From 7d77c2bc1864f978e866fcc5aa8ea02d02ea12e0 Mon Sep 17 00:00:00 2001
From: Ron Buckton <rbuckton@microsoft.com>
Date: Fri, 17 Feb 2017 18:01:13 -0800
Subject: [PATCH] Fix for-await-of emit in async function

---
 src/compiler/transformers/esnext.ts           | 22 ++++++++++++-------
 ...ter.asyncGenerators.classMethods.es2015.js |  9 ++++++++
 ...mitter.asyncGenerators.classMethods.es5.js |  9 ++++++++
 ...cGenerators.functionDeclarations.es2015.js |  7 ++++++
 ...syncGenerators.functionDeclarations.es5.js |  7 ++++++
 ...ncGenerators.functionExpressions.es2015.js |  7 ++++++
 ...asyncGenerators.functionExpressions.es5.js |  7 ++++++
 ...cGenerators.objectLiteralMethods.es2015.js |  7 ++++++
 ...syncGenerators.objectLiteralMethods.es5.js |  7 ++++++
 .../reference/emitter.forAwait.es2015.js      | 14 ++++++++----
 .../reference/emitter.forAwait.es5.js         | 18 ++++++++++-----
 11 files changed, 96 insertions(+), 18 deletions(-)

diff --git a/src/compiler/transformers/esnext.ts b/src/compiler/transformers/esnext.ts
index 482f37d45f9..971dddd20ea 100644
--- a/src/compiler/transformers/esnext.ts
+++ b/src/compiler/transformers/esnext.ts
@@ -357,10 +357,12 @@ namespace ts {
             const values = createAsyncValuesHelper(context, expression, /*location*/ node.expression);
             const next = createYield(
                 /*asteriskToken*/ undefined,
-                createArrayLiteral([
-                    createLiteral("await"),
-                    createCall(createPropertyAccess(iterator, "next" ), /*typeArguments*/ undefined, [])
-                ])
+                enclosingFunctionFlags & FunctionFlags.Generator
+                    ? createArrayLiteral([
+                        createLiteral("await"),
+                        createCall(createPropertyAccess(iterator, "next" ), /*typeArguments*/ undefined, [])
+                    ])
+                    : createCall(createPropertyAccess(iterator, "next" ), /*typeArguments*/ undefined, [])
             );
 
             hoistVariableDeclaration(errorRecord);
@@ -431,10 +433,12 @@ namespace ts {
                                     createStatement(
                                         createYield(
                                             /*asteriskToken*/ undefined,
-                                            createArrayLiteral([
-                                                createLiteral("await"),
-                                                createFunctionCall(returnMethod, iterator, [])
-                                            ])
+                                            enclosingFunctionFlags & FunctionFlags.Generator
+                                                ? createArrayLiteral([
+                                                    createLiteral("await"),
+                                                    createFunctionCall(returnMethod, iterator, [])
+                                                ])
+                                                : createFunctionCall(returnMethod, iterator, [])
                                         )
                                     )
                                 ),
@@ -872,6 +876,7 @@ namespace ts {
         scoped: false,
         text: `
             var __asyncGenerator = (this && this.__asyncGenerator) || function (thisArg, _arguments, generator) {
+                if (!Symbol.asyncIterator) throw new TypeError("Symbol.asyncIterator is not defined.");
                 var g = generator.apply(thisArg, _arguments || []), q = [], c, i;
                 return i = { next: verb("next"), "throw": verb("throw"), "return": verb("return") }, i[Symbol.asyncIterator] = function () { return this; }, i;
                 function verb(n) { return function (v) { return new Promise(function (a, b) { q.push([n, v, a, b]), next(); }); }; }
@@ -932,6 +937,7 @@ namespace ts {
         scoped: false,
         text: `
             var __asyncValues = (this && this.__asyncIterator) || function (o) {
+                if (!Symbol.asyncIterator) throw new TypeError("Symbol.asyncIterator is not defined.");
                 var m = o[Symbol.asyncIterator];
                 return m ? m.call(o) : typeof __values === "function" ? __values(o) : o[Symbol.iterator]();
             };
diff --git a/tests/baselines/reference/emitter.asyncGenerators.classMethods.es2015.js b/tests/baselines/reference/emitter.asyncGenerators.classMethods.es2015.js
index 2edcfd99e4b..ba4902102b1 100644
--- a/tests/baselines/reference/emitter.asyncGenerators.classMethods.es2015.js
+++ b/tests/baselines/reference/emitter.asyncGenerators.classMethods.es2015.js
@@ -62,6 +62,7 @@ class C9 extends B9 {
 
 //// [C1.js]
 var __asyncGenerator = (this && this.__asyncGenerator) || function (thisArg, _arguments, generator) {
+    if (!Symbol.asyncIterator) throw new TypeError("Symbol.asyncIterator is not defined.");
     var g = generator.apply(thisArg, _arguments || []), q = [], c, i;
     return i = { next: verb("next"), "throw": verb("throw"), "return": verb("return") }, i[Symbol.asyncIterator] = function () { return this; }, i;
     function verb(n) { return function (v) { return new Promise(function (a, b) { q.push([n, v, a, b]), next(); }); }; }
@@ -81,6 +82,7 @@ class C1 {
 }
 //// [C2.js]
 var __asyncGenerator = (this && this.__asyncGenerator) || function (thisArg, _arguments, generator) {
+    if (!Symbol.asyncIterator) throw new TypeError("Symbol.asyncIterator is not defined.");
     var g = generator.apply(thisArg, _arguments || []), q = [], c, i;
     return i = { next: verb("next"), "throw": verb("throw"), "return": verb("return") }, i[Symbol.asyncIterator] = function () { return this; }, i;
     function verb(n) { return function (v) { return new Promise(function (a, b) { q.push([n, v, a, b]), next(); }); }; }
@@ -101,6 +103,7 @@ class C2 {
 }
 //// [C3.js]
 var __asyncGenerator = (this && this.__asyncGenerator) || function (thisArg, _arguments, generator) {
+    if (!Symbol.asyncIterator) throw new TypeError("Symbol.asyncIterator is not defined.");
     var g = generator.apply(thisArg, _arguments || []), q = [], c, i;
     return i = { next: verb("next"), "throw": verb("throw"), "return": verb("return") }, i[Symbol.asyncIterator] = function () { return this; }, i;
     function verb(n) { return function (v) { return new Promise(function (a, b) { q.push([n, v, a, b]), next(); }); }; }
@@ -126,6 +129,7 @@ var __asyncDelegator = (this && this.__asyncDelegator) || function (o) {
     function verb(n, f) { return function (v) { return { value: ["delegate", (o[n] || f).call(o, v)], done: false }; }; }
 };
 var __asyncGenerator = (this && this.__asyncGenerator) || function (thisArg, _arguments, generator) {
+    if (!Symbol.asyncIterator) throw new TypeError("Symbol.asyncIterator is not defined.");
     var g = generator.apply(thisArg, _arguments || []), q = [], c, i;
