class Main{
    main():Int { while a loop a pool };
    main():Int { while {a;a;} loop a pool };
    main():Int { while while a loop a pool loop a pool };
    main():Int { while if a then b else c fi loop a pool };
-------------------------------------
    main():Int { while  loop a pool }; --missing expr after while
    main():Int { while  a loop  pool }; --missing expr after loop
    main():Int { while   loop  pool }; --missing both exprs
    main():Int { while  pool }; --missing many things!
    main():Int { while a loop a }; --missing pool
    main():Int { a loop a pool }; --missing while
    main():Int { while {a a} loop a pool }; --wrong expr
    main():Int { while {a, a} loop a pool }; --wrong expr
    main():Int { while while a loop a loop a pool }; --missing pool
    main():Int { while a loop a loop a pool }; --missing pool
    main():Int { while while a a loop a pool }; --incorrect nesting
    main():Int { while if a then b else c loop a pool }; --incorrect construct
};