Note that in chapter 3.8.1 he writes "As you can imagine, implementing [closures] adds some complexity because we can no longer assume variable scope works stri

Note that in chapter 3.8.1 he writes "As you can imagine, implementing [closures] adds some complexity because we can no longer assume variable scope works strictly like a stack where local variables evaporate the moment the function returns. We’re going to have a fun time learning how to make these work and do so efficiently."