core: wrap macro expanders in fn (not fn*) so destructured arglists compile

Follow-up to the staged macro-compile change. The macro-recompile pass
wrapped each expander in the raw fn* primitive, which punts on a
destructuring rest param — so if-not/if-let/if-some/assert (using the
canonical '& [else]') couldn't compile and had been rewritten to plain
rest params as a workaround.

Root cause: fn* is the primitive; the fn MACRO is what desugars
destructuring (rest, map, nested) into the body before lowering. Wrapping
expanders in fn instead of fn* compiles any destructured macro arglist
uniformly, so the workaround is unnecessary — reverted those 4 macros to
the canonical '& [else]' forms.

Net: rest-destructuring is fully compiled for all normal code (fn/defn/
let/macro params). Only the hand-written raw fn* primitive still punts
(jolt-f79, downgraded to P4 — falls back to interpreter, still correct).

47/47 overlay macros compiled. Gate green: conformance 267x3,
fallback-zero 31/5, bootstrap-fixpoint stage1==2==3, self-host,
staged-bootstrap, lazy-infinite 44/44, clojure-test-suite >=4034/67,
sci-bootstrap, features, all unit+spec.

jolt-core/clojure/core/30-macros.clj

@@ -12,27 +12,25 @@
 
 (defmacro comment [& body] nil)
 
-;; Single arglist (Jolt defmacro is single-arity); the optional else is the head of
-;; a plain rest param — (first else) is the else form or nil. (A `& [else]`-style
-;; rest-destructure reads the same but the analyzer can't yet compile destructuring
-;; in a rest param, which would force this expander to stay interpreted — jolt-f79.)
-(defmacro if-not [test then & else]
-  `(if (not ~test) ~then ~(first else)))
+;; Single arglist (Jolt defmacro is single-arity); the optional else defaults nil
+;; via rest-destructuring.
+(defmacro if-not [test then & [else]]
+  `(if (not ~test) ~then ~else))
 
 ;; Conditional binding macros: the name is bound ONLY in the taken branch (the
 ;; auto-gensym temp# tests the value; the else/empty branch sees the surrounding
 ;; scope). temp# is a single template-local gensym — referenced twice, same symbol.
-(defmacro if-let [bindings then & else]
+(defmacro if-let [bindings then & [else]]
   (let [form (bindings 0) tst (bindings 1)]
     `(let [temp# ~tst]
-       (if temp# (let [~form temp#] ~then) ~(first else)))))
+       (if temp# (let [~form temp#] ~then) ~else))))
 
 ;; when-let lives in 00-syntax (not here): 20-coll uses it, which loads before this tier.
 
-(defmacro if-some [bindings then & else]
+(defmacro if-some [bindings then & [else]]
   (let [form (bindings 0) tst (bindings 1)]
     `(let [temp# ~tst]
-       (if (some? temp#) (let [~form temp#] ~then) ~(first else)))))
+       (if (some? temp#) (let [~form temp#] ~then) ~else))))
 
 (defmacro when-some [bindings & body]
   (let [form (bindings 0) tst (bindings 1)]
@@ -93,9 +91,8 @@
                    (partition 2 clauses))]
     `(let [~g ~expr ~@(thread-binds g steps)] ~(if (empty? steps) g (last steps)))))
 
-(defmacro assert [x & message]
-  (let [m (first message)
-        msg (if m m (str "Assert failed: " (pr-str x)))]
+(defmacro assert [x & [message]]
+  (let [msg (if message message (str "Assert failed: " (pr-str x)))]
     `(when-not ~x (throw (ex-info ~msg {})))))
 
 (defmacro delay [& body]

src/jolt/api.janet

@@ -14,18 +14,21 @@
 (import ./stdlib_embed :as stdlib-embed)
 (import ./host_iface :as host)
 
-# A defmacro expander compiles to a native fn (built as (fn* args body...) and run
+# A defmacro expander compiles to a native fn (built as (fn args body...) and run
 # through the self-hosted pipeline) so macro expansion is COMPILED code, zero runtime
 # cost — instead of an interpreted closure, mirroring Clojure (macros are ordinary
-# compiled fns). Returns nil when the analyzer isn't built yet (the early macros,
-# expanded WHILE the analyzer is being bootstrapped) or the body isn't compilable; in
-# that case defmacro keeps an interpreted closure, and backend/recompile-macros!
-# replaces it with a compiled expander once the analyzer comes alive (staged
-# bootstrap — the interpreter is a build-time crutch, gone by steady state).
+# compiled fns). Wrapped in the `fn` MACRO (not the `fn*` primitive) so a destructured
+# macro arglist — `[a & [b]]`, `[& {:keys [x]}]`, nested — desugars before lowering;
+# raw fn* punts on a destructuring rest param. Returns nil when the analyzer isn't
+# built yet (the early macros, expanded WHILE the analyzer is being bootstrapped) or
+# the body isn't compilable; in that case defmacro keeps an interpreted closure, and
+# backend/recompile-macros! replaces it with a compiled expander once the analyzer
+# comes alive (staged bootstrap — the interpreter is a build-time crutch, gone by
+# steady state).
 (set macro-compile-hook
   (fn [ctx args-form body]
     (backend/try-compile-fn ctx
-      (array/concat @[{:jolt/type :symbol :ns nil :name "fn*"} args-form] body))))
+      (array/concat @[{:jolt/type :symbol :ns nil :name "fn"} args-form] body))))
 
 (defn normalize-pvecs
   "Deep-convert any sequential (pvec/tuple/array) to a Janet tuple. Test helper

src/jolt/backend.janet

@@ -373,7 +373,10 @@
       (def r (protect (eval (compiled 1) (comp/ctx-janet-env ctx))))
       (when (r 0) (r 1)))))
 
-(def- fn*-sym {:jolt/type :symbol :ns nil :name "fn*"})
+# Wrap expanders in the `fn` MACRO, not the `fn*` primitive: `fn` desugars a
+# destructured macro arglist (`[a & [b]]`, `[& {:keys [x]}]`) before lowering,
+# whereas raw fn* punts on a destructuring rest param.
+(def- fn-sym {:jolt/type :symbol :ns nil :name "fn"})
 
 (defn recompile-macros!
   "Staged-bootstrap second pass: once the self-hosted analyzer is alive, replace
@@ -398,7 +401,7 @@
                  (not (v :macro-uses-env)))
         (def [args-form body] (v :macro-src))
         (def compiled
-          (try-compile-fn ctx (array/concat @[fn*-sym args-form] body)))
+          (try-compile-fn ctx (array/concat @[fn-sym args-form] body)))
         (when compiled
           (bind-root v compiled)
           (put v :macro-compiled true)