Bind thisArg in the array callback methods of dynamic arrays

forEach, map, filter, some, every, find, findIndex, findLast,
findLastIndex and flatMap on a dynamic array, and through
Array.prototype.<method>.call on a native array, called the callback
without its thisArg, so `this` in the callback was not the second
argument. These methods now bind `this` to the thisArg, or undefined
when there is none, once per call, around all of the method's callbacks.

tests/corpus/array-prototype-call-native-arrays.ts

@@ -20,3 +20,46 @@ console.log(words.join(","), Array.prototype.includes.call(words, "a"));
 const records: { id: number }[] = [{ id: 1 }, { id: 2 }, { id: 3 }];
 Array.prototype.copyWithin.call(records, 1, 0, 1);
 console.log(records.map((r) => r.id).join(","), records[0] === records[1]);
+
+// The callback methods bind `this` to their thisArg, for native arrays
+// through .call and for dynamic arrays called directly.
+type Scale = { k: number; seen: number[] };
+const scale: Scale = { k: 10, seen: [] };
+const values: number[] = [1, 2, 3, 4];
+Array.prototype.forEach.call(values, function (this: Scale, v: number) {
+  this.seen.push(v);
+}, scale);
+console.log(scale.seen.join(","));
+console.log(Array.prototype.map.call(values, function (this: Scale, v: number) {
+  return v * this.k;
+}, scale).join(","));
+console.log(Array.prototype.filter.call(values, function (this: Scale, v: number) {
+  return v * this.k > 15;
+}, scale).join(","));
+console.log(
+  Array.prototype.some.call(values, function (this: Scale, v: number) { return v === this.k / 5; }, scale),
+  Array.prototype.every.call(values, function (this: Scale, v: number) { return v < this.k; }, scale),
+  Array.prototype.find.call(values, function (this: Scale, v: number) { return v * this.k === 30; }, scale),
+  Array.prototype.findIndex.call(values, function (this: Scale, v: number) { return v * this.k === 30; }, scale),
+  Array.prototype.findLast.call(values, function (this: Scale, v: number) { return v * this.k < 30; }, scale),
+  Array.prototype.findLastIndex.call(values, function (this: Scale, v: number) { return v * this.k < 30; }, scale),
+);
+console.log(Array.prototype.flatMap.call(values, function (this: unknown, v: number) {
+  return [v, v * (this as Scale).k];
+}, scale).join(","));
+const parsed: any = JSON.parse("[1, 2, 3]");
+const sum = { total: 0 };
+parsed.forEach(function (this: { total: number }, v: number) {
+  this.total += v;
+}, sum);
+console.log(sum.total, parsed.map(function (this: Scale, v: number) { return v * this.k; }, scale).join(","));
+class Counter {
+  total = 0;
+  addAll(items: number[]): number {
+    Array.prototype.forEach.call(items, (v: number) => {
+      this.total += v;
+    });
+    return this.total;
+  }
+}
+console.log(new Counter().addAll(values));