diff --git a/src/compiler/transformers/es2017.ts b/src/compiler/transformers/es2017.ts
index 8d20f94afed..9c2d5700d43 100644
--- a/src/compiler/transformers/es2017.ts
+++ b/src/compiler/transformers/es2017.ts
@@ -775,10 +775,11 @@ namespace ts {
         priority: 5,
         text: `
             var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+                function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
                 return new (P || (P = Promise))(function (resolve, reject) {
                     function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
                     function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
-                    function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+                    function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
                     step((generator = generator.apply(thisArg, _arguments || [])).next());
                 });
             };`
diff --git a/src/compiler/transformers/es2018.ts b/src/compiler/transformers/es2018.ts
index 084bbd5d1f0..94ccf6a08a9 100644
--- a/src/compiler/transformers/es2018.ts
+++ b/src/compiler/transformers/es2018.ts
@@ -229,14 +229,39 @@ namespace ts {
             if (node.transformFlags & TransformFlags.ContainsObjectRestOrSpread) {
                 // spread elements emit like so:
                 // non-spread elements are chunked together into object literals, and then all are passed to __assign:
-                //     { a, ...o, b } => __assign({a}, o, {b});
+                //     { a, ...o, b } => __assign(__assign({a}, o), {b});
                 // If the first element is a spread element, then the first argument to __assign is {}:
-                //     { ...o, a, b, ...o2 } => __assign({}, o, {a, b}, o2)
+                //     { ...o, a, b, ...o2 } => __assign(__assign(__assign({}, o), {a, b}), o2)
+                //
+                // We cannot call __assign with more than two elements, since any element could cause side effects. For
+                // example:
+                //      var k = { a: 1, b: 2 };
+                //      var o = { a: 3, ...k, b: k.a++ };
+                //      // expected: { a: 1, b: 1 }
+                // If we translate the above to `__assign({ a: 3 }, k, { b: k.a++ })`, the `k.a++` will evaluate before
+                // `k` is spread and we end up with `{ a: 2, b: 1 }`.
+                //
+                // This also occurs for spread elements, not just property assignments:
+                //      var k = { a: 1, get b() { l = { z: 9 }; return 2; } };
+                //      var l = { c: 3 };
+                //      var o = { ...k, ...l };
+                //      // expected: { a: 1, b: 2, z: 9 }
+                // If we translate the above to `__assign({}, k, l)`, the `l` will evaluate before `k` is spread and we
+                // end up with `{ a: 1, b: 2, c: 3 }`
                 const objects = chunkObjectLiteralElements(node.properties);
                 if (objects.length && objects[0].kind !== SyntaxKind.ObjectLiteralExpression) {
                     objects.unshift(createObjectLiteral());
                 }
-                return createAssignHelper(context, objects);
+                let expression: Expression = objects[0];
+                if (objects.length > 1) {
+                    for (let i = 1; i < objects.length; i++) {
+                        expression = createAssignHelper(context, [expression, objects[i]]);
+                    }
+                    return expression;
+                }
+                else {
+                    return createAssignHelper(context, objects);
+                }
             }
             return visitEachChild(node, visitor, context);
         }
diff --git a/src/testRunner/tsconfig.json b/src/testRunner/tsconfig.json
index b2e7e3e78b9..659dd426b79 100644
--- a/src/testRunner/tsconfig.json
+++ b/src/testRunner/tsconfig.json
@@ -73,7 +73,9 @@
         "unittests/config/tsconfigParsing.ts",
         "unittests/evaluation/asyncArrow.ts",
         "unittests/evaluation/asyncGenerator.ts",
+        "unittests/evaluation/awaiter.ts",
         "unittests/evaluation/forAwaitOf.ts",
+        "unittests/evaluation/objectRest.ts",
         "unittests/services/cancellableLanguageServiceOperations.ts",
         "unittests/services/colorization.ts",
         "unittests/services/convertToAsyncFunction.ts",
diff --git a/src/testRunner/unittests/evaluation/awaiter.ts b/src/testRunner/unittests/evaluation/awaiter.ts
new file mode 100644
index 00000000000..65cb4e0ead9
--- /dev/null
+++ b/src/testRunner/unittests/evaluation/awaiter.ts
@@ -0,0 +1,24 @@
+describe("unittests:: evaluation:: awaiter", () => {
+    // NOTE: This could break if the ECMAScript spec ever changes the timing behavior for Promises (again)
+    it("await (es5)", async () => {
+        const result = evaluator.evaluateTypeScript(`
+        async function a(msg: string) {
+            await Promise.resolve();
+            output.push(msg);
+        }
+        function b(msg: string) {
+            return Promise.resolve().then(() => {
+                output.push(msg);
+            });
+        }
+        export const output: string[] = [];
+        export async function main() {
+            const p1 = a('1');
+            const p2 = b('2');
+            await Promise.all([p1, p2]);
+        }
+        `);
+        await result.main();
+        assert.deepEqual(result.output, ["1", "2"]);
+    });
+});
diff --git a/src/testRunner/unittests/evaluation/objectRest.ts b/src/testRunner/unittests/evaluation/objectRest.ts
new file mode 100644
index 00000000000..272ba51ffbe
--- /dev/null
+++ b/src/testRunner/unittests/evaluation/objectRest.ts
@@ -0,0 +1,28 @@
+describe("unittests:: evaluation:: objectRest", () => {
+    // https://github.com/microsoft/TypeScript/issues/31469
+    it("side effects in property assignment", async () => {
+        const result = evaluator.evaluateTypeScript(`
+            const k = { a: 1, b: 2 };
+            const o = { a: 3, ...k, b: k.a++ };
+            export const output = o;
+        `);
+        assert.deepEqual(result.output, { a: 1, b: 1 });
+    });
+    it("side effects in during spread", async () => {
+        const result = evaluator.evaluateTypeScript(`
+            const k = { a: 1, get b() { l = { c: 9 }; return 2; } };
+            let l = { c: 3 };
+            const o = { ...k, ...l };
+            export const output = o;
+        `);
+        assert.deepEqual(result.output, { a: 1, b: 2, c: 9 });
+    });
+    it("trailing literal-valued object-literal", async () => {
+        const result = evaluator.evaluateTypeScript(`
+            const k = { a: 1 }
+            const o = { ...k, ...{ b: 2 } };
+            export const output = o;
+        `);
+        assert.deepEqual(result.output, { a: 1, b: 2 });
+    });
+});
diff --git a/tests/baselines/reference/asyncArrowFunction11_es5.js b/tests/baselines/reference/asyncArrowFunction11_es5.js
index 5f234f2fbf6..a16ce36e840 100644
--- a/tests/baselines/reference/asyncArrowFunction11_es5.js
+++ b/tests/baselines/reference/asyncArrowFunction11_es5.js
@@ -9,10 +9,11 @@ class A {
 
 //// [asyncArrowFunction11_es5.js]
 var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
     return new (P || (P = Promise))(function (resolve, reject) {
         function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
         function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
-        function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
         step((generator = generator.apply(thisArg, _arguments || [])).next());
     });
 };
diff --git a/tests/baselines/reference/asyncAwaitIsolatedModules_es5.js b/tests/baselines/reference/asyncAwaitIsolatedModules_es5.js
index 58b887c61a3..934f6be814a 100644
--- a/tests/baselines/reference/asyncAwaitIsolatedModules_es5.js
+++ b/tests/baselines/reference/asyncAwaitIsolatedModules_es5.js
@@ -42,10 +42,11 @@ module M {
 //// [asyncAwaitIsolatedModules_es5.js]
 "use strict";
 var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
     return new (P || (P = Promise))(function (resolve, reject) {
         function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
         function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
-        function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
         step((generator = generator.apply(thisArg, _arguments || [])).next());
     });
 };
diff --git a/tests/baselines/reference/asyncAwaitIsolatedModules_es6.js b/tests/baselines/reference/asyncAwaitIsolatedModules_es6.js
index 046b74e6569..2b956515ba1 100644
--- a/tests/baselines/reference/asyncAwaitIsolatedModules_es6.js
+++ b/tests/baselines/reference/asyncAwaitIsolatedModules_es6.js
@@ -41,10 +41,11 @@ module M {
 
 //// [asyncAwaitIsolatedModules_es6.js]
 var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
     return new (P || (P = Promise))(function (resolve, reject) {
         function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
         function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
-        function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
         step((generator = generator.apply(thisArg, _arguments || [])).next());
     });
 };
diff --git a/tests/baselines/reference/asyncAwait_es5.js b/tests/baselines/reference/asyncAwait_es5.js
index ee8f160b2a4..6a6433e85c6 100644
--- a/tests/baselines/reference/asyncAwait_es5.js
+++ b/tests/baselines/reference/asyncAwait_es5.js
@@ -48,10 +48,11 @@ async function f14() {
 
 //// [asyncAwait_es5.js]
 var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
     return new (P || (P = Promise))(function (resolve, reject) {
         function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
         function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
-        function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
         step((generator = generator.apply(thisArg, _arguments || [])).next());
     });
 };
diff --git a/tests/baselines/reference/asyncAwait_es6.js b/tests/baselines/reference/asyncAwait_es6.js
index 3cfe3b3ceec..caab72bad9a 100644
--- a/tests/baselines/reference/asyncAwait_es6.js
+++ b/tests/baselines/reference/asyncAwait_es6.js
@@ -48,10 +48,11 @@ async function f14() {
 
 //// [asyncAwait_es6.js]
 var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
     return new (P || (P = Promise))(function (resolve, reject) {
         function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
         function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
-        function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
         step((generator = generator.apply(thisArg, _arguments || [])).next());
     });
 };
diff --git a/tests/baselines/reference/asyncFunctionNoReturnType.js b/tests/baselines/reference/asyncFunctionNoReturnType.js
index b376e398d17..430210cbdbc 100644
--- a/tests/baselines/reference/asyncFunctionNoReturnType.js
+++ b/tests/baselines/reference/asyncFunctionNoReturnType.js
@@ -7,10 +7,11 @@ async () => {
 
 //// [asyncFunctionNoReturnType.js]
 var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
     return new (P || (P = Promise))(function (resolve, reject) {
         function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
         function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
-        function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
         step((generator = generator.apply(thisArg, _arguments || [])).next());
     });
 };
diff --git a/tests/baselines/reference/asyncFunctionReturnExpressionErrorSpans.js b/tests/baselines/reference/asyncFunctionReturnExpressionErrorSpans.js
index d60a7df66d0..887484e933a 100644
--- a/tests/baselines/reference/asyncFunctionReturnExpressionErrorSpans.js
+++ b/tests/baselines/reference/asyncFunctionReturnExpressionErrorSpans.js
@@ -23,10 +23,11 @@ async function asyncFoo(): Promise<Foo> {
 
 //// [asyncFunctionReturnExpressionErrorSpans.js]
 var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
     return new (P || (P = Promise))(function (resolve, reject) {
         function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
         function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
-        function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
         step((generator = generator.apply(thisArg, _arguments || [])).next());
     });
 };
diff --git a/tests/baselines/reference/asyncFunctionReturnType.js b/tests/baselines/reference/asyncFunctionReturnType.js
index 6e39e72ae4c..04b3a04a036 100644
--- a/tests/baselines/reference/asyncFunctionReturnType.js
+++ b/tests/baselines/reference/asyncFunctionReturnType.js
@@ -77,10 +77,11 @@ async function fGenericIndexedTypeForExplicitPromiseOfKProp<TObj extends Obj, K
 
