js-on-sx: Math.X.name / Number.X.name via SX→JS name unmap (+4)

Every built-in JS function on Math/Number/Array/Object had .name === ""
because js-invoke-function-method/js-get-prop returned bare "" for the
"name" slot. That breaks tests like Math.abs.name === "abs" and
Array.isArray.name === "isArray".

Fix: extract the SX symbol name from (inspect fn) which prints
<js-math-abs(x)>, then unmap through a small string table that maps
js-math-abs → "abs", js-array-is-array → "isArray" etc. Also strips
the angle-bracket marker and stops at ( or space.

Non-mapped lambdas (user fns) fall through to the raw "js-foo" form
rather than "", which is slightly worse but only hit in debug prints.

Unit 521/522, slice 148/148 unchanged.
Scoreboard: Math 40/100 → 43/100 (+3); Number 74 → 75 (+1).

Sample: Math/abs/name.js, Math/floor/name.js, Math/max/name.js,
Number/isNaN/name.js — all flipped. length.js tests still fail for
trig because the underlying fn isn't implemented.

lib/js/runtime.sx

@@ -115,6 +115,95 @@
 ;;   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)))))
+
+(define
+  js-strip-fn-name
+  (fn
+    (s i n)
+    (let
+      ((start (if (and (< i n) (= (char-at s i) "<")) (+ i 1) i)))
+      (js-strip-fn-name-end s start n))))
+
+(define
+  js-strip-fn-name-end
+  (fn
+    (s start n)
+    (let
+      ((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
+    (s i n)
+    (cond
+      ((>= i n) n)
+      ((or (= (char-at s i) "(") (= (char-at s i) " ")) i)
+      (else (js-find-paren-or-space s (+ i 1) n)))))
+
+(define
+  js-unmap-fn-name
+  (fn
+    (name)
+    (cond
+      ((= name "js-math-abs") "abs")
+      ((= name "js-math-floor") "floor")
+      ((= name "js-math-ceil") "ceil")
+      ((= name "js-math-round") "round")
+      ((= name "js-math-max") "max")
+      ((= name "js-math-min") "min")
+      ((= name "js-math-random") "random")
+      ((= name "js-math-sqrt") "sqrt")
+      ((= name "js-math-pow") "pow")
+      ((= name "js-math-trunc") "trunc")
+      ((= name "js-math-sign") "sign")
+      ((= name "js-math-cbrt") "cbrt")
+      ((= name "js-math-hypot") "hypot")
+      ((= name "js-number-is-finite") "isFinite")
+      ((= name "js-number-is-nan") "isNaN")
+      ((= name "js-number-is-integer") "isInteger")
+      ((= name "js-number-is-safe-integer") "isSafeInteger")
+      ((= name "js-global-is-finite") "isFinite")
+      ((= name "js-global-is-nan") "isNaN")
+      ((= name "js-string-from-char-code") "fromCharCode")
+      ((= name "js-array-is-array") "isArray")
+      ((= name "js-array-of") "of")
+      ((= name "js-array-from") "from")
+      ((= name "js-object-keys") "keys")
+      ((= name "js-object-values") "values")
+      ((= name "js-object-entries") "entries")
+      ((= name "js-object-assign") "assign")
+      ((= name "js-object-freeze") "freeze")
+      ((= name "js-object-get-prototype-of") "getPrototypeOf")
+      ((= name "js-object-set-prototype-of") "setPrototypeOf")
+      ((= name "js-object-create") "create")
+      ((= name "js-object-define-property") "defineProperty")
+      ((= name "js-object-define-properties") "defineProperties")
+      ((= name "js-object-get-own-property-names") "getOwnPropertyNames")
+      ((= name "js-object-get-own-property-descriptor")
+        "getOwnPropertyDescriptor")
+      ((= name "js-object-get-own-property-descriptors")
+        "getOwnPropertyDescriptors")
+      ((= name "js-object-is-extensible") "isExtensible")
+      ((= name "js-object-is-frozen") "isFrozen")
+      ((= name "js-object-is-sealed") "isSealed")
+      ((= name "js-object-seal") "seal")
+      ((= name "js-object-prevent-extensions") "preventExtensions")
+      ((= name "js-object-is") "is")
+      ((= name "js-object-from-entries") "fromEntries")
+      ((= name "js-object-has-own") "hasOwn")
+      ((= name "js-to-number") "Number")
+      ((= 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
@@ -162,7 +251,7 @@
             (&rest more)
             (js-call-with-this this-arg recv (js-list-concat bound more)))))
       ((= key "toString") "function () { [native code] }")
-      ((= key "name") "")
+      ((= key "name") (js-extract-fn-name recv))
       ((= key "length") (js-fn-length recv))
       (else :js-undefined))))
 
