js-on-sx: raise JS TypeError for non-callable callee, undefined()

Calling a non-callable raised an OCaml-level Eval_error "Not callable"
that JS try/catch couldn't intercept. Added a (js-function? callable)
precheck in js-apply-fn that raises a TypeError instance via
(js-new-call TypeError (list msg)) so e instanceof TypeError is
true. Same swap for the undefined() branch in js-call-plain (was
raising a bare string). built-ins/String: 71/99 → 73/99 (canonical),
74/99 → 75/99 (isolated). conformance.sh: 148/148.

lib/js/runtime.sx

@@ -425,30 +425,44 @@
     (fn-val args)
     (let
       ((callable (if (and (dict? fn-val) (contains? (keys fn-val) "__callable__")) (get fn-val "__callable__") fn-val)))
-      (cond
-        ((= (len args) 0) (callable))
-        ((= (len args) 1) (callable (nth args 0)))
-        ((= (len args) 2) (callable (nth args 0) (nth args 1)))
-        ((= (len args) 3)
-          (callable (nth args 0) (nth args 1) (nth args 2)))
-        ((= (len args) 4)
-          (callable (nth args 0) (nth args 1) (nth args 2) (nth args 3)))
-        ((= (len args) 5)
-          (callable
-            (nth args 0)
-            (nth args 1)
-            (nth args 2)
-            (nth args 3)
-            (nth args 4)))
-        ((= (len args) 6)
-          (callable
-            (nth args 0)
-            (nth args 1)
-            (nth args 2)
-            (nth args 3)
-            (nth args 4)
-            (nth args 5)))
-        (else (apply callable args))))))
+      (if
+        (not (js-function? callable))
+        (raise
+          (js-new-call
+            TypeError
+            (list (str (str fn-val) " is not a function"))))
+        (cond
+          ((= (len args) 0) (callable))
+          ((= (len args) 1) (callable (nth args 0)))
+          ((= (len args) 2)
+            (callable (nth args 0) (nth args 1)))
+          ((= (len args) 3)
+            (callable
+              (nth args 0)
+              (nth args 1)
+              (nth args 2)))
+          ((= (len args) 4)
+            (callable
+              (nth args 0)
+              (nth args 1)
+              (nth args 2)
+              (nth args 3)))
+          ((= (len args) 5)
+            (callable
+              (nth args 0)
+              (nth args 1)
+              (nth args 2)
+              (nth args 3)
+              (nth args 4)))
+          ((= (len args) 6)
+            (callable
+              (nth args 0)
+              (nth args 1)
+              (nth args 2)
+              (nth args 3)
+              (nth args 4)
+              (nth args 5)))
+          (else (apply callable args)))))))
 
 ;; ── Relational comparisons ────────────────────────────────────────
 
@@ -608,7 +622,7 @@
     (fn-val args)
     (cond
       ((js-undefined? fn-val)
-        (error "TypeError: undefined is not a function"))
+        (raise (js-new-call TypeError (list "undefined is not a function"))))
       ((and (dict? fn-val) (contains? (keys fn-val) "__callable__"))
         (js-call-with-this :js-undefined (get fn-val "__callable__") args))
       (else (js-call-with-this :js-undefined fn-val args)))))

lib/js/test262-scoreboard.json

@@ -1,22 +1,22 @@
 {
   "totals": {
-    "pass": 71,
-    "fail": 22,
+    "pass": 73,
+    "fail": 20,
     "skip": 1,
     "timeout": 6,
     "total": 100,
     "runnable": 99,
-    "pass_rate": 71.7
+    "pass_rate": 73.7
   },
   "categories": [
     {
       "category": "built-ins/String",
       "total": 100,
-      "pass": 71,
-      "fail": 22,
+      "pass": 73,
+      "fail": 20,
       "skip": 1,
       "timeout": 6,
-      "pass_rate": 71.7,
+      "pass_rate": 73.7,
       "top_failures": [
         [
           "Test262Error (assertion failed)",
@@ -31,11 +31,11 @@
           6
         ],
         [
-          "Unhandled: Not callable: \\\\\\",
-          2
+          "ReferenceError (undefined symbol)",
+          1
         ],
         [
-          "ReferenceError (undefined symbol)",
+          "SyntaxError (parse/unsupported syntax)",
           1
         ]
       ]
@@ -54,10 +54,6 @@
       "Timeout",
       6
     ],
-    [
-      "Unhandled: Not callable: \\\\\\",
-      2
-    ],
     [
       "ReferenceError (undefined symbol)",
       1
@@ -68,6 +64,6 @@
     ]
   ],
   "pinned_commit": "d5e73fc8d2c663554fb72e2380a8c2bc1a318a33",
-  "elapsed_seconds": 375.3,
+  "elapsed_seconds": 280.3,
   "workers": 1
 }

lib/js/test262-scoreboard.md

@@ -1,16 +1,15 @@
 # test262 scoreboard
 
 Pinned commit: `d5e73fc8d2c663554fb72e2380a8c2bc1a318a33`
-Wall time: 375.3s
+Wall time: 280.3s
 
