anchor.diff:          typevar_item
           | TOKINTEGER | TOKBOOL | TOKSTRING | TOKREAL | TOKNAT | TOKACTION
   
  -    rule function_return_type:
  -        ( TOKACTION VAR [call_params]
  -        | TOKACTIONVALUE
  -        | typevar_item_or_var
  -        )
  -
  -    rule Type_nitem:
  -        Type_item
  -        | VAR [ LBRACKET NUM (COLON NUM)* RBRACKET ]
  -        | CLASSVAR function_return_type
  -
       rule param_item:
           (   LPAREN param_item RPAREN
           |   ( [ TOKNUMERIC | TOKPARAMETER ] TOKTYPE VAR
  -            | argument_item
  +            | formal_item
               | NUM
               | STR
               )
  
positive.code: 
      rule method_declaration:
          TOKMETHOD 
          ( (TOKACTIONVALUE | Type_item) VAR [ argument_list ]
          | VAR [ VAR ] [ argument_list [ VAR ] ]
          )
          #| [ output_port ] VAR
          #    LPAREN LBRACE input_ports RBRACE RPAREN
  
negative.code:         | TOKBDPI [ VAR  EQUAL ]
              TOKFUNCTION typevar_item_or_var
              function_name
              formal_list
              [ provisos_clause ] SEMICOLON
          | TOKBVI [ VAR [ EQUAL ] ]
              TOKMODULE typevar_item_or_var
              [ formal_list ]
              [ provisos_clause ] SEMICOLON
              (   method_declaration
              |   TOKPARAMETER VAR  EQUAL expr<<[]>> SEMICOLON
  