effect A {
    fun a() -> Unit;
}

effect B {
    fun b() -> Unit;
}

pub fun main() ! Io -> Unit {
    try {
        A.a!();

        try {
            A.a!();

            try {
                B.b!();
            } handle B {
                fun b() {
                    print!("b start\n");
                    A.a!();
                    print!("b end\n");
                    resume;
                }
            }

            A.a!();
        } handle A {
            fun a() {
                print!("a inner start\n");
                A.a!();
                print!("a inner end\n");
                resume;
            }
        }

        A.a!();
    } handle A {
        fun a() {
            print!("a outer\n");
            resume;
        }
    }
}