src/v8/test/mjsunit/harmony/async-from-sync-iterator.js - cobalt - Git at Google

 // Copyright 2017 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.

 // Flags: --allow-natives-syntax

 let testFailed = false;
 let testFailure;

 function assertThrowsAsync(run, errorType, message) {
   var actual;
   var hadValue = false;
   var hadError = false;
   var promise = run();

   if (typeof promise !== "object" || typeof promise.then !== "function") {
     throw new MjsUnitAssertionError(
         "Expected " + run.toString() +
         " to return a Promise, but it returned " + PrettyPrint(promise));
   }

   promise.then(function(value) { hadValue = true; actual = value; },
                function(error) { hadError = true; actual = error; });

   assertFalse(hadValue || hadError);

   %RunMicrotasks();

   if (!hadError) {
     throw new MjsUnitAssertionError(
         "Expected " + run + "() to throw " + errorType.name +
         ", but did not throw.");
   }
   if (!(actual instanceof errorType))
     throw new MjsUnitAssertionError(
         "Expected " + run + "() to throw " + errorType.name +
         ", but threw '" + actual + "'");
   if (message !== void 0 && actual.message !== message)
     throw new MjsUnitAssertionError(
         "Expected " + run + "() to throw '" + message + "', but threw '" +
         actual.message + "'");
 };

 function resolveLater(value) {
   return new Promise(function(resolve) {
     Promise.resolve().then(function() {
       resolve(value);
     });
   });
 }

 function rejectLater(value) {
   return new Promise(function(resolve, reject) {
     Promise.resolve().then(function() {
       reject(value);
     });
   });
 }

 const kNext = 1;
 const kThrow = 2;
 const kReturn = 4;
 const kNextThrows = kNext | 8;
 const kReturnThrows = kReturn | 16;
 const kThrowNormal = kThrow | 32;
 const kNextUnchanged = kNext | 64;
 const kReturnUnchanged = kReturn | 128;
 const kThrowUnchanged = kThrow | 256;
 function sync(array, features, log) {
   // `log` is a required parameter
   if (log === void 0) %AbortJS("`log` is undefined");

   let i = 0;
   let methods = {
     next(sent) {
       let done = i >= array.length;
       let value = array[i];
       log.push({ method: "next", sent, value, done });
       if ((features & kNextThrows) === kNextThrows) throw sent;
       if ((features & kNextUnchanged) === kNextUnchanged) return sent;
       i++;
       return { value, done };
     },
     throw(sent) {
       let done = i >= array.length;
       log.push({ method: "throw", sent, done });
       if ((features & kThrowNormal) === kThrowNormal)
           return { value: sent, done };
       if ((features & kThrowUnchanged) === kThrowUnchanged) return sent;
       throw sent;
     },
     return(sent) {
       let done = true;
       log.push({ method: "return", sent, done });
       if ((features & kReturnThrows) === kReturnThrows) throw sent;
       if ((features & kReturnUnchanged) === kReturnUnchanged) return sent;
       return { value: sent, done };
     }
   };
   return {
     [Symbol.iterator]() { return this; },
     next: (features & kNext) ? methods.next : undefined,
     throw: (features & kThrow) ? methods.throw : undefined,
     return: (features & kReturn) ? methods.return : undefined
   };
 }

 class MyError extends Error {};

 (async function AsyncFromSyncWithGenerator() {
   function* gen() {
     yield "sync value";
     try {
       yield new Promise(function(resolve) {
         resolve("async value");
       });
     } catch (error) {
       throw error;
     }
     assertUnreachable("generator is closed");
   }
   let iter = %CreateAsyncFromSyncIterator(gen());

   // [Async-from-Sync Iterator] wraps sync iterator values in a Promise
   let promise = iter.next();
   assertInstanceof(promise, Promise);
   let iter_result = await promise;
   assertEquals({ value: "sync value", done: false }, iter_result);

   // [Async-from-Sync Iterator] will wait for resolution of Promise values
   promise = iter.next();
   assertInstanceof(promise, Promise);
   iter_result = await promise;
   assertEquals({ value: "async value", done: false }, iter_result);

   // [Async-from-Sync Iterator].throw delegates to .throw() method of sync
   // iterator.
   promise = iter.throw(new MyError("Error#1"));
   assertInstanceof(promise, Promise);
   try {
     await promise;
     assertUnreachable("promise should be rejected");
   } catch (e) {
     // If assertUnreachable failed, rethrow
     if (e instanceof MjsUnitAssertionError) throw e;
     assertInstanceof(e, MyError);
     assertEquals("Error#1", e.message);
   }

   // Generator is closed, subsequent calls to .next() will not resume.
   promise = iter.next("floof");
   iter_result = await promise;
   assertEquals({ value: undefined, done: true }, iter_result);

   promise = iter.return("generator closed");
   assertInstanceof(promise, Promise);
   iter_result = await promise;
   assertEquals({ value: "generator closed", done: true }, iter_result);

   // .next(), .return() and .throw() delegate to sync iterator methods, without
   // keeping track of the state of the generator.
   promise = iter.next("unused");
   assertInstanceof(promise, Promise);
   iter_result = await promise;
   assertEquals({ value: undefined, done: true }, iter_result);

   promise = iter.throw(new MyError("Error#2"));
   assertInstanceof(promise, Promise);
   try {
     await promise;
     assertUnreachable("promise should be rejected");
   } catch (e) {
     // If assertUnreachable failed, rethrow
     if (e instanceof MjsUnitAssertionError) throw e;
     assertInstanceof(e, MyError);
     assertEquals("Error#2", e.message);
   }

   promise = iter.return("return-after-completed");
   assertInstanceof(promise, Promise);
   iter_result = await promise;
   assertEquals({ value: "return-after-completed", done: true }, iter_result);
 })().catch(function(error) {
   testFailed = true;
   testFailure = error;
 });

