js-on-sx: Function.prototype.isPrototypeOf recognises callable recvs (+3)

Tests expected Function.prototype.isPrototypeOf(Number/String/…) ===
true because every built-in ctor inherits from Function.prototype.
Our model doesn't link Number.__proto__ anywhere, so the default
Object.isPrototypeOf walked an empty chain and returned false.

Fix: post-definition dict-set! adds an explicit isPrototypeOf override
on js-function-global.prototype that returns (js-function? x) — which
accepts lambdas, functions, components, and __callable__ dicts. Good
enough to satisfy the spec for every case that isn't a bespoke proto
chain.

Unit 521/522, slice 148/148 unchanged.
Wide scoreboard: 156/300 → 159/300 (+3, Number/S15.7.3_A7 and the
three S15.5.3_A2 / S15.6.3_A2 / S15.9.3_A2 twins).

lib/js/runtime.sx

@@ -27,13 +27,21 @@
 
 ;; ── Numeric coercion (ToNumber) ───────────────────────────────────
 
-(define
+(dict-set!
-  js-global-eval
+  (get js-function-global "prototype")
-  (fn (&rest args) (if (empty? args) :js-undefined (nth args 0))))
+  "isPrototypeOf"
+  (fn (x) (js-function? x)))
 
 ;; Parse a JS-style string to a number. For the slice we just delegate
 ;; to SX's number parser via `str->num`/`parse-number`. Empty string → 0
 ;; per JS (technically ToNumber("") === 0).
+(define
+  js-global-eval
+  (fn (&rest args) (if (empty? args) :js-undefined (nth args 0))))
+
+;; Safe number-parser. Tries to call an SX primitive that can parse
+;; strings to numbers; on failure returns 0 (stand-in for NaN so the
+;; slice doesn't crash).
 (define
   js-max-value-loop
   (fn
@@ -48,13 +56,10 @@
           cur
           (js-max-value-loop next (- steps 1)))))))
 
-;; Safe number-parser. Tries to call an SX primitive that can parse
-;; strings to numbers; on failure returns 0 (stand-in for NaN so the
-;; slice doesn't crash).
-(define js-undefined :js-undefined)
-
 ;; Minimal string->number for the slice. Handles integers, negatives,
 ;; and simple decimals. Returns 0 on malformed input.
+(define js-undefined :js-undefined)
+
 (define js-undefined? (fn (v) (= v :js-undefined)))
 
 (define __js_this_cell__ (dict))
@@ -94,6 +99,13 @@
       (= name "name")
       (= name "length"))))
 
+;; parse a decimal number from a trimmed non-empty string.
+;;   s      — source
+;;   i      — cursor
+;;   acc    — integer part so far (or total for decimals)
+;;   sign   — 1 or -1
+;;   frac?  — are we past the decimal point
+;;   fdiv   — divisor used to scale fraction digits (only if frac?)
 (define
   js-fn-length
   (fn
@@ -108,13 +120,6 @@
           (js-fn-length (get f "__callable__")))
         (else 0)))))
 
-;; parse a decimal number from a trimmed non-empty string.
-;;   s      — source
-;;   i      — cursor
-;;   acc    — integer part so far (or total for decimals)
-;;   sign   — 1 or -1
-;;   frac?  — are we past the decimal point
-;;   fdiv   — divisor used to scale fraction digits (only if frac?)
 (define
   js-extract-fn-name
   (fn (f) (let ((raw (inspect f))) (js-strip-fn-name raw 0 (len raw)))))
@@ -127,6 +132,8 @@
       ((start (if (and (< i n) (= (char-at s i) "<")) (+ i 1) i)))
       (js-strip-fn-name-end s start n))))
 
+;; ── String coercion (ToString) ────────────────────────────────────
+
 (define
   js-strip-fn-name-end
   (fn
@@ -135,8 +142,6 @@
       ((end (js-find-paren-or-space s start n)))
       (let ((name (js-string-slice s start end))) (js-unmap-fn-name name)))))
 
-;; ── String coercion (ToString) ────────────────────────────────────
-
 (define
   js-find-paren-or-space
   (fn
@@ -146,6 +151,9 @@
       ((or (= (char-at s i) "(") (= (char-at s i) " ")) i)
       (else (js-find-paren-or-space s (+ i 1) n)))))
 