 //// [asyncFunctionReturnType.js]
 var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
     return new (P || (P = Promise))(function (resolve, reject) {
         function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
         function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
-        function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
         step((generator = generator.apply(thisArg, _arguments || [])).next());
     });
 };
diff --git a/tests/baselines/reference/asyncFunctionTempVariableScoping.js b/tests/baselines/reference/asyncFunctionTempVariableScoping.js
index 0e258b81284..3a6da56c993 100644
--- a/tests/baselines/reference/asyncFunctionTempVariableScoping.js
+++ b/tests/baselines/reference/asyncFunctionTempVariableScoping.js
@@ -6,10 +6,11 @@ async ({ foo, bar, ...rest }) => bar(await foo);
 //// [asyncFunctionTempVariableScoping.js]
 // https://github.com/Microsoft/TypeScript/issues/19187
 var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
     return new (P || (P = Promise))(function (resolve, reject) {
         function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
         function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
-        function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
         step((generator = generator.apply(thisArg, _arguments || [])).next());
     });
 };
diff --git a/tests/baselines/reference/asyncFunctionWithForStatementNoInitializer.js b/tests/baselines/reference/asyncFunctionWithForStatementNoInitializer.js
index 99394281a15..055a751f523 100644
--- a/tests/baselines/reference/asyncFunctionWithForStatementNoInitializer.js
+++ b/tests/baselines/reference/asyncFunctionWithForStatementNoInitializer.js
@@ -26,10 +26,11 @@ async function test4() {
 
 //// [asyncFunctionWithForStatementNoInitializer.js]
 var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
     return new (P || (P = Promise))(function (resolve, reject) {
         function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
         function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
-        function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
         step((generator = generator.apply(thisArg, _arguments || [])).next());
     });
 };
diff --git a/tests/baselines/reference/asyncFunctionsAcrossFiles.js b/tests/baselines/reference/asyncFunctionsAcrossFiles.js
index b1a766e4e41..cd86f20c69d 100644
--- a/tests/baselines/reference/asyncFunctionsAcrossFiles.js
+++ b/tests/baselines/reference/asyncFunctionsAcrossFiles.js
@@ -17,10 +17,11 @@ export const b = {
 
 //// [b.js]
 var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
     return new (P || (P = Promise))(function (resolve, reject) {
         function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
         function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
-        function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
         step((generator = generator.apply(thisArg, _arguments || [])).next());
     });
 };
@@ -32,10 +33,11 @@ export const b = {
 };
 //// [a.js]
 var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
     return new (P || (P = Promise))(function (resolve, reject) {
         function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
         function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
-        function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
         step((generator = generator.apply(thisArg, _arguments || [])).next());
     });
 };
diff --git a/tests/baselines/reference/asyncFunctionsAndStrictNullChecks.js b/tests/baselines/reference/asyncFunctionsAndStrictNullChecks.js
index 2afcf5d7dfd..a13f2f8b219 100644
--- a/tests/baselines/reference/asyncFunctionsAndStrictNullChecks.js
+++ b/tests/baselines/reference/asyncFunctionsAndStrictNullChecks.js
@@ -27,10 +27,11 @@ async function sample2(x?: number) {
 
 //// [asyncFunctionsAndStrictNullChecks.js]
 var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
     return new (P || (P = Promise))(function (resolve, reject) {
         function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
         function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
-        function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
         step((generator = generator.apply(thisArg, _arguments || [])).next());
     });
 };
diff --git a/tests/baselines/reference/asyncIIFE.js b/tests/baselines/reference/asyncIIFE.js
index 8ca87781113..e2096b4c6de 100644
--- a/tests/baselines/reference/asyncIIFE.js
+++ b/tests/baselines/reference/asyncIIFE.js
@@ -11,10 +11,11 @@ function f1() {
 
 //// [asyncIIFE.js]
 var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
     return new (P || (P = Promise))(function (resolve, reject) {
         function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
         function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
-        function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
         step((generator = generator.apply(thisArg, _arguments || [])).next());
     });
 };
diff --git a/tests/baselines/reference/asyncImportedPromise_es5.js b/tests/baselines/reference/asyncImportedPromise_es5.js
index f17459321c8..11699f6ab1e 100644
--- a/tests/baselines/reference/asyncImportedPromise_es5.js
+++ b/tests/baselines/reference/asyncImportedPromise_es5.js
@@ -36,10 +36,11 @@ exports.Task = Task;
 //// [test.js]
 "use strict";
 var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
     return new (P || (P = Promise))(function (resolve, reject) {
         function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
         function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
-        function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
         step((generator = generator.apply(thisArg, _arguments || [])).next());
     });
 };
diff --git a/tests/baselines/reference/asyncImportedPromise_es6.js b/tests/baselines/reference/asyncImportedPromise_es6.js
index 6b84f5615b3..41bf0f26087 100644
--- a/tests/baselines/reference/asyncImportedPromise_es6.js
+++ b/tests/baselines/reference/asyncImportedPromise_es6.js
@@ -18,10 +18,11 @@ exports.Task = Task;
 //// [test.js]
 "use strict";
 var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
     return new (P || (P = Promise))(function (resolve, reject) {
         function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
         function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
-        function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
         step((generator = generator.apply(thisArg, _arguments || [])).next());
     });
 };
diff --git a/tests/baselines/reference/asyncMethodWithSuperConflict_es6.js b/tests/baselines/reference/asyncMethodWithSuperConflict_es6.js
index 2a910226703..5e2a152b9e0 100644
--- a/tests/baselines/reference/asyncMethodWithSuperConflict_es6.js
+++ b/tests/baselines/reference/asyncMethodWithSuperConflict_es6.js
@@ -61,10 +61,11 @@ class B extends A {
 
 //// [asyncMethodWithSuperConflict_es6.js]
 var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
     return new (P || (P = Promise))(function (resolve, reject) {
         function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
         function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
-        function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
         step((generator = generator.apply(thisArg, _arguments || [])).next());
     });
 };
diff --git a/tests/baselines/reference/asyncMultiFile_es5.js b/tests/baselines/reference/asyncMultiFile_es5.js
index a6dbb44ef9e..392a4456cc2 100644
--- a/tests/baselines/reference/asyncMultiFile_es5.js
+++ b/tests/baselines/reference/asyncMultiFile_es5.js
@@ -7,10 +7,11 @@ function g() { }
 
 //// [a.js]
 var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
     return new (P || (P = Promise))(function (resolve, reject) {
         function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
         function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
-        function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
         step((generator = generator.apply(thisArg, _arguments || [])).next());
     });
 };
diff --git a/tests/baselines/reference/asyncMultiFile_es6.js b/tests/baselines/reference/asyncMultiFile_es6.js
index e7dd854b95b..7fbb00063c7 100644
--- a/tests/baselines/reference/asyncMultiFile_es6.js
+++ b/tests/baselines/reference/asyncMultiFile_es6.js
@@ -7,10 +7,11 @@ function g() { }
 
 //// [a.js]
 var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
     return new (P || (P = Promise))(function (resolve, reject) {
         function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
         function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
-        function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
         step((generator = generator.apply(thisArg, _arguments || [])).next());
     });
 };
diff --git a/tests/baselines/reference/awaitUnionPromise.js b/tests/baselines/reference/awaitUnionPromise.js
index 90b894ee0f5..723339b9f71 100644
--- a/tests/baselines/reference/awaitUnionPromise.js
+++ b/tests/baselines/reference/awaitUnionPromise.js
@@ -23,10 +23,11 @@ async function main() {
 /// @target: es2015
 // https://github.com/Microsoft/TypeScript/issues/18186
 var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
     return new (P || (P = Promise))(function (resolve, reject) {
         function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
         function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
-        function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
         step((generator = generator.apply(thisArg, _arguments || [])).next());
     });
 };
diff --git a/tests/baselines/reference/await_unaryExpression_es6.js b/tests/baselines/reference/await_unaryExpression_es6.js
index 1361f80bc8e..69eef173613 100644
--- a/tests/baselines/reference/await_unaryExpression_es6.js
+++ b/tests/baselines/reference/await_unaryExpression_es6.js
@@ -17,10 +17,11 @@ async function bar4() {
 
 //// [await_unaryExpression_es6.js]
 var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
     return new (P || (P = Promise))(function (resolve, reject) {
         function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
         function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
-        function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
         step((generator = generator.apply(thisArg, _arguments || [])).next());
     });
 };
diff --git a/tests/baselines/reference/await_unaryExpression_es6_1.js b/tests/baselines/reference/await_unaryExpression_es6_1.js
index 297299e4462..3a205f05ea9 100644
--- a/tests/baselines/reference/await_unaryExpression_es6_1.js
+++ b/tests/baselines/reference/await_unaryExpression_es6_1.js
@@ -21,10 +21,11 @@ async function bar4() {
 
 //// [await_unaryExpression_es6_1.js]
 var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
     return new (P || (P = Promise))(function (resolve, reject) {
         function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
         function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
-        function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
         step((generator = generator.apply(thisArg, _arguments || [])).next());
     });
 };
diff --git a/tests/baselines/reference/await_unaryExpression_es6_2.js b/tests/baselines/reference/await_unaryExpression_es6_2.js
index fdf83e3def1..ee59f5825ae 100644
--- a/tests/baselines/reference/await_unaryExpression_es6_2.js
+++ b/tests/baselines/reference/await_unaryExpression_es6_2.js
@@ -13,10 +13,11 @@ async function bar3() {
 
 //// [await_unaryExpression_es6_2.js]
 var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
     return new (P || (P = Promise))(function (resolve, reject) {
         function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
         function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
-        function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
         step((generator = generator.apply(thisArg, _arguments || [])).next());
     });
 };
diff --git a/tests/baselines/reference/await_unaryExpression_es6_3.js b/tests/baselines/reference/await_unaryExpression_es6_3.js
index 23985832ce1..42643caa262 100644
--- a/tests/baselines/reference/await_unaryExpression_es6_3.js
+++ b/tests/baselines/reference/await_unaryExpression_es6_3.js
@@ -19,10 +19,11 @@ async function bar4() {
 
 //// [await_unaryExpression_es6_3.js]
 var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
     return new (P || (P = Promise))(function (resolve, reject) {
         function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
         function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
-        function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
         step((generator = generator.apply(thisArg, _arguments || [])).next());
     });
 };
diff --git a/tests/baselines/reference/capturedParametersInInitializers1.js b/tests/baselines/reference/capturedParametersInInitializers1.js
index 7ec393e2e39..ec5ff77d84b 100644
--- a/tests/baselines/reference/capturedParametersInInitializers1.js
+++ b/tests/baselines/reference/capturedParametersInInitializers1.js
@@ -42,10 +42,11 @@ function foo9(y = {[z]() { return z; }}, z = 1) {
 
 //// [capturedParametersInInitializers1.js]
 var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
     return new (P || (P = Promise))(function (resolve, reject) {
         function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
         function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
-        function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
         step((generator = generator.apply(thisArg, _arguments || [])).next());
     });
 };
diff --git a/tests/baselines/reference/castOfAwait.js b/tests/baselines/reference/castOfAwait.js
index 9f67f74b11b..c00c1b028f4 100644
--- a/tests/baselines/reference/castOfAwait.js
+++ b/tests/baselines/reference/castOfAwait.js
@@ -10,10 +10,11 @@ async function f() {
 
