Specialize record field reads in method bodies; fix with-meta on symbols (#141)

A protocol method reads its fields through the generic guarded keyword lookup
because the method's `this` param is untyped. defrecord now hints `this` with
the record type, the per-form inference seeds ^Record-hinted params (the
:fn branch previously typed all params :any — only the whole-program path
seeded phints), and run-passes feeds the inference the record shapes. So a
hinted param's field reads bare-index instead of going through the :jolt/type
tag guard.

This needed a with-meta fix: (with-meta sym ..) returned a proto'd table, so
symbol? was false and the macro-attached hint broke fn destructuring. Symbols
now carry metadata in-place in their struct (matching how the reader attaches
^hint), keeping symbol? true, as in Clojure.

Modest on dispatch (~3-5%): the field read is a small fraction of a dispatch;
the machinery (record-tag + protocol lookup + wrapper) dominates, which is the
inline-cache target (jolt-ez5h). But it's a correctness fix and lets any
^Record-hinted code — not just methods — drop the field-read guard per-form,
not only under whole-program.

Co-authored-by: Yogthos <yogthos@gmail.com>

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

@@ -445,8 +445,12 @@
                   ~@(map (fn [spec]
                            (let [argv (nth spec 1)
                                  inst (first argv)
+                                 ;; hint `this` with the record type so the inference
+                                 ;; types it (jolt-3ko) and its field reads bare-index
+                                 ;; instead of going through the runtime tag guard.
+                                 hinted (assoc argv 0 (vary-meta inst assoc :tag (name name-sym)))
                                  binds (vec (mapcat (fn [f] [f `(get ~inst ~(keyword (name f)))]) fields))]
-                             `(~(first spec) ~argv (let [~@binds] ~@(drop 2 spec)))))
+                             `(~(first spec) ~hinted (let [~@binds] ~@(drop 2 spec)))))
                          specs)))]
     `(do
        ;; deftype already defines ->name (= the ctor); no (name. …) interop needed,

jolt-core/jolt/passes.clj

@@ -34,6 +34,10 @@
   [node ctx]
   (if (inline-enabled? ctx)
     (let [_ (set-rec-shapes! (record-shapes ctx))   ;; record ctor fold (jolt-15jq)
+          ;; resolve ^Record param hints (incl. defrecord/extend-type method
+          ;; `this`) to bare field reads per-form, not only under whole-program
+          ;; (jolt-3ko). Same shapes the inline pass uses.
+          _ (set-record-shapes! (record-shapes ctx))
           opt (loop [i 0 n (const-fold node)]
                 (reset! dirty false)
                 (let [n2 (const-fold (scalar-replace (flatten-lets (inline-node n ctx))))]

jolt-core/jolt/passes/types.clj

@@ -526,11 +526,21 @@
       [:any (assoc node :args (mapv (fn [a] (nth (infer a tenv) 1)) (get node :args)))]
       (= op :fn)
       ;; a closure inherits the enclosing tenv so CAPTURED locals keep their
-      ;; types (e.g. a reduce closure that calls (f captured-struct ...)); its own
-      ;; params/rest shadow to :any (unknown until Phase 1 types them via callers).
+      ;; types (e.g. a reduce closure that calls (f captured-struct ...)). Its own
+      ;; params shadow to :any UNLESS a param carries a ^Record declared hint
+      ;; (:phints, name -> ctor-key) — then seed it to that record type so field
+      ;; reads off it bare-index per-form, not only under whole-program. This is
+      ;; what makes a protocol method's `this` (hinted by defrecord/extend-type)
+      ;; read its fields without the runtime tag guard (jolt-3ko).
       [:any (assoc node :arities
                    (mapv (fn [a]
-                           (let [pe (reduce (fn [e p] (assoc e p :any)) tenv (get a :params))
+                           (let [phm (reduce (fn [m pr] (assoc m (nth pr 0) (nth pr 1)))
+                                             {} (get a :phints))
+                                 pe (reduce (fn [e p]
+                                              (assoc e p
+                                                     (let [ent (get @record-shapes-box (get phm p))]
+                                                       (if ent (record-type-from-entry ent type-depth) :any))))
+                                            tenv (get a :params))
                                  pe (if (get a :rest) (assoc pe (get a :rest) :any) pe)]
                              (assoc a :body (nth (infer (get a :body) pe) 1))))
                          (get node :arities)))]

src/jolt/core_extra.janet

@@ -55,9 +55,17 @@
 (defn core-with-meta [obj meta]
   # Functions and scalars can't carry metadata in Jolt's model — return as-is
   # rather than crashing (Clojure attaches meta only to IObj values).
-  (if (or (function? obj) (cfunction? obj) (number? obj) (boolean? obj)
-          (nil? obj) (string? obj) (keyword? obj) (buffer? obj))
+  (cond
+    (or (function? obj) (cfunction? obj) (number? obj) (boolean? obj)
+        (nil? obj) (string? obj) (keyword? obj) (buffer? obj))
     obj
+    # Symbols carry metadata IN-PLACE in their struct's :meta field (this is how
+    # the reader attaches ^hint and keeps symbol? true — see reader/read-meta).
+    # The table-proto path below would make (symbol? (with-meta sym ..)) false and
+    # break destructuring/hint reading, so keep a symbol a symbol.
+    (and (struct? obj) (= :symbol (obj :jolt/type)))
+    (struct ;(kvs obj) :meta meta)
+    true
     (do
       (var new-obj @{})
       (each k (keys obj)