On the other hand, I can't count how many times I've written some code like

    let iteration_1_id = 10;
    dostuff(iteration_1_id);
    let iteration_2_id = 11; // warning, unused variable!!
    dostuff(iteration_1_id);

and then spent 10 minutes debugging why iteration_2 wasn't working, when it would have been resolved instantly if I had paid attention to the warnings.