diff --git a/src/lib/es2015.promise.d.ts b/src/lib/es2015.promise.d.ts
index 83776137c33c1..72ebe87ba07d8 100644
--- a/src/lib/es2015.promise.d.ts
+++ b/src/lib/es2015.promise.d.ts
@@ -10,7 +10,7 @@ interface PromiseConstructor {
      * a resolve callback used to resolve the promise with a value or the result of another promise,
      * and a reject callback used to reject the promise with a provided reason or error.
      */
-    new <T>(executor: (resolve: (value?: T | PromiseLike<T>) => void, reject: (reason?: any) => void) => void): Promise<T>;
+    new <T>(executor: (resolve: (value?: T) => void, reject: (reason?: any) => void) => void): Promise<T extends PromiseLike<infer U> ? U : T>;
 
     /**
      * Creates a Promise that is resolved with an array of results when all of the provided Promises
diff --git a/tests/baselines/reference/asyncArrowFunction10_es5.errors.txt b/tests/baselines/reference/asyncArrowFunction10_es5.errors.txt
index 5b4505ebfde2e..e8b5e78cb3c1c 100644
--- a/tests/baselines/reference/asyncArrowFunction10_es5.errors.txt
+++ b/tests/baselines/reference/asyncArrowFunction10_es5.errors.txt
@@ -1,8 +1,33 @@
+tests/cases/conformance/async/es5/asyncArrowFunction/asyncArrowFunction10_es5.ts(1,21): error TS1055: Type 'PromiseConstructor' is not a valid async function return type in ES5/ES3 because it does not refer to a Promise-compatible constructor value.
+  Type 'Promise<T | (T extends PromiseLike<infer U> ? U : T)>' is not assignable to type 'PromiseLike<T>'.
+    Types of property 'then' are incompatible.
+      Type '<TResult1 = T | (T extends PromiseLike<infer U> ? U : T), TResult2 = never>(onfulfilled?: (value: T | (T extends PromiseLike<infer U> ? U : T)) => TResult1 | PromiseLike<TResult1>, onrejected?: (reason: any) => TResult2 | PromiseLike<TResult2>) => Promise<TResult1 | TResult2>' is not assignable to type '<TResult1 = T, TResult2 = never>(onfulfilled?: (value: T) => TResult1 | PromiseLike<TResult1>, onrejected?: (reason: any) => TResult2 | PromiseLike<TResult2>) => PromiseLike<TResult1 | TResult2>'.
+        Types of parameters 'onfulfilled' and 'onfulfilled' are incompatible.
+          Types of parameters 'value' and 'value' are incompatible.
+            Type 'T | (T extends PromiseLike<infer U> ? U : T)' is not assignable to type 'T'.
+              'T | (T extends PromiseLike<infer U> ? U : T)' is assignable to the constraint of type 'T', but 'T' could be instantiated with a different subtype of constraint '{}'.
+                Type 'T extends PromiseLike<infer U> ? U : T' is not assignable to type 'T'.
+                  'T extends PromiseLike<infer U> ? U : T' is assignable to the constraint of type 'T', but 'T' could be instantiated with a different subtype of constraint '{}'.
+                    Type 'unknown' is not assignable to type 'T'.
+                      'unknown' is assignable to the constraint of type 'T', but 'T' could be instantiated with a different subtype of constraint '{}'.
 tests/cases/conformance/async/es5/asyncArrowFunction/asyncArrowFunction10_es5.ts(3,11): error TS2304: Cannot find name 'await'.
 
 
-==== tests/cases/conformance/async/es5/asyncArrowFunction/asyncArrowFunction10_es5.ts (1 errors) ====
+==== tests/cases/conformance/async/es5/asyncArrowFunction/asyncArrowFunction10_es5.ts (2 errors) ====
     var foo = async (): Promise<void> => {
+                        ~~~~~~~~~~~~~
+!!! error TS1055: Type 'PromiseConstructor' is not a valid async function return type in ES5/ES3 because it does not refer to a Promise-compatible constructor value.
+!!! error TS1055:   Type 'Promise<T | (T extends PromiseLike<infer U> ? U : T)>' is not assignable to type 'PromiseLike<T>'.
+!!! error TS1055:     Types of property 'then' are incompatible.
+!!! error TS1055:       Type '<TResult1 = T | (T extends PromiseLike<infer U> ? U : T), TResult2 = never>(onfulfilled?: (value: T | (T extends PromiseLike<infer U> ? U : T)) => TResult1 | PromiseLike<TResult1>, onrejected?: (reason: any) => TResult2 | PromiseLike<TResult2>) => Promise<TResult1 | TResult2>' is not assignable to type '<TResult1 = T, TResult2 = never>(onfulfilled?: (value: T) => TResult1 | PromiseLike<TResult1>, onrejected?: (reason: any) => TResult2 | PromiseLike<TResult2>) => PromiseLike<TResult1 | TResult2>'.
+!!! error TS1055:         Types of parameters 'onfulfilled' and 'onfulfilled' are incompatible.
+!!! error TS1055:           Types of parameters 'value' and 'value' are incompatible.
+!!! error TS1055:             Type 'T | (T extends PromiseLike<infer U> ? U : T)' is not assignable to type 'T'.
+!!! error TS1055:               'T | (T extends PromiseLike<infer U> ? U : T)' is assignable to the constraint of type 'T', but 'T' could be instantiated with a different subtype of constraint '{}'.
+!!! error TS1055:                 Type 'T extends PromiseLike<infer U> ? U : T' is not assignable to type 'T'.
+!!! error TS1055:                   'T extends PromiseLike<infer U> ? U : T' is assignable to the constraint of type 'T', but 'T' could be instantiated with a different subtype of constraint '{}'.
+!!! error TS1055:                     Type 'unknown' is not assignable to type 'T'.
+!!! error TS1055:                       'unknown' is assignable to the constraint of type 'T', but 'T' could be instantiated with a different subtype of constraint '{}'.
        // Legal to use 'await' in a type context.
        var v: await;
               ~~~~~
diff --git a/tests/baselines/reference/asyncArrowFunction6_es5.errors.txt b/tests/baselines/reference/asyncArrowFunction6_es5.errors.txt
index 9d0dbd748807a..87bc3690e6d7e 100644
--- a/tests/baselines/reference/asyncArrowFunction6_es5.errors.txt
+++ b/tests/baselines/reference/asyncArrowFunction6_es5.errors.txt
@@ -1,11 +1,36 @@
 tests/cases/conformance/async/es5/asyncArrowFunction/asyncArrowFunction6_es5.ts(1,22): error TS2524: 'await' expressions cannot be used in a parameter initializer.
 tests/cases/conformance/async/es5/asyncArrowFunction/asyncArrowFunction6_es5.ts(1,27): error TS1109: Expression expected.
+tests/cases/conformance/async/es5/asyncArrowFunction/asyncArrowFunction6_es5.ts(1,30): error TS1055: Type 'PromiseConstructor' is not a valid async function return type in ES5/ES3 because it does not refer to a Promise-compatible constructor value.
+  Type 'Promise<T | (T extends PromiseLike<infer U> ? U : T)>' is not assignable to type 'PromiseLike<T>'.
+    Types of property 'then' are incompatible.