 //// [castOfAwait.js]
 var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
     return new (P || (P = Promise))(function (resolve, reject) {
         function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
         function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
-        function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
         step((generator = generator.apply(thisArg, _arguments || [])).next());
     });
 };
diff --git a/tests/baselines/reference/checkJsxSubtleSkipContextSensitiveBug.js b/tests/baselines/reference/checkJsxSubtleSkipContextSensitiveBug.js
index 704781dbe58..d1d6dd7eeec 100644
--- a/tests/baselines/reference/checkJsxSubtleSkipContextSensitiveBug.js
+++ b/tests/baselines/reference/checkJsxSubtleSkipContextSensitiveBug.js
@@ -40,10 +40,11 @@ var __extends = (this && this.__extends) || (function () {
     };
 })();
 var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
     return new (P || (P = Promise))(function (resolve, reject) {
         function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
         function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
-        function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
         step((generator = generator.apply(thisArg, _arguments || [])).next());
     });
 };
diff --git a/tests/baselines/reference/circularInferredTypeOfVariable.js b/tests/baselines/reference/circularInferredTypeOfVariable.js
index e7ba96ebaf8..d3e4dd0dc58 100644
--- a/tests/baselines/reference/circularInferredTypeOfVariable.js
+++ b/tests/baselines/reference/circularInferredTypeOfVariable.js
@@ -21,10 +21,11 @@
 //// [circularInferredTypeOfVariable.js]
 // Repro from #14428
 var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
     return new (P || (P = Promise))(function (resolve, reject) {
         function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
         function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
-        function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
         step((generator = generator.apply(thisArg, _arguments || [])).next());
     });
 };
diff --git a/tests/baselines/reference/controlFlowForCatchAndFinally.js b/tests/baselines/reference/controlFlowForCatchAndFinally.js
index b3dfc4e7bb8..48075ffb6b4 100644
--- a/tests/baselines/reference/controlFlowForCatchAndFinally.js
+++ b/tests/baselines/reference/controlFlowForCatchAndFinally.js
@@ -43,10 +43,11 @@ class Foo {
 //// [controlFlowForCatchAndFinally.js]
 "use strict";
 var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
     return new (P || (P = Promise))(function (resolve, reject) {
         function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
         function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
-        function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
         step((generator = generator.apply(thisArg, _arguments || [])).next());
     });
 };
diff --git a/tests/baselines/reference/correctOrderOfPromiseMethod.js b/tests/baselines/reference/correctOrderOfPromiseMethod.js
index 4c273d3c0f2..58c98189a43 100644
--- a/tests/baselines/reference/correctOrderOfPromiseMethod.js
+++ b/tests/baselines/reference/correctOrderOfPromiseMethod.js
@@ -27,10 +27,11 @@ async function countEverything(): Promise<number> {
 
 //// [correctOrderOfPromiseMethod.js]
 var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
     return new (P || (P = Promise))(function (resolve, reject) {
         function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
         function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
-        function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
         step((generator = generator.apply(thisArg, _arguments || [])).next());
     });
 };
diff --git a/tests/baselines/reference/declarationEmitPrivateAsync.js b/tests/baselines/reference/declarationEmitPrivateAsync.js
index deeb9fd15d9..89f33267b8a 100644
--- a/tests/baselines/reference/declarationEmitPrivateAsync.js
+++ b/tests/baselines/reference/declarationEmitPrivateAsync.js
@@ -8,10 +8,11 @@ export class Foo {
 //// [declarationEmitPrivateAsync.js]
 "use strict";
 var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
     return new (P || (P = Promise))(function (resolve, reject) {
         function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
         function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
-        function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
         step((generator = generator.apply(thisArg, _arguments || [])).next());
     });
 };
diff --git a/tests/baselines/reference/declarationEmitPromise.js b/tests/baselines/reference/declarationEmitPromise.js
index 6822dc56c3d..313ffa04183 100644
--- a/tests/baselines/reference/declarationEmitPromise.js
+++ b/tests/baselines/reference/declarationEmitPromise.js
@@ -24,10 +24,11 @@ export async function runSampleBreaks<A, B, C, D, E>(
 //// [declarationEmitPromise.js]
 "use strict";
 var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
     return new (P || (P = Promise))(function (resolve, reject) {
         function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
         function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
-        function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
         step((generator = generator.apply(thisArg, _arguments || [])).next());
     });
 };
diff --git a/tests/baselines/reference/declarationsWithRecursiveInternalTypesProduceUniqueTypeParams.js b/tests/baselines/reference/declarationsWithRecursiveInternalTypesProduceUniqueTypeParams.js
index 913e82292bf..b043fe275cc 100644
--- a/tests/baselines/reference/declarationsWithRecursiveInternalTypesProduceUniqueTypeParams.js
+++ b/tests/baselines/reference/declarationsWithRecursiveInternalTypesProduceUniqueTypeParams.js
@@ -73,7 +73,7 @@ exports.testRecFun = function (parent) {
     return {
         result: parent,
         deeper: function (child) {
-            return exports.testRecFun(__assign({}, parent, child));
+            return exports.testRecFun(__assign(__assign({}, parent), child));
         }
     };
 };
diff --git a/tests/baselines/reference/decoratorMetadataPromise.js b/tests/baselines/reference/decoratorMetadataPromise.js
index a370df936d5..41bb42e2732 100644
--- a/tests/baselines/reference/decoratorMetadataPromise.js
+++ b/tests/baselines/reference/decoratorMetadataPromise.js
@@ -22,10 +22,11 @@ var __metadata = (this && this.__metadata) || function (k, v) {
     if (typeof Reflect === "object" && typeof Reflect.metadata === "function") return Reflect.metadata(k, v);
 };
 var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
     return new (P || (P = Promise))(function (resolve, reject) {
         function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
         function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
-        function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
         step((generator = generator.apply(thisArg, _arguments || [])).next());
     });
 };
diff --git a/tests/baselines/reference/defaultExportInAwaitExpression01.js b/tests/baselines/reference/defaultExportInAwaitExpression01.js
index 6a31461fe3c..950c1141136 100644
--- a/tests/baselines/reference/defaultExportInAwaitExpression01.js
+++ b/tests/baselines/reference/defaultExportInAwaitExpression01.js
@@ -29,10 +29,11 @@ import x from './a';
 });
 //// [b.js]
 var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
     return new (P || (P = Promise))(function (resolve, reject) {
         function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
         function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
-        function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
         step((generator = generator.apply(thisArg, _arguments || [])).next());
     });
 };
diff --git a/tests/baselines/reference/defaultExportInAwaitExpression02.js b/tests/baselines/reference/defaultExportInAwaitExpression02.js
index 565cfb41617..8aa41a6b52a 100644
--- a/tests/baselines/reference/defaultExportInAwaitExpression02.js
+++ b/tests/baselines/reference/defaultExportInAwaitExpression02.js
@@ -20,10 +20,11 @@ exports.default = x;
 //// [b.js]
 "use strict";
 var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
     return new (P || (P = Promise))(function (resolve, reject) {
         function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
         function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
-        function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
         step((generator = generator.apply(thisArg, _arguments || [])).next());
     });
 };
diff --git a/tests/baselines/reference/emitter.forAwait.es2015.js b/tests/baselines/reference/emitter.forAwait.es2015.js
index e5764747765..2b2cc3ce08d 100644
--- a/tests/baselines/reference/emitter.forAwait.es2015.js
+++ b/tests/baselines/reference/emitter.forAwait.es2015.js
@@ -43,10 +43,11 @@ async function* f6() {
 
 //// [file1.js]
 var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
     return new (P || (P = Promise))(function (resolve, reject) {
         function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
         function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
-        function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
         step((generator = generator.apply(thisArg, _arguments || [])).next());
     });
 };
@@ -77,10 +78,11 @@ function f1() {
 }
 //// [file2.js]
 var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
     return new (P || (P = Promise))(function (resolve, reject) {
         function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
         function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
-        function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
         step((generator = generator.apply(thisArg, _arguments || [])).next());
     });
 };
@@ -187,10 +189,11 @@ function f4() {
 }
 //// [file5.js]
 var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
     return new (P || (P = Promise))(function (resolve, reject) {
         function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
         function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
-        function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
         step((generator = generator.apply(thisArg, _arguments || [])).next());
     });
 };
diff --git a/tests/baselines/reference/emitter.forAwait.es5.js b/tests/baselines/reference/emitter.forAwait.es5.js
index 0d67c591e30..f33af25dcc1 100644
--- a/tests/baselines/reference/emitter.forAwait.es5.js
+++ b/tests/baselines/reference/emitter.forAwait.es5.js
@@ -43,10 +43,11 @@ async function* f6() {
 
 //// [file1.js]
 var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
     return new (P || (P = Promise))(function (resolve, reject) {
         function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
         function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
-        function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
         step((generator = generator.apply(thisArg, _arguments || [])).next());
     });
 };
@@ -124,10 +125,11 @@ function f1() {
 }
 //// [file2.js]
 var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
     return new (P || (P = Promise))(function (resolve, reject) {
         function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
         function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
-        function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
         step((generator = generator.apply(thisArg, _arguments || [])).next());
     });
 };
@@ -375,10 +377,11 @@ function f4() {
 }
 //// [file5.js]
 var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
     return new (P || (P = Promise))(function (resolve, reject) {
         function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
         function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
-        function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
         step((generator = generator.apply(thisArg, _arguments || [])).next());
     });
 };
diff --git a/tests/baselines/reference/es5-asyncFunction.js b/tests/baselines/reference/es5-asyncFunction.js
index 9b5744be31e..805e4d4a4c7 100644
--- a/tests/baselines/reference/es5-asyncFunction.js
+++ b/tests/baselines/reference/es5-asyncFunction.js
@@ -10,10 +10,11 @@ async function singleAwait() {
 
 //// [es5-asyncFunction.js]
 var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
     return new (P || (P = Promise))(function (resolve, reject) {
         function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
         function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
-        function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
         step((generator = generator.apply(thisArg, _arguments || [])).next());
     });
 };
diff --git a/tests/baselines/reference/es5-importHelpersAsyncFunctions.js b/tests/baselines/reference/es5-importHelpersAsyncFunctions.js
index 932fd8185eb..75ac303d3c0 100644
--- a/tests/baselines/reference/es5-importHelpersAsyncFunctions.js
+++ b/tests/baselines/reference/es5-importHelpersAsyncFunctions.js
@@ -31,10 +31,11 @@ function foo() {
 exports.foo = foo;
 //// [script.js]
 var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
     return new (P || (P = Promise))(function (resolve, reject) {
         function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
         function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
-        function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
         step((generator = generator.apply(thisArg, _arguments || [])).next());
     });
 };
diff --git a/tests/baselines/reference/excessPropertyCheckWithSpread.js b/tests/baselines/reference/excessPropertyCheckWithSpread.js
index c08e4738965..1b105de7918 100644
--- a/tests/baselines/reference/excessPropertyCheckWithSpread.js
+++ b/tests/baselines/reference/excessPropertyCheckWithSpread.js
@@ -30,4 +30,4 @@ var __assign = (this && this.__assign) || function () {
     return __assign.apply(this, arguments);
 };
 f(__assign({ a: 1 }, i));
-f(__assign({ a: 1 }, l, r));
+f(__assign(__assign({ a: 1 }, l), r));
diff --git a/tests/baselines/reference/exportDefaultAsyncFunction.js b/tests/baselines/reference/exportDefaultAsyncFunction.js
index 9931d1f1eea..31460daae84 100644
--- a/tests/baselines/reference/exportDefaultAsyncFunction.js
+++ b/tests/baselines/reference/exportDefaultAsyncFunction.js
@@ -5,10 +5,11 @@ foo();
 