     return i = { next: verb("next"), "throw": verb("throw"), "return": verb("return") }, i[Symbol.asyncIterator] = function () { return this; }, i;
     function verb(n) { return function (v) { return new Promise(function (a, b) { q.push([n, v, a, b]), next(); }); }; }
@@ -146,6 +150,7 @@ class C4 {
 }
 //// [C5.js]
 var __asyncGenerator = (this && this.__asyncGenerator) || function (thisArg, _arguments, generator) {
+    if (!Symbol.asyncIterator) throw new TypeError("Symbol.asyncIterator is not defined.");
     var g = generator.apply(thisArg, _arguments || []), q = [], c, i;
     return i = { next: verb("next"), "throw": verb("throw"), "return": verb("return") }, i[Symbol.asyncIterator] = function () { return this; }, i;
     function verb(n) { return function (v) { return new Promise(function (a, b) { q.push([n, v, a, b]), next(); }); }; }
@@ -171,6 +176,7 @@ class C5 {
 }
 //// [C6.js]
 var __asyncGenerator = (this && this.__asyncGenerator) || function (thisArg, _arguments, generator) {
+    if (!Symbol.asyncIterator) throw new TypeError("Symbol.asyncIterator is not defined.");
     var g = generator.apply(thisArg, _arguments || []), q = [], c, i;
     return i = { next: verb("next"), "throw": verb("throw"), "return": verb("return") }, i[Symbol.asyncIterator] = function () { return this; }, i;
     function verb(n) { return function (v) { return new Promise(function (a, b) { q.push([n, v, a, b]), next(); }); }; }
@@ -191,6 +197,7 @@ class C6 {
 }
 //// [C7.js]
 var __asyncGenerator = (this && this.__asyncGenerator) || function (thisArg, _arguments, generator) {
+    if (!Symbol.asyncIterator) throw new TypeError("Symbol.asyncIterator is not defined.");
     var g = generator.apply(thisArg, _arguments || []), q = [], c, i;
     return i = { next: verb("next"), "throw": verb("throw"), "return": verb("return") }, i[Symbol.asyncIterator] = function () { return this; }, i;
     function verb(n) { return function (v) { return new Promise(function (a, b) { q.push([n, v, a, b]), next(); }); }; }
@@ -211,6 +218,7 @@ class C7 {
 }
 //// [C8.js]
 var __asyncGenerator = (this && this.__asyncGenerator) || function (thisArg, _arguments, generator) {
+    if (!Symbol.asyncIterator) throw new TypeError("Symbol.asyncIterator is not defined.");
     var g = generator.apply(thisArg, _arguments || []), q = [], c, i;
     return i = { next: verb("next"), "throw": verb("throw"), "return": verb("return") }, i[Symbol.asyncIterator] = function () { return this; }, i;
     function verb(n) { return function (v) { return new Promise(function (a, b) { q.push([n, v, a, b]), next(); }); }; }
@@ -233,6 +241,7 @@ class C8 {
 }
 //// [C9.js]
 var __asyncGenerator = (this && this.__asyncGenerator) || function (thisArg, _arguments, generator) {
+    if (!Symbol.asyncIterator) throw new TypeError("Symbol.asyncIterator is not defined.");
     var g = generator.apply(thisArg, _arguments || []), q = [], c, i;
     return i = { next: verb("next"), "throw": verb("throw"), "return": verb("return") }, i[Symbol.asyncIterator] = function () { return this; }, i;
     function verb(n) { return function (v) { return new Promise(function (a, b) { q.push([n, v, a, b]), next(); }); }; }
diff --git a/tests/baselines/reference/emitter.asyncGenerators.classMethods.es5.js b/tests/baselines/reference/emitter.asyncGenerators.classMethods.es5.js
index 2b296936368..74a65673e5a 100644
--- a/tests/baselines/reference/emitter.asyncGenerators.classMethods.es5.js
+++ b/tests/baselines/reference/emitter.asyncGenerators.classMethods.es5.js
@@ -89,6 +89,7 @@ var __generator = (this && this.__generator) || function (thisArg, body) {
     }
 };
 var __asyncGenerator = (this && this.__asyncGenerator) || function (thisArg, _arguments, generator) {
+    if (!Symbol.asyncIterator) throw new TypeError("Symbol.asyncIterator is not defined.");
     var g = generator.apply(thisArg, _arguments || []), q = [], c, i;
     return i = { next: verb("next"), "throw": verb("throw"), "return": verb("return") }, i[Symbol.asyncIterator] = function () { return this; }, i;
     function verb(n) { return function (v) { return new Promise(function (a, b) { q.push([n, v, a, b]), next(); }); }; }
@@ -141,6 +142,7 @@ var __generator = (this && this.__generator) || function (thisArg, body) {
     }
 };
 var __asyncGenerator = (this && this.__asyncGenerator) || function (thisArg, _arguments, generator) {
+    if (!Symbol.asyncIterator) throw new TypeError("Symbol.asyncIterator is not defined.");
     var g = generator.apply(thisArg, _arguments || []), q = [], c, i;
     return i = { next: verb("next"), "throw": verb("throw"), "return": verb("return") }, i[Symbol.asyncIterator] = function () { return this; }, i;
     function verb(n) { return function (v) { return new Promise(function (a, b) { q.push([n, v, a, b]), next(); }); }; }
@@ -199,6 +201,7 @@ var __generator = (this && this.__generator) || function (thisArg, body) {
     }
 };
 var __asyncGenerator = (this && this.__asyncGenerator) || function (thisArg, _arguments, generator) {
+    if (!Symbol.asyncIterator) throw new TypeError("Symbol.asyncIterator is not defined.");
     var g = generator.apply(thisArg, _arguments || []), q = [], c, i;
     return i = { next: verb("next"), "throw": verb("throw"), "return": verb("return") }, i[Symbol.asyncIterator] = function () { return this; }, i;
     function verb(n) { return function (v) { return new Promise(function (a, b) { q.push([n, v, a, b]), next(); }); }; }
@@ -262,6 +265,7 @@ var __asyncDelegator = (this && this.__asyncDelegator) || function (o) {
     function verb(n, f) { return function (v) { return { value: ["delegate", (o[n] || f).call(o, v)], done: false }; }; }
 };
 var __asyncGenerator = (this && this.__asyncGenerator) || function (thisArg, _arguments, generator) {
+    if (!Symbol.asyncIterator) throw new TypeError("Symbol.asyncIterator is not defined.");
     var g = generator.apply(thisArg, _arguments || []), q = [], c, i;
     return i = { next: verb("next"), "throw": verb("throw"), "return": verb("return") }, i[Symbol.asyncIterator] = function () { return this; }, i;
     function verb(n) { return function (v) { return new Promise(function (a, b) { q.push([n, v, a, b]), next(); }); }; }
@@ -330,6 +334,7 @@ var __generator = (this && this.__generator) || function (thisArg, body) {
     }
 };
 var __asyncGenerator = (this && this.__asyncGenerator) || function (thisArg, _arguments, generator) {
+    if (!Symbol.asyncIterator) throw new TypeError("Symbol.asyncIterator is not defined.");
     var g = generator.apply(thisArg, _arguments || []), q = [], c, i;
     return i = { next: verb("next"), "throw": verb("throw"), "return": verb("return") }, i[Symbol.asyncIterator] = function () { return this; }, i;
     function verb(n) { return function (v) { return new Promise(function (a, b) { q.push([n, v, a, b]), next(); }); }; }
