Ah, but in this case you have already done the spec, otherwise the type system couldn't have checked it. With a more loose way of going about things, you don't

Ah, but in this case you have already done the spec, otherwise the type system couldn't have checked it. With a more loose way of going about things, you don't have to write the spec. Spec'ing is hard, sometimes harder than actually solving the problem. I feel like someone is going to point out that spec'ing is a lifesaver in a certain situation, and I would agree. But perhaps not all situations.