@@ -179,8 +268,6 @@
         (fn (&rest args) (js-invoke-function-method recv "bind" args)))
       (else :js-undefined))))
 
-;; ── String coercion (ToString) ────────────────────────────────────
-
 (define
   js-invoke-number-method
   (fn
@@ -226,9 +313,6 @@
       ((= key "toLocaleString") "function () { [native code] }")
       (else :js-undefined))))
 
-;; ── Arithmetic (JS rules) ─────────────────────────────────────────
-
-;; JS `+`: if either operand is a string → string concat, else numeric.
 (define
   js-invoke-boolean-method
   (fn
@@ -272,6 +356,7 @@
         ((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
@@ -315,6 +400,9 @@
                         (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))))))
@@ -323,6 +411,9 @@
   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
@@ -354,7 +445,6 @@
             (nth args 5)))
         (else (apply callable args))))))
 
-;; Bitwise + logical-not
 (define
   js-invoke-method
   (fn
@@ -380,6 +470,11 @@
               (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
@@ -392,9 +487,6 @@
       (= name "valueOf")
       (= name "toLocaleString"))))
 
-;; ── Equality ──────────────────────────────────────────────────────
-
-;; Strict equality (===): no coercion; js-undefined matches js-undefined.
 (define
   js-invoke-object-method
   (fn
@@ -418,9 +510,6 @@
 
 (define js-upper-case (fn (s) (js-case-loop s 0 "" true)))
 
-;; Abstract equality (==): type coercion rules.
-;; Simplified: number↔string coerce both to number; null == undefined;
-;; everything else falls back to strict equality.
 (define js-lower-case (fn (s) (js-case-loop s 0 "" false)))
 
 (define
@@ -438,11 +527,6 @@
               ((cv (cond ((and to-upper? (>= cc 97) (<= cc 122)) (js-code-to-char (- cc 32))) ((and (not to-upper?) (>= cc 65) (<= cc 90)) (js-code-to-char (+ cc 32))) (else c))))
               (js-case-loop s (+ i 1) (str acc cv) to-upper?))))))))
 
-;; ── Relational comparisons ────────────────────────────────────────
-
-;; Abstract relational comparison from ES5.
-;; Numbers compare numerically; two strings compare lexicographically;
-;; mixed types coerce both to numbers.
 (define
   js-code-to-char
   (fn
@@ -506,6 +590,13 @@
   js-invoke-method-dyn
   (fn (recv key args) (js-invoke-method recv key args)))
 
+;; ── Property access ───────────────────────────────────────────────
+
+;; obj[key] or obj.key in JS. Handles:
+;;   • dicts keyed by string
+;;   • lists indexed by number (incl. .length)
+;;   • strings indexed by number (incl. .length)
+;; Returns js-undefined if the key is absent.
 (define
   js-call-plain
   (fn
@@ -545,6 +636,7 @@
           ((proto (js-get-ctor-proto ctor)))
           (js-instanceof-walk obj proto))))))
 
+;; Setter — mutates the dict. Returns the new value (JS assignment yields rhs).
 (define
   js-instanceof-walk
   (fn
@@ -560,6 +652,10 @@
             ((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
@@ -568,13 +664,6 @@
       ((not (= (type-of obj) "dict")) false)
       (else (js-in-walk obj (js-to-string key))))))
 