+      Type '<TResult1 = T | (T extends PromiseLike<infer U> ? U : T), TResult2 = never>(onfulfilled?: (value: T | (T extends PromiseLike<infer U> ? U : T)) => TResult1 | PromiseLike<TResult1>, onrejected?: (reason: any) => TResult2 | PromiseLike<TResult2>) => Promise<TResult1 | TResult2>' is not assignable to type '<TResult1 = T, TResult2 = never>(onfulfilled?: (value: T) => TResult1 | PromiseLike<TResult1>, onrejected?: (reason: any) => TResult2 | PromiseLike<TResult2>) => PromiseLike<TResult1 | TResult2>'.
+        Types of parameters 'onfulfilled' and 'onfulfilled' are incompatible.
+          Types of parameters 'value' and 'value' are incompatible.
+            Type 'T | (T extends PromiseLike<infer U> ? U : T)' is not assignable to type 'T'.
+              'T | (T extends PromiseLike<infer U> ? U : T)' is assignable to the constraint of type 'T', but 'T' could be instantiated with a different subtype of constraint '{}'.
+                Type 'T extends PromiseLike<infer U> ? U : T' is not assignable to type 'T'.
+                  'T extends PromiseLike<infer U> ? U : T' is assignable to the constraint of type 'T', but 'T' could be instantiated with a different subtype of constraint '{}'.
+                    Type 'unknown' is not assignable to type 'T'.
+                      'unknown' is assignable to the constraint of type 'T', but 'T' could be instantiated with a different subtype of constraint '{}'.
 
 
-==== tests/cases/conformance/async/es5/asyncArrowFunction/asyncArrowFunction6_es5.ts (2 errors) ====
+==== tests/cases/conformance/async/es5/asyncArrowFunction/asyncArrowFunction6_es5.ts (3 errors) ====
     var foo = async (a = await): Promise<void> => {
                          ~~~~~
 !!! error TS2524: 'await' expressions cannot be used in a parameter initializer.
                               ~
 !!! error TS1109: Expression expected.
+                                 ~~~~~~~~~~~~~
+!!! error TS1055: Type 'PromiseConstructor' is not a valid async function return type in ES5/ES3 because it does not refer to a Promise-compatible constructor value.
+!!! error TS1055:   Type 'Promise<T | (T extends PromiseLike<infer U> ? U : T)>' is not assignable to type 'PromiseLike<T>'.
+!!! error TS1055:     Types of property 'then' are incompatible.
+!!! error TS1055:       Type '<TResult1 = T | (T extends PromiseLike<infer U> ? U : T), TResult2 = never>(onfulfilled?: (value: T | (T extends PromiseLike<infer U> ? U : T)) => TResult1 | PromiseLike<TResult1>, onrejected?: (reason: any) => TResult2 | PromiseLike<TResult2>) => Promise<TResult1 | TResult2>' is not assignable to type '<TResult1 = T, TResult2 = never>(onfulfilled?: (value: T) => TResult1 | PromiseLike<TResult1>, onrejected?: (reason: any) => TResult2 | PromiseLike<TResult2>) => PromiseLike<TResult1 | TResult2>'.
+!!! error TS1055:         Types of parameters 'onfulfilled' and 'onfulfilled' are incompatible.
+!!! error TS1055:           Types of parameters 'value' and 'value' are incompatible.
+!!! error TS1055:             Type 'T | (T extends PromiseLike<infer U> ? U : T)' is not assignable to type 'T'.
+!!! error TS1055:               'T | (T extends PromiseLike<infer U> ? U : T)' is assignable to the constraint of type 'T', but 'T' could be instantiated with a different subtype of constraint '{}'.
+!!! error TS1055:                 Type 'T extends PromiseLike<infer U> ? U : T' is not assignable to type 'T'.
+!!! error TS1055:                   'T extends PromiseLike<infer U> ? U : T' is assignable to the constraint of type 'T', but 'T' could be instantiated with a different subtype of constraint '{}'.
+!!! error TS1055:                     Type 'unknown' is not assignable to type 'T'.
+!!! error TS1055:                       'unknown' is assignable to the constraint of type 'T', but 'T' could be instantiated with a different subtype of constraint '{}'.
     }
\ No newline at end of file
diff --git a/tests/baselines/reference/asyncArrowFunction7_es5.errors.txt b/tests/baselines/reference/asyncArrowFunction7_es5.errors.txt
index 5d4f03cbc41b8..7113901f5c102 100644
--- a/tests/baselines/reference/asyncArrowFunction7_es5.errors.txt
+++ b/tests/baselines/reference/asyncArrowFunction7_es5.errors.txt
@@ -1,14 +1,42 @@
+tests/cases/conformance/async/es5/asyncArrowFunction/asyncArrowFunction7_es5.ts(1,21): error TS1055: Type 'PromiseConstructor' is not a valid async function return type in ES5/ES3 because it does not refer to a Promise-compatible constructor value.
+  Type 'Promise<T | (T extends PromiseLike<infer U> ? U : T)>' is not assignable to type 'PromiseLike<T>'.
+    Types of property 'then' are incompatible.
+      Type '<TResult1 = T | (T extends PromiseLike<infer U> ? U : T), TResult2 = never>(onfulfilled?: (value: T | (T extends PromiseLike<infer U> ? U : T)) => TResult1 | PromiseLike<TResult1>, onrejected?: (reason: any) => TResult2 | PromiseLike<TResult2>) => Promise<TResult1 | TResult2>' is not assignable to type '<TResult1 = T, TResult2 = never>(onfulfilled?: (value: T) => TResult1 | PromiseLike<TResult1>, onrejected?: (reason: any) => TResult2 | PromiseLike<TResult2>) => PromiseLike<TResult1 | TResult2>'.
+        Types of parameters 'onfulfilled' and 'onfulfilled' are incompatible.
+          Types of parameters 'value' and 'value' are incompatible.
+            Type 'T | (T extends PromiseLike<infer U> ? U : T)' is not assignable to type 'T'.
+              'T | (T extends PromiseLike<infer U> ? U : T)' is assignable to the constraint of type 'T', but 'T' could be instantiated with a different subtype of constraint '{}'.
+                Type 'T extends PromiseLike<infer U> ? U : T' is not assignable to type 'T'.
+                  'T extends PromiseLike<infer U> ? U : T' is assignable to the constraint of type 'T', but 'T' could be instantiated with a different subtype of constraint '{}'.
+                    Type 'unknown' is not assignable to type 'T'.
+                      'unknown' is assignable to the constraint of type 'T', but 'T' could be instantiated with a different subtype of constraint '{}'.
 tests/cases/conformance/async/es5/asyncArrowFunction/asyncArrowFunction7_es5.ts(3,24): error TS2524: 'await' expressions cannot be used in a parameter initializer.
 tests/cases/conformance/async/es5/asyncArrowFunction/asyncArrowFunction7_es5.ts(3,29): error TS1109: Expression expected.
+tests/cases/conformance/async/es5/asyncArrowFunction/asyncArrowFunction7_es5.ts(3,32): error TS1055: Type 'PromiseConstructor' is not a valid async function return type in ES5/ES3 because it does not refer to a Promise-compatible constructor value.