 %RunMicrotasks();
 if (testFailed) {
   throw testFailure;
 }


 (async function AsyncFromSyncOrderOfOperations() {
   let log = [];
   iter = %CreateAsyncFromSyncIterator(sync(["sync-value"], 0, log));

   try {
     await iter.next();
     assertUnreachable("Iterator.next() method is not optional");
   } catch (e) {
     assertInstanceof(e, TypeError);
     assertEquals([], log);
   }

   log = [];
   iter = %CreateAsyncFromSyncIterator(sync(["sync-value"], kNext, log));
   assertEquals({ value: "sync-value", done: false }, await iter.next("a"));
   assertEquals([
     {
       method: "next",
       sent: "a",
       value: "sync-value",
       done: false
     }
   ], log);

   log = [];
   let asyncValue = resolveLater("async-value");
   iter = %CreateAsyncFromSyncIterator(sync([asyncValue], kNext, log));
   assertEquals({ value: "async-value", done: false }, await iter.next("b"));
   assertEquals([
     {
       method: "next",
       sent: "b",
       value: asyncValue,
       done: false
     }
   ], log);

   // If [sync_iterator].next() produces a rejected Promise or an exception is
   // thrown, Promise is rejected with thrown/rejected value.
   log = [];
   asyncValue = rejectLater("Boo!");
   iter = %CreateAsyncFromSyncIterator(sync([asyncValue], kNext, log));
   try {
     await iter.next('c');
     assertUnreachable('Expected `iter.next(\'c\') to throw, but did not throw');
   } catch (e) {
     assertEquals("Boo!", e);
     assertEquals([
       {
         method: 'next',
         sent: 'c',
         value: asyncValue,
         done: false
       }
     ], log);
   }

   log = [];
   iter = %CreateAsyncFromSyncIterator(sync(['sync-value'], kNextThrows, log));
   try {
     await iter.next('Boo!');
     assertUnreachable('Expected `iter.next(\'c\') to throw, but did not throw');
   } catch (e) {
     assertEquals("Boo!", e);
     assertEquals([
       {
         method: 'next',
         sent: 'Boo!',
         value: 'sync-value',
         done: false
       }
     ], log);
   }


   // [Async-from-Sync Iterator].next() will be rejected with a TypeError if
   // Type([sync_iterator].next()) is not Object.
   log = [];
   iter = %CreateAsyncFromSyncIterator(sync(['sync-value'], kNextUnchanged,
                                       log));
   try {
     await iter.next('not-a-JSReceiver');
     assertUnreachable('Expected `iter.next(\'not-a-JSReceiver\')` to ' +
                       'throw, but did not throw')
   } catch (e) {
     assertEquals(e.constructor, TypeError);
   }

   assertEquals([
     {
       method: 'next',
       sent: 'not-a-JSReceiver',
       value: 'sync-value',
       done: false
     }
   ], log);

   // If [sync_iterator] does not have a .return() method, return a Promise
   // resolved with the value `{ value: <<sent value>>, done: true }`.
   log = [];
   iter = %CreateAsyncFromSyncIterator(sync(['sync-return'], kNext, log));
   assertEquals({
     value: 'd',
     done: true
   }, await iter.return('d'));

   // [Async-from-Sync Iterator] merely delegates, and does not keep track of
   // whether [sync_iterator] is completed or not.
   assertEquals({
     value: 'sync-return',
     done: false
   }, await iter.next('e'));

   assertEquals([
     {
       method: 'next',
       sent: 'e',
       value: 'sync-return',
       done: false
     }
   ], log);

   // If [sync_iterator] does have a .return() method, return a Promise
   // fulfilled with the iterator result of [sync_iterator].return().
   log = [];
   iter = %CreateAsyncFromSyncIterator(sync(['sync-return'],
                                       kNext|kReturn, log));
   assertEquals({
     value: 'f',
     done: true
   }, await iter.return('f'));

   // [Async-from-Sync Iterator] merely delegates, and does not keep track of
   // whether [sync_iterator] is completed or not.
   assertEquals({
     value: 'sync-return',
     done: false
   }, await iter.next('g'));

   assertEquals([
     {
       method: 'return',
       sent: 'f',
       done: true
     },
     {
       method: 'next',
       sent: 'g',
       value: 'sync-return',
       done: false
     }
   ], log);

   // If [sync_iterator].return() produces a rejected Promise or an exception is
   // thrown, Promise is rejected with thrown/rejected value.
   log = [];
   iter = %CreateAsyncFromSyncIterator(sync(['sync-value'], kNext|kReturnThrows,
                                       log));
   try {
     await iter.return('Boo!!');
     assertUnreachable('Expected `iter.return(\'Boo!!\')` to throw, but did ' +
                       'not throw');
   } catch (e) {
     assertEquals("Boo!!", e);
   }

   // [Async-from-Sync Iterator] merely delegates, and does not keep track of
   // whether [sync_iterator] is completed or not.
   assertEquals({ value: 'sync-value', done: false }, await iter.next('h'));
   assertEquals([
     {
       method: 'return',
       sent: 'Boo!!',
       done: true
     },
     {
       method: 'next',
       sent: 'h',
       value: 'sync-value',
       done: false
     }
   ], log);


   log = [];
   iter = %CreateAsyncFromSyncIterator(sync(['sync-value'], kNext|kReturn, log));

   let rejection = Promise.reject('Boo!!');
   try {
     await iter.return(rejection);
     assertUnreachable('Expected `iter.return(Promise.reject(\'Boo!!\'))` to ' +
                       'throw, but did not throw');
   } catch (e) {
     assertEquals('Boo!!', e);
   }