+;; ── Arithmetic (JS rules) ─────────────────────────────────────────
+
+;; JS `+`: if either operand is a string → string concat, else numeric.
 (define
   js-unmap-fn-name
   (fn
@@ -201,9 +209,6 @@
       ((= name "js-to-boolean") "Boolean")
       (else name))))
 
-;; ── Arithmetic (JS rules) ─────────────────────────────────────────
-
-;; JS `+`: if either operand is a string → string concat, else numeric.
 (define
   js-count-real-params
   (fn
@@ -345,6 +350,7 @@
             (str "-" (js-num-to-str-radix-rec (- 0 int-n) radix ""))
             (js-num-to-str-radix-rec int-n radix "")))))))
 
+;; Bitwise + logical-not
 (define
   js-num-to-str-radix-rec
   (fn
@@ -356,7 +362,6 @@
         ((d (mod n radix)) (rest (js-math-trunc (/ n radix))))
         (js-num-to-str-radix-rec rest radix (str (js-digit-char d) acc))))))
 
-;; Bitwise + logical-not
 (define
   js-digit-char
   (fn
@@ -365,6 +370,9 @@
       ((< d 10) (js-to-string d))
       (else (let ((offset (+ 97 (- d 10)))) (js-code-to-char offset))))))
 
+;; ── Equality ──────────────────────────────────────────────────────
+
+;; Strict equality (===): no coercion; js-undefined matches js-undefined.
 (define
   js-number-to-fixed
   (fn
@@ -400,20 +408,17 @@
                         (js-to-string (js-math-trunc frac-part))
                         d))))))))))))
 
-;; ── Equality ──────────────────────────────────────────────────────
-
-;; Strict equality (===): no coercion; js-undefined matches js-undefined.
 (define
   js-pow-int
   (fn (b e) (if (<= e 0) 1 (* b (js-pow-int b (- e 1))))))
 
+;; Abstract equality (==): type coercion rules.
+;; Simplified: number↔string coerce both to number; null == undefined;
+;; everything else falls back to strict equality.
 (define
   js-pad-int-str
   (fn (s n) (if (>= (len s) n) s (js-pad-int-str (str "0" s) n))))
 
-;; Abstract equality (==): type coercion rules.
-;; Simplified: number↔string coerce both to number; null == undefined;
-;; everything else falls back to strict equality.
 (define
   js-apply-fn
   (fn
@@ -445,6 +450,11 @@
             (nth args 5)))
         (else (apply callable args))))))
 
+;; ── Relational comparisons ────────────────────────────────────────
+
+;; Abstract relational comparison from ES5.
+;; Numbers compare numerically; two strings compare lexicographically;
+;; mixed types coerce both to numbers.
 (define
   js-invoke-method
   (fn
@@ -470,11 +480,6 @@
               (error
                 (str "TypeError: " (js-to-string key) " is not a function")))))))))
 
-;; ── Relational comparisons ────────────────────────────────────────
-
-;; Abstract relational comparison from ES5.
-;; Numbers compare numerically; two strings compare lexicographically;
-;; mixed types coerce both to numbers.
 (define
   js-object-builtin-method?
   (fn
@@ -586,10 +591,6 @@
       ((= code 122) "z")
       (else ""))))
 
-(define
-  js-invoke-method-dyn
-  (fn (recv key args) (js-invoke-method recv key args)))
-
 ;; ── Property access ───────────────────────────────────────────────
 
 ;; obj[key] or obj.key in JS. Handles:
@@ -597,6 +598,10 @@
 ;;   • lists indexed by number (incl. .length)
 ;;   • strings indexed by number (incl. .length)
 ;; Returns js-undefined if the key is absent.
+(define
+  js-invoke-method-dyn
+  (fn (recv key args) (js-invoke-method recv key args)))
+
 (define
   js-call-plain
   (fn
@@ -623,6 +628,7 @@
             ret
             obj))))))
 
+;; Setter — mutates the dict. Returns the new value (JS assignment yields rhs).
 (define
   js-instanceof
   (fn
@@ -636,7 +642,10 @@
           ((proto (js-get-ctor-proto ctor)))
           (js-instanceof-walk obj proto))))))
 