 
 
-==== tests/cases/conformance/async/es5/asyncArrowFunction/asyncArrowFunction7_es5.ts (2 errors) ====
+==== tests/cases/conformance/async/es5/asyncArrowFunction/asyncArrowFunction7_es5.ts (4 errors) ====
     var bar = async (): Promise<void> => {
+                        ~~~~~~~~~~~~~
+!!! error TS1055: Type 'PromiseConstructor' is not a valid async function return type in ES5/ES3 because it does not refer to a Promise-compatible constructor value.
+!!! error TS1055:   Type 'Promise<T | (T extends PromiseLike<infer U> ? U : T)>' is not assignable to type 'PromiseLike<T>'.
+!!! error TS1055:     Types of property 'then' are incompatible.
+!!! error TS1055:       Type '<TResult1 = T | (T extends PromiseLike<infer U> ? U : T), TResult2 = never>(onfulfilled?: (value: T | (T extends PromiseLike<infer U> ? U : T)) => TResult1 | PromiseLike<TResult1>, onrejected?: (reason: any) => TResult2 | PromiseLike<TResult2>) => Promise<TResult1 | TResult2>' is not assignable to type '<TResult1 = T, TResult2 = never>(onfulfilled?: (value: T) => TResult1 | PromiseLike<TResult1>, onrejected?: (reason: any) => TResult2 | PromiseLike<TResult2>) => PromiseLike<TResult1 | TResult2>'.
+!!! error TS1055:         Types of parameters 'onfulfilled' and 'onfulfilled' are incompatible.
+!!! error TS1055:           Types of parameters 'value' and 'value' are incompatible.
+!!! error TS1055:             Type 'T | (T extends PromiseLike<infer U> ? U : T)' is not assignable to type 'T'.
+!!! error TS1055:               'T | (T extends PromiseLike<infer U> ? U : T)' is assignable to the constraint of type 'T', but 'T' could be instantiated with a different subtype of constraint '{}'.
+!!! error TS1055:                 Type 'T extends PromiseLike<infer U> ? U : T' is not assignable to type 'T'.
+!!! error TS1055:                   'T extends PromiseLike<infer U> ? U : T' is assignable to the constraint of type 'T', but 'T' could be instantiated with a different subtype of constraint '{}'.
+!!! error TS1055:                     Type 'unknown' is not assignable to type 'T'.
+!!! error TS1055:                       'unknown' is assignable to the constraint of type 'T', but 'T' could be instantiated with a different subtype of constraint '{}'.
       // 'await' here is an identifier, and not an await expression.
       var foo = async (a = await): Promise<void> => {
                            ~~~~~
 !!! error TS2524: 'await' expressions cannot be used in a parameter initializer.
                                 ~
 !!! error TS1109: Expression expected.
+                                   ~~~~~~~~~~~~~
+!!! error TS1055: Type 'PromiseConstructor' is not a valid async function return type in ES5/ES3 because it does not refer to a Promise-compatible constructor value.
       }
     }
\ No newline at end of file
diff --git a/tests/baselines/reference/asyncArrowFunction8_es5.errors.txt b/tests/baselines/reference/asyncArrowFunction8_es5.errors.txt
index 620d0b5653b7c..ea00b222c7582 100644
--- a/tests/baselines/reference/asyncArrowFunction8_es5.errors.txt
+++ b/tests/baselines/reference/asyncArrowFunction8_es5.errors.txt
@@ -1,8 +1,33 @@
+tests/cases/conformance/async/es5/asyncArrowFunction/asyncArrowFunction8_es5.ts(1,21): error TS1055: Type 'PromiseConstructor' is not a valid async function return type in ES5/ES3 because it does not refer to a Promise-compatible constructor value.
+  Type 'Promise<T | (T extends PromiseLike<infer U> ? U : T)>' is not assignable to type 'PromiseLike<T>'.
+    Types of property 'then' are incompatible.
+      Type '<TResult1 = T | (T extends PromiseLike<infer U> ? U : T), TResult2 = never>(onfulfilled?: (value: T | (T extends PromiseLike<infer U> ? U : T)) => TResult1 | PromiseLike<TResult1>, onrejected?: (reason: any) => TResult2 | PromiseLike<TResult2>) => Promise<TResult1 | TResult2>' is not assignable to type '<TResult1 = T, TResult2 = never>(onfulfilled?: (value: T) => TResult1 | PromiseLike<TResult1>, onrejected?: (reason: any) => TResult2 | PromiseLike<TResult2>) => PromiseLike<TResult1 | TResult2>'.
+        Types of parameters 'onfulfilled' and 'onfulfilled' are incompatible.
+          Types of parameters 'value' and 'value' are incompatible.
+            Type 'T | (T extends PromiseLike<infer U> ? U : T)' is not assignable to type 'T'.
+              'T | (T extends PromiseLike<infer U> ? U : T)' is assignable to the constraint of type 'T', but 'T' could be instantiated with a different subtype of constraint '{}'.
+                Type 'T extends PromiseLike<infer U> ? U : T' is not assignable to type 'T'.
+                  'T extends PromiseLike<infer U> ? U : T' is assignable to the constraint of type 'T', but 'T' could be instantiated with a different subtype of constraint '{}'.
+                    Type 'unknown' is not assignable to type 'T'.
+                      'unknown' is assignable to the constraint of type 'T', but 'T' could be instantiated with a different subtype of constraint '{}'.
 tests/cases/conformance/async/es5/asyncArrowFunction/asyncArrowFunction8_es5.ts(2,19): error TS1109: Expression expected.
 
 
-==== tests/cases/conformance/async/es5/asyncArrowFunction/asyncArrowFunction8_es5.ts (1 errors) ====
+==== tests/cases/conformance/async/es5/asyncArrowFunction/asyncArrowFunction8_es5.ts (2 errors) ====
     var foo = async (): Promise<void> => {
+                        ~~~~~~~~~~~~~
+!!! error TS1055: Type 'PromiseConstructor' is not a valid async function return type in ES5/ES3 because it does not refer to a Promise-compatible constructor value.
+!!! error TS1055:   Type 'Promise<T | (T extends PromiseLike<infer U> ? U : T)>' is not assignable to type 'PromiseLike<T>'.
+!!! error TS1055:     Types of property 'then' are incompatible.
+!!! error TS1055:       Type '<TResult1 = T | (T extends PromiseLike<infer U> ? U : T), TResult2 = never>(onfulfilled?: (value: T | (T extends PromiseLike<infer U> ? U : T)) => TResult1 | PromiseLike<TResult1>, onrejected?: (reason: any) => TResult2 | PromiseLike<TResult2>) => Promise<TResult1 | TResult2>' is not assignable to type '<TResult1 = T, TResult2 = never>(onfulfilled?: (value: T) => TResult1 | PromiseLike<TResult1>, onrejected?: (reason: any) => TResult2 | PromiseLike<TResult2>) => PromiseLike<TResult1 | TResult2>'.
+!!! error TS1055:         Types of parameters 'onfulfilled' and 'onfulfilled' are incompatible.
+!!! error TS1055:           Types of parameters 'value' and 'value' are incompatible.
+!!! error TS1055:             Type 'T | (T extends PromiseLike<infer U> ? U : T)' is not assignable to type 'T'.
+!!! error TS1055:               'T | (T extends PromiseLike<infer U> ? U : T)' is assignable to the constraint of type 'T', but 'T' could be instantiated with a different subtype of constraint '{}'.