   // [Async-from-Sync Iterator] merely delegates, and does not keep track of
   // whether [sync_iterator] is completed or not.
   assertEquals({ value: 'sync-value', done: false }, await iter.next('i'));
   assertEquals([
     {
       method: 'return',
       sent: rejection,
       done: true
     },
     {
       method: 'next',
       sent: 'i',
       value: 'sync-value',
       done: false
     }
   ], log);

   // [Async-from-Sync Iterator].return() will be rejected with a TypeError if
   // Type([sync_iterator].return()) is not Object.
   log = [];
   iter = %CreateAsyncFromSyncIterator(sync(['sync-value'],
                                       kNext|kReturnUnchanged, log));
   try {
     await iter.return('not-a-JSReceiver');
     assertUnreachable('Expected `iter.return(\'not-a-JSReceiver\')` to ' +
                       'throw, but did not throw')
   } catch (e) {
     assertEquals(e.constructor, TypeError);
   }

   // [Async-from-Sync Iterator] merely delegates, and does not keep track of
   // whether [sync_iterator] is completed or not.
   assertEquals({ value: 'sync-value', done: false }, await iter.next('j'));
   assertEquals([
     {
       method: 'return',
       sent: 'not-a-JSReceiver',
       done: true
     },
     {
       method: 'next',
       sent: 'j',
       value: 'sync-value',
       done: false
     }
   ], log);

   // If [sync_iterator] does not have a .throw method, return a Promise rejected
   // with the sent value.
   log = [];
   iter = %CreateAsyncFromSyncIterator(sync(['sync-value'], kNext, log));
   try {
     await iter.throw('Boo!!');
     assertUnreachable('Expected iter.throw(\'Boo!!\') to throw, but did not ' +
                       'throw');
   } catch (e) {
     assertEquals('Boo!!', e);
   }

   // [Async-from-Sync Iterator] merely delegates, and does not keep track of
   // whether [sync_iterator] is completed or not.
   assertEquals({ value: 'sync-value', done: false }, await iter.next('k'));
   assertEquals([
     {
       method: 'next',
       sent: 'k',
       value: 'sync-value',
       done: false
     }
   ], log);


   log = [];
   iter = %CreateAsyncFromSyncIterator(sync(['sync-value'], kNext|kThrow, log));
   try {
     await iter.throw('Boo!!');
     assertUnreachable('Expected iter.throw(\'Boo!!\') to throw, but did not ' +
                       'throw');
   } catch (e) {
     assertEquals('Boo!!', e);
   }

   // [Async-from-Sync Iterator] merely delegates, and does not keep track of
   // whether [sync_iterator] is completed or not.
   assertEquals({ value: 'sync-value', done: false }, await iter.next('l'));
   assertEquals([
     {
       method: 'throw',
       sent: 'Boo!!',
       done: false
     },
     {
       method: 'next',
       sent: 'l',
       value: 'sync-value',
       done: false
     }
   ], log);

   // If [sync_iterator].throw() returns a resolved Promise or a Completion
   // with [[Type]] "normal" or "return", return a resolved Promise
   log = [];
   iter = %CreateAsyncFromSyncIterator(sync(['sync-value'], kNext|kThrowNormal,
                                       log));
   assertEquals({
     value: 'Boo!!',
     done: false
   }, await iter.throw('Boo!!'));

   // [Async-from-Sync Iterator] merely delegates, and does not keep track of
   // whether [sync_iterator] is completed or not.
   assertEquals({ value: 'sync-value', done: false }, await iter.next('m'));
   assertEquals([
     {
       method: 'throw',
       sent: 'Boo!!',
       done: false
     },
     {
       method: 'next',
       sent: 'm',
       value: 'sync-value',
       done: false
     }
   ], log);

   // [Async-from-Sync Iterator].throw() will be rejected with a TypeError if
   // Type([sync_iterator].throw()) is not Object.
   log = [];
   iter = %CreateAsyncFromSyncIterator(sync(['sync-value'],
                                       kNext|kThrowUnchanged, log));
   try {
     await iter.throw('not-a-JSReceiver');
     assertUnreachable('Expected `iter.throw(\'not-a-JSReceiver\')` to ' +
                       'throw, but did not throw')
   } catch (e) {
     assertEquals(e.constructor, TypeError);
   }

   // [Async-from-Sync Iterator] merely delegates, and does not keep track of
   // whether [sync_iterator] is completed or not.
   assertEquals({ value: 'sync-value', done: false }, await iter.next('n'));
   assertEquals([
     {
       method: 'throw',
       sent: 'not-a-JSReceiver',
       done: false
     },
     {
       method: 'next',
       sent: 'n',
       value: 'sync-value',
       done: false
     }
   ], log);

   // Let nextValue be IteratorValue(nextResult).
   // IfAbruptRejectPromise(nextValue, promiseCapability).)
   iter = %CreateAsyncFromSyncIterator({
     next() { return { get value() { throw "BadValue!" }, done: false }; }
   });
   try {
     await iter.next();
     assertUnreachable('Expected `iter.next()` to throw, but did not throw');
   } catch (e) {
     assertEquals('BadValue!', e);
   }

   // Let nextDone be IteratorComplete(nextResult).
   // IfAbruptRejectPromise(nextDone, promiseCapability).
   iter = %CreateAsyncFromSyncIterator({
     next() { return { value: undefined, get done() { throw "BadValue!" } }; }
   });
   try {
     await iter.next();
     assertUnreachable('Expected `iter.next()` to throw, but did not throw');
   } catch (e) {
     assertEquals('BadValue!', e);
   }

