Running code in your head is another issue that AI won't solve (yet); we had different people/scientists working on this; the most famous person there being Brett Victor, but also Jonathan Edwards [0] and Chris Granger (lighttable). I find the example in [0] the best; you are sitting there with your very logically weak brain trying to think wtf will this code do while there is a very powerful computer next to you that can tell you. But doesn't. And yet, we are mostly restricted to first think out the code to at least some extent before we can see it in action, same for the AI.

[0] https://vimeo.com/140738254