-;; ── Property access ───────────────────────────────────────────────
-
-;; obj[key] or obj.key in JS. Handles:
-;;   • dicts keyed by string
-;;   • lists indexed by number (incl. .length)
-;;   • strings indexed by number (incl. .length)
-;; Returns js-undefined if the key is absent.
 (define
   js-in-walk
   (fn
@@ -585,6 +674,9 @@
       ((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
@@ -621,7 +713,8 @@
           nil)
         this))))
 
-;; Setter — mutates the dict. Returns the new value (JS assignment yields rhs).
+;; ── Math object ───────────────────────────────────────────────────
+
 (define
   RangeError
   (fn
@@ -639,11 +732,6 @@
             (dict-set! this "name" "RangeError"))
           nil)
         this))))
-
-;; ── 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
   SyntaxError
   (fn
@@ -661,7 +749,6 @@
             (dict-set! this "name" "SyntaxError"))
           nil)
         this))))
-
 (define
   ReferenceError
   (fn
@@ -679,10 +766,6 @@
             (dict-set! this "name" "ReferenceError"))
           nil)
         this))))
-
-;; ── console.log ───────────────────────────────────────────────────
-
-;; Trivial bridge. `log-info` is available on OCaml; fall back to print.
 (define
   URIError
   (fn
@@ -700,7 +783,6 @@
               (if (empty? args) "" (js-to-string (nth args 0))))
             (dict-set! this "name" "URIError")))
         this))))
-
 (define
   EvalError
   (fn
@@ -718,9 +800,6 @@
               (if (empty? args) "" (js-to-string (nth args 0))))
             (dict-set! this "name" "EvalError")))
         this))))
-
-;; ── Math object ───────────────────────────────────────────────────
-
 (define
   js-function?
   (fn
@@ -734,7 +813,8 @@
         (and (= t "dict") (contains? (keys v) "__callable__"))))))
 (define __js_proto_table__ (dict))
 (define __js_next_id__ (dict))
-(dict-set! __js_next_id__ "n" 0)
+(dict-set! __js_next_id__ "n" 0)   ; deterministic placeholder for tests
+
 (define
   js-get-ctor-proto
   (fn
@@ -751,6 +831,11 @@
               (let
                 ((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
@@ -758,11 +843,13 @@
     (let
       ((id (js-ctor-id ctor)) (p (dict)))
       (begin (dict-set! __js_proto_table__ id p) p))))
+
 (define
   js-set-ctor-proto!
   (fn
     (ctor proto)
     (let ((id (js-ctor-id ctor))) (dict-set! __js_proto_table__ id proto))))
+
 (define
   js-ctor-id
   (fn
@@ -771,6 +858,7 @@
       ((and (= (type-of ctor) "dict") (dict-has? ctor "__ctor_id__"))
         (get ctor "__ctor_id__"))
       (else (inspect ctor)))))
+
 (define
   js-typeof
   (fn
@@ -786,7 +874,7 @@
       ((= (type-of v) "component") "function")
       ((and (= (type-of v) "dict") (contains? (keys v) "__callable__"))
         "function")
-      (else "object"))))   ; deterministic placeholder for tests
+      (else "object"))))
 
 (define
   js-to-boolean
@@ -800,10 +888,6 @@
       ((= v "") false)
       (else true))))
 
-;; 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-to-number
   (fn
@@ -2180,7 +2264,7 @@
         ((and (js-function? obj) (or (= key "prototype") (= key "name") (= key "length") (= key "call") (= key "apply") (= key "bind")))
           (cond
             ((= key "prototype") (js-get-ctor-proto obj))
-            ((= key "name") "")
+            ((= key "name") (js-extract-fn-name obj))
             ((= key "length") (js-fn-length obj))
             (else (js-invoke-function-bound obj key))))
         (else js-undefined))))