+!!! error TS1055:                 Type 'T extends PromiseLike<infer U> ? U : T' is not assignable to type 'T'.
+!!! error TS1055:                   'T extends PromiseLike<infer U> ? U : T' is assignable to the constraint of type 'T', but 'T' could be instantiated with a different subtype of constraint '{}'.
+!!! error TS1055:                     Type 'unknown' is not assignable to type 'T'.
+!!! error TS1055:                       'unknown' is assignable to the constraint of type 'T', but 'T' could be instantiated with a different subtype of constraint '{}'.
       var v = { [await]: foo }
                       ~
 !!! error TS1109: Expression expected.
diff --git a/tests/baselines/reference/asyncAwaitIsolatedModules_es5.errors.txt b/tests/baselines/reference/asyncAwaitIsolatedModules_es5.errors.txt
index 7d46517ca159f..20c7d0ad15aeb 100644
--- a/tests/baselines/reference/asyncAwaitIsolatedModules_es5.errors.txt
+++ b/tests/baselines/reference/asyncAwaitIsolatedModules_es5.errors.txt
@@ -1,7 +1,25 @@
 tests/cases/conformance/async/es5/asyncAwaitIsolatedModules_es5.ts(1,27): error TS2307: Cannot find module 'missing'.
+tests/cases/conformance/async/es5/asyncAwaitIsolatedModules_es5.ts(7,22): error TS1055: Type 'PromiseConstructor' is not a valid async function return type in ES5/ES3 because it does not refer to a Promise-compatible constructor value.
+  Type 'Promise<T | (T extends PromiseLike<infer U> ? U : T)>' is not assignable to type 'PromiseLike<T>'.
+    Types of property 'then' are incompatible.
+      Type '<TResult1 = T | (T extends PromiseLike<infer U> ? U : T), TResult2 = never>(onfulfilled?: (value: T | (T extends PromiseLike<infer U> ? U : T)) => TResult1 | PromiseLike<TResult1>, onrejected?: (reason: any) => TResult2 | PromiseLike<TResult2>) => Promise<TResult1 | TResult2>' is not assignable to type '<TResult1 = T, TResult2 = never>(onfulfilled?: (value: T) => TResult1 | PromiseLike<TResult1>, onrejected?: (reason: any) => TResult2 | PromiseLike<TResult2>) => PromiseLike<TResult1 | TResult2>'.
+        Types of parameters 'onfulfilled' and 'onfulfilled' are incompatible.
+          Types of parameters 'value' and 'value' are incompatible.
+            Type 'T | (T extends PromiseLike<infer U> ? U : T)' is not assignable to type 'T'.
+              'T | (T extends PromiseLike<infer U> ? U : T)' is assignable to the constraint of type 'T', but 'T' could be instantiated with a different subtype of constraint '{}'.
+                Type 'T extends PromiseLike<infer U> ? U : T' is not assignable to type 'T'.
+                  'T extends PromiseLike<infer U> ? U : T' is assignable to the constraint of type 'T', but 'T' could be instantiated with a different subtype of constraint '{}'.
+                    Type 'unknown' is not assignable to type 'T'.
+                      'unknown' is assignable to the constraint of type 'T', but 'T' could be instantiated with a different subtype of constraint '{}'.
+tests/cases/conformance/async/es5/asyncAwaitIsolatedModules_es5.ts(11,28): error TS1055: Type 'PromiseConstructor' is not a valid async function return type in ES5/ES3 because it does not refer to a Promise-compatible constructor value.
+tests/cases/conformance/async/es5/asyncAwaitIsolatedModules_es5.ts(15,20): error TS1055: Type 'PromiseConstructor' is not a valid async function return type in ES5/ES3 because it does not refer to a Promise-compatible constructor value.
+tests/cases/conformance/async/es5/asyncAwaitIsolatedModules_es5.ts(19,21): error TS1055: Type 'PromiseConstructor' is not a valid async function return type in ES5/ES3 because it does not refer to a Promise-compatible constructor value.
+tests/cases/conformance/async/es5/asyncAwaitIsolatedModules_es5.ts(24,14): error TS1055: Type 'PromiseConstructor' is not a valid async function return type in ES5/ES3 because it does not refer to a Promise-compatible constructor value.
+tests/cases/conformance/async/es5/asyncAwaitIsolatedModules_es5.ts(30,14): error TS1055: Type 'PromiseConstructor' is not a valid async function return type in ES5/ES3 because it does not refer to a Promise-compatible constructor value.
+tests/cases/conformance/async/es5/asyncAwaitIsolatedModules_es5.ts(33,21): error TS1055: Type 'PromiseConstructor' is not a valid async function return type in ES5/ES3 because it does not refer to a Promise-compatible constructor value.
 
 
-==== tests/cases/conformance/async/es5/asyncAwaitIsolatedModules_es5.ts (1 errors) ====
+==== tests/cases/conformance/async/es5/asyncAwaitIsolatedModules_es5.ts (8 errors) ====
     import { MyPromise } from "missing";
                               ~~~~~~~~~
 !!! error TS2307: Cannot find module 'missing'.
@@ -11,32 +29,57 @@ tests/cases/conformance/async/es5/asyncAwaitIsolatedModules_es5.ts(1,27): error
     
     async function f0() { }
     async function f1(): Promise<void> { }
+                         ~~~~~~~~~~~~~
+!!! error TS1055: Type 'PromiseConstructor' is not a valid async function return type in ES5/ES3 because it does not refer to a Promise-compatible constructor value.
+!!! error TS1055:   Type 'Promise<T | (T extends PromiseLike<infer U> ? U : T)>' is not assignable to type 'PromiseLike<T>'.
+!!! error TS1055:     Types of property 'then' are incompatible.
+!!! error TS1055:       Type '<TResult1 = T | (T extends PromiseLike<infer U> ? U : T), TResult2 = never>(onfulfilled?: (value: T | (T extends PromiseLike<infer U> ? U : T)) => TResult1 | PromiseLike<TResult1>, onrejected?: (reason: any) => TResult2 | PromiseLike<TResult2>) => Promise<TResult1 | TResult2>' is not assignable to type '<TResult1 = T, TResult2 = never>(onfulfilled?: (value: T) => TResult1 | PromiseLike<TResult1>, onrejected?: (reason: any) => TResult2 | PromiseLike<TResult2>) => PromiseLike<TResult1 | TResult2>'.
+!!! error TS1055:         Types of parameters 'onfulfilled' and 'onfulfilled' are incompatible.
+!!! error TS1055:           Types of parameters 'value' and 'value' are incompatible.
+!!! error TS1055:             Type 'T | (T extends PromiseLike<infer U> ? U : T)' is not assignable to type 'T'.
+!!! error TS1055:               'T | (T extends PromiseLike<infer U> ? U : T)' is assignable to the constraint of type 'T', but 'T' could be instantiated with a different subtype of constraint '{}'.
+!!! error TS1055:                 Type 'T extends PromiseLike<infer U> ? U : T' is not assignable to type 'T'.
+!!! error TS1055:                   'T extends PromiseLike<infer U> ? U : T' is assignable to the constraint of type 'T', but 'T' could be instantiated with a different subtype of constraint '{}'.
+!!! error TS1055:                     Type 'unknown' is not assignable to type 'T'.