@@ -410,6 +415,7 @@ var __generator = (this && this.__generator) || function (thisArg, body) {
     }
 };
 var __asyncGenerator = (this && this.__asyncGenerator) || function (thisArg, _arguments, generator) {
+    if (!Symbol.asyncIterator) throw new TypeError("Symbol.asyncIterator is not defined.");
     var g = generator.apply(thisArg, _arguments || []), q = [], c, i;
     return i = { next: verb("next"), "throw": verb("throw"), "return": verb("return") }, i[Symbol.asyncIterator] = function () { return this; }, i;
     function verb(n) { return function (v) { return new Promise(function (a, b) { q.push([n, v, a, b]), next(); }); }; }
@@ -468,6 +474,7 @@ var __generator = (this && this.__generator) || function (thisArg, body) {
     }
 };
 var __asyncGenerator = (this && this.__asyncGenerator) || function (thisArg, _arguments, generator) {
+    if (!Symbol.asyncIterator) throw new TypeError("Symbol.asyncIterator is not defined.");
     var g = generator.apply(thisArg, _arguments || []), q = [], c, i;
     return i = { next: verb("next"), "throw": verb("throw"), "return": verb("return") }, i[Symbol.asyncIterator] = function () { return this; }, i;
     function verb(n) { return function (v) { return new Promise(function (a, b) { q.push([n, v, a, b]), next(); }); }; }
@@ -520,6 +527,7 @@ var __generator = (this && this.__generator) || function (thisArg, body) {
     }
 };
 var __asyncGenerator = (this && this.__asyncGenerator) || function (thisArg, _arguments, generator) {
+    if (!Symbol.asyncIterator) throw new TypeError("Symbol.asyncIterator is not defined.");
     var g = generator.apply(thisArg, _arguments || []), q = [], c, i;
     return i = { next: verb("next"), "throw": verb("throw"), "return": verb("return") }, i[Symbol.asyncIterator] = function () { return this; }, i;
     function verb(n) { return function (v) { return new Promise(function (a, b) { q.push([n, v, a, b]), next(); }); }; }
@@ -585,6 +593,7 @@ var __generator = (this && this.__generator) || function (thisArg, body) {
     }
 };
 var __asyncGenerator = (this && this.__asyncGenerator) || function (thisArg, _arguments, generator) {
+    if (!Symbol.asyncIterator) throw new TypeError("Symbol.asyncIterator is not defined.");
     var g = generator.apply(thisArg, _arguments || []), q = [], c, i;
     return i = { next: verb("next"), "throw": verb("throw"), "return": verb("return") }, i[Symbol.asyncIterator] = function () { return this; }, i;
     function verb(n) { return function (v) { return new Promise(function (a, b) { q.push([n, v, a, b]), next(); }); }; }
diff --git a/tests/baselines/reference/emitter.asyncGenerators.functionDeclarations.es2015.js b/tests/baselines/reference/emitter.asyncGenerators.functionDeclarations.es2015.js
index 97df064bbe8..2b0d6db5353 100644
--- a/tests/baselines/reference/emitter.asyncGenerators.functionDeclarations.es2015.js
+++ b/tests/baselines/reference/emitter.asyncGenerators.functionDeclarations.es2015.js
@@ -31,6 +31,7 @@ async function * f7() {
 
 //// [F1.js]
 var __asyncGenerator = (this && this.__asyncGenerator) || function (thisArg, _arguments, generator) {
+    if (!Symbol.asyncIterator) throw new TypeError("Symbol.asyncIterator is not defined.");
     var g = generator.apply(thisArg, _arguments || []), q = [], c, i;
     return i = { next: verb("next"), "throw": verb("throw"), "return": verb("return") }, i[Symbol.asyncIterator] = function () { return this; }, i;
     function verb(n) { return function (v) { return new Promise(function (a, b) { q.push([n, v, a, b]), next(); }); }; }
@@ -48,6 +49,7 @@ function f1() {
 }
 //// [F2.js]
 var __asyncGenerator = (this && this.__asyncGenerator) || function (thisArg, _arguments, generator) {
+    if (!Symbol.asyncIterator) throw new TypeError("Symbol.asyncIterator is not defined.");
     var g = generator.apply(thisArg, _arguments || []), q = [], c, i;
     return i = { next: verb("next"), "throw": verb("throw"), "return": verb("return") }, i[Symbol.asyncIterator] = function () { return this; }, i;
     function verb(n) { return function (v) { return new Promise(function (a, b) { q.push([n, v, a, b]), next(); }); }; }
@@ -66,6 +68,7 @@ function f2() {
 }
 //// [F3.js]
 var __asyncGenerator = (this && this.__asyncGenerator) || function (thisArg, _arguments, generator) {
+    if (!Symbol.asyncIterator) throw new TypeError("Symbol.asyncIterator is not defined.");
     var g = generator.apply(thisArg, _arguments || []), q = [], c, i;
     return i = { next: verb("next"), "throw": verb("throw"), "return": verb("return") }, i[Symbol.asyncIterator] = function () { return this; }, i;
     function verb(n) { return function (v) { return new Promise(function (a, b) { q.push([n, v, a, b]), next(); }); }; }
@@ -89,6 +92,7 @@ var __asyncDelegator = (this && this.__asyncDelegator) || function (o) {
     function verb(n, f) { return function (v) { return { value: ["delegate", (o[n] || f).call(o, v)], done: false }; }; }
 };
 var __asyncGenerator = (this && this.__asyncGenerator) || function (thisArg, _arguments, generator) {
+    if (!Symbol.asyncIterator) throw new TypeError("Symbol.asyncIterator is not defined.");
     var g = generator.apply(thisArg, _arguments || []), q = [], c, i;
     return i = { next: verb("next"), "throw": verb("throw"), "return": verb("return") }, i[Symbol.asyncIterator] = function () { return this; }, i;
     function verb(n) { return function (v) { return new Promise(function (a, b) { q.push([n, v, a, b]), next(); }); }; }
@@ -107,6 +111,7 @@ function f4() {
 }
 //// [F5.js]
 var __asyncGenerator = (this && this.__asyncGenerator) || function (thisArg, _arguments, generator) {
+    if (!Symbol.asyncIterator) throw new TypeError("Symbol.asyncIterator is not defined.");
     var g = generator.apply(thisArg, _arguments || []), q = [], c, i;
     return i = { next: verb("next"), "throw": verb("throw"), "return": verb("return") }, i[Symbol.asyncIterator] = function () { return this; }, i;
     function verb(n) { return function (v) { return new Promise(function (a, b) { q.push([n, v, a, b]), next(); }); }; }
@@ -130,6 +135,7 @@ function f5() {
 }
 //// [F6.js]
 var __asyncGenerator = (this && this.__asyncGenerator) || function (thisArg, _arguments, generator) {
+    if (!Symbol.asyncIterator) throw new TypeError("Symbol.asyncIterator is not defined.");
     var g = generator.apply(thisArg, _arguments || []), q = [], c, i;
     return i = { next: verb("next"), "throw": verb("throw"), "return": verb("return") }, i[Symbol.asyncIterator] = function () { return this; }, i;
     function verb(n) { return function (v) { return new Promise(function (a, b) { q.push([n, v, a, b]), next(); }); }; }
@@ -148,6 +154,7 @@ function f6() {
 }
 //// [F7.js]
 var __asyncGenerator = (this && this.__asyncGenerator) || function (thisArg, _arguments, generator) {
+    if (!Symbol.asyncIterator) throw new TypeError("Symbol.asyncIterator is not defined.");
