Add support for yield expressions

test/mjsunit/harmony/generators-iteration.js

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 221 matching lines @@
       },
       [1, 2, undefined],
       "foo",
       [1, 2, undefined]);
 }
 // TODO(wingo): Enable this test.  Currently accessing "this" doesn't work as
 // prior to generators, nothing needed to heap-allocate the receiver.
 // TestReceivers();
 
 TestGenerator(
+    function* g20() { yield (1 + (yield 2) + 3); },
+    [2, NaN, undefined],
+    "foo",
+    [2, "1foo3", undefined]);
+
+TestGenerator(
+    function* g21() { return (1 + (yield 2) + 3); },
+    [2, NaN],
+    "foo",
+    [2, "1foo3"]);
+
+TestGenerator(
+    function* g22() { yield (1 + (yield 2) + 3); yield (4 + (yield 5) + 6); },
+    [2, NaN, 5, NaN, undefined],
+    "foo",
+    [2, "1foo3", 5, "4foo6", undefined]);
+
+TestGenerator(
+    function* g23() {
+      return (yield (1 + (yield 2) + 3)) + (yield (4 + (yield 5) + 6));
+    },
+    [2, NaN, 5, NaN, NaN],
+    "foo",
+    [2, "1foo3", 5, "4foo6", "foofoo"]);
+
+TestGenerator(
     function* g() {
       var x = 1;
       yield x;
       with({x:2}) { yield x; }
       yield x;
     },
     [1, 2, 1, undefined],
     "foo",
     [1, 2, 1, undefined]);
 
@@ skipping 11 matching lines @@
   function TestThrowRecursion() {
     function* g() { yield iter.throw(1); }
     var iter = g();
     return iter.next();
   }
   assertThrows(TestNextRecursion, Error);
   assertThrows(TestSendRecursion, Error);
   assertThrows(TestThrowRecursion, Error);
 }
 TestRecursion();