function_parameter
          (identifier)
          (identifier))
        (function_parameter
          (identifier)
          (identifier))))
    (block
      (dollar_quote)
      (dollar_quote))
    (identifier)))

================================================================================
Wrong - trailing comma (1)
================================================================================
CREATE FUNCTION FOO (foo bar,) AS $$ $$ LANGUAGE sql;
--------------------------------------------------------------------------------

(source_file
  (create_function_statement
    (function_signature
      (identifier)
      (function_parameters
        (function_parameter
          (identifier)
          (identifier))
        (ERROR)))
    (block
      (dollar_quote)
      (dollar_quote))
    (identifier)))

================================================================================
Wrong - trailing comma (2)
================================================================================
CREATE FUNCTION FOO (foo bar, foo bar,) AS $$ $$ LANGUAGE sql;
--------------------------------------------------------------------------------

(source_file
  (create_function_statement
    (function_signature
      (identifier)
      (function_parameters
        (function_parameter
          (identifier)
          (identifier))
        (function_parameter
          (identifier)
          (identifier))
        (ERROR)))
    (block
      (dollar_quote)
      (dollar_quote))
    (identifier)))

================================================================================
Wrong - missing type
================================================================================
CREATE FUNCTION FOO (foo,) AS $$ $$ LANGUAGE sql;
--------------------------------------------------------------------------------

(source_file
  (create_function_statement
    (function_signature
      (identifier)
      (function_parameters
        (ERROR
          (identifier))))
    (block
      (dollar_quote)
      (dollar_quote))
    (identifier)))

================================================================================
arrays
================================================================================
CREATE FUNCTION FOO (foo bar[], foo bar[][]) AS $$ $$ LANGUAGE sql;
--------------------------------------------------------------------------------

(source_file
  (create_function_statement
    (function_signature
      (identifier)
      (function_parameters
        (function_parameter
          (identifier)
          (identifier))
        (function_parameter
          (identifier)
          (identifier))))
    (block
      (dollar_quote)
      (dollar_quote))
    (identifier)))