Iterator.concat no longer reuses IteratorResult object of concatenated iterators

tc39/proposal-iterator-sequencing#26

Author: zloirock

CHANGELOG.md

@@ -1,7 +1,8 @@
 ## Changelog
 ##### Unreleased
-- `clamp` no longer throws an error on `NaN` as `min` or `max`, following [proposal-math-clamp#d2387791c265edf66fbe2455eab919016717ce6f](https://github.com/tc39/proposal-math-clamp/commit/d2387791c265edf66fbe2455eab919016717ce6f) 
-- Use `Get` in `Iterator.zipKeyed`, following [proposal-joint-iteration#43](https://github.com/tc39/proposal-joint-iteration/pull/43)
+- `clamp` no longer throws an error on `NaN` as `min` or `max`, following [tc39/proposal-math-clamp#d2387791c265edf66fbe2455eab919016717ce6f](https://github.com/tc39/proposal-math-clamp/commit/d2387791c265edf66fbe2455eab919016717ce6f) 
+- `Iterator.concat` no longer reuses `IteratorResult` object of concatenated iterators, following [tc39/proposal-iterator-sequencing#26](https://github.com/tc39/proposal-iterator-sequencing/pull/26)
+- Use `Get` in `Iterator.zipKeyed`, following [tc39/proposal-joint-iteration#43](https://github.com/tc39/proposal-joint-iteration/pull/43)
 - Fixed [several V8 bugs](https://github.com/zloirock/core-js/issues/1439) in `Uint8Array.fromHex` and `Uint8Array.prototype.{ setFromBase64, toBase64, toHex }`, thanks [**@brc-dd**](https://github.com/brc-dd)
 - Fixed some cases of `Set.prototype.{ symmetricDifference, union }` detection
 - Added missing dependencies to some entries of static `Iterator` methods

packages/core-js/modules/esnext.iterator.concat.js

@@ -5,7 +5,6 @@ var aCallable = require('../internals/a-callable');
 var anObject = require('../internals/an-object');
 var getIteratorMethod = require('../internals/get-iterator-method');
 var createIteratorProxy = require('../internals/iterator-create-proxy');
-var createIterResultObject = require('../internals/create-iter-result-object');
 
 var $Array = Array;
 
@@ -17,7 +16,7 @@ var IteratorProxy = createIteratorProxy(function () {
       var iterables = this.iterables;
       if (iterableIndex >= iterables.length) {
         this.done = true;
-        return createIterResultObject(undefined, true);
+        return;
       }
       var entry = iterables[iterableIndex];
       this.iterables[iterableIndex] = null;
@@ -30,9 +29,9 @@ var IteratorProxy = createIteratorProxy(function () {
       this.next = null;
       continue;
     }
-    return result;
+    return result.value;
   }
-}, false, true);
+});
 
 // `Iterator.concat` method
 // https://github.com/tc39/proposal-iterator-sequencing

tests/unit-global/esnext.iterator.concat.js

@@ -81,7 +81,8 @@ QUnit.test('Iterator.concat', assert => {
   const iterResult = iterator.next();
   assert.same(iterResult.done, false);
   assert.same(iterResult.value, 123);
-  assert.same(iterResult, oldIterResult);
+  // https://github.com/tc39/proposal-iterator-sequencing/pull/26
+  assert.notSame(iterResult, oldIterResult);
 
   assert.throws(() => concat(createIterator([1, 2, 3])), TypeError, 'non-iterable iterator #1');
   assert.throws(() => concat([], createIterator([1, 2, 3])), TypeError, 'non-iterable iterator #2');

tests/unit-pure/esnext.iterator.concat.js

@@ -80,7 +80,8 @@ QUnit.test('Iterator.concat', assert => {
   const iterResult = iterator.next();
   assert.same(iterResult.done, false);
   assert.same(iterResult.value, 123);
-  assert.same(iterResult, oldIterResult);
+  // https://github.com/tc39/proposal-iterator-sequencing/pull/26
+  assert.notSame(iterResult, oldIterResult);
 
   assert.throws(() => concat(createIterator([1, 2, 3])), TypeError, 'non-iterable iterator #1');
   assert.throws(() => concat([], createIterator([1, 2, 3])), TypeError, 'non-iterable iterator #2');