anchor.diff:          | TOKPAR statement_list TOKENDPAR
           | return_statement
           | rule_statement
  -        | TOKWHILE paren_expression
  -            (    group_statement
  -            |    VAR SEMICOLON
  -            )
  +        | TOKWHILE paren_expression ( group_statement | VAR SEMICOLON)
           | builtin_type declared_item ( COMMA declared_item )* SEMICOLON
           | expr<<[]>>
               [   ( declared_item ( COMMA declared_item )*
  
positive.code: ############################################################################
  
      rule method_declaration:
          TOKMETHOD 
          type_decl [ VAR ] [ formal_list [VAR] ]
          #( builtin_type VAR [ formal_list ]
          #| VAR [ VAR ] [ formal_list [ VAR ] ]
          #)
          ( ( TOKIF | TOKCLOCKED_BY | TOKRESET_BY | TOKENABLE | TOKREADY) paren_expression )*
          [ equal_value ]
          [ provisos_clause ] SEMICOLON
  
negative.code:         TOKENDCASE
  
      rule let_statement:
          TOKLET ( VAR | LBRACE VAR (COMMA VAR)* RBRACE) assign_opvalue SEMICOLON
  
      rule rule_statement:
          TOKRULE VAR [paren_expression] SEMICOLON
  