fix(async/unstable): validate Semaphore max is a positive integer (#6934)

Author: tomas-zijdemans

async/unstable_semaphore.ts

@@ -36,11 +36,12 @@ export class Semaphore {
    * Creates a new semaphore with the specified number of permits.
    *
    * @param max Maximum concurrent permits. Defaults to 1 (mutex).
+   * @throws {TypeError} If `max` is not a positive integer.
    */
   constructor(max: number = 1) {
-    if (max < 1) {
+    if (!Number.isInteger(max) || max < 1) {
       throw new TypeError(
-        `Cannot create semaphore as 'max' must be at least 1: current value is ${max}`,
+        `Cannot create semaphore as 'max' must be a positive integer: received ${max}`,
       );
     }
     this.#count = this.#max = max;

async/unstable_semaphore_test.ts

@@ -28,6 +28,12 @@ Deno.test("Semaphore constructor throws for non-positive max", () => {
   assertThrows(() => new Semaphore(-1), TypeError);
 });
 
+Deno.test("Semaphore constructor throws for non-integer max", () => {
+  assertThrows(() => new Semaphore(NaN), TypeError);
+  assertThrows(() => new Semaphore(Infinity), TypeError);
+  assertThrows(() => new Semaphore(1.5), TypeError);
+});
+
 Deno.test("Semaphore constructor defaults to 1", async () => {
   const sem = new Semaphore();
   await sem.acquire();