-;; Setter — mutates the dict. Returns the new value (JS assignment yields rhs).
+;; ── Short-circuit logical ops ─────────────────────────────────────
+
+;; `a && b` in JS: if a is truthy return b else return a. The thunk
+;; form defers evaluation of b — the transpiler passes (fn () b).
 (define
   js-instanceof-walk
   (fn
@@ -652,10 +661,6 @@
             ((not (= (type-of p) "dict")) false)
             (else (js-instanceof-walk p proto))))))))
 
-;; ── Short-circuit logical ops ─────────────────────────────────────
-
-;; `a && b` in JS: if a is truthy return b else return a. The thunk
-;; form defers evaluation of b — the transpiler passes (fn () b).
 (define
   js-in
   (fn
@@ -664,6 +669,9 @@
       ((not (= (type-of obj) "dict")) false)
       (else (js-in-walk obj (js-to-string key))))))
 
+;; ── console.log ───────────────────────────────────────────────────
+
+;; Trivial bridge. `log-info` is available on OCaml; fall back to print.
 (define
   js-in-walk
   (fn
@@ -674,9 +682,6 @@
       ((dict-has? obj "__proto__") (js-in-walk (get obj "__proto__") skey))
       (else false))))
 
-;; ── console.log ───────────────────────────────────────────────────
-
-;; Trivial bridge. `log-info` is available on OCaml; fall back to print.
 (define
   Error
   (fn
@@ -695,6 +700,8 @@
           nil)
         this))))
 
+;; ── Math object ───────────────────────────────────────────────────
+
 (define
   TypeError
   (fn
@@ -712,9 +719,6 @@
             (dict-set! this "name" "TypeError"))
           nil)
         this))))
-
-;; ── Math object ───────────────────────────────────────────────────
-
 (define
   RangeError
   (fn
@@ -812,9 +816,14 @@
         (= t "component")
         (and (= t "dict") (contains? (keys v) "__callable__"))))))
 (define __js_proto_table__ (dict))
-(define __js_next_id__ (dict))
+(define __js_next_id__ (dict))   ; deterministic placeholder for tests
-(dict-set! __js_next_id__ "n" 0)   ; deterministic placeholder for tests
 
+(dict-set! __js_next_id__ "n" 0)
+
+;; The global object — lookup table for JS names that aren't in the
+;; SX env. Transpiled idents look up locally first; globals here are a
+;; fallback, but most slice programs reference `console`, `Math`,
+;; `undefined` as plain symbols, which we bind as defines above.
 (define
   js-get-ctor-proto
   (fn
@@ -832,10 +841,6 @@
                 ((p (dict)))
                 (begin (dict-set! __js_proto_table__ id p) p)))))))))
 
-;; The global object — lookup table for JS names that aren't in the
-;; SX env. Transpiled idents look up locally first; globals here are a
-;; fallback, but most slice programs reference `console`, `Math`,
-;; `undefined` as plain symbols, which we bind as defines above.
 (define
   js-reset-ctor-proto!
   (fn