 //// [exportDefaultAsyncFunction.js]
 var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
     return new (P || (P = Promise))(function (resolve, reject) {
         function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
         function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
-        function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
         step((generator = generator.apply(thisArg, _arguments || [])).next());
     });
 };
diff --git a/tests/baselines/reference/exportDefaultAsyncFunction2.js b/tests/baselines/reference/exportDefaultAsyncFunction2.js
index 8f889381140..ad9b9086a74 100644
--- a/tests/baselines/reference/exportDefaultAsyncFunction2.js
+++ b/tests/baselines/reference/exportDefaultAsyncFunction2.js
@@ -35,10 +35,11 @@ import { async, await } from 'asyncawait';
 export default async(() => await(Promise.resolve(1)));
 //// [b.js]
 var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
     return new (P || (P = Promise))(function (resolve, reject) {
         function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
         function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
-        function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
         step((generator = generator.apply(thisArg, _arguments || [])).next());
     });
 };
diff --git a/tests/baselines/reference/exportDefaultFunctionInNamespace.js b/tests/baselines/reference/exportDefaultFunctionInNamespace.js
index 3a0c260ff01..482611413b7 100644
--- a/tests/baselines/reference/exportDefaultFunctionInNamespace.js
+++ b/tests/baselines/reference/exportDefaultFunctionInNamespace.js
@@ -10,10 +10,11 @@ namespace ns_async_function {
 
 //// [exportDefaultFunctionInNamespace.js]
 var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
     return new (P || (P = Promise))(function (resolve, reject) {
         function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
         function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
-        function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
         step((generator = generator.apply(thisArg, _arguments || [])).next());
     });
 };
diff --git a/tests/baselines/reference/expressionsForbiddenInParameterInitializers.js b/tests/baselines/reference/expressionsForbiddenInParameterInitializers.js
index e12f4b6a232..a23a820e8e5 100644
--- a/tests/baselines/reference/expressionsForbiddenInParameterInitializers.js
+++ b/tests/baselines/reference/expressionsForbiddenInParameterInitializers.js
@@ -9,10 +9,11 @@ export function* foo2({ foo = yield "a" }) {
 //// [bar.js]
 "use strict";
 var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
     return new (P || (P = Promise))(function (resolve, reject) {
         function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
         function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
-        function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
         step((generator = generator.apply(thisArg, _arguments || [])).next());
     });
 };
diff --git a/tests/baselines/reference/genericIsNeverEmptyObject.js b/tests/baselines/reference/genericIsNeverEmptyObject.js
index 692f34bfcc4..ec489da75a9 100644
--- a/tests/baselines/reference/genericIsNeverEmptyObject.js
+++ b/tests/baselines/reference/genericIsNeverEmptyObject.js
@@ -37,7 +37,7 @@ var __rest = (this && this.__rest) || function (s, e) {
 };
 function test(obj) {
     var a = obj.a, rest = __rest(obj, ["a"]);
-    return __assign({}, rest, { b: a });
+    return __assign(__assign({}, rest), { b: a });
 }
 var o1 = { a: 'hello', x: 42 };
 var o2 = test(o1);
diff --git a/tests/baselines/reference/importCallExpressionAsyncES3AMD.js b/tests/baselines/reference/importCallExpressionAsyncES3AMD.js
index 7a8776ebe10..9b4f7f76cc7 100644
--- a/tests/baselines/reference/importCallExpressionAsyncES3AMD.js
+++ b/tests/baselines/reference/importCallExpressionAsyncES3AMD.js
@@ -30,10 +30,11 @@ export const l = async () => {
 
 //// [test.js]
 var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
     return new (P || (P = Promise))(function (resolve, reject) {
         function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
         function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
-        function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
         step((generator = generator.apply(thisArg, _arguments || [])).next());
     });
 };
diff --git a/tests/baselines/reference/importCallExpressionAsyncES3CJS.js b/tests/baselines/reference/importCallExpressionAsyncES3CJS.js
index ba16d3bbd27..43b4c868529 100644
--- a/tests/baselines/reference/importCallExpressionAsyncES3CJS.js
+++ b/tests/baselines/reference/importCallExpressionAsyncES3CJS.js
@@ -31,10 +31,11 @@ export const l = async () => {
 //// [test.js]
 "use strict";
 var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
     return new (P || (P = Promise))(function (resolve, reject) {
         function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
         function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
-        function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
         step((generator = generator.apply(thisArg, _arguments || [])).next());
     });
 };
diff --git a/tests/baselines/reference/importCallExpressionAsyncES3System.js b/tests/baselines/reference/importCallExpressionAsyncES3System.js
index f8b7e54e5cd..6369c73b68b 100644
--- a/tests/baselines/reference/importCallExpressionAsyncES3System.js
+++ b/tests/baselines/reference/importCallExpressionAsyncES3System.js
@@ -32,10 +32,11 @@ export const l = async () => {
 System.register([], function (exports_1, context_1) {
     "use strict";
     var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+        function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
         return new (P || (P = Promise))(function (resolve, reject) {
             function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
             function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
-            function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+            function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
             step((generator = generator.apply(thisArg, _arguments || [])).next());
         });
     };
diff --git a/tests/baselines/reference/importCallExpressionAsyncES3UMD.js b/tests/baselines/reference/importCallExpressionAsyncES3UMD.js
index 0f13a0252a6..794678e871d 100644
--- a/tests/baselines/reference/importCallExpressionAsyncES3UMD.js
+++ b/tests/baselines/reference/importCallExpressionAsyncES3UMD.js
@@ -30,10 +30,11 @@ export const l = async () => {
 
 //// [test.js]
 var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
     return new (P || (P = Promise))(function (resolve, reject) {
         function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
         function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
-        function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
         step((generator = generator.apply(thisArg, _arguments || [])).next());
     });
 };
diff --git a/tests/baselines/reference/importCallExpressionAsyncES5AMD.js b/tests/baselines/reference/importCallExpressionAsyncES5AMD.js
index 17ba4f7e8bf..2451190c793 100644
--- a/tests/baselines/reference/importCallExpressionAsyncES5AMD.js
+++ b/tests/baselines/reference/importCallExpressionAsyncES5AMD.js
@@ -30,10 +30,11 @@ export const l = async () => {
 
 //// [test.js]
 var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
     return new (P || (P = Promise))(function (resolve, reject) {
         function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
         function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
-        function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
         step((generator = generator.apply(thisArg, _arguments || [])).next());
     });
 };
diff --git a/tests/baselines/reference/importCallExpressionAsyncES5CJS.js b/tests/baselines/reference/importCallExpressionAsyncES5CJS.js
index 8e00d5b9739..cd60c69c4cf 100644
--- a/tests/baselines/reference/importCallExpressionAsyncES5CJS.js
+++ b/tests/baselines/reference/importCallExpressionAsyncES5CJS.js
@@ -31,10 +31,11 @@ export const l = async () => {
 //// [test.js]
 "use strict";
 var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
     return new (P || (P = Promise))(function (resolve, reject) {
         function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
         function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
-        function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
         step((generator = generator.apply(thisArg, _arguments || [])).next());
     });
 };
diff --git a/tests/baselines/reference/importCallExpressionAsyncES5System.js b/tests/baselines/reference/importCallExpressionAsyncES5System.js
index f63d41bf9a5..da510e8d098 100644
--- a/tests/baselines/reference/importCallExpressionAsyncES5System.js
+++ b/tests/baselines/reference/importCallExpressionAsyncES5System.js
@@ -32,10 +32,11 @@ export const l = async () => {
 System.register([], function (exports_1, context_1) {
     "use strict";
     var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+        function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
         return new (P || (P = Promise))(function (resolve, reject) {
             function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
             function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
-            function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+            function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
             step((generator = generator.apply(thisArg, _arguments || [])).next());
         });
     };
diff --git a/tests/baselines/reference/importCallExpressionAsyncES5UMD.js b/tests/baselines/reference/importCallExpressionAsyncES5UMD.js
index 1c8ecdc5118..111b747ff32 100644
--- a/tests/baselines/reference/importCallExpressionAsyncES5UMD.js
+++ b/tests/baselines/reference/importCallExpressionAsyncES5UMD.js
@@ -30,10 +30,11 @@ export const l = async () => {
 
 //// [test.js]
 var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
     return new (P || (P = Promise))(function (resolve, reject) {
         function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
         function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
-        function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
         step((generator = generator.apply(thisArg, _arguments || [])).next());
     });
 };
diff --git a/tests/baselines/reference/importCallExpressionAsyncES6AMD.js b/tests/baselines/reference/importCallExpressionAsyncES6AMD.js
index 7f86625bbfc..80cf843ade9 100644
--- a/tests/baselines/reference/importCallExpressionAsyncES6AMD.js
+++ b/tests/baselines/reference/importCallExpressionAsyncES6AMD.js
@@ -30,10 +30,11 @@ export const l = async () => {
 
 //// [test.js]
 var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
     return new (P || (P = Promise))(function (resolve, reject) {
         function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
         function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
-        function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
         step((generator = generator.apply(thisArg, _arguments || [])).next());
     });
 };
diff --git a/tests/baselines/reference/importCallExpressionAsyncES6CJS.js b/tests/baselines/reference/importCallExpressionAsyncES6CJS.js
index 20961f96330..7ce2b69b44c 100644
--- a/tests/baselines/reference/importCallExpressionAsyncES6CJS.js
+++ b/tests/baselines/reference/importCallExpressionAsyncES6CJS.js
@@ -31,10 +31,11 @@ export const l = async () => {
 //// [test.js]
 "use strict";
 var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
     return new (P || (P = Promise))(function (resolve, reject) {
         function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
         function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
-        function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
         step((generator = generator.apply(thisArg, _arguments || [])).next());
     });
 };
diff --git a/tests/baselines/reference/importCallExpressionAsyncES6System.js b/tests/baselines/reference/importCallExpressionAsyncES6System.js
index 1f605dcc3f8..8dd7e2f32e8 100644
--- a/tests/baselines/reference/importCallExpressionAsyncES6System.js
+++ b/tests/baselines/reference/importCallExpressionAsyncES6System.js
@@ -32,10 +32,11 @@ export const l = async () => {
 System.register([], function (exports_1, context_1) {
     "use strict";
     var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+        function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
         return new (P || (P = Promise))(function (resolve, reject) {
             function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
             function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
-            function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+            function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
             step((generator = generator.apply(thisArg, _arguments || [])).next());
         });
     };
diff --git a/tests/baselines/reference/importCallExpressionAsyncES6UMD.js b/tests/baselines/reference/importCallExpressionAsyncES6UMD.js
index 1d4aff02670..f7dfe0d9934 100644
--- a/tests/baselines/reference/importCallExpressionAsyncES6UMD.js
+++ b/tests/baselines/reference/importCallExpressionAsyncES6UMD.js
@@ -30,10 +30,11 @@ export const l = async () => {
 
