Fix bug where generators got closed prematurely.

test/mjsunit/es6/generators-states.js

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Test generator states.
 
 function Foo() {}
 function Bar() {}
 
 function assertIteratorResult(value, done, result) {
   assertEquals({ value: value, done: done}, result);
 }
 
 function assertIteratorIsClosed(iter) {
   assertIteratorResult(undefined, true, iter.next());
   // Next and throw on a closed iterator.
   assertDoesNotThrow(function() { iter.next(); });
   assertThrows(function() { iter.throw(new Bar); }, Bar);
 }
 
 var iter;
 function* nextGenerator() { yield iter.next(); }
 function* throwGenerator() { yield iter.throw(new Bar); }
 
 // Throw on a suspendedStart iterator.
 iter = nextGenerator();
 assertThrows(function() { iter.throw(new Foo) }, Foo)
+assertIteratorIsClosed(iter);
 assertThrows(function() { iter.throw(new Foo) }, Foo)
 assertIteratorIsClosed(iter);
 
 // The same.
 iter = throwGenerator();
 assertThrows(function() { iter.throw(new Foo) }, Foo)
 assertThrows(function() { iter.throw(new Foo) }, Foo)
 assertIteratorIsClosed(iter);
 
 // Next on an executing iterator raises a TypeError.
@@ skipping 20 matching lines @@
       yield 2;
     } catch (e) {
       yield 3;
     }
   }
   yield 4;
 })();
 assertIteratorResult(3, false, iter.next());
 assertIteratorResult(4, false, iter.next());
 assertIteratorIsClosed(iter);
+
+
+// return that doesn't close

[Michael Starzinger, 2016/01/25 12:56:05]

nit: Please capitalize and punctuate comment.

+{
+  let g = function*() { try {return 42} finally {yield 43} };
+
+  let x = g();
+  assertEquals({value: 43, done: false}, x.next());
+  assertEquals({value: 42, done: true}, x.next());
+}
+{
+  let x;
+  let g = function*() { try {return 42} finally {x.throw(666)} };

[Michael Starzinger, 2016/01/25 12:56:05]

As discussed offline, can we add another test case of the following structure on
top of the existings ones here, just to make this clearer:

let x;
let g = function*() {
  try { return 42 } finally {
    try { x.throw(666) } catch(e) {}
  }
}

x = g();
assertEquals({value: 42, done: true}, x.next());

+
+  x = g();
+  assertThrows(() => x.next(), TypeError);  // still executing
+}