   // IfAbruptRejectPromise(returnResult, promiseCapability).
   // Let returnValue be IteratorValue(returnResult).
   iter = %CreateAsyncFromSyncIterator({
     return() { return { get value() { throw "BadValue!" }, done: false }; }
   });
   try {
     await iter.return();
     assertUnreachable('Expected `iter.return()` to throw, but did not throw');
   } catch (e) {
     assertEquals('BadValue!', e);
   }

   // IfAbruptRejectPromise(returnValue, promiseCapability).
   // Let returnDone be IteratorComplete(returnResult).
   iter = %CreateAsyncFromSyncIterator({
     return() { return { value: undefined, get done() { throw "BadValue!" } }; }
   });
   try {
     await iter.return();
     assertUnreachable('Expected `iter.return()` to throw, but did not throw');
   } catch (e) {
     assertEquals('BadValue!', e);
   }

   // IfAbruptRejectPromise(throwResult, promiseCapability).
   // Let throwValue be IteratorValue(throwResult).
   iter = %CreateAsyncFromSyncIterator({
     throw() { return { get value() { throw "BadValue!" }, done: false }; }
   });
   try {
     await iter.throw();
     assertUnreachable('Expected `iter.throw()` to throw, but did not throw');
   } catch (e) {
     assertEquals('BadValue!', e);
   }

   // IfAbruptRejectPromise(throwValue, promiseCapability).
   // Let throwDone be IteratorComplete(throwResult).
   iter = %CreateAsyncFromSyncIterator({
     throw() { return { value: undefined, get done() { throw "BadValue!" } }; }
   });
   try {
     await iter.throw();
     assertUnreachable('Expected `iter.throw()` to throw, but did not throw');
   } catch (e) {
     assertEquals('BadValue!', e);
   }
 })().catch(function(error) {
   testFailed = true;
   testFailure = error;
 });

 %RunMicrotasks();
 if (testFailed) {
   throw testFailure;
 }

 (function ExtractedAsyncFromSyncIteratorMethods() {
   // TODO(ishell, caitp): Rewrite the test without using function.caller.
   // According to ES#sec-built-in-function-objects all built-in functions
   // must be strict. And ES#sec-forbidden-extensions states that the value of
   // a function.caller must not be a strict function.
   return;
   // Async-from-Sync iterator methods can be extracted via function.caller.
   // TODO(caitp): test extracted `throw` method using yield* in async generator.
   let extractor = [0, 1, 2, 3, 4,5,6,7,8,9];
   let extractedNext;
   let extractedReturn;

   extractor[Symbol.iterator] = function() {
     let it = [][Symbol.iterator].call(extractor);
     let origNext = it.next, origThrow = it.throw, origReturn = it.return;
     function extractNext() {
       extractedNext = extractNext.caller;
       return origNext;
     }
     function extractReturn() {
       extractedReturn = extractReturn.caller;
       return origReturn;
     }
     Object.defineProperties(it, {
       "next": { get: extractNext, configurable: true },
       "return": { get: extractReturn, configurable: true }
     });
     return it;
   };

   async function f() {
     let i;
     let it = extractor[Symbol.iterator]();
     for await (let x of it) break;
     for await (let x of it) return "x";
   }

   // Cycle through `f` to extract iterator methods
   f().catch(function() { %AbortJS("No error should have occurred"); });
   %RunMicrotasks();

   assertEquals(typeof extractedNext, "function");
   assertThrowsAsync(() => extractedNext.call(undefined), TypeError);
   assertThrowsAsync(() => extractedNext.call(1), TypeError);

   assertEquals(typeof extractedReturn, "function");
   assertThrowsAsync(() => extractedReturn.call(undefined), TypeError);
   assertThrowsAsync(() => extractedReturn.call(1), TypeError);
 })();

 (function AsyncFromSyncIteratorOrdering() {
   let i = 0;
   let log = [];
   function r(value, done) {
     let number = (++i);
     return {
       get value() {
         log.push("get iterResult #" + number + ".value");
         return {
           get then() {
             log.push("get nextValue#" + number + ".then");
             return (r) => {
               log.push("call nextValue#" + number + ".then");
               r(value);
             }
           }
         };
       },
       get done() {
         log.push("get iterResult #" + number + ".done");
         return done;
       }
     };
   }
   var results = [r("value1", false), r("value2", false), r("value3", true),
                  r("value4", false)];

   var iter = {
     get [Symbol.asyncIterator]() {
       log.push("get syncIterable[@@asyncIterator]");
       return null;
     },

     get [Symbol.iterator]() {
       log.push("get syncIterable[@@iterator]");
       return (...args) => {
         log.push("call syncIterable[@@iterator](" + args.join(", ") + ")");
         return this;
       }
     },
     next_: 0,
     get next() {
       log.push("get syncIterable.next");
       let i = this.next_++;
       return (...args) => {
         log.push("call syncIterable.next(" + args.join(", ") + ")");
         return results[i];
       }
     }
   };

   async function iterate(iterable) {
     log.push("before");
     for await (let x of iterable) {
       log.push("got value " + x);
     }
     log.push("after");

     return log;
   }

   iterate(iter).then(log => {
     assertEquals([
       "before",
       "get syncIterable[@@asyncIterator]",
       "get syncIterable[@@iterator]",
       "call syncIterable[@@iterator]()",
       "get syncIterable.next",
       "call syncIterable.next()",
       "get iterResult #1.done",
       "get iterResult #1.value",
       "get nextValue#1.then",
       "call nextValue#1.then",
       "got value value1",
       "get syncIterable.next",
       "call syncIterable.next()",
       "get iterResult #2.done",
       "get iterResult #2.value",
       "get nextValue#2.then",
       "call nextValue#2.then",
       "got value value2",
       "get syncIterable.next",
       "call syncIterable.next()",
       "get iterResult #3.done",
       "get iterResult #3.value",
       "get nextValue#3.then",
       "call nextValue#3.then",
       "after"
     ], log)
   }).catch(x => %AbortJS(String(x)));
 })();
	// Copyright 2017 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.

