Proposal of new design of async

async.t

task do_a(n: int32): int32 { ... }
task do_b(n: int32): int32 { ... }

task test(target: Domain): void
{
    do_a(1); // call do_a
    do_b(2); // call do_b

    16: do_a(1); // call do_a with 16 times
    16: do_b(2); // call do_b with 16 times

    -> do_a(1); // async call do_a
    -> do_b(2); // async call do_b

    -> 16: do_a(1); // async call do_a with 16 times
    -> 16: do_b(2); // async call do_b with 16 times

    -> { var i = 0; do_a(i + 1); } // async call piece of code
    -> { var i = 0; do_b(i + 2); } // async call piece of code

    -> 16: { var i = 0; do_a(i + 1); } // async call piece of code with 16 times
    -> 16: { var i = 0; do_b(i + 2); } // async call piece of code with 16 times

    on target: do_a(1); // ERROR, waiting for remote invocation is not allowed.
    on target: do_b(1); // ERROR, waiting for remote invocation is not allowed.

    on target, 16: do_a(1); // ERROR, waiting for remote invocation is not allowed.
    on target, 16: do_b(1); // ERROR, waiting for remote invocation is not allowed.

    -> on target: do_a(1); // async call do_a on target
    -> on target: do_b(1); // async call do_b on target

    -> on target, 16: do_a(1); // async call do_a on target with 16 times
    -> on target, 16: do_b(1); // async call do_a on target with 16 times
}