+!!! error TS1055:                       'unknown' is assignable to the constraint of type 'T', but 'T' could be instantiated with a different subtype of constraint '{}'.
     async function f3(): MyPromise<void> { }
     
     let f4 = async function() { }
     let f5 = async function(): Promise<void> { }
+                               ~~~~~~~~~~~~~
+!!! error TS1055: Type 'PromiseConstructor' is not a valid async function return type in ES5/ES3 because it does not refer to a Promise-compatible constructor value.
     let f6 = async function(): MyPromise<void> { }
     
     let f7 = async () => { };
     let f8 = async (): Promise<void> => { };
+                       ~~~~~~~~~~~~~
+!!! error TS1055: Type 'PromiseConstructor' is not a valid async function return type in ES5/ES3 because it does not refer to a Promise-compatible constructor value.
     let f9 = async (): MyPromise<void> => { };
     let f10 = async () => p;
     let f11 = async () => mp;
     let f12 = async (): Promise<number> => mp;
+                        ~~~~~~~~~~~~~~~
+!!! error TS1055: Type 'PromiseConstructor' is not a valid async function return type in ES5/ES3 because it does not refer to a Promise-compatible constructor value.
     let f13 = async (): MyPromise<number> => p;
     
     let o = {
     	async m1() { },
     	async m2(): Promise<void> { },
+    	            ~~~~~~~~~~~~~
+!!! error TS1055: Type 'PromiseConstructor' is not a valid async function return type in ES5/ES3 because it does not refer to a Promise-compatible constructor value.
     	async m3(): MyPromise<void> { }
     };
     
     class C {
     	async m1() { }
     	async m2(): Promise<void> { }
+    	            ~~~~~~~~~~~~~
+!!! error TS1055: Type 'PromiseConstructor' is not a valid async function return type in ES5/ES3 because it does not refer to a Promise-compatible constructor value.
     	async m3(): MyPromise<void> { }
     	static async m4() { }
     	static async m5(): Promise<void> { }
+    	                   ~~~~~~~~~~~~~
+!!! error TS1055: Type 'PromiseConstructor' is not a valid async function return type in ES5/ES3 because it does not refer to a Promise-compatible constructor value.
     	static async m6(): MyPromise<void> { }
     }
     
diff --git a/tests/baselines/reference/asyncAwaitNestedClasses_es5.types b/tests/baselines/reference/asyncAwaitNestedClasses_es5.types
index 40f0e5ce9b900..ceba067940be1 100644
--- a/tests/baselines/reference/asyncAwaitNestedClasses_es5.types
+++ b/tests/baselines/reference/asyncAwaitNestedClasses_es5.types
@@ -14,10 +14,10 @@ class A {
             return new Promise((resolve) => { resolve(null); });
 >new Promise((resolve) => { resolve(null); }) : Promise<void>
 >Promise : PromiseConstructor
->(resolve) => { resolve(null); } : (resolve: (value?: void | PromiseLike<void>) => void) => void
->resolve : (value?: void | PromiseLike<void>) => void
+>(resolve) => { resolve(null); } : (resolve: (value?: void) => void) => void
+>resolve : (value?: void) => void
 >resolve(null) : void
->resolve : (value?: void | PromiseLike<void>) => void
+>resolve : (value?: void) => void
 >null : null
         }
         static C = class C {
diff --git a/tests/baselines/reference/asyncDeclare_es5.errors.txt b/tests/baselines/reference/asyncDeclare_es5.errors.txt
index bfa467acca219..55d2aad950716 100644
--- a/tests/baselines/reference/asyncDeclare_es5.errors.txt
+++ b/tests/baselines/reference/asyncDeclare_es5.errors.txt
@@ -1,7 +1,32 @@
 tests/cases/conformance/async/es5/asyncDeclare_es5.ts(1,9): error TS1040: 'async' modifier cannot be used in an ambient context.
+tests/cases/conformance/async/es5/asyncDeclare_es5.ts(1,31): error TS1055: Type 'PromiseConstructor' is not a valid async function return type in ES5/ES3 because it does not refer to a Promise-compatible constructor value.
+  Type 'Promise<T | (T extends PromiseLike<infer U> ? U : T)>' is not assignable to type 'PromiseLike<T>'.
+    Types of property 'then' are incompatible.
+      Type '<TResult1 = T | (T extends PromiseLike<infer U> ? U : T), TResult2 = never>(onfulfilled?: (value: T | (T extends PromiseLike<infer U> ? U : T)) => TResult1 | PromiseLike<TResult1>, onrejected?: (reason: any) => TResult2 | PromiseLike<TResult2>) => Promise<TResult1 | TResult2>' is not assignable to type '<TResult1 = T, TResult2 = never>(onfulfilled?: (value: T) => TResult1 | PromiseLike<TResult1>, onrejected?: (reason: any) => TResult2 | PromiseLike<TResult2>) => PromiseLike<TResult1 | TResult2>'.
+        Types of parameters 'onfulfilled' and 'onfulfilled' are incompatible.
+          Types of parameters 'value' and 'value' are incompatible.
+            Type 'T | (T extends PromiseLike<infer U> ? U : T)' is not assignable to type 'T'.
+              'T | (T extends PromiseLike<infer U> ? U : T)' is assignable to the constraint of type 'T', but 'T' could be instantiated with a different subtype of constraint '{}'.
+                Type 'T extends PromiseLike<infer U> ? U : T' is not assignable to type 'T'.
+                  'T extends PromiseLike<infer U> ? U : T' is assignable to the constraint of type 'T', but 'T' could be instantiated with a different subtype of constraint '{}'.
+                    Type 'unknown' is not assignable to type 'T'.
+                      'unknown' is assignable to the constraint of type 'T', but 'T' could be instantiated with a different subtype of constraint '{}'.
 
 
-==== tests/cases/conformance/async/es5/asyncDeclare_es5.ts (1 errors) ====
+==== tests/cases/conformance/async/es5/asyncDeclare_es5.ts (2 errors) ====
     declare async function foo(): Promise<void>;
             ~~~~~
-!!! error TS1040: 'async' modifier cannot be used in an ambient context.
\ No newline at end of file
+!!! error TS1040: 'async' modifier cannot be used in an ambient context.
+                                  ~~~~~~~~~~~~~
+!!! error TS1055: Type 'PromiseConstructor' is not a valid async function return type in ES5/ES3 because it does not refer to a Promise-compatible constructor value.
+!!! error TS1055:   Type 'Promise<T | (T extends PromiseLike<infer U> ? U : T)>' is not assignable to type 'PromiseLike<T>'.
+!!! error TS1055:     Types of property 'then' are incompatible.
+!!! error TS1055:       Type '<TResult1 = T | (T extends PromiseLike<infer U> ? U : T), TResult2 = never>(onfulfilled?: (value: T | (T extends PromiseLike<infer U> ? U : T)) => TResult1 | PromiseLike<TResult1>, onrejected?: (reason: any) => TResult2 | PromiseLike<TResult2>) => Promise<TResult1 | TResult2>' is not assignable to type '<TResult1 = T, TResult2 = never>(onfulfilled?: (value: T) => TResult1 | PromiseLike<TResult1>, onrejected?: (reason: any) => TResult2 | PromiseLike<TResult2>) => PromiseLike<TResult1 | TResult2>'.