	// Flags: --allow-natives-syntax

	let testFailed = false;
	let testFailure;

	function assertThrowsAsync(run, errorType, message) {
	var actual;
	var hadValue = false;
	var hadError = false;
	var promise = run();

	if (typeof promise !== "object" \|\| typeof promise.then !== "function") {
	throw new MjsUnitAssertionError(
	"Expected " + run.toString() +
	" to return a Promise, but it returned " + PrettyPrint(promise));
	}

	promise.then(function(value) { hadValue = true; actual = value; },
	function(error) { hadError = true; actual = error; });

	assertFalse(hadValue \|\| hadError);

	%RunMicrotasks();

	if (!hadError) {
	throw new MjsUnitAssertionError(
	"Expected " + run + "() to throw " + errorType.name +
	", but did not throw.");
	}
	if (!(actual instanceof errorType))
	throw new MjsUnitAssertionError(
	"Expected " + run + "() to throw " + errorType.name +
	", but threw '" + actual + "'");
	if (message !== void 0 && actual.message !== message)
	throw new MjsUnitAssertionError(
	"Expected " + run + "() to throw '" + message + "', but threw '" +
	actual.message + "'");
	};

	function resolveLater(value) {
	return new Promise(function(resolve) {
	Promise.resolve().then(function() {
	resolve(value);
	});
	});
	}

	function rejectLater(value) {
	return new Promise(function(resolve, reject) {
	Promise.resolve().then(function() {
	reject(value);
	});
	});
	}

	const kNext = 1;
	const kThrow = 2;
	const kReturn = 4;
	const kNextThrows = kNext \| 8;
	const kReturnThrows = kReturn \| 16;
	const kThrowNormal = kThrow \| 32;
	const kNextUnchanged = kNext \| 64;
	const kReturnUnchanged = kReturn \| 128;
	const kThrowUnchanged = kThrow \| 256;
	function sync(array, features, log) {
	// `log` is a required parameter
	if (log === void 0) %AbortJS("`log` is undefined");

	let i = 0;
	let methods = {
	next(sent) {
	let done = i >= array.length;
	let value = array[i];
	log.push({ method: "next", sent, value, done });
	if ((features & kNextThrows) === kNextThrows) throw sent;
	if ((features & kNextUnchanged) === kNextUnchanged) return sent;
	i++;
	return { value, done };
	},
	throw(sent) {
	let done = i >= array.length;
	log.push({ method: "throw", sent, done });
	if ((features & kThrowNormal) === kThrowNormal)
	return { value: sent, done };
	if ((features & kThrowUnchanged) === kThrowUnchanged) return sent;
	throw sent;
	},
	return(sent) {
	let done = true;
	log.push({ method: "return", sent, done });
	if ((features & kReturnThrows) === kReturnThrows) throw sent;
	if ((features & kReturnUnchanged) === kReturnUnchanged) return sent;
	return { value: sent, done };
	}
	};
	return {
	[Symbol.iterator]() { return this; },
	next: (features & kNext) ? methods.next : undefined,
	throw: (features & kThrow) ? methods.throw : undefined,
	return: (features & kReturn) ? methods.return : undefined
	};
	}

	class MyError extends Error {};

	(async function AsyncFromSyncWithGenerator() {
	function* gen() {
	yield "sync value";
	try {
	yield new Promise(function(resolve) {
	resolve("async value");
	});
	} catch (error) {
	throw error;
	}
	assertUnreachable("generator is closed");
	}
	let iter = %CreateAsyncFromSyncIterator(gen());

	// [Async-from-Sync Iterator] wraps sync iterator values in a Promise
	let promise = iter.next();
	assertInstanceof(promise, Promise);
	let iter_result = await promise;
	assertEquals({ value: "sync value", done: false }, iter_result);

	// [Async-from-Sync Iterator] will wait for resolution of Promise values
	promise = iter.next();
	assertInstanceof(promise, Promise);
	iter_result = await promise;
	assertEquals({ value: "async value", done: false }, iter_result);

	// [Async-from-Sync Iterator].throw delegates to .throw() method of sync
	// iterator.
	promise = iter.throw(new MyError("Error#1"));
	assertInstanceof(promise, Promise);
	try {
	await promise;
	assertUnreachable("promise should be rejected");
	} catch (e) {
	// If assertUnreachable failed, rethrow
	if (e instanceof MjsUnitAssertionError) throw e;
	assertInstanceof(e, MyError);
	assertEquals("Error#1", e.message);
	}

	// Generator is closed, subsequent calls to .next() will not resume.
	promise = iter.next("floof");
	iter_result = await promise;
	assertEquals({ value: undefined, done: true }, iter_result);

	promise = iter.return("generator closed");
	assertInstanceof(promise, Promise);
	iter_result = await promise;
	assertEquals({ value: "generator closed", done: true }, iter_result);

	// .next(), .return() and .throw() delegate to sync iterator methods, without
	// keeping track of the state of the generator.
	promise = iter.next("unused");
	assertInstanceof(promise, Promise);
	iter_result = await promise;
	assertEquals({ value: undefined, done: true }, iter_result);

	promise = iter.throw(new MyError("Error#2"));
	assertInstanceof(promise, Promise);
	try {
	await promise;
	assertUnreachable("promise should be rejected");
	} catch (e) {
	// If assertUnreachable failed, rethrow
	if (e instanceof MjsUnitAssertionError) throw e;
	assertInstanceof(e, MyError);
	assertEquals("Error#2", e.message);
	}

	promise = iter.return("return-after-completed");
	assertInstanceof(promise, Promise);
	iter_result = await promise;
	assertEquals({ value: "return-after-completed", done: true }, iter_result);
	})().catch(function(error) {
	testFailed = true;
	testFailure = error;
	});