     var g = generator.apply(thisArg, _arguments || []), q = [], c, i;
     return i = { next: verb("next"), "throw": verb("throw"), "return": verb("return") }, i[Symbol.asyncIterator] = function () { return this; }, i;
     function verb(n) { return function (v) { return new Promise(function (a, b) { q.push([n, v, a, b]), next(); }); }; }
diff --git a/tests/baselines/reference/emitter.asyncGenerators.functionDeclarations.es5.js b/tests/baselines/reference/emitter.asyncGenerators.functionDeclarations.es5.js
index 2a1b4393a9b..42098455ed1 100644
--- a/tests/baselines/reference/emitter.asyncGenerators.functionDeclarations.es5.js
+++ b/tests/baselines/reference/emitter.asyncGenerators.functionDeclarations.es5.js
@@ -58,6 +58,7 @@ var __generator = (this && this.__generator) || function (thisArg, body) {
     }
 };
 var __asyncGenerator = (this && this.__asyncGenerator) || function (thisArg, _arguments, generator) {
+    if (!Symbol.asyncIterator) throw new TypeError("Symbol.asyncIterator is not defined.");
     var g = generator.apply(thisArg, _arguments || []), q = [], c, i;
     return i = { next: verb("next"), "throw": verb("throw"), "return": verb("return") }, i[Symbol.asyncIterator] = function () { return this; }, i;
     function verb(n) { return function (v) { return new Promise(function (a, b) { q.push([n, v, a, b]), next(); }); }; }
@@ -105,6 +106,7 @@ var __generator = (this && this.__generator) || function (thisArg, body) {
     }
 };
 var __asyncGenerator = (this && this.__asyncGenerator) || function (thisArg, _arguments, generator) {
+    if (!Symbol.asyncIterator) throw new TypeError("Symbol.asyncIterator is not defined.");
     var g = generator.apply(thisArg, _arguments || []), q = [], c, i;
     return i = { next: verb("next"), "throw": verb("throw"), "return": verb("return") }, i[Symbol.asyncIterator] = function () { return this; }, i;
     function verb(n) { return function (v) { return new Promise(function (a, b) { q.push([n, v, a, b]), next(); }); }; }
@@ -158,6 +160,7 @@ var __generator = (this && this.__generator) || function (thisArg, body) {
     }
 };
 var __asyncGenerator = (this && this.__asyncGenerator) || function (thisArg, _arguments, generator) {
+    if (!Symbol.asyncIterator) throw new TypeError("Symbol.asyncIterator is not defined.");
     var g = generator.apply(thisArg, _arguments || []), q = [], c, i;
     return i = { next: verb("next"), "throw": verb("throw"), "return": verb("return") }, i[Symbol.asyncIterator] = function () { return this; }, i;
     function verb(n) { return function (v) { return new Promise(function (a, b) { q.push([n, v, a, b]), next(); }); }; }
@@ -216,6 +219,7 @@ var __asyncDelegator = (this && this.__asyncDelegator) || function (o) {
     function verb(n, f) { return function (v) { return { value: ["delegate", (o[n] || f).call(o, v)], done: false }; }; }
 };
 var __asyncGenerator = (this && this.__asyncGenerator) || function (thisArg, _arguments, generator) {
+    if (!Symbol.asyncIterator) throw new TypeError("Symbol.asyncIterator is not defined.");
     var g = generator.apply(thisArg, _arguments || []), q = [], c, i;
     return i = { next: verb("next"), "throw": verb("throw"), "return": verb("return") }, i[Symbol.asyncIterator] = function () { return this; }, i;
     function verb(n) { return function (v) { return new Promise(function (a, b) { q.push([n, v, a, b]), next(); }); }; }
@@ -279,6 +283,7 @@ var __generator = (this && this.__generator) || function (thisArg, body) {
     }
 };
 var __asyncGenerator = (this && this.__asyncGenerator) || function (thisArg, _arguments, generator) {
+    if (!Symbol.asyncIterator) throw new TypeError("Symbol.asyncIterator is not defined.");
     var g = generator.apply(thisArg, _arguments || []), q = [], c, i;
     return i = { next: verb("next"), "throw": verb("throw"), "return": verb("return") }, i[Symbol.asyncIterator] = function () { return this; }, i;
     function verb(n) { return function (v) { return new Promise(function (a, b) { q.push([n, v, a, b]), next(); }); }; }
@@ -354,6 +359,7 @@ var __generator = (this && this.__generator) || function (thisArg, body) {
     }
 };
 var __asyncGenerator = (this && this.__asyncGenerator) || function (thisArg, _arguments, generator) {
+    if (!Symbol.asyncIterator) throw new TypeError("Symbol.asyncIterator is not defined.");
     var g = generator.apply(thisArg, _arguments || []), q = [], c, i;
     return i = { next: verb("next"), "throw": verb("throw"), "return": verb("return") }, i[Symbol.asyncIterator] = function () { return this; }, i;
     function verb(n) { return function (v) { return new Promise(function (a, b) { q.push([n, v, a, b]), next(); }); }; }
@@ -407,6 +413,7 @@ var __generator = (this && this.__generator) || function (thisArg, body) {
     }
 };
 var __asyncGenerator = (this && this.__asyncGenerator) || function (thisArg, _arguments, generator) {
+    if (!Symbol.asyncIterator) throw new TypeError("Symbol.asyncIterator is not defined.");
     var g = generator.apply(thisArg, _arguments || []), q = [], c, i;
     return i = { next: verb("next"), "throw": verb("throw"), "return": verb("return") }, i[Symbol.asyncIterator] = function () { return this; }, i;
     function verb(n) { return function (v) { return new Promise(function (a, b) { q.push([n, v, a, b]), next(); }); }; }
diff --git a/tests/baselines/reference/emitter.asyncGenerators.functionExpressions.es2015.js b/tests/baselines/reference/emitter.asyncGenerators.functionExpressions.es2015.js
index bc64f029289..90f4b70e9bd 100644
--- a/tests/baselines/reference/emitter.asyncGenerators.functionExpressions.es2015.js
+++ b/tests/baselines/reference/emitter.asyncGenerators.functionExpressions.es2015.js
@@ -31,6 +31,7 @@ const f7 = async function * () {
 
 //// [F1.js]
 var __asyncGenerator = (this && this.__asyncGenerator) || function (thisArg, _arguments, generator) {
+    if (!Symbol.asyncIterator) throw new TypeError("Symbol.asyncIterator is not defined.");
     var g = generator.apply(thisArg, _arguments || []), q = [], c, i;
     return i = { next: verb("next"), "throw": verb("throw"), "return": verb("return") }, i[Symbol.asyncIterator] = function () { return this; }, i;
     function verb(n) { return function (v) { return new Promise(function (a, b) { q.push([n, v, a, b]), next(); }); }; }
@@ -48,6 +49,7 @@ const f1 = function () {
 };
 //// [F2.js]
 var __asyncGenerator = (this && this.__asyncGenerator) || function (thisArg, _arguments, generator) {
+    if (!Symbol.asyncIterator) throw new TypeError("Symbol.asyncIterator is not defined.");
     var g = generator.apply(thisArg, _arguments || []), q = [], c, i;
     return i = { next: verb("next"), "throw": verb("throw"), "return": verb("return") }, i[Symbol.asyncIterator] = function () { return this; }, i;
     function verb(n) { return function (v) { return new Promise(function (a, b) { q.push([n, v, a, b]), next(); }); }; }