+!!! error TS1055:         Types of parameters 'onfulfilled' and 'onfulfilled' are incompatible.
+!!! error TS1055:           Types of parameters 'value' and 'value' are incompatible.
+!!! error TS1055:             Type 'T | (T extends PromiseLike<infer U> ? U : T)' is not assignable to type 'T'.
+!!! error TS1055:               'T | (T extends PromiseLike<infer U> ? U : T)' is assignable to the constraint of type 'T', but 'T' could be instantiated with a different subtype of constraint '{}'.
+!!! error TS1055:                 Type 'T extends PromiseLike<infer U> ? U : T' is not assignable to type 'T'.
+!!! error TS1055:                   'T extends PromiseLike<infer U> ? U : T' is assignable to the constraint of type 'T', but 'T' could be instantiated with a different subtype of constraint '{}'.
+!!! error TS1055:                     Type 'unknown' is not assignable to type 'T'.
+!!! error TS1055:                       'unknown' is assignable to the constraint of type 'T', but 'T' could be instantiated with a different subtype of constraint '{}'.
\ No newline at end of file
diff --git a/tests/baselines/reference/asyncFunctionDeclaration13_es5.errors.txt b/tests/baselines/reference/asyncFunctionDeclaration13_es5.errors.txt
index ce83aabc4bed8..bb56490c2e64a 100644
--- a/tests/baselines/reference/asyncFunctionDeclaration13_es5.errors.txt
+++ b/tests/baselines/reference/asyncFunctionDeclaration13_es5.errors.txt
@@ -1,8 +1,33 @@
+tests/cases/conformance/async/es5/functionDeclarations/asyncFunctionDeclaration13_es5.ts(1,23): error TS1055: Type 'PromiseConstructor' is not a valid async function return type in ES5/ES3 because it does not refer to a Promise-compatible constructor value.
+  Type 'Promise<T | (T extends PromiseLike<infer U> ? U : T)>' is not assignable to type 'PromiseLike<T>'.
+    Types of property 'then' are incompatible.
+      Type '<TResult1 = T | (T extends PromiseLike<infer U> ? U : T), TResult2 = never>(onfulfilled?: (value: T | (T extends PromiseLike<infer U> ? U : T)) => TResult1 | PromiseLike<TResult1>, onrejected?: (reason: any) => TResult2 | PromiseLike<TResult2>) => Promise<TResult1 | TResult2>' is not assignable to type '<TResult1 = T, TResult2 = never>(onfulfilled?: (value: T) => TResult1 | PromiseLike<TResult1>, onrejected?: (reason: any) => TResult2 | PromiseLike<TResult2>) => PromiseLike<TResult1 | TResult2>'.
+        Types of parameters 'onfulfilled' and 'onfulfilled' are incompatible.
+          Types of parameters 'value' and 'value' are incompatible.
+            Type 'T | (T extends PromiseLike<infer U> ? U : T)' is not assignable to type 'T'.
+              'T | (T extends PromiseLike<infer U> ? U : T)' is assignable to the constraint of type 'T', but 'T' could be instantiated with a different subtype of constraint '{}'.
+                Type 'T extends PromiseLike<infer U> ? U : T' is not assignable to type 'T'.
+                  'T extends PromiseLike<infer U> ? U : T' is assignable to the constraint of type 'T', but 'T' could be instantiated with a different subtype of constraint '{}'.
+                    Type 'unknown' is not assignable to type 'T'.
+                      'unknown' is assignable to the constraint of type 'T', but 'T' could be instantiated with a different subtype of constraint '{}'.
 tests/cases/conformance/async/es5/functionDeclarations/asyncFunctionDeclaration13_es5.ts(3,11): error TS2304: Cannot find name 'await'.
 
 
-==== tests/cases/conformance/async/es5/functionDeclarations/asyncFunctionDeclaration13_es5.ts (1 errors) ====
+==== tests/cases/conformance/async/es5/functionDeclarations/asyncFunctionDeclaration13_es5.ts (2 errors) ====
     async function foo(): Promise<void> {
+                          ~~~~~~~~~~~~~
+!!! error TS1055: Type 'PromiseConstructor' is not a valid async function return type in ES5/ES3 because it does not refer to a Promise-compatible constructor value.
+!!! error TS1055:   Type 'Promise<T | (T extends PromiseLike<infer U> ? U : T)>' is not assignable to type 'PromiseLike<T>'.
+!!! error TS1055:     Types of property 'then' are incompatible.
+!!! error TS1055:       Type '<TResult1 = T | (T extends PromiseLike<infer U> ? U : T), TResult2 = never>(onfulfilled?: (value: T | (T extends PromiseLike<infer U> ? U : T)) => TResult1 | PromiseLike<TResult1>, onrejected?: (reason: any) => TResult2 | PromiseLike<TResult2>) => Promise<TResult1 | TResult2>' is not assignable to type '<TResult1 = T, TResult2 = never>(onfulfilled?: (value: T) => TResult1 | PromiseLike<TResult1>, onrejected?: (reason: any) => TResult2 | PromiseLike<TResult2>) => PromiseLike<TResult1 | TResult2>'.
+!!! error TS1055:         Types of parameters 'onfulfilled' and 'onfulfilled' are incompatible.
+!!! error TS1055:           Types of parameters 'value' and 'value' are incompatible.
+!!! error TS1055:             Type 'T | (T extends PromiseLike<infer U> ? U : T)' is not assignable to type 'T'.
+!!! error TS1055:               'T | (T extends PromiseLike<infer U> ? U : T)' is assignable to the constraint of type 'T', but 'T' could be instantiated with a different subtype of constraint '{}'.
+!!! error TS1055:                 Type 'T extends PromiseLike<infer U> ? U : T' is not assignable to type 'T'.
+!!! error TS1055:                   'T extends PromiseLike<infer U> ? U : T' is assignable to the constraint of type 'T', but 'T' could be instantiated with a different subtype of constraint '{}'.
+!!! error TS1055:                     Type 'unknown' is not assignable to type 'T'.
+!!! error TS1055:                       'unknown' is assignable to the constraint of type 'T', but 'T' could be instantiated with a different subtype of constraint '{}'.
        // Legal to use 'await' in a type context.
        var v: await;
               ~~~~~
diff --git a/tests/baselines/reference/asyncFunctionDeclaration6_es5.errors.txt b/tests/baselines/reference/asyncFunctionDeclaration6_es5.errors.txt
index d8cf82fbc28e3..2556e617efc1b 100644
--- a/tests/baselines/reference/asyncFunctionDeclaration6_es5.errors.txt
+++ b/tests/baselines/reference/asyncFunctionDeclaration6_es5.errors.txt
@@ -1,11 +1,36 @@
 tests/cases/conformance/async/es5/functionDeclarations/asyncFunctionDeclaration6_es5.ts(1,24): error TS2524: 'await' expressions cannot be used in a parameter initializer.
 tests/cases/conformance/async/es5/functionDeclarations/asyncFunctionDeclaration6_es5.ts(1,29): error TS1109: Expression expected.
+tests/cases/conformance/async/es5/functionDeclarations/asyncFunctionDeclaration6_es5.ts(1,32): error TS1055: Type 'PromiseConstructor' is not a valid async function return type in ES5/ES3 because it does not refer to a Promise-compatible constructor value.
