fix style of %IteratorPrototype%.reduce feature detection

Author: zloirock

packages/core-js/modules/es.iterator.reduce.js

@@ -2,35 +2,28 @@
 var $ = require('../internals/export');
 var iterate = require('../internals/iterate');
 var anObject = require('../internals/an-object');
+var aCallable = require('../internals/a-callable');
 var getIteratorDirect = require('../internals/get-iterator-direct');
 var iteratorClose = require('../internals/iterator-close');
 var globalThis = require('../internals/global-this');
 var checkIteratorClosingOnEarlyError = require('../internals/check-iterator-closing-on-early-error');
 var call = require('../internals/function-call');
-var aCallable = require('../internals/a-callable');
+var fails = require('../internals/fails');
 
 var $TypeError = TypeError;
 var Iterator = globalThis.Iterator;
 var nativeReduce = Iterator && Iterator.prototype && Iterator.prototype.reduce;
 
 // https://bugs.webkit.org/show_bug.cgi?id=291651
-var nativeMethodFailsOnUndefinedInitialParam = function () {
-  try {
-    // eslint-disable-next-line es/no-iterator-prototype-reduce, es/no-array-prototype-keys -- required for testing
-    [].keys().reduce(function () { return false; }, undefined);
-    return false;
-  } catch (err) {
-    return true;
-  }
-};
+var FAILS_ON_INITIAL_UNDEFINED = nativeReduce && fails(function () {
+  // eslint-disable-next-line es/no-iterator-prototype-reduce, es/no-array-prototype-keys, array-callback-return -- required for testing
+  [].keys().reduce(function () { /* empty */ }, undefined);
+});
 
-var NATIVE_METHOD_WITHOUT_CLOSING_ON_EARLY_ERROR = false;
-var nativeMethodWithoutClosingOnEarlyError = function () {
-  NATIVE_METHOD_WITHOUT_CLOSING_ON_EARLY_ERROR = !checkIteratorClosingOnEarlyError(TypeError, nativeReduce, null);
-  return NATIVE_METHOD_WITHOUT_CLOSING_ON_EARLY_ERROR;
-};
+var NATIVE_METHOD_WITHOUT_CLOSING_ON_EARLY_ERROR = nativeReduce && !FAILS_ON_INITIAL_UNDEFINED &&
+  !checkIteratorClosingOnEarlyError(TypeError, nativeReduce, null);
 
-var FORCED = !nativeReduce || nativeMethodFailsOnUndefinedInitialParam() || nativeMethodWithoutClosingOnEarlyError();
+var FORCED = FAILS_ON_INITIAL_UNDEFINED || NATIVE_METHOD_WITHOUT_CLOSING_ON_EARLY_ERROR;
 
 // `Iterator.prototype.reduce` method
 // https://tc39.es/ecma262/#sec-iterator.prototype.reduce