@@ -66,6 +68,7 @@ const f2 = function () {
 };
 //// [F3.js]
 var __asyncGenerator = (this && this.__asyncGenerator) || function (thisArg, _arguments, generator) {
+    if (!Symbol.asyncIterator) throw new TypeError("Symbol.asyncIterator is not defined.");
     var g = generator.apply(thisArg, _arguments || []), q = [], c, i;
     return i = { next: verb("next"), "throw": verb("throw"), "return": verb("return") }, i[Symbol.asyncIterator] = function () { return this; }, i;
     function verb(n) { return function (v) { return new Promise(function (a, b) { q.push([n, v, a, b]), next(); }); }; }
@@ -89,6 +92,7 @@ var __asyncDelegator = (this && this.__asyncDelegator) || function (o) {
     function verb(n, f) { return function (v) { return { value: ["delegate", (o[n] || f).call(o, v)], done: false }; }; }
 };
 var __asyncGenerator = (this && this.__asyncGenerator) || function (thisArg, _arguments, generator) {
+    if (!Symbol.asyncIterator) throw new TypeError("Symbol.asyncIterator is not defined.");
     var g = generator.apply(thisArg, _arguments || []), q = [], c, i;
     return i = { next: verb("next"), "throw": verb("throw"), "return": verb("return") }, i[Symbol.asyncIterator] = function () { return this; }, i;
     function verb(n) { return function (v) { return new Promise(function (a, b) { q.push([n, v, a, b]), next(); }); }; }
@@ -107,6 +111,7 @@ const f4 = function () {
 };
 //// [F5.js]
 var __asyncGenerator = (this && this.__asyncGenerator) || function (thisArg, _arguments, generator) {
+    if (!Symbol.asyncIterator) throw new TypeError("Symbol.asyncIterator is not defined.");
     var g = generator.apply(thisArg, _arguments || []), q = [], c, i;
     return i = { next: verb("next"), "throw": verb("throw"), "return": verb("return") }, i[Symbol.asyncIterator] = function () { return this; }, i;
     function verb(n) { return function (v) { return new Promise(function (a, b) { q.push([n, v, a, b]), next(); }); }; }
@@ -130,6 +135,7 @@ const f5 = function () {
 };
 //// [F6.js]
 var __asyncGenerator = (this && this.__asyncGenerator) || function (thisArg, _arguments, generator) {
+    if (!Symbol.asyncIterator) throw new TypeError("Symbol.asyncIterator is not defined.");
     var g = generator.apply(thisArg, _arguments || []), q = [], c, i;
     return i = { next: verb("next"), "throw": verb("throw"), "return": verb("return") }, i[Symbol.asyncIterator] = function () { return this; }, i;
     function verb(n) { return function (v) { return new Promise(function (a, b) { q.push([n, v, a, b]), next(); }); }; }
@@ -148,6 +154,7 @@ const f6 = function () {
 };
 //// [F7.js]
 var __asyncGenerator = (this && this.__asyncGenerator) || function (thisArg, _arguments, generator) {
+    if (!Symbol.asyncIterator) throw new TypeError("Symbol.asyncIterator is not defined.");
     var g = generator.apply(thisArg, _arguments || []), q = [], c, i;
     return i = { next: verb("next"), "throw": verb("throw"), "return": verb("return") }, i[Symbol.asyncIterator] = function () { return this; }, i;
     function verb(n) { return function (v) { return new Promise(function (a, b) { q.push([n, v, a, b]), next(); }); }; }
diff --git a/tests/baselines/reference/emitter.asyncGenerators.functionExpressions.es5.js b/tests/baselines/reference/emitter.asyncGenerators.functionExpressions.es5.js
index 9593562987b..a6265063fde 100644
--- a/tests/baselines/reference/emitter.asyncGenerators.functionExpressions.es5.js
+++ b/tests/baselines/reference/emitter.asyncGenerators.functionExpressions.es5.js
@@ -58,6 +58,7 @@ var __generator = (this && this.__generator) || function (thisArg, body) {
     }
 };
 var __asyncGenerator = (this && this.__asyncGenerator) || function (thisArg, _arguments, generator) {
+    if (!Symbol.asyncIterator) throw new TypeError("Symbol.asyncIterator is not defined.");
     var g = generator.apply(thisArg, _arguments || []), q = [], c, i;
     return i = { next: verb("next"), "throw": verb("throw"), "return": verb("return") }, i[Symbol.asyncIterator] = function () { return this; }, i;
     function verb(n) { return function (v) { return new Promise(function (a, b) { q.push([n, v, a, b]), next(); }); }; }
@@ -105,6 +106,7 @@ var __generator = (this && this.__generator) || function (thisArg, body) {
     }
 };
 var __asyncGenerator = (this && this.__asyncGenerator) || function (thisArg, _arguments, generator) {
+    if (!Symbol.asyncIterator) throw new TypeError("Symbol.asyncIterator is not defined.");
     var g = generator.apply(thisArg, _arguments || []), q = [], c, i;
     return i = { next: verb("next"), "throw": verb("throw"), "return": verb("return") }, i[Symbol.asyncIterator] = function () { return this; }, i;
     function verb(n) { return function (v) { return new Promise(function (a, b) { q.push([n, v, a, b]), next(); }); }; }
@@ -158,6 +160,7 @@ var __generator = (this && this.__generator) || function (thisArg, body) {
     }
 };
 var __asyncGenerator = (this && this.__asyncGenerator) || function (thisArg, _arguments, generator) {
+    if (!Symbol.asyncIterator) throw new TypeError("Symbol.asyncIterator is not defined.");
     var g = generator.apply(thisArg, _arguments || []), q = [], c, i;
     return i = { next: verb("next"), "throw": verb("throw"), "return": verb("return") }, i[Symbol.asyncIterator] = function () { return this; }, i;
     function verb(n) { return function (v) { return new Promise(function (a, b) { q.push([n, v, a, b]), next(); }); }; }
@@ -216,6 +219,7 @@ var __asyncDelegator = (this && this.__asyncDelegator) || function (o) {
     function verb(n, f) { return function (v) { return { value: ["delegate", (o[n] || f).call(o, v)], done: false }; }; }
 };
 var __asyncGenerator = (this && this.__asyncGenerator) || function (thisArg, _arguments, generator) {
+    if (!Symbol.asyncIterator) throw new TypeError("Symbol.asyncIterator is not defined.");
     var g = generator.apply(thisArg, _arguments || []), q = [], c, i;
     return i = { next: verb("next"), "throw": verb("throw"), "return": verb("return") }, i[Symbol.asyncIterator] = function () { return this; }, i;
     function verb(n) { return function (v) { return new Promise(function (a, b) { q.push([n, v, a, b]), next(); }); }; }
@@ -279,6 +283,7 @@ var __generator = (this && this.__generator) || function (thisArg, body) {
     }
 };
 var __asyncGenerator = (this && this.__asyncGenerator) || function (thisArg, _arguments, generator) {
+    if (!Symbol.asyncIterator) throw new TypeError("Symbol.asyncIterator is not defined.");
     var g = generator.apply(thisArg, _arguments || []), q = [], c, i;
     return i = { next: verb("next"), "throw": verb("throw"), "return": verb("return") }, i[Symbol.asyncIterator] = function () { return this; }, i;
     function verb(n) { return function (v) { return new Promise(function (a, b) { q.push([n, v, a, b]), next(); }); }; }
@@ -354,6 +359,7 @@ var __generator = (this && this.__generator) || function (thisArg, body) {