+  Type 'Promise<T | (T extends PromiseLike<infer U> ? U : T)>' is not assignable to type 'PromiseLike<T>'.
+    Types of property 'then' are incompatible.
+      Type '<TResult1 = T | (T extends PromiseLike<infer U> ? U : T), TResult2 = never>(onfulfilled?: (value: T | (T extends PromiseLike<infer U> ? U : T)) => TResult1 | PromiseLike<TResult1>, onrejected?: (reason: any) => TResult2 | PromiseLike<TResult2>) => Promise<TResult1 | TResult2>' is not assignable to type '<TResult1 = T, TResult2 = never>(onfulfilled?: (value: T) => TResult1 | PromiseLike<TResult1>, onrejected?: (reason: any) => TResult2 | PromiseLike<TResult2>) => PromiseLike<TResult1 | TResult2>'.
+        Types of parameters 'onfulfilled' and 'onfulfilled' are incompatible.
+          Types of parameters 'value' and 'value' are incompatible.
+            Type 'T | (T extends PromiseLike<infer U> ? U : T)' is not assignable to type 'T'.
+              'T | (T extends PromiseLike<infer U> ? U : T)' is assignable to the constraint of type 'T', but 'T' could be instantiated with a different subtype of constraint '{}'.
+                Type 'T extends PromiseLike<infer U> ? U : T' is not assignable to type 'T'.
+                  'T extends PromiseLike<infer U> ? U : T' is assignable to the constraint of type 'T', but 'T' could be instantiated with a different subtype of constraint '{}'.
+                    Type 'unknown' is not assignable to type 'T'.
+                      'unknown' is assignable to the constraint of type 'T', but 'T' could be instantiated with a different subtype of constraint '{}'.
 
 
-==== tests/cases/conformance/async/es5/functionDeclarations/asyncFunctionDeclaration6_es5.ts (2 errors) ====
+==== tests/cases/conformance/async/es5/functionDeclarations/asyncFunctionDeclaration6_es5.ts (3 errors) ====
     async function foo(a = await): Promise<void> {
                            ~~~~~
 !!! error TS2524: 'await' expressions cannot be used in a parameter initializer.
                                 ~
 !!! error TS1109: Expression expected.
+                                   ~~~~~~~~~~~~~
+!!! error TS1055: Type 'PromiseConstructor' is not a valid async function return type in ES5/ES3 because it does not refer to a Promise-compatible constructor value.
+!!! error TS1055:   Type 'Promise<T | (T extends PromiseLike<infer U> ? U : T)>' is not assignable to type 'PromiseLike<T>'.
+!!! error TS1055:     Types of property 'then' are incompatible.
+!!! error TS1055:       Type '<TResult1 = T | (T extends PromiseLike<infer U> ? U : T), TResult2 = never>(onfulfilled?: (value: T | (T extends PromiseLike<infer U> ? U : T)) => TResult1 | PromiseLike<TResult1>, onrejected?: (reason: any) => TResult2 | PromiseLike<TResult2>) => Promise<TResult1 | TResult2>' is not assignable to type '<TResult1 = T, TResult2 = never>(onfulfilled?: (value: T) => TResult1 | PromiseLike<TResult1>, onrejected?: (reason: any) => TResult2 | PromiseLike<TResult2>) => PromiseLike<TResult1 | TResult2>'.
+!!! error TS1055:         Types of parameters 'onfulfilled' and 'onfulfilled' are incompatible.
+!!! error TS1055:           Types of parameters 'value' and 'value' are incompatible.
+!!! error TS1055:             Type 'T | (T extends PromiseLike<infer U> ? U : T)' is not assignable to type 'T'.
+!!! error TS1055:               'T | (T extends PromiseLike<infer U> ? U : T)' is assignable to the constraint of type 'T', but 'T' could be instantiated with a different subtype of constraint '{}'.
+!!! error TS1055:                 Type 'T extends PromiseLike<infer U> ? U : T' is not assignable to type 'T'.
+!!! error TS1055:                   'T extends PromiseLike<infer U> ? U : T' is assignable to the constraint of type 'T', but 'T' could be instantiated with a different subtype of constraint '{}'.
+!!! error TS1055:                     Type 'unknown' is not assignable to type 'T'.
+!!! error TS1055:                       'unknown' is assignable to the constraint of type 'T', but 'T' could be instantiated with a different subtype of constraint '{}'.
     }
\ No newline at end of file
diff --git a/tests/baselines/reference/asyncFunctionDeclaration7_es5.errors.txt b/tests/baselines/reference/asyncFunctionDeclaration7_es5.errors.txt
index 48984724e4c16..672f4be43e6d9 100644
--- a/tests/baselines/reference/asyncFunctionDeclaration7_es5.errors.txt
+++ b/tests/baselines/reference/asyncFunctionDeclaration7_es5.errors.txt
@@ -1,14 +1,42 @@
+tests/cases/conformance/async/es5/functionDeclarations/asyncFunctionDeclaration7_es5.ts(1,23): error TS1055: Type 'PromiseConstructor' is not a valid async function return type in ES5/ES3 because it does not refer to a Promise-compatible constructor value.
+  Type 'Promise<T | (T extends PromiseLike<infer U> ? U : T)>' is not assignable to type 'PromiseLike<T>'.
+    Types of property 'then' are incompatible.
+      Type '<TResult1 = T | (T extends PromiseLike<infer U> ? U : T), TResult2 = never>(onfulfilled?: (value: T | (T extends PromiseLike<infer U> ? U : T)) => TResult1 | PromiseLike<TResult1>, onrejected?: (reason: any) => TResult2 | PromiseLike<TResult2>) => Promise<TResult1 | TResult2>' is not assignable to type '<TResult1 = T, TResult2 = never>(onfulfilled?: (value: T) => TResult1 | PromiseLike<TResult1>, onrejected?: (reason: any) => TResult2 | PromiseLike<TResult2>) => PromiseLike<TResult1 | TResult2>'.
+        Types of parameters 'onfulfilled' and 'onfulfilled' are incompatible.
+          Types of parameters 'value' and 'value' are incompatible.
+            Type 'T | (T extends PromiseLike<infer U> ? U : T)' is not assignable to type 'T'.
+              'T | (T extends PromiseLike<infer U> ? U : T)' is assignable to the constraint of type 'T', but 'T' could be instantiated with a different subtype of constraint '{}'.
+                Type 'T extends PromiseLike<infer U> ? U : T' is not assignable to type 'T'.
+                  'T extends PromiseLike<infer U> ? U : T' is assignable to the constraint of type 'T', but 'T' could be instantiated with a different subtype of constraint '{}'.
+                    Type 'unknown' is not assignable to type 'T'.
+                      'unknown' is assignable to the constraint of type 'T', but 'T' could be instantiated with a different subtype of constraint '{}'.
 tests/cases/conformance/async/es5/functionDeclarations/asyncFunctionDeclaration7_es5.ts(3,26): error TS2524: 'await' expressions cannot be used in a parameter initializer.
 tests/cases/conformance/async/es5/functionDeclarations/asyncFunctionDeclaration7_es5.ts(3,31): error TS1109: Expression expected.
