anchor.diff:              )
           ]
   
  -    rule interface_body:
  -        ( method_declaration
  -        | TOKINTERFACE
  -            ( typevar_item VAR SEMICOLON
  -            | VAR ( equal_value SEMICOLON
  -                  | VAR ( equal_value SEMICOLON
  -                        | SEMICOLON [ method_declaration+ TOKENDINTERFACE [ COLON VAR ] ]
  -                        )
  -                  )
  -            )
  -        )+
  -
       rule interface_declaration:
           TOKINTERFACE CLASSVAR*
           typevar_item_or_var [ VAR ]
               ( equal_value
  -            | [ SEMICOLON ] [ interface_body ] TOKENDINTERFACE [ COLON VAR ]
  -            )
  -
  -    rule function_declaration:
  -        TOKFUNCTION [ Type_list ]
  -        [function_name]
  -        [ formal_list ]
  -        [ provisos_clause ]
  -        ( equal_value SEMICOLON
  -        | SEMICOLON [ ( single_statement)+ TOKENDFUNCTION [ COLON  function_name] ]
  -        )
  +            | [ SEMICOLON ]
  +                ( method_declaration
  +                | TOKINTERFACE
  +                    ( typevar_item VAR SEMICOLON
  +                    | VAR ( equal_value SEMICOLON
  +                          | VAR ( equal_value SEMICOLON
  +                                | SEMICOLON [ method_declaration+ TOKENDINTERFACE [ COLON VAR ] ]
  +                                )
  +                          )
  +                    )
  +                )*
  +                TOKENDINTERFACE [ COLON VAR ]
  +            )
   
       rule import_arg:
           ( VAR | var_list )
  
positive.code:         | TOKMATCH ( TOKTAGGED VAR dot_field_list | match_brace ) assign_opvalue SEMICOLON
          | TOKPAR statement_list TOKENDPAR
          | TOKRETURN assign_rvalue SEMICOLON
          | TOKWHILE paren_expression ( statement_with_value | VAR SEMICOLON)
          | statement_with_value
  
      rule single_statement:
            function_declaration
          | let_statement
          | rule_statement
          | single_statement_not_decl
  
      rule statement_list:
          ( single_statement )*
  
negative.code:     rule declared_item:
          term<<[]>> [ assign_opvalue ]
  
      rule rule_statement:
          TOKRULE VAR [paren_expression] SEMICOLON
          statement_list
  