     }
 };
 var __asyncGenerator = (this && this.__asyncGenerator) || function (thisArg, _arguments, generator) {
+    if (!Symbol.asyncIterator) throw new TypeError("Symbol.asyncIterator is not defined.");
     var g = generator.apply(thisArg, _arguments || []), q = [], c, i;
     return i = { next: verb("next"), "throw": verb("throw"), "return": verb("return") }, i[Symbol.asyncIterator] = function () { return this; }, i;
     function verb(n) { return function (v) { return new Promise(function (a, b) { q.push([n, v, a, b]), next(); }); }; }
@@ -407,6 +413,7 @@ var __generator = (this && this.__generator) || function (thisArg, body) {
     }
 };
 var __asyncGenerator = (this && this.__asyncGenerator) || function (thisArg, _arguments, generator) {
+    if (!Symbol.asyncIterator) throw new TypeError("Symbol.asyncIterator is not defined.");
     var g = generator.apply(thisArg, _arguments || []), q = [], c, i;
     return i = { next: verb("next"), "throw": verb("throw"), "return": verb("return") }, i[Symbol.asyncIterator] = function () { return this; }, i;
     function verb(n) { return function (v) { return new Promise(function (a, b) { q.push([n, v, a, b]), next(); }); }; }
diff --git a/tests/baselines/reference/emitter.asyncGenerators.objectLiteralMethods.es2015.js b/tests/baselines/reference/emitter.asyncGenerators.objectLiteralMethods.es2015.js
index 3d3af24d030..817b3904f02 100644
--- a/tests/baselines/reference/emitter.asyncGenerators.objectLiteralMethods.es2015.js
+++ b/tests/baselines/reference/emitter.asyncGenerators.objectLiteralMethods.es2015.js
@@ -45,6 +45,7 @@ const o7 = {
 
 //// [O1.js]
 var __asyncGenerator = (this && this.__asyncGenerator) || function (thisArg, _arguments, generator) {
+    if (!Symbol.asyncIterator) throw new TypeError("Symbol.asyncIterator is not defined.");
     var g = generator.apply(thisArg, _arguments || []), q = [], c, i;
     return i = { next: verb("next"), "throw": verb("throw"), "return": verb("return") }, i[Symbol.asyncIterator] = function () { return this; }, i;
     function verb(n) { return function (v) { return new Promise(function (a, b) { q.push([n, v, a, b]), next(); }); }; }
@@ -64,6 +65,7 @@ const o1 = {
 };
 //// [O2.js]
 var __asyncGenerator = (this && this.__asyncGenerator) || function (thisArg, _arguments, generator) {
+    if (!Symbol.asyncIterator) throw new TypeError("Symbol.asyncIterator is not defined.");
     var g = generator.apply(thisArg, _arguments || []), q = [], c, i;
     return i = { next: verb("next"), "throw": verb("throw"), "return": verb("return") }, i[Symbol.asyncIterator] = function () { return this; }, i;
     function verb(n) { return function (v) { return new Promise(function (a, b) { q.push([n, v, a, b]), next(); }); }; }
@@ -84,6 +86,7 @@ const o2 = {
 };
 //// [O3.js]
 var __asyncGenerator = (this && this.__asyncGenerator) || function (thisArg, _arguments, generator) {
+    if (!Symbol.asyncIterator) throw new TypeError("Symbol.asyncIterator is not defined.");
     var g = generator.apply(thisArg, _arguments || []), q = [], c, i;
     return i = { next: verb("next"), "throw": verb("throw"), "return": verb("return") }, i[Symbol.asyncIterator] = function () { return this; }, i;
     function verb(n) { return function (v) { return new Promise(function (a, b) { q.push([n, v, a, b]), next(); }); }; }
@@ -109,6 +112,7 @@ var __asyncDelegator = (this && this.__asyncDelegator) || function (o) {
     function verb(n, f) { return function (v) { return { value: ["delegate", (o[n] || f).call(o, v)], done: false }; }; }
 };
 var __asyncGenerator = (this && this.__asyncGenerator) || function (thisArg, _arguments, generator) {
+    if (!Symbol.asyncIterator) throw new TypeError("Symbol.asyncIterator is not defined.");
     var g = generator.apply(thisArg, _arguments || []), q = [], c, i;
     return i = { next: verb("next"), "throw": verb("throw"), "return": verb("return") }, i[Symbol.asyncIterator] = function () { return this; }, i;
     function verb(n) { return function (v) { return new Promise(function (a, b) { q.push([n, v, a, b]), next(); }); }; }
@@ -129,6 +133,7 @@ const o4 = {
 };
 //// [O5.js]
 var __asyncGenerator = (this && this.__asyncGenerator) || function (thisArg, _arguments, generator) {
+    if (!Symbol.asyncIterator) throw new TypeError("Symbol.asyncIterator is not defined.");
     var g = generator.apply(thisArg, _arguments || []), q = [], c, i;
     return i = { next: verb("next"), "throw": verb("throw"), "return": verb("return") }, i[Symbol.asyncIterator] = function () { return this; }, i;
     function verb(n) { return function (v) { return new Promise(function (a, b) { q.push([n, v, a, b]), next(); }); }; }
@@ -154,6 +159,7 @@ const o5 = {
 };
 //// [O6.js]
 var __asyncGenerator = (this && this.__asyncGenerator) || function (thisArg, _arguments, generator) {
+    if (!Symbol.asyncIterator) throw new TypeError("Symbol.asyncIterator is not defined.");
     var g = generator.apply(thisArg, _arguments || []), q = [], c, i;
     return i = { next: verb("next"), "throw": verb("throw"), "return": verb("return") }, i[Symbol.asyncIterator] = function () { return this; }, i;
     function verb(n) { return function (v) { return new Promise(function (a, b) { q.push([n, v, a, b]), next(); }); }; }
@@ -174,6 +180,7 @@ const o6 = {
 };
 //// [O7.js]
 var __asyncGenerator = (this && this.__asyncGenerator) || function (thisArg, _arguments, generator) {
+    if (!Symbol.asyncIterator) throw new TypeError("Symbol.asyncIterator is not defined.");
     var g = generator.apply(thisArg, _arguments || []), q = [], c, i;
     return i = { next: verb("next"), "throw": verb("throw"), "return": verb("return") }, i[Symbol.asyncIterator] = function () { return this; }, i;
     function verb(n) { return function (v) { return new Promise(function (a, b) { q.push([n, v, a, b]), next(); }); }; }
diff --git a/tests/baselines/reference/emitter.asyncGenerators.objectLiteralMethods.es5.js b/tests/baselines/reference/emitter.asyncGenerators.objectLiteralMethods.es5.js
index f819945f288..a0839d8258d 100644
--- a/tests/baselines/reference/emitter.asyncGenerators.objectLiteralMethods.es5.js
+++ b/tests/baselines/reference/emitter.asyncGenerators.objectLiteralMethods.es5.js
@@ -72,6 +72,7 @@ var __generator = (this && this.__generator) || function (thisArg, body) {
     }
 };
 var __asyncGenerator = (this && this.__asyncGenerator) || function (thisArg, _arguments, generator) {
+    if (!Symbol.asyncIterator) throw new TypeError("Symbol.asyncIterator is not defined.");
     var g = generator.apply(thisArg, _arguments || []), q = [], c, i;
     return i = { next: verb("next"), "throw": verb("throw"), "return": verb("return") }, i[Symbol.asyncIterator] = function () { return this; }, i;
     function verb(n) { return function (v) { return new Promise(function (a, b) { q.push([n, v, a, b]), next(); }); }; }
