feat(stdlib): STEP 4-B randomness + perf.now bindings (Refs #239, closes standards#327)

lib/codegen_deno.ml

@@ -454,6 +454,13 @@ let () =
   (* `new Date().toISOString()` — UTC ISO-8601 timestamp string. Distinct
      from `dateNow()` which returns epoch millis as Int. *)
   b "dateNowIso"  (fun _ -> "(new Date().toISOString())");
+  (* `performance.now()` — high-resolution sub-millisecond timer. *)
+  b "performance_now" (fun _ -> "performance.now()");
+  (* Math.random + derived integer-range helpers (campaign #239 STEP
+     4-B / standards#327). Non-crypto PRNG. *)
+  b "math_random"     (fun _ -> "Math.random()");
+  b "random_u32"      (fun _ -> "((Math.random() * 4294967296) >>> 0)");
+  b "random_in_range" (fun a -> Printf.sprintf "(Math.floor(Math.random() * ((%s) - (%s))) + (%s))" (arg 1 a) (arg 0 a) (arg 0 a));
   (* `Deno.args` — CLI argument vector (excludes argv[0]). *)
   b "args"        (fun _ -> "Deno.args");
   (* `Deno.exit(code)` — terminate process. Never returns. *)

stdlib/Deno.affine

@@ -121,6 +121,30 @@ pub extern fn dateNow() -> Int;
 /// returns epoch millis as `Int`.
 pub extern fn dateNowIso() -> String;
 
+/// `performance.now()` — high-resolution sub-millisecond timer in
+/// milliseconds since process start. Use for fine-grained timings (the
+/// existing `dateNow()` returns coarse epoch-millis as Int). Standard
+/// JS performance API, present in Deno, Node ≥ 16, and modern browsers.
+pub extern fn performance_now() -> Float;
+
+// ── Randomness (PRNG, non-crypto) ──────────────────────────────────
+//
+// Bound on `Math.random()` — the JS PRNG, **not cryptographically
+// secure**. Sufficient for property-test input generation, sampling,
+// and simulations. For cryptographic random bytes, a separate
+// `crypto_random_bytes` binding routing to `crypto.getRandomValues()`
+// belongs in a different sub-issue (different host call, different
+// threat model).
+
+/// `Math.random()` — uniform pseudo-random Float in `[0, 1)`.
+pub extern fn math_random() -> Float;
+
+/// Uniform u32 in `[0, 2^32)`, derived from `math_random()`.
+pub extern fn random_u32() -> Int;
+
+/// Uniform Int in `[lo, hi)`. Undefined behaviour if `hi <= lo`.
+pub extern fn random_in_range(lo: Int, hi: Int) -> Int;
+
 // ── CLI ────────────────────────────────────────────────────────────
 
 /// `Deno.args` — command-line arguments (excludes argv[0]).

tests/codegen-deno/random_smoke.affine

@@ -0,0 +1,18 @@
+// SPDX-License-Identifier: MPL-2.0
+// campaign #239 STEP 4-B — randomness + perf.now smoke
+//
+// Exercises math_random / random_u32 / random_in_range bindings + the
+// performance_now monotone-clock binding. The harness verifies
+// distribution sanity (not crypto-grade): u32 spans a reasonable
+// fraction of its range, random_in_range stays inside [lo, hi), and
+// performance_now is non-decreasing.
+
+use Deno::{ math_random, random_u32, random_in_range, performance_now };
+
+pub fn draw_u32() -> Int = random_u32();
+
+pub fn draw_unit() -> Float = math_random();
+
+pub fn draw_in_range(lo: Int, hi: Int) -> Int = random_in_range(lo, hi);
+
+pub fn perf_tick() -> Float = performance_now();