 //// [test.js]
 var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
     return new (P || (P = Promise))(function (resolve, reject) {
         function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
         function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
-        function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
         step((generator = generator.apply(thisArg, _arguments || [])).next());
     });
 };
diff --git a/tests/baselines/reference/importCallExpressionNestedAMD.js b/tests/baselines/reference/importCallExpressionNestedAMD.js
index dc211d44003..678c02a8e73 100644
--- a/tests/baselines/reference/importCallExpressionNestedAMD.js
+++ b/tests/baselines/reference/importCallExpressionNestedAMD.js
@@ -16,10 +16,11 @@ define(["require", "exports"], function (require, exports) {
 });
 //// [index.js]
 var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
     return new (P || (P = Promise))(function (resolve, reject) {
         function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
         function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
-        function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
         step((generator = generator.apply(thisArg, _arguments || [])).next());
     });
 };
diff --git a/tests/baselines/reference/importCallExpressionNestedAMD2.js b/tests/baselines/reference/importCallExpressionNestedAMD2.js
index f6ebbe32c7b..ffc42963975 100644
--- a/tests/baselines/reference/importCallExpressionNestedAMD2.js
+++ b/tests/baselines/reference/importCallExpressionNestedAMD2.js
@@ -16,10 +16,11 @@ define(["require", "exports"], function (require, exports) {
 });
 //// [index.js]
 var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
     return new (P || (P = Promise))(function (resolve, reject) {
         function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
         function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
-        function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
         step((generator = generator.apply(thisArg, _arguments || [])).next());
     });
 };
diff --git a/tests/baselines/reference/importCallExpressionNestedCJS.js b/tests/baselines/reference/importCallExpressionNestedCJS.js
index 07c0f234bf7..5b6abef5e0e 100644
--- a/tests/baselines/reference/importCallExpressionNestedCJS.js
+++ b/tests/baselines/reference/importCallExpressionNestedCJS.js
@@ -14,10 +14,11 @@ Object.defineProperty(exports, "__esModule", { value: true });
 exports.default = "./foo";
 //// [index.js]
 var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
     return new (P || (P = Promise))(function (resolve, reject) {
         function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
         function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
-        function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
         step((generator = generator.apply(thisArg, _arguments || [])).next());
     });
 };
diff --git a/tests/baselines/reference/importCallExpressionNestedCJS2.js b/tests/baselines/reference/importCallExpressionNestedCJS2.js
index 97728dfb41f..104a01b5bd9 100644
--- a/tests/baselines/reference/importCallExpressionNestedCJS2.js
+++ b/tests/baselines/reference/importCallExpressionNestedCJS2.js
@@ -14,10 +14,11 @@ Object.defineProperty(exports, "__esModule", { value: true });
 exports.default = "./foo";
 //// [index.js]
 var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
     return new (P || (P = Promise))(function (resolve, reject) {
         function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
         function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
-        function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
         step((generator = generator.apply(thisArg, _arguments || [])).next());
     });
 };
diff --git a/tests/baselines/reference/importCallExpressionNestedES2015.js b/tests/baselines/reference/importCallExpressionNestedES2015.js
index 5c8a6a9edb5..8bbb7c7b1f3 100644
--- a/tests/baselines/reference/importCallExpressionNestedES2015.js
+++ b/tests/baselines/reference/importCallExpressionNestedES2015.js
@@ -12,10 +12,11 @@ async function foo() {
 export default "./foo";
 //// [index.js]
 var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
     return new (P || (P = Promise))(function (resolve, reject) {
         function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
         function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
-        function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
         step((generator = generator.apply(thisArg, _arguments || [])).next());
     });
 };
diff --git a/tests/baselines/reference/importCallExpressionNestedES20152.js b/tests/baselines/reference/importCallExpressionNestedES20152.js
index 0baee242a60..c0b888df2fb 100644
--- a/tests/baselines/reference/importCallExpressionNestedES20152.js
+++ b/tests/baselines/reference/importCallExpressionNestedES20152.js
@@ -12,10 +12,11 @@ async function foo() {
 export default "./foo";
 //// [index.js]
 var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
     return new (P || (P = Promise))(function (resolve, reject) {
         function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
         function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
-        function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
         step((generator = generator.apply(thisArg, _arguments || [])).next());
     });
 };
diff --git a/tests/baselines/reference/importCallExpressionNestedESNext.js b/tests/baselines/reference/importCallExpressionNestedESNext.js
index 8ec9b988201..77ade8e8928 100644
--- a/tests/baselines/reference/importCallExpressionNestedESNext.js
+++ b/tests/baselines/reference/importCallExpressionNestedESNext.js
@@ -12,10 +12,11 @@ async function foo() {
 export default "./foo";
 //// [index.js]
 var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
     return new (P || (P = Promise))(function (resolve, reject) {
         function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
         function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
-        function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
         step((generator = generator.apply(thisArg, _arguments || [])).next());
     });
 };
diff --git a/tests/baselines/reference/importCallExpressionNestedESNext2.js b/tests/baselines/reference/importCallExpressionNestedESNext2.js
index 07bfaf89d40..cfe3fca6aeb 100644
--- a/tests/baselines/reference/importCallExpressionNestedESNext2.js
+++ b/tests/baselines/reference/importCallExpressionNestedESNext2.js
@@ -12,10 +12,11 @@ async function foo() {
 export default "./foo";
 //// [index.js]
 var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
     return new (P || (P = Promise))(function (resolve, reject) {
         function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
         function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
-        function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
         step((generator = generator.apply(thisArg, _arguments || [])).next());
     });
 };
diff --git a/tests/baselines/reference/importCallExpressionNestedSystem.js b/tests/baselines/reference/importCallExpressionNestedSystem.js
index 839a3601e38..15a825c8a76 100644
--- a/tests/baselines/reference/importCallExpressionNestedSystem.js
+++ b/tests/baselines/reference/importCallExpressionNestedSystem.js
@@ -22,10 +22,11 @@ System.register([], function (exports_1, context_1) {
 //// [index.js]
 System.register([], function (exports_1, context_1) {
     var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+        function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
         return new (P || (P = Promise))(function (resolve, reject) {
             function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
             function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
-            function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+            function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
             step((generator = generator.apply(thisArg, _arguments || [])).next());
         });
     };
diff --git a/tests/baselines/reference/importCallExpressionNestedSystem2.js b/tests/baselines/reference/importCallExpressionNestedSystem2.js
index 1685ca93943..60861b7aca7 100644
--- a/tests/baselines/reference/importCallExpressionNestedSystem2.js
+++ b/tests/baselines/reference/importCallExpressionNestedSystem2.js
@@ -22,10 +22,11 @@ System.register([], function (exports_1, context_1) {
 //// [index.js]
 System.register([], function (exports_1, context_1) {
     var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+        function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
         return new (P || (P = Promise))(function (resolve, reject) {
             function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
             function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
-            function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+            function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
             step((generator = generator.apply(thisArg, _arguments || [])).next());
         });
     };
diff --git a/tests/baselines/reference/importCallExpressionNestedUMD.js b/tests/baselines/reference/importCallExpressionNestedUMD.js
index c61e35c3399..29f0e0974ed 100644
--- a/tests/baselines/reference/importCallExpressionNestedUMD.js
+++ b/tests/baselines/reference/importCallExpressionNestedUMD.js
@@ -24,10 +24,11 @@ async function foo() {
 });
 //// [index.js]
 var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
     return new (P || (P = Promise))(function (resolve, reject) {
         function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
         function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
-        function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
         step((generator = generator.apply(thisArg, _arguments || [])).next());
     });
 };
diff --git a/tests/baselines/reference/importCallExpressionNestedUMD2.js b/tests/baselines/reference/importCallExpressionNestedUMD2.js
index 5d1646d090a..33d3d608e14 100644
--- a/tests/baselines/reference/importCallExpressionNestedUMD2.js
+++ b/tests/baselines/reference/importCallExpressionNestedUMD2.js
@@ -24,10 +24,11 @@ async function foo() {
 });
 //// [index.js]
 var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
     return new (P || (P = Promise))(function (resolve, reject) {
         function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
         function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
-        function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
         step((generator = generator.apply(thisArg, _arguments || [])).next());
     });
 };
diff --git a/tests/baselines/reference/importCallExpressionNoModuleKindSpecified.js b/tests/baselines/reference/importCallExpressionNoModuleKindSpecified.js
index 4f662c4be4f..9c54007d33f 100644
--- a/tests/baselines/reference/importCallExpressionNoModuleKindSpecified.js
+++ b/tests/baselines/reference/importCallExpressionNoModuleKindSpecified.js
@@ -45,10 +45,11 @@ function backup() { return "backup"; }
 exports.backup = backup;
 //// [2.js]
 var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
     return new (P || (P = Promise))(function (resolve, reject) {
         function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
         function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
-        function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
         step((generator = generator.apply(thisArg, _arguments || [])).next());
     });
 };
diff --git a/tests/baselines/reference/importMetaES5.js b/tests/baselines/reference/importMetaES5.js
index e618f695869..6b69557e419 100644
--- a/tests/baselines/reference/importMetaES5.js
+++ b/tests/baselines/reference/importMetaES5.js
@@ -41,10 +41,11 @@ const { a, b, c } = import.meta.wellKnownProperty;
 //// [example.js]
 "use strict";
 var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
     return new (P || (P = Promise))(function (resolve, reject) {
         function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
         function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
-        function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
         step((generator = generator.apply(thisArg, _arguments || [])).next());
     });
 };
diff --git a/tests/baselines/reference/inferenceLimit.js b/tests/baselines/reference/inferenceLimit.js
index 997cbcd5b79..e27d155d616 100644
--- a/tests/baselines/reference/inferenceLimit.js
+++ b/tests/baselines/reference/inferenceLimit.js
@@ -46,10 +46,11 @@ Object.defineProperty(exports, "__esModule", { value: true });
 //// [file1.js]
 "use strict";
 var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
     return new (P || (P = Promise))(function (resolve, reject) {
         function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
         function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
-        function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
         step((generator = generator.apply(thisArg, _arguments || [])).next());
     });
 };
diff --git a/tests/baselines/reference/invalidContinueInDownlevelAsync.js b/tests/baselines/reference/invalidContinueInDownlevelAsync.js
index 793a9451f87..9a2fc08f4a8 100644
--- a/tests/baselines/reference/invalidContinueInDownlevelAsync.js
+++ b/tests/baselines/reference/invalidContinueInDownlevelAsync.js
@@ -10,10 +10,11 @@ async function func() {
 
 //// [invalidContinueInDownlevelAsync.js]
 var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
     return new (P || (P = Promise))(function (resolve, reject) {
         function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
         function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
-        function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
         step((generator = generator.apply(thisArg, _arguments || [])).next());
     });
 };
diff --git a/tests/baselines/reference/labeledStatementWithLabel.js b/tests/baselines/reference/labeledStatementWithLabel.js
index ada819c9908..92c0472c222 100644
--- a/tests/baselines/reference/labeledStatementWithLabel.js
+++ b/tests/baselines/reference/labeledStatementWithLabel.js
@@ -16,10 +16,11 @@ label: type T = {}
 
 //// [labeledStatementWithLabel.js]
 var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
     return new (P || (P = Promise))(function (resolve, reject) {
         function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
         function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
-        function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
         step((generator = generator.apply(thisArg, _arguments || [])).next());
     });
 };
diff --git a/tests/baselines/reference/labeledStatementWithLabel_es2015.js b/tests/baselines/reference/labeledStatementWithLabel_es2015.js
index 34ceb7bc17a..93d76684c6d 100644
--- a/tests/baselines/reference/labeledStatementWithLabel_es2015.js
+++ b/tests/baselines/reference/labeledStatementWithLabel_es2015.js
@@ -16,10 +16,11 @@ label: type T = {}
 
 //// [labeledStatementWithLabel_es2015.js]
 var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
     return new (P || (P = Promise))(function (resolve, reject) {
         function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
         function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
-        function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
         step((generator = generator.apply(thisArg, _arguments || [])).next());
     });
 };
diff --git a/tests/baselines/reference/labeledStatementWithLabel_strict.js b/tests/baselines/reference/labeledStatementWithLabel_strict.js
index bcf211fdbfd..124c6c0bde2 100644
--- a/tests/baselines/reference/labeledStatementWithLabel_strict.js
+++ b/tests/baselines/reference/labeledStatementWithLabel_strict.js
@@ -18,10 +18,11 @@ label: type T = {}
 //// [labeledStatementWithLabel_strict.js]
 "use strict";
 var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
     return new (P || (P = Promise))(function (resolve, reject) {
         function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
         function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
-        function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
         step((generator = generator.apply(thisArg, _arguments || [])).next());
     });
 };
diff --git a/tests/baselines/reference/modularizeLibrary_NoErrorDuplicateLibOptions1.js b/tests/baselines/reference/modularizeLibrary_NoErrorDuplicateLibOptions1.js
index 8fdb55a0f26..5c16fa2a389 100644
--- a/tests/baselines/reference/modularizeLibrary_NoErrorDuplicateLibOptions1.js
+++ b/tests/baselines/reference/modularizeLibrary_NoErrorDuplicateLibOptions1.js
@@ -82,10 +82,11 @@ const o1 = {
 