@@ -121,6 +122,7 @@ var __generator = (this && this.__generator) || function (thisArg, body) {
     }
 };
 var __asyncGenerator = (this && this.__asyncGenerator) || function (thisArg, _arguments, generator) {
+    if (!Symbol.asyncIterator) throw new TypeError("Symbol.asyncIterator is not defined.");
     var g = generator.apply(thisArg, _arguments || []), q = [], c, i;
     return i = { next: verb("next"), "throw": verb("throw"), "return": verb("return") }, i[Symbol.asyncIterator] = function () { return this; }, i;
     function verb(n) { return function (v) { return new Promise(function (a, b) { q.push([n, v, a, b]), next(); }); }; }
@@ -176,6 +178,7 @@ var __generator = (this && this.__generator) || function (thisArg, body) {
     }
 };
 var __asyncGenerator = (this && this.__asyncGenerator) || function (thisArg, _arguments, generator) {
+    if (!Symbol.asyncIterator) throw new TypeError("Symbol.asyncIterator is not defined.");
     var g = generator.apply(thisArg, _arguments || []), q = [], c, i;
     return i = { next: verb("next"), "throw": verb("throw"), "return": verb("return") }, i[Symbol.asyncIterator] = function () { return this; }, i;
     function verb(n) { return function (v) { return new Promise(function (a, b) { q.push([n, v, a, b]), next(); }); }; }
@@ -236,6 +239,7 @@ var __asyncDelegator = (this && this.__asyncDelegator) || function (o) {
     function verb(n, f) { return function (v) { return { value: ["delegate", (o[n] || f).call(o, v)], done: false }; }; }
 };
 var __asyncGenerator = (this && this.__asyncGenerator) || function (thisArg, _arguments, generator) {
+    if (!Symbol.asyncIterator) throw new TypeError("Symbol.asyncIterator is not defined.");
     var g = generator.apply(thisArg, _arguments || []), q = [], c, i;
     return i = { next: verb("next"), "throw": verb("throw"), "return": verb("return") }, i[Symbol.asyncIterator] = function () { return this; }, i;
     function verb(n) { return function (v) { return new Promise(function (a, b) { q.push([n, v, a, b]), next(); }); }; }
@@ -301,6 +305,7 @@ var __generator = (this && this.__generator) || function (thisArg, body) {
     }
 };
 var __asyncGenerator = (this && this.__asyncGenerator) || function (thisArg, _arguments, generator) {
+    if (!Symbol.asyncIterator) throw new TypeError("Symbol.asyncIterator is not defined.");
     var g = generator.apply(thisArg, _arguments || []), q = [], c, i;
     return i = { next: verb("next"), "throw": verb("throw"), "return": verb("return") }, i[Symbol.asyncIterator] = function () { return this; }, i;
     function verb(n) { return function (v) { return new Promise(function (a, b) { q.push([n, v, a, b]), next(); }); }; }
@@ -378,6 +383,7 @@ var __generator = (this && this.__generator) || function (thisArg, body) {
     }
 };
 var __asyncGenerator = (this && this.__asyncGenerator) || function (thisArg, _arguments, generator) {
+    if (!Symbol.asyncIterator) throw new TypeError("Symbol.asyncIterator is not defined.");
     var g = generator.apply(thisArg, _arguments || []), q = [], c, i;
     return i = { next: verb("next"), "throw": verb("throw"), "return": verb("return") }, i[Symbol.asyncIterator] = function () { return this; }, i;
     function verb(n) { return function (v) { return new Promise(function (a, b) { q.push([n, v, a, b]), next(); }); }; }
@@ -433,6 +439,7 @@ var __generator = (this && this.__generator) || function (thisArg, body) {
     }
 };
 var __asyncGenerator = (this && this.__asyncGenerator) || function (thisArg, _arguments, generator) {
+    if (!Symbol.asyncIterator) throw new TypeError("Symbol.asyncIterator is not defined.");
     var g = generator.apply(thisArg, _arguments || []), q = [], c, i;
     return i = { next: verb("next"), "throw": verb("throw"), "return": verb("return") }, i[Symbol.asyncIterator] = function () { return this; }, i;
     function verb(n) { return function (v) { return new Promise(function (a, b) { q.push([n, v, a, b]), next(); }); }; }
diff --git a/tests/baselines/reference/emitter.forAwait.es2015.js b/tests/baselines/reference/emitter.forAwait.es2015.js
index bfd44581b82..a76c3e0b545 100644
--- a/tests/baselines/reference/emitter.forAwait.es2015.js
+++ b/tests/baselines/reference/emitter.forAwait.es2015.js
@@ -35,6 +35,7 @@ var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, ge
     });
 };
 var __asyncValues = (this && this.__asyncIterator) || function (o) {
+    if (!Symbol.asyncIterator) throw new TypeError("Symbol.asyncIterator is not defined.");
     var m = o[Symbol.asyncIterator];
     return m ? m.call(o) : typeof __values === "function" ? __values(o) : o[Symbol.iterator]();
 };
@@ -42,14 +43,14 @@ function f1() {
     return __awaiter(this, void 0, void 0, function* () {
         let y;
         try {
-            for (var y_1 = __asyncValues(y), y_1_1 = yield ["await", y_1.next()]; !y_1_1.done; y_1_1 = yield ["await", y_1.next()]) {
+            for (var y_1 = __asyncValues(y), y_1_1 = yield y_1.next(); !y_1_1.done; y_1_1 = yield y_1.next()) {
                 const x = y_1_1.value;
             }
         }
         catch (e_1_1) { e_1 = { error: e_1_1 }; }
         finally {
             try {
-                if (y_1_1 && !y_1_1.done && (_a = y_1.return)) yield ["await", _a.call(y_1)];
+                if (y_1_1 && !y_1_1.done && (_a = y_1.return)) yield _a.call(y_1);
             }
             finally { if (e_1) throw e_1.error; }
         }
@@ -66,6 +67,7 @@ var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, ge
     });
 };
 var __asyncValues = (this && this.__asyncIterator) || function (o) {
+    if (!Symbol.asyncIterator) throw new TypeError("Symbol.asyncIterator is not defined.");
     var m = o[Symbol.asyncIterator];
     return m ? m.call(o) : typeof __values === "function" ? __values(o) : o[Symbol.iterator]();
 };
@@ -73,14 +75,14 @@ function f2() {
     return __awaiter(this, void 0, void 0, function* () {
         let x, y;
         try {
-            for (var y_1 = __asyncValues(y), y_1_1 = yield ["await", y_1.next()]; !y_1_1.done; y_1_1 = yield ["await", y_1.next()]) {
+            for (var y_1 = __asyncValues(y), y_1_1 = yield y_1.next(); !y_1_1.done; y_1_1 = yield y_1.next()) {
                 x = y_1_1.value;
             }
         }
         catch (e_1_1) { e_1 = { error: e_1_1 }; }
         finally {
             try {
-                if (y_1_1 && !y_1_1.done && (_a = y_1.return)) yield ["await", _a.call(y_1)];
+                if (y_1_1 && !y_1_1.done && (_a = y_1.return)) yield _a.call(y_1);
             }
             finally { if (e_1) throw e_1.error; }
         }
@@ -89,10 +91,12 @@ function f2() {
 }
 //// [file3.js]
 var __asyncValues = (this && this.__asyncIterator) || function (o) {
+    if (!Symbol.asyncIterator) throw new TypeError("Symbol.asyncIterator is not defined.");
     var m = o[Symbol.asyncIterator];