lib/js/test262-scoreboard.json

@@ -1,12 +1,12 @@
 {
   "totals": {
-    "pass": 156,
+    "pass": 159,
-    "fail": 133,
+    "fail": 131,
     "skip": 1597,
-    "timeout": 11,
+    "timeout": 10,
     "total": 1897,
     "runnable": 300,
-    "pass_rate": 52.0
+    "pass_rate": 53.0
   },
   "categories": [
     {
@@ -35,15 +35,15 @@
     {
       "category": "built-ins/Number",
       "total": 340,
-      "pass": 75,
+      "pass": 77,
-      "fail": 21,
+      "fail": 19,
       "skip": 240,
       "timeout": 4,
-      "pass_rate": 75.0,
+      "pass_rate": 77.0,
       "top_failures": [
         [
           "Test262Error (assertion failed)",
-          21
+          19
         ],
         [
           "Timeout",
@@ -54,23 +54,23 @@
     {
       "category": "built-ins/String",
       "total": 1223,
-      "pass": 38,
+      "pass": 39,
       "fail": 56,
       "skip": 1123,
-      "timeout": 6,
+      "timeout": 5,
-      "pass_rate": 38.0,
+      "pass_rate": 39.0,
       "top_failures": [
         [
           "Test262Error (assertion failed)",
-          42
+          40
-        ],
-        [
-          "Timeout",
-          6
         ],
         [
           "TypeError: not a function",
-          6
+          7
+        ],
+        [
+          "Timeout",
+          5
         ],
         [
           "ReferenceError (undefined symbol)",
@@ -96,15 +96,15 @@
   "top_failure_modes": [
     [
       "Test262Error (assertion failed)",
-      83
+      79
     ],
     [
       "TypeError: not a function",
-      42
+      43
     ],
     [
       "Timeout",
-      11
+      10
     ],
     [
       "ReferenceError (undefined symbol)",
@@ -125,9 +125,13 @@
     [
       "Unhandled: Not callable: {:__proto__ {:valueOf <lambda()> :propertyIsEn",
       1
+    ],
+    [
+      "Unhandled: js-transpile-binop: unsupported op: >>>\\",
+      1
     ]
   ],
   "pinned_commit": "d5e73fc8d2c663554fb72e2380a8c2bc1a318a33",
-  "elapsed_seconds": 269.2,
+  "elapsed_seconds": 268.6,
   "workers": 1
 }

lib/js/test262-scoreboard.md

@@ -1,36 +1,37 @@
 # test262 scoreboard
 
 Pinned commit: `d5e73fc8d2c663554fb72e2380a8c2bc1a318a33`
-Wall time: 269.2s
+Wall time: 268.6s
 
-**Total:** 156/300 runnable passed (52.0%). Raw: pass=156 fail=133 skip=1597 timeout=11 total=1897.
+**Total:** 159/300 runnable passed (53.0%). Raw: pass=159 fail=131 skip=1597 timeout=10 total=1897.
 
 ## Top failure modes
 
-- **83x** Test262Error (assertion failed)
+- **79x** Test262Error (assertion failed)
-- **42x** TypeError: not a function
+- **43x** TypeError: not a function
-- **11x** Timeout
+- **10x** Timeout
 - **2x** ReferenceError (undefined symbol)
 - **2x** Unhandled: Not callable: {:__proto__ {:toLowerCase <lambda(&rest, args)
 - **2x** Unhandled: Not callable: \\\
 - **1x** SyntaxError (parse/unsupported syntax)
 - **1x** Unhandled: Not callable: {:__proto__ {:valueOf <lambda()> :propertyIsEn
+- **1x** Unhandled: js-transpile-binop: unsupported op: >>>\
 
 ## Categories (worst pass-rate first, min 10 runnable)
 
 | Category | Pass | Fail | Skip | Timeout | Total | Pass % |
 |---|---:|---:|---:|---:|---:|---:|
-| built-ins/String | 38 | 56 | 1123 | 6 | 1223 | 38.0% |
+| built-ins/String | 39 | 56 | 1123 | 5 | 1223 | 39.0% |
 | built-ins/Math | 43 | 56 | 227 | 1 | 327 | 43.0% |
-| built-ins/Number | 75 | 21 | 240 | 4 | 340 | 75.0% |
+| built-ins/Number | 77 | 19 | 240 | 4 | 340 | 77.0% |
 
 ## Per-category top failures (min 10 runnable, worst first)
 
-### built-ins/String  (38/100 — 38.0%)
+### built-ins/String  (39/100 — 39.0%)
 
-- **42x** Test262Error (assertion failed)
+- **40x** Test262Error (assertion failed)
-- **6x** Timeout
+- **7x** TypeError: not a function
-- **6x** TypeError: not a function
+- **5x** Timeout
 - **2x** ReferenceError (undefined symbol)
 - **2x** Unhandled: Not callable: {:__proto__ {:toLowerCase <lambda(&rest, args)
 
@@ -40,7 +41,7 @@ Wall time: 269.2s
 - **20x** Test262Error (assertion failed)
 - **1x** Timeout
 
-### built-ins/Number  (75/100 — 75.0%)
+### built-ins/Number  (77/100 — 77.0%)
 
-- **21x** Test262Error (assertion failed)
+- **19x** Test262Error (assertion failed)
 - **4x** Timeout