Q18 feedback : Make the closure more obvious

[Mazwak]

I was puzzled with the first line in the program.
Even with my ruby background, I had to search a little, and found it in cheat.rs.

You might want to make the closure more obvious, since it is not the subject of the quizz.

[dtolnay]

Thanks for the feedback. I would prefer to keep this question as is. There are going to be many things required to know to answer each question correctly.