================================================================================
basic
================================================================================
drop function foo(bigint, text);
--------------------------------------------------------------------------------

(source_file
  (drop_function_statement
    (drop_function_item
      (identifier)
      (identifier)
      (identifier))))

================================================================================
many at once
================================================================================
drop function foo(bigint, text), foo(bigint);
--------------------------------------------------------------------------------

(source_file
  (drop_function_statement
    (drop_function_item
      (identifier)
      (identifier)
      (identifier))
    (drop_function_item
      (identifier)
      (identifier))))

================================================================================
without args
================================================================================
drop function foo;
--------------------------------------------------------------------------------

(source_file
  (drop_function_statement
    (drop_function_item
      (identifier))))

================================================================================
with no args
================================================================================
drop function foo();
--------------------------------------------------------------------------------

(source_file
  (drop_function_statement
    (drop_function_item
      (identifier))))

================================================================================
cascade
================================================================================
drop function foo(bigint) cascade;
--------------------------------------------------------------------------------

(source_file
  (drop_function_statement
    (drop_function_item
      (identifier)
      (identifier))))

================================================================================
restrict
================================================================================
drop function foo(bigint) restrict;
--------------------------------------------------------------------------------

(source_file
  (drop_function_statement
    (drop_function_item
      (identifier)
      (identifier))))

================================================================================
if exists
================================================================================
drop function if exists foo();
--------------------------------------------------------------------------------

(source_file
  (drop_function_statement
    (drop_function_item
      (if_exists)
      (identifier))))

================================================================================
with argnames
================================================================================
drop function if exists foo(bar text, bigint);
--------------------------------------------------------------------------------

(source_file
  (drop_function_statement
    (drop_function_item
      (if_exists)
      (identifier)
      (var_declaration
        (identifier)
        (identifier))
      (identifier))))