 //// [modularizeLibrary_NoErrorDuplicateLibOptions1.js]
 var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
     return new (P || (P = Promise))(function (resolve, reject) {
         function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
         function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
-        function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
         step((generator = generator.apply(thisArg, _arguments || [])).next());
     });
 };
diff --git a/tests/baselines/reference/modularizeLibrary_NoErrorDuplicateLibOptions2.js b/tests/baselines/reference/modularizeLibrary_NoErrorDuplicateLibOptions2.js
index 21a8fa48b1f..9d340096491 100644
--- a/tests/baselines/reference/modularizeLibrary_NoErrorDuplicateLibOptions2.js
+++ b/tests/baselines/reference/modularizeLibrary_NoErrorDuplicateLibOptions2.js
@@ -82,10 +82,11 @@ const o1 = {
 
 //// [modularizeLibrary_NoErrorDuplicateLibOptions2.js]
 var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
     return new (P || (P = Promise))(function (resolve, reject) {
         function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
         function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
-        function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
         step((generator = generator.apply(thisArg, _arguments || [])).next());
     });
 };
diff --git a/tests/baselines/reference/modularizeLibrary_TargetES5UsingES6Lib.js b/tests/baselines/reference/modularizeLibrary_TargetES5UsingES6Lib.js
index 093f3bde868..57fca626c06 100644
--- a/tests/baselines/reference/modularizeLibrary_TargetES5UsingES6Lib.js
+++ b/tests/baselines/reference/modularizeLibrary_TargetES5UsingES6Lib.js
@@ -82,10 +82,11 @@ const o1 = {
 
 //// [modularizeLibrary_TargetES5UsingES6Lib.js]
 var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
     return new (P || (P = Promise))(function (resolve, reject) {
         function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
         function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
-        function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
         step((generator = generator.apply(thisArg, _arguments || [])).next());
     });
 };
diff --git a/tests/baselines/reference/noImplicitReturnsInAsync1.js b/tests/baselines/reference/noImplicitReturnsInAsync1.js
index e165cafe3b1..d803694056f 100644
--- a/tests/baselines/reference/noImplicitReturnsInAsync1.js
+++ b/tests/baselines/reference/noImplicitReturnsInAsync1.js
@@ -8,10 +8,11 @@ async function test(isError: boolean = false) {
 
 //// [noImplicitReturnsInAsync1.js]
 var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
     return new (P || (P = Promise))(function (resolve, reject) {
         function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
         function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
-        function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
         step((generator = generator.apply(thisArg, _arguments || [])).next());
     });
 };
diff --git a/tests/baselines/reference/noImplicitReturnsInAsync2.js b/tests/baselines/reference/noImplicitReturnsInAsync2.js
index e84b42e8a55..64f267459c3 100644
--- a/tests/baselines/reference/noImplicitReturnsInAsync2.js
+++ b/tests/baselines/reference/noImplicitReturnsInAsync2.js
@@ -37,10 +37,11 @@ async function test7(isError: boolean = true) {
 
 //// [noImplicitReturnsInAsync2.js]
 var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
     return new (P || (P = Promise))(function (resolve, reject) {
         function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
         function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
-        function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
         step((generator = generator.apply(thisArg, _arguments || [])).next());
     });
 };
diff --git a/tests/baselines/reference/objectLiteralFreshnessWithSpread.js b/tests/baselines/reference/objectLiteralFreshnessWithSpread.js
index 73962db32ab..ad87fd0557d 100644
--- a/tests/baselines/reference/objectLiteralFreshnessWithSpread.js
+++ b/tests/baselines/reference/objectLiteralFreshnessWithSpread.js
@@ -16,4 +16,4 @@ var __assign = (this && this.__assign) || function () {
     return __assign.apply(this, arguments);
 };
 var x = { b: 1, extra: 2 };
-var xx = __assign({ a: 1 }, x, { z: 3 }); // error for 'z', no error for 'extra'
+var xx = __assign(__assign({ a: 1 }, x), { z: 3 }); // error for 'z', no error for 'extra'
diff --git a/tests/baselines/reference/objectLiteralNormalization.js b/tests/baselines/reference/objectLiteralNormalization.js
index 1a8aa8d4b04..aa37bdc2c5e 100644
--- a/tests/baselines/reference/objectLiteralNormalization.js
+++ b/tests/baselines/reference/objectLiteralNormalization.js
@@ -80,7 +80,7 @@ a2 = { a: "def" };
 a2 = {};
 a2 = { a: "def", b: 20 }; // Error
 a2 = { a: 1 }; // Error
-var b2 = __assign({}, b1, { z: 55 });
+var b2 = __assign(__assign({}, b1), { z: 55 });
 var b3 = __assign({}, b2);
 var c1 = !true ? {} : opts;
 var c2 = !true ? opts : {};
diff --git a/tests/baselines/reference/objectRest2.js b/tests/baselines/reference/objectRest2.js
index e46d22db80a..e97e1a0498e 100644
--- a/tests/baselines/reference/objectRest2.js
+++ b/tests/baselines/reference/objectRest2.js
@@ -16,10 +16,11 @@ rootConnection('test');
 
