Janet's `break` does NOT return a value from a loop — `(break val)` in a `while` loop just exits, discarding val. To return from a loop, set a variable before break: `(do (set result val) (break))`. Hit us in phm-bucket-assoc where `(break nb)` silently returned nil instead of the new bucket. Fixed by capturing index before break and building the result array after the loop.
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Clojure .clj source files loaded via eval-form cannot have docstrings. If a defn form has 5 elements (defn, name, docstring, params, body), the evaluator's defn macro handler gets 4 args instead of 3, breaking with "macro arity mismatch". All .clj files in src/jolt/clojure/ must use 4-element defn forms: (defn name [params] body). Docstrings on defn are a Clojure feature not supported by Jolt's defn macro.
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PHM internal key leak: Core functions iterating over PHM maps with keys/pairs get internal metadata keys (:jolt/deftype, :cnt, :buckets, :_meta). Always check for set?/phm? first and use type-aware helpers (phm-to-struct, phs-seq, phm-keys, phm-entries) before generic iteration. Hit us in core-merge, core-reduce, core-every?, core-filter which all needed set?/phm? checks added.