anchor.diff:          | TOKRULES [ COLON  VAR]
               ( rule_statement)*
               TOKENDRULES [ COLON  VAR]
  -        | TOKFUNCTION function_argument
  +        | function_parameter
           | function_operator [expr<<[]>>]
           | expr<<[]>> ( LEQ expr<<[]>> )* [expr<<[]>>]
           | QUESTION
  
positive.code:         TOKMATCH
          match_brace
          ( EQUAL | LARROW ) assign_value SEMICOLON
  
      rule module_param:
          Type_nitem [ VAR | STAR ]
  
      rule module_declaration:
          TOKMODULE [ LBRACKET assign_value RBRACKET ] typevar_item_or_var
  
negative.code:         VAR | function_operator
  
      rule import_arg:
          ( VAR | var_list )
  
      rule var_list:
          LPAREN [VAR (COMMA VAR)*] RPAREN
  
      rule provisos_clause:
          TOKPROVISOS param_list
  