 //// [objectRest2.js]
 var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
     return new (P || (P = Promise))(function (resolve, reject) {
         function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
         function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
-        function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
         step((generator = generator.apply(thisArg, _arguments || [])).next());
     });
 };
diff --git a/tests/baselines/reference/objectRestForOf.js b/tests/baselines/reference/objectRestForOf.js
index f946e42444c..49ebf7c4c17 100644
--- a/tests/baselines/reference/objectRestForOf.js
+++ b/tests/baselines/reference/objectRestForOf.js
@@ -37,7 +37,7 @@ for (let _b of array) {
     ({ x: xx } = _b, rrestOff = __rest(_b, ["x"]));
     [xx, rrestOff];
 }
-for (const norest of array.map(a => (Object.assign({}, a, { x: 'a string' })))) {
+for (const norest of array.map(a => (Object.assign(Object.assign({}, a), { x: 'a string' })))) {
     [norest.x, norest.y];
     // x is now a string. who knows why.
 }
diff --git a/tests/baselines/reference/objectSpread.js b/tests/baselines/reference/objectSpread.js
index b7d3e858c79..1265cc889ff 100644
--- a/tests/baselines/reference/objectSpread.js
+++ b/tests/baselines/reference/objectSpread.js
@@ -171,45 +171,45 @@ var __assign = (this && this.__assign) || function () {
 var o = { a: 1, b: 'no' };
 var o2 = { b: 'yes', c: true };
 var swap = { a: 'yes', b: -1 };
-var addAfter = __assign({}, o, { c: false });
+var addAfter = __assign(__assign({}, o), { c: false });
 var addBefore = __assign({ c: false }, o);
 // Note: ignore still changes the order that properties are printed
 var ignore = __assign({ b: 'ignored' }, o);
-var override = __assign({}, o, { b: 'override' });
-var nested = __assign({}, __assign({ a: 3 }, { b: false, c: 'overriden' }), { c: 'whatever' });
-var combined = __assign({}, o, o2);
-var combinedBefore = __assign({ b: 'ok' }, o, o2);
-var combinedMid = __assign({}, o, { b: 'ok' }, o2);
-var combinedAfter = __assign({}, o, o2, { b: 'ok' });
-var combinedNested = __assign({}, __assign({ a: 4 }, { b: false, c: 'overriden' }), { d: 'actually new' }, { a: 5, d: 'maybe new' });
-var combinedNestedChangeType = __assign({}, __assign({ a: 1 }, { b: false, c: 'overriden' }), { c: -1 });
+var override = __assign(__assign({}, o), { b: 'override' });
+var nested = __assign(__assign({}, __assign({ a: 3 }, { b: false, c: 'overriden' })), { c: 'whatever' });
+var combined = __assign(__assign({}, o), o2);
+var combinedBefore = __assign(__assign({ b: 'ok' }, o), o2);
+var combinedMid = __assign(__assign(__assign({}, o), { b: 'ok' }), o2);
+var combinedAfter = __assign(__assign(__assign({}, o), o2), { b: 'ok' });
+var combinedNested = __assign(__assign(__assign({}, __assign({ a: 4 }, { b: false, c: 'overriden' })), { d: 'actually new' }), { a: 5, d: 'maybe new' });
+var combinedNestedChangeType = __assign(__assign({}, __assign({ a: 1 }, { b: false, c: 'overriden' })), { c: -1 });
 var propertyNested = { a: __assign({}, o) };
 // accessors don't copy the descriptor
 // (which means that readonly getters become read/write properties)
 var op = { get a() { return 6; } };
-var getter = __assign({}, op, { c: 7 });
+var getter = __assign(__assign({}, op), { c: 7 });
 getter.a = 12;
 // functions result in { }
 var spreadFunc = __assign({}, (function () { }));
 function from16326(header, authToken) {
-    return __assign({}, this.header, header, authToken && { authToken: authToken });
+    return __assign(__assign(__assign({}, this.header), header), authToken && { authToken: authToken });
 }
 // boolean && T results in Partial<T>
 function conditionalSpreadBoolean(b) {
     var o = { x: 12, y: 13 };
-    o = __assign({}, o, b && { x: 14 });
+    o = __assign(__assign({}, o), b && { x: 14 });
     var o2 = __assign({}, b && { x: 21 });
     return o;
 }
 function conditionalSpreadNumber(nt) {
     var o = { x: 15, y: 16 };
-    o = __assign({}, o, nt && { x: nt });
+    o = __assign(__assign({}, o), nt && { x: nt });
     var o2 = __assign({}, nt && { x: nt });
     return o;
 }
 function conditionalSpreadString(st) {
     var o = { x: 'hi', y: 17 };
-    o = __assign({}, o, st && { x: st });
+    o = __assign(__assign({}, o), st && { x: st });
     var o2 = __assign({}, st && { x: st });
     return o;
 }
@@ -227,31 +227,31 @@ var C = /** @class */ (function () {
 var c = new C();
 var spreadC = __assign({}, c);
 // own methods are enumerable
-var cplus = __assign({}, c, { plus: function () { return this.p + 1; } });
+var cplus = __assign(__assign({}, c), { plus: function () { return this.p + 1; } });
 cplus.plus();
 // new field's type conflicting with existing field is OK
-var changeTypeAfter = __assign({}, o, { a: 'wrong type?' });
+var changeTypeAfter = __assign(__assign({}, o), { a: 'wrong type?' });
 var changeTypeBefore = __assign({ a: 'wrong type?' }, o);
-var changeTypeBoth = __assign({}, o, swap);
+var changeTypeBoth = __assign(__assign({}, o), swap);
 // optional
 function container(definiteBoolean, definiteString, optionalString, optionalNumber) {
     var _a, _b, _c;
-    var optionalUnionStops = __assign({}, definiteBoolean, definiteString, optionalNumber);
-    var optionalUnionDuplicates = __assign({}, definiteBoolean, definiteString, optionalString, optionalNumber);
-    var allOptional = __assign({}, optionalString, optionalNumber);
+    var optionalUnionStops = __assign(__assign(__assign({}, definiteBoolean), definiteString), optionalNumber);
+    var optionalUnionDuplicates = __assign(__assign(__assign(__assign({}, definiteBoolean), definiteString), optionalString), optionalNumber);
+    var allOptional = __assign(__assign({}, optionalString), optionalNumber);
     // computed property
-    var computedFirst = __assign((_a = {}, _a['before everything'] = 12, _a), o, { b: 'yes' });
-    var computedMiddle = __assign({}, o, (_b = {}, _b['in the middle'] = 13, _b.b = 'maybe?', _b), o2);
-    var computedAfter = __assign({}, o, (_c = { b: 'yeah' }, _c['at the end'] = 14, _c));
+    var computedFirst = __assign(__assign((_a = {}, _a['before everything'] = 12, _a), o), { b: 'yes' });
+    var computedMiddle = __assign(__assign(__assign({}, o), (_b = {}, _b['in the middle'] = 13, _b.b = 'maybe?', _b)), o2);
+    var computedAfter = __assign(__assign({}, o), (_c = { b: 'yeah' }, _c['at the end'] = 14, _c));
 }
 // shortcut syntax
 var a = 12;
-var shortCutted = __assign({}, o, { a: a });
+var shortCutted = __assign(__assign({}, o), { a: a });
 // non primitive
 var spreadNonPrimitive = __assign({}, {});
 // generic spreads
 function f(t, u) {
-    return __assign({}, t, u, { id: 'id' });
+    return __assign(__assign(__assign({}, t), u), { id: 'id' });
 }
 var exclusive = f({ a: 1, b: 'yes' }, { c: 'no', d: false });
 var overlap = f({ a: 1 }, { a: 2, b: 'extra' });
@@ -259,20 +259,20 @@ var overlapConflict = f({ a: 1 }, { a: 'mismatch' });
 var overwriteId = f({ a: 1, id: true }, { c: 1, d: 'no' });
 function genericSpread(t, u, v, w, obj) {
     var x01 = __assign({}, t);
-    var x02 = __assign({}, t, t);
-    var x03 = __assign({}, t, u);
-    var x04 = __assign({}, u, t);
+    var x02 = __assign(__assign({}, t), t);
+    var x03 = __assign(__assign({}, t), u);
+    var x04 = __assign(__assign({}, u), t);
     var x05 = __assign({ a: 5, b: 'hi' }, t);
-    var x06 = __assign({}, t, { a: 5, b: 'hi' });
-    var x07 = __assign({ a: 5, b: 'hi' }, t, { c: true }, obj);
-    var x09 = __assign({ a: 5 }, t, { b: 'hi', c: true }, obj);
-    var x10 = __assign({ a: 5 }, t, { b: 'hi' }, u, obj);
+    var x06 = __assign(__assign({}, t), { a: 5, b: 'hi' });
+    var x07 = __assign(__assign(__assign({ a: 5, b: 'hi' }, t), { c: true }), obj);
+    var x09 = __assign(__assign(__assign({ a: 5 }, t), { b: 'hi', c: true }), obj);
+    var x10 = __assign(__assign(__assign(__assign({ a: 5 }, t), { b: 'hi' }), u), obj);
     var x11 = __assign({}, v);
-    var x12 = __assign({}, v, obj);
+    var x12 = __assign(__assign({}, v), obj);
     var x13 = __assign({}, w);
-    var x14 = __assign({}, w, obj);
-    var x15 = __assign({}, t, v);
-    var x16 = __assign({}, t, w);
-    var x17 = __assign({}, t, w, obj);
-    var x18 = __assign({}, t, v, w);
+    var x14 = __assign(__assign({}, w), obj);
+    var x15 = __assign(__assign({}, t), v);
+    var x16 = __assign(__assign({}, t), w);
+    var x17 = __assign(__assign(__assign({}, t), w), obj);
+    var x18 = __assign(__assign(__assign({}, t), v), w);
 }
diff --git a/tests/baselines/reference/objectSpreadComputedProperty.js b/tests/baselines/reference/objectSpreadComputedProperty.js
index b81b889b2cc..a28ceab111f 100644
--- a/tests/baselines/reference/objectSpreadComputedProperty.js
+++ b/tests/baselines/reference/objectSpreadComputedProperty.js
@@ -30,5 +30,5 @@ function f() {
     var a = null;
     var o1 = __assign({}, (_a = {}, _a[n] = n, _a));
     var o2 = __assign({}, (_b = {}, _b[a] = n, _b));
-    var o3 = __assign((_c = {}, _c[a] = n, _c), {}, (_d = {}, _d[n] = n, _d), {}, (_e = {}, _e[m] = m, _e));
+    var o3 = __assign(__assign(__assign(__assign((_c = {}, _c[a] = n, _c), {}), (_d = {}, _d[n] = n, _d)), {}), (_e = {}, _e[m] = m, _e));
 }
diff --git a/tests/baselines/reference/objectSpreadIndexSignature.js b/tests/baselines/reference/objectSpreadIndexSignature.js
index aef78611f38..8c461e39971 100644
--- a/tests/baselines/reference/objectSpreadIndexSignature.js
+++ b/tests/baselines/reference/objectSpreadIndexSignature.js
@@ -30,10 +30,10 @@ var __assign = (this && this.__assign) || function () {
     };
     return __assign.apply(this, arguments);
 };
-var i = __assign({}, indexed1, { b: 11 });
+var i = __assign(__assign({}, indexed1), { b: 11 });
 // only indexed has indexer, so i[101]: any
 i[101];
-var ii = __assign({}, indexed1, indexed2);
+var ii = __assign(__assign({}, indexed1), indexed2);
 // both have indexer, so i[1001]: number | boolean
 ii[1001];
 indexed3 = __assign({}, b ? indexed3 : undefined);
diff --git a/tests/baselines/reference/objectSpreadNegative.js b/tests/baselines/reference/objectSpreadNegative.js
index 23de5699ce6..6151f2d30b7 100644
--- a/tests/baselines/reference/objectSpreadNegative.js
+++ b/tests/baselines/reference/objectSpreadNegative.js
@@ -85,11 +85,11 @@ var PublicX = /** @class */ (function () {
 }());
 var publicX;
 var privateOptionalX;
-var o2 = __assign({}, publicX, privateOptionalX);
+var o2 = __assign(__assign({}, publicX), privateOptionalX);
 var sn = o2.x; // error, x is private
 var optionalString;
 var optionalNumber;
-var allOptional = __assign({}, optionalString, optionalNumber);
+var allOptional = __assign(__assign({}, optionalString), optionalNumber);
 ;
 ;
 var spread = __assign({ b: true }, { s: "foo" });
@@ -97,8 +97,8 @@ spread = { s: "foo" }; // error, missing 'b'
 var b = { b: false };
 spread = b; // error, missing 's'
 // literal repeats are not allowed, but spread repeats are fine
-var duplicated = __assign({ b: 'bad' }, o, { b: 'bad' }, o2, { b: 'bad' });
-var duplicatedSpread = __assign({}, o, o);
+var duplicated = __assign(__assign(__assign(__assign({ b: 'bad' }, o), { b: 'bad' }), o2), { b: 'bad' });
+var duplicatedSpread = __assign(__assign({}, o), o);
 // primitives are not allowed, except for falsy ones
 var spreadNum = __assign({}, 12);
 var spreadSum = __assign({}, 1 + 1);
diff --git a/tests/baselines/reference/objectSpreadNegativeParse.js b/tests/baselines/reference/objectSpreadNegativeParse.js
index 1eb384383fb..11809b96b92 100644
--- a/tests/baselines/reference/objectSpreadNegativeParse.js
+++ b/tests/baselines/reference/objectSpreadNegativeParse.js
@@ -21,4 +21,4 @@ var o7 = __assign({}, o ?  : );
 var o8 = __assign({},  * o);
 var o9 = __assign({}, matchMedia()), _a = void 0;
 ;
-var o10 = __assign({}, get, { x: function () { return 12; } });
+var o10 = __assign(__assign({}, get), { x: function () { return 12; } });
diff --git a/tests/baselines/reference/objectSpreadStrictNull.js b/tests/baselines/reference/objectSpreadStrictNull.js
index 737c1d3e038..f95c2582b26 100644
--- a/tests/baselines/reference/objectSpreadStrictNull.js
+++ b/tests/baselines/reference/objectSpreadStrictNull.js
@@ -58,21 +58,21 @@ var __assign = (this && this.__assign) || function () {
 };
 function f(definiteBoolean, definiteString, optionalString, optionalNumber, undefinedString, undefinedNumber) {
     // optional
-    var optionalUnionStops = __assign({}, definiteBoolean, definiteString, optionalNumber);
-    var optionalUnionDuplicates = __assign({}, definiteBoolean, definiteString, optionalString, optionalNumber);
-    var allOptional = __assign({}, optionalString, optionalNumber);
+    var optionalUnionStops = __assign(__assign(__assign({}, definiteBoolean), definiteString), optionalNumber);
+    var optionalUnionDuplicates = __assign(__assign(__assign(__assign({}, definiteBoolean), definiteString), optionalString), optionalNumber);
+    var allOptional = __assign(__assign({}, optionalString), optionalNumber);
     // undefined
-    var undefinedUnionStops = __assign({}, definiteBoolean, definiteString, undefinedNumber);
-    var undefinedUnionDuplicates = __assign({}, definiteBoolean, definiteString, undefinedString, undefinedNumber);
-    var allUndefined = __assign({}, undefinedString, undefinedNumber);
-    var undefinedWithOptionalContinues = __assign({}, definiteBoolean, undefinedString, optionalNumber);
+    var undefinedUnionStops = __assign(__assign(__assign({}, definiteBoolean), definiteString), undefinedNumber);
+    var undefinedUnionDuplicates = __assign(__assign(__assign(__assign({}, definiteBoolean), definiteString), undefinedString), undefinedNumber);
+    var allUndefined = __assign(__assign({}, undefinedString), undefinedNumber);
+    var undefinedWithOptionalContinues = __assign(__assign(__assign({}, definiteBoolean), undefinedString), optionalNumber);
 }
 var m = { title: "The Matrix", yearReleased: 1999 };
 // should error here because title: undefined is not assignable to string
-var x = __assign({}, m, { title: undefined });
+var x = __assign(__assign({}, m), { title: undefined });
 function g(fields, partialFields, nearlyPartialFields) {
     // ok, undefined is stripped from optional properties when spread
-    fields = __assign({}, fields, partialFields);
+    fields = __assign(__assign({}, fields), partialFields);
     // error: not optional, undefined remains
-    fields = __assign({}, fields, nearlyPartialFields);
+    fields = __assign(__assign({}, fields), nearlyPartialFields);
 }
diff --git a/tests/baselines/reference/objectSpreadWithinMethodWithinObjectWithSpread.js b/tests/baselines/reference/objectSpreadWithinMethodWithinObjectWithSpread.js
index 89744f9f8e5..900dd89a820 100644
--- a/tests/baselines/reference/objectSpreadWithinMethodWithinObjectWithSpread.js
+++ b/tests/baselines/reference/objectSpreadWithinMethodWithinObjectWithSpread.js
@@ -24,6 +24,6 @@ var __assign = (this && this.__assign) || function () {
     return __assign.apply(this, arguments);
 };
 var obj = {};
-var a = __assign({}, obj, { prop: function () {
-        return __assign({}, obj, { metadata: 213 });
+var a = __assign(__assign({}, obj), { prop: function () {
+        return __assign(__assign({}, obj), { metadata: 213 });
     } });
diff --git a/tests/baselines/reference/operationsAvailableOnPromisedType.js b/tests/baselines/reference/operationsAvailableOnPromisedType.js
index c9f8851fcc8..5772f603037 100644
--- a/tests/baselines/reference/operationsAvailableOnPromisedType.js
+++ b/tests/baselines/reference/operationsAvailableOnPromisedType.js
@@ -31,10 +31,11 @@ async function fn(
 
