5 lines
1.3 KiB
Markdown
5 lines
1.3 KiB
Markdown
Janet structs silently omit entries with nil values: `(struct ;[:x nil :y 1])` → `{:y 1}`. The `:x` key is completely dropped from the struct, not just set to nil. Use `@{}` (mutable table) when map needs nil-valued entries. This caused the `&env` implicit binding to fail — `(put new-bindings "&env" {'ns nil})` created a struct that became empty `{}`, so `(:ns &env)` failed with unknown method. Fix: use `@{}` table for bindings that may contain nil values, or use a non-nil sentinel.
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Janet `(put table key nil)` silently drops the key — it's a no-op, not a way to store nil. This is SEPARATE from struct-nil-drop: even mutable `@{}` tables drop nil values on `put`. The `bind-put` helper in evaluator.janet stores nil as `:jolt/nil` sentinel; `resolve-sym` unwraps it back to `nil`. All binding `put` calls in `fn*`, `let*`, `loop*`, macro bodies, and `deftype` reify MUST use `bind-put`, not raw `put`.
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Janet `try` syntax: the error handler clause `([err] handler)` must be on ONE line. Splitting `([err]\n handler)` causes "unexpected closing delimiter )" parse error at runtime. This is a Janet parser limitation, not a Jolt issue. Fix: always write `(try body ([err] handler-body))` on one line, or use `(do ...)` for multi-line handlers: `(try body ([err] (do ...)))`.
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