JSTests/test262/test/language/expressions/yield/star-rhs-iter-thrw-violation-no-rtrn.js

// Copyright (C) 2016 the V8 project authors. All rights reserved.
// This code is governed by the BSD license found in the LICENSE file.
/*---
esid: sec-generator-function-definitions-runtime-semantics-evaluation
es6id: 14.4.14
description: >
  Abrupt completion returned after protocol violation (and a `return` method
  is not defined)
info: |
  YieldExpression : yield * AssignmentExpression

  1. Let exprRef be the result of evaluating AssignmentExpression.
  2. Let value be ? GetValue(exprRef).
  3. Let iterator be ? GetIterator(value).
  4. Let received be NormalCompletion(undefined).
  5. Repeat
     a. If received.[[Type]] is normal, then
        [...]
     b. Else if received.[[Type]] is throw, then
        i. Let throw be ? GetMethod(iterator, "throw").
        ii. If throw is not undefined, then
            [...]
        iii. Else,
             1. NOTE: If iterator does not have a throw method, this throw is
                going to terminate the yield* loop. But first we need to give
                iterator a chance to clean up.
             2. Perform ? IteratorClose(iterator, Completion{[[Type]]: normal,
                [[Value]]: empty, [[Target]]: empty}).
             3. NOTE: The next step throws a TypeError to indicate that there
                was a yield* protocol violation: iterator does not have a throw
                method.
             4. Throw a TypeError exception.

  7.4.6 IteratorClose

  1. Assert: Type(iterator) is Object.
  2. Assert: completion is a Completion Record.
  3. Let return be ? GetMethod(iterator, "return").
  4. If return is undefined, return Completion(completion).
features: [generators, Symbol.iterator]
---*/

var badIter = {};
var throwCount = 0;
var returnCount = 0;
var spyResult = {
  next: function() {
    return { done: false };
  }
};
Object.defineProperty(spyResult, 'throw', {
  get: function() {
    throwCount += 1;
  }
});
Object.defineProperty(spyResult, 'return', {
  get: function() {
    returnCount += 1;
  }
});
badIter[Symbol.iterator] = function() {
  return spyResult;
};
function* g() {
  try {
    yield * badIter;
  } catch (err) {
    caught = err;
  }
}
var iter = g();
var caught;

iter.next();
iter.throw();

assert.sameValue(throwCount, 1, '`throw` property access');
assert.sameValue(returnCount, 1, '`return` property access');
assert.sameValue(typeof caught, 'object');
assert.sameValue(caught.constructor, TypeError);