I like to refer to code that has been overly injected with syntactic sugar as "caramelized". We need more culinary metaphors for programming jargon!
However, I wouldn't define bruijn as being caramelized just yet. Personally, I view as syntactic sugar only syntax that's expanded to the target language by the parser/compiler. In bruijn's case, there is barely any of such syntax sugar aside of number/string/char encodings. Everything else is part of the infix/prefix/mixfix standard library definitions which get substituted as part of the translation to LC.
Is there any hope for a "hashlife" style cache for a TC language? My understanding is that hashlife exploits spatial locality / "causation speed" in GoL, which isn't available in LC because of beta reduction. Thoughts?
There's also graph encodings like interaction nets, which have entirely local reduction behavior. Compared to de Bruijn indices, bindings are represented by edges, which makes them more applicable to hash consing. I once spent some time trying to add this kind of memoization but there are some further challenges involved, unfortunately.
Maybe it's a soufflé? Highly unstable, but occasionally very nice.