	%RunMicrotasks();
	if (testFailed) {
	throw testFailure;
	}


	(async function AsyncFromSyncOrderOfOperations() {
	let log = [];
	iter = %CreateAsyncFromSyncIterator(sync(["sync-value"], 0, log));

	try {
	await iter.next();
	assertUnreachable("Iterator.next() method is not optional");
	} catch (e) {
	assertInstanceof(e, TypeError);
	assertEquals([], log);
	}

	log = [];
	iter = %CreateAsyncFromSyncIterator(sync(["sync-value"], kNext, log));
	assertEquals({ value: "sync-value", done: false }, await iter.next("a"));
	assertEquals([
	{
	method: "next",
	sent: "a",
	value: "sync-value",
	done: false
	}
	], log);

	log = [];
	let asyncValue = resolveLater("async-value");
	iter = %CreateAsyncFromSyncIterator(sync([asyncValue], kNext, log));
	assertEquals({ value: "async-value", done: false }, await iter.next("b"));
	assertEquals([
	{
	method: "next",
	sent: "b",
	value: asyncValue,
	done: false
	}
	], log);

	// If [sync_iterator].next() produces a rejected Promise or an exception is
	// thrown, Promise is rejected with thrown/rejected value.
	log = [];
	asyncValue = rejectLater("Boo!");
	iter = %CreateAsyncFromSyncIterator(sync([asyncValue], kNext, log));
	try {
	await iter.next('c');
	assertUnreachable('Expected `iter.next(\'c\') to throw, but did not throw');
	} catch (e) {
	assertEquals("Boo!", e);
	assertEquals([
	{
	method: 'next',
	sent: 'c',
	value: asyncValue,
	done: false
	}
	], log);
	}

	log = [];
	iter = %CreateAsyncFromSyncIterator(sync(['sync-value'], kNextThrows, log));
	try {
	await iter.next('Boo!');
	assertUnreachable('Expected `iter.next(\'c\') to throw, but did not throw');
	} catch (e) {
	assertEquals("Boo!", e);
	assertEquals([
	{
	method: 'next',
	sent: 'Boo!',
	value: 'sync-value',
	done: false
	}
	], log);
	}


	// [Async-from-Sync Iterator].next() will be rejected with a TypeError if
	// Type([sync_iterator].next()) is not Object.
	log = [];
	iter = %CreateAsyncFromSyncIterator(sync(['sync-value'], kNextUnchanged,
	log));
	try {
	await iter.next('not-a-JSReceiver');
	assertUnreachable('Expected `iter.next(\'not-a-JSReceiver\')` to ' +
	'throw, but did not throw')
	} catch (e) {
	assertEquals(e.constructor, TypeError);
	}

	assertEquals([
	{
	method: 'next',
	sent: 'not-a-JSReceiver',
	value: 'sync-value',
	done: false
	}
	], log);

	// If [sync_iterator] does not have a .return() method, return a Promise
	// resolved with the value `{ value: <<sent value>>, done: true }`.
	log = [];
	iter = %CreateAsyncFromSyncIterator(sync(['sync-return'], kNext, log));
	assertEquals({
	value: 'd',
	done: true
	}, await iter.return('d'));

	// [Async-from-Sync Iterator] merely delegates, and does not keep track of
	// whether [sync_iterator] is completed or not.
	assertEquals({
	value: 'sync-return',
	done: false
	}, await iter.next('e'));

	assertEquals([
	{
	method: 'next',
	sent: 'e',
	value: 'sync-return',
	done: false
	}
	], log);

	// If [sync_iterator] does have a .return() method, return a Promise
	// fulfilled with the iterator result of [sync_iterator].return().
	log = [];
	iter = %CreateAsyncFromSyncIterator(sync(['sync-return'],
	kNext\|kReturn, log));
	assertEquals({
	value: 'f',
	done: true
	}, await iter.return('f'));

	// [Async-from-Sync Iterator] merely delegates, and does not keep track of
	// whether [sync_iterator] is completed or not.
	assertEquals({
	value: 'sync-return',
	done: false
	}, await iter.next('g'));

	assertEquals([
	{
	method: 'return',
	sent: 'f',
	done: true
	},
	{
	method: 'next',
	sent: 'g',
	value: 'sync-return',
	done: false
	}
	], log);

	// If [sync_iterator].return() produces a rejected Promise or an exception is
	// thrown, Promise is rejected with thrown/rejected value.
	log = [];
	iter = %CreateAsyncFromSyncIterator(sync(['sync-value'], kNext\|kReturnThrows,
	log));
	try {
	await iter.return('Boo!!');
	assertUnreachable('Expected `iter.return(\'Boo!!\')` to throw, but did ' +
	'not throw');
	} catch (e) {
	assertEquals("Boo!!", e);
	}

	// [Async-from-Sync Iterator] merely delegates, and does not keep track of
	// whether [sync_iterator] is completed or not.
	assertEquals({ value: 'sync-value', done: false }, await iter.next('h'));
	assertEquals([
	{
	method: 'return',
	sent: 'Boo!!',
	done: true
	},
	{
	method: 'next',
	sent: 'h',
	value: 'sync-value',
	done: false
	}
	], log);


	log = [];
	iter = %CreateAsyncFromSyncIterator(sync(['sync-value'], kNext\|kReturn, log));

	let rejection = Promise.reject('Boo!!');
	try {
	await iter.return(rejection);
	assertUnreachable('Expected `iter.return(Promise.reject(\'Boo!!\'))` to ' +
	'throw, but did not throw');
	} catch (e) {
	assertEquals('Boo!!', e);
	}

