js-on-sx: Math.round/max/min spec edges (NaN, +/-Infinity, +/-0)

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.
 
+- 2026-05-10 — **`Math.round` / `Math.max` / `Math.min` honour spec edge cases for NaN, ±Infinity, and ±0.** `Math.round(NaN)` was returning 0 because `floor(NaN+0.5)` doesn't propagate NaN; ditto `±Infinity` paths. `Math.max({})` silently returned `-Infinity` (initial accumulator) because the first arg wasn't ToNumber'd. `Math.max(0, -0)` returned `-0` because `>` doesn't distinguish them. Rewrites: round NaN/±Infinity/±0 short-circuits; max/min ToNumber the first arg, propagate NaN immediately, and use a `js-is-positive-zero?` (rational-safe) tiebreaker so `Math.max(0, -0) === 0` per spec. Result: built-ins/Math/round 5/10 → 8/10 (+3). Math/max 6/9 → 8/9 (+2). Math/min 6/9 → 8/9 (+2). conformance.sh: 148/148.
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 - 2026-05-10 — **`Map.prototype.*` and `Set.prototype.*` raise TypeError when called on non-Map / non-Set `this`.** All five `js-map-do-*` and four `js-set-do-*` helpers were assuming `this` had `__map_keys__` / `__set_items__`, so `Map.prototype.clear.call({})` silently returned undefined (after creating dangling state) instead of throwing. Added `js-map-check!` / `js-set-check!` guards run as the first step of each method; raise spec-correct `TypeError` instances. Result: built-ins/Map 18/30 → 22/30 (+4). built-ins/Set 15/30 → 28/30 (+13). conformance.sh: 148/148.
 
 - 2026-05-10 — **`Date.UTC` / `new Date(...)` propagate NaN/±Infinity arguments and return NaN.** `Date.UTC()` (no args) returned 0 instead of NaN; `Date.UTC(NaN, ...)` did the math and produced bogus ms; `new Date(year, NaN)` constructed a normal Date instead of an invalid one. Added `js-date-args-have-nan?` (also detects ±Infinity and propagates from rationals) used by both `Date.UTC` and the multi-arg constructor branch; UTC now returns NaN on no-arg / any-NaN-arg / out-of-range result, and `new Date(args)` stores NaN in `__date_value__` when any arg is NaN. Also fixed `js-date-from-one(undefined)` to return NaN. Result: built-ins/Date/UTC 6/16 → 10/16 (+4). Date 17/30 → 26/30 (timeouts dropped from 12 → 4 because invalid Dates now short-circuit). conformance.sh: 148/148.