[patch] change Symbol.iterator fallback from callable check to nullish check

See tc39/proposal-iterator-helpers#272

Author: ljharb

aos/GetIteratorFlattenable.js

@@ -7,9 +7,8 @@ var $TypeError = GetIntrinsic('%TypeError%');
 var AdvanceStringIndex = require('es-abstract/2022/AdvanceStringIndex');
 var Call = require('es-abstract/2022/Call');
 var GetIteratorDirect = require('./GetIteratorDirect');
-var GetV = require('es-abstract/2022/GetV');
+var GetMethod = require('es-abstract/2022/GetMethod');
 var IsArray = require('es-abstract/2022/IsArray');
-var IsCallable = require('es-abstract/2022/IsCallable');
 var Type = require('es-abstract/2022/Type');
 
 var getIteratorMethod = require('es-abstract/helpers/getIteratorMethod');
@@ -21,18 +20,18 @@ module.exports = function GetIteratorFlattenable(obj) {
 
 	var method = void undefined; // step 2
 
-	// method = Get(obj, Symbol.iterator); // step 5.a
+	// method = GetMethod(obj, Symbol.iterator); // step 5.a
 	method = getIteratorMethod(
 		{
 			AdvanceStringIndex: AdvanceStringIndex,
-			GetMethod: GetV,
+			GetMethod: GetMethod,
 			IsArray: IsArray
 		},
 		obj
 	);
 
 	var iterator;
-	if (!IsCallable(method)) { // step 3
+	if (typeof method === 'undefined') { // step 3
 		iterator = obj; // step 3.a
 	} else { // step 4
 		iterator = Call(method, obj); // step 4.a

test/Iterator.prototype.flatMap.js

@@ -116,7 +116,7 @@ module.exports = {
 						return n.next();
 					}
 				};
-				ret[Symbol.iterator] = 0;
+				ret[Symbol.iterator] = null;
 				return ret;
 			}), [0, 1, 2], st, 'test262: test/built-ins/Iterator/prototype/flatMap/iterable-to-iterator-fallback');