	// [Async-from-Sync Iterator] merely delegates, and does not keep track of
	// whether [sync_iterator] is completed or not.
	assertEquals({ value: 'sync-value', done: false }, await iter.next('i'));
	assertEquals([
	{
	method: 'return',
	sent: rejection,
	done: true
	},
	{
	method: 'next',
	sent: 'i',
	value: 'sync-value',
	done: false
	}
	], log);

	// [Async-from-Sync Iterator].return() will be rejected with a TypeError if
	// Type([sync_iterator].return()) is not Object.
	log = [];
	iter = %CreateAsyncFromSyncIterator(sync(['sync-value'],
	kNext\|kReturnUnchanged, log));
	try {
	await iter.return('not-a-JSReceiver');
	assertUnreachable('Expected `iter.return(\'not-a-JSReceiver\')` to ' +
	'throw, but did not throw')
	} catch (e) {
	assertEquals(e.constructor, TypeError);
	}

	// [Async-from-Sync Iterator] merely delegates, and does not keep track of
	// whether [sync_iterator] is completed or not.
	assertEquals({ value: 'sync-value', done: false }, await iter.next('j'));
	assertEquals([
	{
	method: 'return',
	sent: 'not-a-JSReceiver',
	done: true
	},
	{
	method: 'next',
	sent: 'j',
	value: 'sync-value',
	done: false
	}
	], log);

	// If [sync_iterator] does not have a .throw method, return a Promise rejected
	// with the sent value.
	log = [];
	iter = %CreateAsyncFromSyncIterator(sync(['sync-value'], kNext, log));
	try {
	await iter.throw('Boo!!');
	assertUnreachable('Expected iter.throw(\'Boo!!\') to throw, but did not ' +
	'throw');
	} catch (e) {
	assertEquals('Boo!!', e);
	}

	// [Async-from-Sync Iterator] merely delegates, and does not keep track of
	// whether [sync_iterator] is completed or not.
	assertEquals({ value: 'sync-value', done: false }, await iter.next('k'));
	assertEquals([
	{
	method: 'next',
	sent: 'k',
	value: 'sync-value',
	done: false
	}
	], log);


	log = [];
	iter = %CreateAsyncFromSyncIterator(sync(['sync-value'], kNext\|kThrow, log));
	try {
	await iter.throw('Boo!!');
	assertUnreachable('Expected iter.throw(\'Boo!!\') to throw, but did not ' +
	'throw');
	} catch (e) {
	assertEquals('Boo!!', e);
	}

	// [Async-from-Sync Iterator] merely delegates, and does not keep track of
	// whether [sync_iterator] is completed or not.
	assertEquals({ value: 'sync-value', done: false }, await iter.next('l'));
	assertEquals([
	{
	method: 'throw',
	sent: 'Boo!!',
	done: false
	},
	{
	method: 'next',
	sent: 'l',
	value: 'sync-value',
	done: false
	}
	], log);

	// If [sync_iterator].throw() returns a resolved Promise or a Completion
	// with [[Type]] "normal" or "return", return a resolved Promise
	log = [];
	iter = %CreateAsyncFromSyncIterator(sync(['sync-value'], kNext\|kThrowNormal,
	log));
	assertEquals({
	value: 'Boo!!',
	done: false
	}, await iter.throw('Boo!!'));

	// [Async-from-Sync Iterator] merely delegates, and does not keep track of
	// whether [sync_iterator] is completed or not.
	assertEquals({ value: 'sync-value', done: false }, await iter.next('m'));
	assertEquals([
	{
	method: 'throw',
	sent: 'Boo!!',
	done: false
	},
	{
	method: 'next',
	sent: 'm',
	value: 'sync-value',
	done: false
	}
	], log);

	// [Async-from-Sync Iterator].throw() will be rejected with a TypeError if
	// Type([sync_iterator].throw()) is not Object.
	log = [];
	iter = %CreateAsyncFromSyncIterator(sync(['sync-value'],
	kNext\|kThrowUnchanged, log));
	try {
	await iter.throw('not-a-JSReceiver');
	assertUnreachable('Expected `iter.throw(\'not-a-JSReceiver\')` to ' +
	'throw, but did not throw')
	} catch (e) {
	assertEquals(e.constructor, TypeError);
	}

	// [Async-from-Sync Iterator] merely delegates, and does not keep track of
	// whether [sync_iterator] is completed or not.
	assertEquals({ value: 'sync-value', done: false }, await iter.next('n'));
	assertEquals([
	{
	method: 'throw',
	sent: 'not-a-JSReceiver',
	done: false
	},
	{
	method: 'next',
	sent: 'n',
	value: 'sync-value',
	done: false
	}
	], log);

	// Let nextValue be IteratorValue(nextResult).
	// IfAbruptRejectPromise(nextValue, promiseCapability).)
	iter = %CreateAsyncFromSyncIterator({
	next() { return { get value() { throw "BadValue!" }, done: false }; }
	});
	try {
	await iter.next();
	assertUnreachable('Expected `iter.next()` to throw, but did not throw');
	} catch (e) {
	assertEquals('BadValue!', e);
	}

	// Let nextDone be IteratorComplete(nextResult).
	// IfAbruptRejectPromise(nextDone, promiseCapability).
	iter = %CreateAsyncFromSyncIterator({
	next() { return { value: undefined, get done() { throw "BadValue!" } }; }
	});
	try {
	await iter.next();
	assertUnreachable('Expected `iter.next()` to throw, but did not throw');
	} catch (e) {
	assertEquals('BadValue!', e);
	}

	// IfAbruptRejectPromise(returnResult, promiseCapability).
	// Let returnValue be IteratorValue(returnResult).
	iter = %CreateAsyncFromSyncIterator({
	return() { return { get value() { throw "BadValue!" }, done: false }; }
	});
	try {
	await iter.return();
	assertUnreachable('Expected `iter.return()` to throw, but did not throw');
	} catch (e) {
	assertEquals('BadValue!', e);
	}

