replace type for shuffle (and test it)

Author: nbogie

test/types/generics.ts

@@ -11,6 +11,8 @@ function setup() {
 
   // The types should fail if the result of random() is any
   logMessage(message);
+  
+  testShuffleMaintainsType();
 }
 
 // From: https://stackoverflow.com/a/50375286/62076
@@ -29,3 +31,23 @@ type NotAny<T> = IsStrictlyAny<T> extends true ? never : T
 function logMessage(message: NotAny<{ content: string }>) {
   console.log(message)
 }
+
+
+
+/** test that shuffle(arr) preserves arr type in return, not just any[] */
+function testShuffleMaintainsType(){
+  
+	type Expect<T extends true> = T;
+	type Equal<X, Y> = 
+		(<T>() => T extends X ? 1 : 2) extends 
+		(<T>() => T extends Y ? 1 : 2) ? true : false;
+
+	const shuffleResult1 = shuffle(["a", "b", "c"]);
+	const shuffleResult2 = shuffle(["a", 10, null]);
+  //check the signature with the optional boolean type-checks, too
+	const shuffleResult3 = shuffle([10, 20, 30], true);
+
+	type ShuffleTest1 = Expect<Equal<typeof shuffleResult1, string[]>>;
+  type ShuffleTest2 = Expect<Equal<typeof shuffleResult2, (string|number|null)[]>>;
+  type ShuffleTest3 = Expect<Equal<typeof shuffleResult3, number[]>>;
+}

utils/patch.mjs

@@ -44,6 +44,12 @@ export function applyPatches() {
     "random<T>(choices: readonly T[]): T;"
   );
 
+  replace(
+    ['p5.d.ts', 'global.d.ts'],
+    'shuffle(array: any[], bool?: boolean): any[];',
+    'shuffle<T>(array: T[], bool?: boolean): T[];'
+  );
+
   replace(
     'p5.d.ts',
     'textToContours(str: string, x: number, y: number, options?: { sampleFactor?: number; simplifyThreshold?: number }): object[][];',