fn now desugars destructuring params like Clojure's maybe-destructured: each
non-symbol param becomes a gensym and the body is wrapped in a let that rebinds the
pattern, so fn* only ever sees plain params and the COMPILER handles it (it rejected
patterns before, falling back to the interpreter). loop follows Clojure too: gensym
one loop var per binding, loop* over those, destructure via an inner let, with an
outer let so later inits see earlier destructured names — recur arity stays correct.
Two representation gotchas: build the param/binding vectors via [~@..] so they're
tuple forms (conj yields a pvec the analyzer rejects), and use (symbol (str
(gensym))) since a bare (gensym) in an overlay macro body is a Janet symbol the
destructurer rejects.
Closes the fn/loop destructuring gaps. conformance 228x3, fixpoint, clojure-test-
suite 3930, full suite green, bench flat.
ad84b2904f