     return m ? m.call(o) : typeof __values === "function" ? __values(o) : o[Symbol.iterator]();
 };
 var __asyncGenerator = (this && this.__asyncGenerator) || function (thisArg, _arguments, generator) {
+    if (!Symbol.asyncIterator) throw new TypeError("Symbol.asyncIterator is not defined.");
     var g = generator.apply(thisArg, _arguments || []), q = [], c, i;
     return i = { next: verb("next"), "throw": verb("throw"), "return": verb("return") }, i[Symbol.asyncIterator] = function () { return this; }, i;
     function verb(n) { return function (v) { return new Promise(function (a, b) { q.push([n, v, a, b]), next(); }); }; }
@@ -124,10 +128,12 @@ function f3() {
 }
 //// [file4.js]
 var __asyncValues = (this && this.__asyncIterator) || function (o) {
+    if (!Symbol.asyncIterator) throw new TypeError("Symbol.asyncIterator is not defined.");
     var m = o[Symbol.asyncIterator];
     return m ? m.call(o) : typeof __values === "function" ? __values(o) : o[Symbol.iterator]();
 };
 var __asyncGenerator = (this && this.__asyncGenerator) || function (thisArg, _arguments, generator) {
+    if (!Symbol.asyncIterator) throw new TypeError("Symbol.asyncIterator is not defined.");
     var g = generator.apply(thisArg, _arguments || []), q = [], c, i;
     return i = { next: verb("next"), "throw": verb("throw"), "return": verb("return") }, i[Symbol.asyncIterator] = function () { return this; }, i;
     function verb(n) { return function (v) { return new Promise(function (a, b) { q.push([n, v, a, b]), next(); }); }; }
diff --git a/tests/baselines/reference/emitter.forAwait.es5.js b/tests/baselines/reference/emitter.forAwait.es5.js
index 5b904cf10a7..efbbe872b3f 100644
--- a/tests/baselines/reference/emitter.forAwait.es5.js
+++ b/tests/baselines/reference/emitter.forAwait.es5.js
@@ -62,6 +62,7 @@ var __generator = (this && this.__generator) || function (thisArg, body) {
     }
 };
 var __asyncValues = (this && this.__asyncIterator) || function (o) {
+    if (!Symbol.asyncIterator) throw new TypeError("Symbol.asyncIterator is not defined.");
     var m = o[Symbol.asyncIterator];
     return m ? m.call(o) : typeof __values === "function" ? __values(o) : o[Symbol.iterator]();
 };
@@ -73,7 +74,7 @@ function f1() {
                 case 0:
                     _c.trys.push([0, 6, 7, 12]);
                     y_1 = __asyncValues(y);
-                    return [4 /*yield*/, ["await", y_1.next()]];
+                    return [4 /*yield*/, y_1.next()];
                 case 1:
                     y_1_1 = _c.sent();
                     _c.label = 2;
@@ -81,7 +82,7 @@ function f1() {
                     if (!!y_1_1.done) return [3 /*break*/, 5];
                     x = y_1_1.value;
                     _c.label = 3;
-                case 3: return [4 /*yield*/, ["await", y_1.next()]];
+                case 3: return [4 /*yield*/, y_1.next()];
                 case 4:
                     y_1_1 = _c.sent();
                     return [3 /*break*/, 2];
@@ -93,7 +94,7 @@ function f1() {
                 case 7:
                     _c.trys.push([7, , 10, 11]);
                     if (!(y_1_1 && !y_1_1.done && (_b = y_1.return))) return [3 /*break*/, 9];
-                    return [4 /*yield*/, ["await", _b.call(y_1)]];
+                    return [4 /*yield*/, _b.call(y_1)];
                 case 8:
                     _c.sent();
                     _c.label = 9;
@@ -144,6 +145,7 @@ var __generator = (this && this.__generator) || function (thisArg, body) {
     }
 };
 var __asyncValues = (this && this.__asyncIterator) || function (o) {
+    if (!Symbol.asyncIterator) throw new TypeError("Symbol.asyncIterator is not defined.");
     var m = o[Symbol.asyncIterator];
     return m ? m.call(o) : typeof __values === "function" ? __values(o) : o[Symbol.iterator]();
 };
@@ -155,7 +157,7 @@ function f2() {
                 case 0:
                     _c.trys.push([0, 6, 7, 12]);
                     y_1 = __asyncValues(y);
-                    return [4 /*yield*/, ["await", y_1.next()]];
+                    return [4 /*yield*/, y_1.next()];
                 case 1:
                     y_1_1 = _c.sent();
                     _c.label = 2;
@@ -163,7 +165,7 @@ function f2() {
                     if (!!y_1_1.done) return [3 /*break*/, 5];
                     x = y_1_1.value;
                     _c.label = 3;
-                case 3: return [4 /*yield*/, ["await", y_1.next()]];
+                case 3: return [4 /*yield*/, y_1.next()];
                 case 4:
                     y_1_1 = _c.sent();
                     return [3 /*break*/, 2];
@@ -175,7 +177,7 @@ function f2() {
                 case 7:
                     _c.trys.push([7, , 10, 11]);
                     if (!(y_1_1 && !y_1_1.done && (_b = y_1.return))) return [3 /*break*/, 9];
-                    return [4 /*yield*/, ["await", _b.call(y_1)]];
+                    return [4 /*yield*/, _b.call(y_1)];
                 case 8:
                     _c.sent();
                     _c.label = 9;
@@ -218,10 +220,12 @@ var __generator = (this && this.__generator) || function (thisArg, body) {
     }
 };
 var __asyncValues = (this && this.__asyncIterator) || function (o) {
+    if (!Symbol.asyncIterator) throw new TypeError("Symbol.asyncIterator is not defined.");
     var m = o[Symbol.asyncIterator];
     return m ? m.call(o) : typeof __values === "function" ? __values(o) : o[Symbol.iterator]();
 };
 var __asyncGenerator = (this && this.__asyncGenerator) || function (thisArg, _arguments, generator) {
+    if (!Symbol.asyncIterator) throw new TypeError("Symbol.asyncIterator is not defined.");
     var g = generator.apply(thisArg, _arguments || []), q = [], c, i;
     return i = { next: verb("next"), "throw": verb("throw"), "return": verb("return") }, i[Symbol.asyncIterator] = function () { return this; }, i;
     function verb(n) { return function (v) { return new Promise(function (a, b) { q.push([n, v, a, b]), next(); }); }; }
@@ -304,10 +308,12 @@ var __generator = (this && this.__generator) || function (thisArg, body) {
     }
 };
 var __asyncValues = (this && this.__asyncIterator) || function (o) {
+    if (!Symbol.asyncIterator) throw new TypeError("Symbol.asyncIterator is not defined.");
     var m = o[Symbol.asyncIterator];
     return m ? m.call(o) : typeof __values === "function" ? __values(o) : o[Symbol.iterator]();
 };
 var __asyncGenerator = (this && this.__asyncGenerator) || function (thisArg, _arguments, generator) {
+    if (!Symbol.asyncIterator) throw new TypeError("Symbol.asyncIterator is not defined.");
     var g = generator.apply(thisArg, _arguments || []), q = [], c, i;
     return i = { next: verb("next"), "throw": verb("throw"), "return": verb("return") }, i[Symbol.asyncIterator] = function () { return this; }, i;
     function verb(n) { return function (v) { return new Promise(function (a, b) { q.push([n, v, a, b]), next(); }); }; }