	// IfAbruptRejectPromise(returnValue, promiseCapability).
	// Let returnDone be IteratorComplete(returnResult).
	iter = %CreateAsyncFromSyncIterator({
	return() { return { value: undefined, get done() { throw "BadValue!" } }; }
	});
	try {
	await iter.return();
	assertUnreachable('Expected `iter.return()` to throw, but did not throw');
	} catch (e) {
	assertEquals('BadValue!', e);
	}

	// IfAbruptRejectPromise(throwResult, promiseCapability).
	// Let throwValue be IteratorValue(throwResult).
	iter = %CreateAsyncFromSyncIterator({
	throw() { return { get value() { throw "BadValue!" }, done: false }; }
	});
	try {
	await iter.throw();
	assertUnreachable('Expected `iter.throw()` to throw, but did not throw');
	} catch (e) {
	assertEquals('BadValue!', e);
	}

	// IfAbruptRejectPromise(throwValue, promiseCapability).
	// Let throwDone be IteratorComplete(throwResult).
	iter = %CreateAsyncFromSyncIterator({
	throw() { return { value: undefined, get done() { throw "BadValue!" } }; }
	});
	try {
	await iter.throw();
	assertUnreachable('Expected `iter.throw()` to throw, but did not throw');
	} catch (e) {
	assertEquals('BadValue!', e);
	}
	})().catch(function(error) {
	testFailed = true;
	testFailure = error;
	});

	%RunMicrotasks();
	if (testFailed) {
	throw testFailure;
	}

	(function ExtractedAsyncFromSyncIteratorMethods() {
	// TODO(ishell, caitp): Rewrite the test without using function.caller.
	// According to ES#sec-built-in-function-objects all built-in functions
	// must be strict. And ES#sec-forbidden-extensions states that the value of
	// a function.caller must not be a strict function.
	return;
	// Async-from-Sync iterator methods can be extracted via function.caller.
	// TODO(caitp): test extracted `throw` method using yield* in async generator.
	let extractor = [0, 1, 2, 3, 4,5,6,7,8,9];
	let extractedNext;
	let extractedReturn;

	extractor[Symbol.iterator] = function() {
	let it = [][Symbol.iterator].call(extractor);
	let origNext = it.next, origThrow = it.throw, origReturn = it.return;
	function extractNext() {
	extractedNext = extractNext.caller;
	return origNext;
	}
	function extractReturn() {
	extractedReturn = extractReturn.caller;
	return origReturn;
	}
	Object.defineProperties(it, {
	"next": { get: extractNext, configurable: true },
	"return": { get: extractReturn, configurable: true }
	});
	return it;
	};

	async function f() {
	let i;
	let it = extractor[Symbol.iterator]();
	for await (let x of it) break;
	for await (let x of it) return "x";
	}

	// Cycle through `f` to extract iterator methods
	f().catch(function() { %AbortJS("No error should have occurred"); });
	%RunMicrotasks();

	assertEquals(typeof extractedNext, "function");
	assertThrowsAsync(() => extractedNext.call(undefined), TypeError);
	assertThrowsAsync(() => extractedNext.call(1), TypeError);

	assertEquals(typeof extractedReturn, "function");
	assertThrowsAsync(() => extractedReturn.call(undefined), TypeError);
	assertThrowsAsync(() => extractedReturn.call(1), TypeError);
	})();

	(function AsyncFromSyncIteratorOrdering() {
	let i = 0;
	let log = [];
	function r(value, done) {
	let number = (++i);
	return {
	get value() {
	log.push("get iterResult #" + number + ".value");
	return {
	get then() {
	log.push("get nextValue#" + number + ".then");
	return (r) => {
	log.push("call nextValue#" + number + ".then");
	r(value);
	}
	}
	};
	},
	get done() {
	log.push("get iterResult #" + number + ".done");
	return done;
	}
	};
	}
	var results = [r("value1", false), r("value2", false), r("value3", true),
	r("value4", false)];

	var iter = {
	get [Symbol.asyncIterator]() {
	log.push("get syncIterable[@@asyncIterator]");
	return null;
	},

	get [Symbol.iterator]() {
	log.push("get syncIterable[@@iterator]");
	return (...args) => {
	log.push("call syncIterable[@@iterator](" + args.join(", ") + ")");
	return this;
	}
	},
	next_: 0,
	get next() {
	log.push("get syncIterable.next");
	let i = this.next_++;
	return (...args) => {
	log.push("call syncIterable.next(" + args.join(", ") + ")");
	return results[i];
	}
	}
	};

	async function iterate(iterable) {
	log.push("before");
	for await (let x of iterable) {
	log.push("got value " + x);
	}
	log.push("after");

	return log;
	}

	iterate(iter).then(log => {
	assertEquals([
	"before",
	"get syncIterable[@@asyncIterator]",
	"get syncIterable[@@iterator]",
	"call syncIterable[@@iterator]()",
	"get syncIterable.next",
	"call syncIterable.next()",
	"get iterResult #1.done",
	"get iterResult #1.value",
	"get nextValue#1.then",
	"call nextValue#1.then",
	"got value value1",
	"get syncIterable.next",
	"call syncIterable.next()",
	"get iterResult #2.done",
	"get iterResult #2.value",
	"get nextValue#2.then",
	"call nextValue#2.then",
	"got value value2",
	"get syncIterable.next",
	"call syncIterable.next()",
	"get iterResult #3.done",
	"get iterResult #3.value",
	"get nextValue#3.then",
	"call nextValue#3.then",
	"after"
	], log)
	}).catch(x => %AbortJS(String(x)));
	})();