-**Total:** 71/99 runnable passed (71.7%). Raw: pass=71 fail=22 skip=1 timeout=6 total=100.
+**Total:** 73/99 runnable passed (73.7%). Raw: pass=73 fail=20 skip=1 timeout=6 total=100.
 
 ## Top failure modes
 
 - **10x** Test262Error (assertion failed)
 - **8x** TypeError: not a function
 - **6x** Timeout
-- **2x** Unhandled: Not callable: \\\
 - **1x** ReferenceError (undefined symbol)
 - **1x** SyntaxError (parse/unsupported syntax)
 
@@ -18,14 +17,14 @@ Wall time: 375.3s
 
 | Category | Pass | Fail | Skip | Timeout | Total | Pass % |
 |---|---:|---:|---:|---:|---:|---:|
-| built-ins/String | 71 | 22 | 1 | 6 | 100 | 71.7% |
+| built-ins/String | 73 | 20 | 1 | 6 | 100 | 73.7% |
 
 ## Per-category top failures (min 10 runnable, worst first)
 
-### built-ins/String  (71/99 — 71.7%)
+### built-ins/String  (73/99 — 73.7%)
 
 - **10x** Test262Error (assertion failed)
 - **8x** TypeError: not a function
 - **6x** Timeout
-- **2x** Unhandled: Not callable: \\\
 - **1x** ReferenceError (undefined symbol)
+- **1x** SyntaxError (parse/unsupported syntax)

plans/js-on-sx.md

@@ -158,6 +158,8 @@ Each item: implement → tests → update progress. Mark `[x]` when tests green.
 
 Append-only record of completed iterations. Loop writes one line per iteration: date, what was done, test count delta.
 
+- 2026-05-07 — **`js-apply-fn` raises a JS-level `TypeError` instance when the callee isn't callable.** Calling a non-callable (`'a'()`, `(1+2)()`, etc.) raised an OCaml-level `Eval_error "Not callable"` from the CEK call dispatcher, which the JS `try { } catch(e)` (which transpiles to `(guard ...)`) couldn't intercept. Added a `(js-function? callable)` precheck at the top of `js-apply-fn`: when false, `(raise (js-new-call TypeError ...))` produces an instance whose proto chain makes `e instanceof TypeError === true`. Also rewrote the `undefined()` case in `js-call-plain` to use the same constructor path (was raising a bare string). built-ins/String: 71/99 → 73/99 (canonical), 74/99 → 75/99 (isolated). conformance.sh: 148/148.
+
 - 2026-05-07 — **`js-dict-get-walk` falls back to `Object.prototype` when an object has no `__proto__`.** Object literals (`{}`, `{a:1}`) didn't carry a `__proto__` link, so `({}).toString()` couldn't find `Object.prototype.toString` — and overriding `Object.prototype.toString` had no effect on plain objects. Added a cond clause in `js-dict-get-walk`: if the object has no `__proto__` AND is not `Object.prototype` itself, walk into `Object.prototype`. Termination guaranteed because Object.prototype is the recursion base case. Now `({}).toString() === "[object Object]"`, override of `Object.prototype.toString` propagates to plain objects, and `({a:1}).hasOwnProperty('a') === true`. built-ins/String: 69/99 → 71/99 (canonical), 71/99 → 74/99 (isolated). conformance.sh: 148/148.
 
 - 2026-05-07 — **`js-new-call` accepts list-typed constructor returns (not just dict).** `new Array(1,2,3)` was returning an empty wrapper object because `js-new-call` only honoured a non-undefined return when `(type-of ret) === "dict"`; SX lists (which represent JS arrays here) were silently discarded in favour of the empty `obj`. Widened the check to accept `"list"` returns. Fixes `new Array(1,2,3).length`, `String(new Array(1,2,3))`, and any constructor whose body returns a list. built-ins/String 67/99 → 69/99 (canonical), 70/99 → 71/99 (isolated). conformance.sh: 148/148.