This kind of programmatic transformation is believed to be easier with statically typed languages. It's interesting to see how this folks identified patterns to effectively figure out the types of the specific bit of the code.

I guess "good code" in the dynamic language tends to have this kind of uniformity / unsurprising nature which helps navigate the code without the type's help. On the other hand, code in statically typed languages tends to gets smarter on types to make it shorter, sometimes ending up hard-to-read (or at least glance) lines.

I don't say which is worse, but this is good counterexample against still-widely-believed idea that dynamically typed languages lead shorter code while statically typed languages have longer (verbose) code.