 //// [operationsAvailableOnPromisedType.js]
 var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
     return new (P || (P = Promise))(function (resolve, reject) {
         function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
         function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
-        function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
         step((generator = generator.apply(thisArg, _arguments || [])).next());
     });
 };
diff --git a/tests/baselines/reference/parenthesizedAsyncArrowFunction.js b/tests/baselines/reference/parenthesizedAsyncArrowFunction.js
index 2009a240f0e..916a0e4a045 100644
--- a/tests/baselines/reference/parenthesizedAsyncArrowFunction.js
+++ b/tests/baselines/reference/parenthesizedAsyncArrowFunction.js
@@ -7,10 +7,11 @@ let foo = (async bar => bar);
 //// [parenthesizedAsyncArrowFunction.js]
 // Repro from #20096
 var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
     return new (P || (P = Promise))(function (resolve, reject) {
         function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
         function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
-        function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
         step((generator = generator.apply(thisArg, _arguments || [])).next());
     });
 };
diff --git a/tests/baselines/reference/promiseDefinitionTest.js b/tests/baselines/reference/promiseDefinitionTest.js
index a0f503e2f03..c502085e362 100644
--- a/tests/baselines/reference/promiseDefinitionTest.js
+++ b/tests/baselines/reference/promiseDefinitionTest.js
@@ -6,10 +6,11 @@ const x = foo();
 
 //// [promiseDefinitionTest.js]
 var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
     return new (P || (P = Promise))(function (resolve, reject) {
         function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
         function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
-        function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
         step((generator = generator.apply(thisArg, _arguments || [])).next());
     });
 };
diff --git a/tests/baselines/reference/promiseType.js b/tests/baselines/reference/promiseType.js
index d6b82ebb4d5..84d9d713b48 100644
--- a/tests/baselines/reference/promiseType.js
+++ b/tests/baselines/reference/promiseType.js
@@ -221,10 +221,11 @@ const pc9 = p.then(() => Promise.reject("1"), () => Promise.reject(1));
 
 //// [promiseType.js]
 var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
     return new (P || (P = Promise))(function (resolve, reject) {
         function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
         function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
-        function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
         step((generator = generator.apply(thisArg, _arguments || [])).next());
     });
 };
diff --git a/tests/baselines/reference/promiseTypeStrictNull.js b/tests/baselines/reference/promiseTypeStrictNull.js
index 60e0b9b61df..cdee87b5666 100644
--- a/tests/baselines/reference/promiseTypeStrictNull.js
+++ b/tests/baselines/reference/promiseTypeStrictNull.js
@@ -221,10 +221,11 @@ const pc9 = p.then(() => Promise.reject("1"), () => Promise.reject(1));
 
 //// [promiseTypeStrictNull.js]
 var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
     return new (P || (P = Promise))(function (resolve, reject) {
         function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
         function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
-        function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
         step((generator = generator.apply(thisArg, _arguments || [])).next());
     });
 };
diff --git a/tests/baselines/reference/reachabilityChecks7.js b/tests/baselines/reference/reachabilityChecks7.js
index 30addff4aec..8421e1ff594 100644
--- a/tests/baselines/reference/reachabilityChecks7.js
+++ b/tests/baselines/reference/reachabilityChecks7.js
@@ -31,10 +31,11 @@ let x1 = () => { use("Test"); }
 
 //// [reachabilityChecks7.js]
 var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
     return new (P || (P = Promise))(function (resolve, reject) {
         function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
         function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
-        function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
         step((generator = generator.apply(thisArg, _arguments || [])).next());
     });
 };
diff --git a/tests/baselines/reference/reactReduxLikeDeferredInferenceAllowsAssignment.js b/tests/baselines/reference/reactReduxLikeDeferredInferenceAllowsAssignment.js
index 69e1108ad30..88ae943f92a 100644
--- a/tests/baselines/reference/reactReduxLikeDeferredInferenceAllowsAssignment.js
+++ b/tests/baselines/reference/reactReduxLikeDeferredInferenceAllowsAssignment.js
@@ -163,10 +163,11 @@ var __extends = (this && this.__extends) || (function () {
     };
 })();
 var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
     return new (P || (P = Promise))(function (resolve, reject) {
         function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
         function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
-        function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
         step((generator = generator.apply(thisArg, _arguments || [])).next());
     });
 };
diff --git a/tests/baselines/reference/spreadContextualTypedBindingPattern.js b/tests/baselines/reference/spreadContextualTypedBindingPattern.js
index 7b2128e4a53..c95cccedbf3 100644
--- a/tests/baselines/reference/spreadContextualTypedBindingPattern.js
+++ b/tests/baselines/reference/spreadContextualTypedBindingPattern.js
@@ -25,4 +25,4 @@ var __assign = (this && this.__assign) || function () {
     return __assign.apply(this, arguments);
 };
 // [ts] Initializer provides no value for this binding element and the binding element has no default value.
-var _a = __assign({}, bob, alice), naam = _a.naam, age = _a.age;
+var _a = __assign(__assign({}, bob), alice), naam = _a.naam, age = _a.age;
diff --git a/tests/baselines/reference/spreadIntersection.js b/tests/baselines/reference/spreadIntersection.js
index 2defebc5ce1..fe746734d6d 100644
--- a/tests/baselines/reference/spreadIntersection.js
+++ b/tests/baselines/reference/spreadIntersection.js
@@ -23,4 +23,4 @@ var intersection;
 var o1;
 var o1 = __assign({}, intersection);
 var o2;
-var o2 = __assign({}, intersection, { c: false });
+var o2 = __assign(__assign({}, intersection), { c: false });
diff --git a/tests/baselines/reference/spreadNonPrimitive.js b/tests/baselines/reference/spreadNonPrimitive.js
index 81b23a584fa..50b2c1cdec8 100644
--- a/tests/baselines/reference/spreadNonPrimitive.js
+++ b/tests/baselines/reference/spreadNonPrimitive.js
@@ -15,4 +15,4 @@ var __assign = (this && this.__assign) || function () {
     };
     return __assign.apply(this, arguments);
 };
-var x = __assign({ a: 1 }, o, { b: 2 });
+var x = __assign(__assign({ a: 1 }, o), { b: 2 });
diff --git a/tests/baselines/reference/spreadUnion.js b/tests/baselines/reference/spreadUnion.js
index 42ec336c67d..03220cef0e8 100644
--- a/tests/baselines/reference/spreadUnion.js
+++ b/tests/baselines/reference/spreadUnion.js
@@ -26,6 +26,6 @@ var union;
 var o3;
 var o3 = __assign({}, union);
 var o4;
-var o4 = __assign({}, union, { a: false });
+var o4 = __assign(__assign({}, union), { a: false });
 var o5;
-var o5 = __assign({}, union, union);
+var o5 = __assign(__assign({}, union), union);
diff --git a/tests/baselines/reference/spreadUnion2.js b/tests/baselines/reference/spreadUnion2.js
index 2678ce707cf..b48209cfc01 100644
--- a/tests/baselines/reference/spreadUnion2.js
+++ b/tests/baselines/reference/spreadUnion2.js
@@ -37,9 +37,9 @@ var o1 = __assign({}, undefinedUnion);
 var o2;
 var o2 = __assign({}, nullUnion);
 var o3;
-var o3 = __assign({}, undefinedUnion, nullUnion);
-var o3 = __assign({}, nullUnion, undefinedUnion);
+var o3 = __assign(__assign({}, undefinedUnion), nullUnion);
+var o3 = __assign(__assign({}, nullUnion), undefinedUnion);
 var o4;
-var o4 = __assign({}, undefinedUnion, undefinedUnion);
+var o4 = __assign(__assign({}, undefinedUnion), undefinedUnion);
 var o5;
-var o5 = __assign({}, nullUnion, nullUnion);
+var o5 = __assign(__assign({}, nullUnion), nullUnion);
diff --git a/tests/baselines/reference/spreadUnion3.js b/tests/baselines/reference/spreadUnion3.js
index 2175889db70..dda735a2dc1 100644
--- a/tests/baselines/reference/spreadUnion3.js
+++ b/tests/baselines/reference/spreadUnion3.js
@@ -42,5 +42,5 @@ function g(t) {
 g();
 g(undefined);
 g(null);
-var x = __assign({}, nullAndUndefinedUnion, nullAndUndefinedUnion);
+var x = __assign(__assign({}, nullAndUndefinedUnion), nullAndUndefinedUnion);
 var y = __assign({}, nullAndUndefinedUnion);
diff --git a/tests/baselines/reference/thisTypeInFunctionsNegative.js b/tests/baselines/reference/thisTypeInFunctionsNegative.js
index ed454ee8b70..a3fe0b8ee59 100644
--- a/tests/baselines/reference/thisTypeInFunctionsNegative.js
+++ b/tests/baselines/reference/thisTypeInFunctionsNegative.js
@@ -181,10 +181,11 @@ const f4 = async <T>(this: {n: number}, m: number) => m + this.n;
 
 //// [thisTypeInFunctionsNegative.js]
 var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
     return new (P || (P = Promise))(function (resolve, reject) {
         function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
         function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
-        function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
         step((generator = generator.apply(thisArg, _arguments || [])).next());
     });
 };
diff --git a/tests/baselines/reference/transformNestedGeneratorsWithTry.js b/tests/baselines/reference/transformNestedGeneratorsWithTry.js
index 28f01e07988..84b933cc6a7 100644
--- a/tests/baselines/reference/transformNestedGeneratorsWithTry.js
+++ b/tests/baselines/reference/transformNestedGeneratorsWithTry.js
@@ -25,10 +25,11 @@ declare module "bluebird" {
 //// [main.js]
 "use strict";
 var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
     return new (P || (P = Promise))(function (resolve, reject) {
         function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
         function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
-        function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
         step((generator = generator.apply(thisArg, _arguments || [])).next());
     });
 };
diff --git a/tests/baselines/reference/unionExcessPropsWithPartialMember.js b/tests/baselines/reference/unionExcessPropsWithPartialMember.js
index cefd480bba8..f7e88d35a41 100644
--- a/tests/baselines/reference/unionExcessPropsWithPartialMember.js
+++ b/tests/baselines/reference/unionExcessPropsWithPartialMember.js
@@ -28,4 +28,4 @@ var __assign = (this && this.__assign) || function () {
     };
     return __assign.apply(this, arguments);
 };
-ab = __assign({}, a, { y: null }); // Should be allowed, since `y` is missing on `A`
+ab = __assign(__assign({}, a), { y: null }); // Should be allowed, since `y` is missing on `A`
diff --git a/tests/baselines/reference/unknownType1.js b/tests/baselines/reference/unknownType1.js
index 688fbf8f93c..8bd340de020 100644
--- a/tests/baselines/reference/unknownType1.js
+++ b/tests/baselines/reference/unknownType1.js
@@ -279,8 +279,8 @@ function f25() {
 // Spread of unknown causes result to be unknown
 function f26(x, y, z) {
     var o1 = __assign({ a: 42 }, x); // { a: number }
-    var o2 = __assign({ a: 42 }, x, y); // unknown
-    var o3 = __assign({ a: 42 }, x, y, z); // any
+    var o2 = __assign(__assign({ a: 42 }, x), y); // unknown
+    var o3 = __assign(__assign(__assign({ a: 42 }, x), y), z); // any
 }
 // Functions with unknown return type don't need return expressions
 function f27() {
diff --git a/tests/baselines/reference/useBeforeDeclaration_propertyAssignment.js b/tests/baselines/reference/useBeforeDeclaration_propertyAssignment.js
index 47968d429ad..4ee81065518 100644
--- a/tests/baselines/reference/useBeforeDeclaration_propertyAssignment.js
+++ b/tests/baselines/reference/useBeforeDeclaration_propertyAssignment.js
@@ -20,7 +20,7 @@ class D {
 //// [useBeforeDeclaration_propertyAssignment.js]
 export class C {
     constructor() {
-        this.a = Object.assign({ b: this.b }, this.c, { [this.b]: `${this.c}` });
+        this.a = Object.assign(Object.assign({ b: this.b }, this.c), { [this.b]: `${this.c}` });
         this.b = 0;
         this.c = { c: this.b };
     }