Leaving a generator via an exception causes it to close

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)
+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.
+iter = nextGenerator();
+assertThrows(function() { iter.next() }, TypeError)
+assertIteratorIsClosed(iter);
+
+// Throw on an executing iterator raises a TypeError.
+iter = throwGenerator();
+assertThrows(function() { iter.next() }, TypeError)
+assertIteratorIsClosed(iter);
+
+// Next on an executing iterator doesn't change the state of the
+// generator.
+iter = (function* () {
+  try {
+    iter.next();
+    yield 1;
+  } catch (e) {
+    try {
+      // This next() should raise the same exception, because the first
+      // next() left the iter in the executing state.
+      iter.next();
+      yield 2;
+    } catch (e) {
+      yield 3;
+    }
+  }
+  yield 4;
+})();
+assertIteratorResult(3, false, iter.next());
+assertIteratorResult(4, false, iter.next());
+assertIteratorIsClosed(iter);