+tests/cases/conformance/async/es5/functionDeclarations/asyncFunctionDeclaration7_es5.ts(3,34): error TS1055: Type 'PromiseConstructor' is not a valid async function return type in ES5/ES3 because it does not refer to a Promise-compatible constructor value.
 
 
-==== tests/cases/conformance/async/es5/functionDeclarations/asyncFunctionDeclaration7_es5.ts (2 errors) ====
+==== tests/cases/conformance/async/es5/functionDeclarations/asyncFunctionDeclaration7_es5.ts (4 errors) ====
     async function bar(): Promise<void> {
+                          ~~~~~~~~~~~~~
+!!! error TS1055: Type 'PromiseConstructor' is not a valid async function return type in ES5/ES3 because it does not refer to a Promise-compatible constructor value.
+!!! error TS1055:   Type 'Promise<T | (T extends PromiseLike<infer U> ? U : T)>' is not assignable to type 'PromiseLike<T>'.
+!!! error TS1055:     Types of property 'then' are incompatible.
+!!! error TS1055:       Type '<TResult1 = T | (T extends PromiseLike<infer U> ? U : T), TResult2 = never>(onfulfilled?: (value: T | (T extends PromiseLike<infer U> ? U : T)) => TResult1 | PromiseLike<TResult1>, onrejected?: (reason: any) => TResult2 | PromiseLike<TResult2>) => Promise<TResult1 | TResult2>' is not assignable to type '<TResult1 = T, TResult2 = never>(onfulfilled?: (value: T) => TResult1 | PromiseLike<TResult1>, onrejected?: (reason: any) => TResult2 | PromiseLike<TResult2>) => PromiseLike<TResult1 | TResult2>'.
+!!! error TS1055:         Types of parameters 'onfulfilled' and 'onfulfilled' are incompatible.
+!!! error TS1055:           Types of parameters 'value' and 'value' are incompatible.
+!!! error TS1055:             Type 'T | (T extends PromiseLike<infer U> ? U : T)' is not assignable to type 'T'.
+!!! error TS1055:               'T | (T extends PromiseLike<infer U> ? U : T)' is assignable to the constraint of type 'T', but 'T' could be instantiated with a different subtype of constraint '{}'.
+!!! error TS1055:                 Type 'T extends PromiseLike<infer U> ? U : T' is not assignable to type 'T'.
+!!! error TS1055:                   'T extends PromiseLike<infer U> ? U : T' is assignable to the constraint of type 'T', but 'T' could be instantiated with a different subtype of constraint '{}'.
+!!! error TS1055:                     Type 'unknown' is not assignable to type 'T'.
+!!! error TS1055:                       'unknown' is assignable to the constraint of type 'T', but 'T' could be instantiated with a different subtype of constraint '{}'.
       // 'await' here is an identifier, and not a yield expression.
       async function foo(a = await): Promise<void> {
                              ~~~~~
 !!! error TS2524: 'await' expressions cannot be used in a parameter initializer.
                                   ~
 !!! error TS1109: Expression expected.
+                                     ~~~~~~~~~~~~~
+!!! error TS1055: Type 'PromiseConstructor' is not a valid async function return type in ES5/ES3 because it does not refer to a Promise-compatible constructor value.
       }
     }
\ No newline at end of file
diff --git a/tests/baselines/reference/asyncFunctionDeclaration9_es5.errors.txt b/tests/baselines/reference/asyncFunctionDeclaration9_es5.errors.txt
index 8eed8dade45bc..ddcc9b69791cb 100644
--- a/tests/baselines/reference/asyncFunctionDeclaration9_es5.errors.txt
+++ b/tests/baselines/reference/asyncFunctionDeclaration9_es5.errors.txt
@@ -1,8 +1,33 @@
+tests/cases/conformance/async/es5/functionDeclarations/asyncFunctionDeclaration9_es5.ts(1,23): error TS1055: Type 'PromiseConstructor' is not a valid async function return type in ES5/ES3 because it does not refer to a Promise-compatible constructor value.
+  Type 'Promise<T | (T extends PromiseLike<infer U> ? U : T)>' is not assignable to type 'PromiseLike<T>'.
+    Types of property 'then' are incompatible.
+      Type '<TResult1 = T | (T extends PromiseLike<infer U> ? U : T), TResult2 = never>(onfulfilled?: (value: T | (T extends PromiseLike<infer U> ? U : T)) => TResult1 | PromiseLike<TResult1>, onrejected?: (reason: any) => TResult2 | PromiseLike<TResult2>) => Promise<TResult1 | TResult2>' is not assignable to type '<TResult1 = T, TResult2 = never>(onfulfilled?: (value: T) => TResult1 | PromiseLike<TResult1>, onrejected?: (reason: any) => TResult2 | PromiseLike<TResult2>) => PromiseLike<TResult1 | TResult2>'.
+        Types of parameters 'onfulfilled' and 'onfulfilled' are incompatible.
+          Types of parameters 'value' and 'value' are incompatible.
+            Type 'T | (T extends PromiseLike<infer U> ? U : T)' is not assignable to type 'T'.
+              'T | (T extends PromiseLike<infer U> ? U : T)' is assignable to the constraint of type 'T', but 'T' could be instantiated with a different subtype of constraint '{}'.
+                Type 'T extends PromiseLike<infer U> ? U : T' is not assignable to type 'T'.
+                  'T extends PromiseLike<infer U> ? U : T' is assignable to the constraint of type 'T', but 'T' could be instantiated with a different subtype of constraint '{}'.
+                    Type 'unknown' is not assignable to type 'T'.
+                      'unknown' is assignable to the constraint of type 'T', but 'T' could be instantiated with a different subtype of constraint '{}'.
 tests/cases/conformance/async/es5/functionDeclarations/asyncFunctionDeclaration9_es5.ts(2,19): error TS1109: Expression expected.
 
 
-==== tests/cases/conformance/async/es5/functionDeclarations/asyncFunctionDeclaration9_es5.ts (1 errors) ====
+==== tests/cases/conformance/async/es5/functionDeclarations/asyncFunctionDeclaration9_es5.ts (2 errors) ====
     async function foo(): Promise<void> {
+                          ~~~~~~~~~~~~~
+!!! error TS1055: Type 'PromiseConstructor' is not a valid async function return type in ES5/ES3 because it does not refer to a Promise-compatible constructor value.
+!!! error TS1055:   Type 'Promise<T | (T extends PromiseLike<infer U> ? U : T)>' is not assignable to type 'PromiseLike<T>'.
+!!! error TS1055:     Types of property 'then' are incompatible.
+!!! error TS1055:       Type '<TResult1 = T | (T extends PromiseLike<infer U> ? U : T), TResult2 = never>(onfulfilled?: (value: T | (T extends PromiseLike<infer U> ? U : T)) => TResult1 | PromiseLike<TResult1>, onrejected?: (reason: any) => TResult2 | PromiseLike<TResult2>) => Promise<TResult1 | TResult2>' is not assignable to type '<TResult1 = T, TResult2 = never>(onfulfilled?: (value: T) => TResult1 | PromiseLike<TResult1>, onrejected?: (reason: any) => TResult2 | PromiseLike<TResult2>) => PromiseLike<TResult1 | TResult2>'.
+!!! error TS1055:         Types of parameters 'onfulfilled' and 'onfulfilled' are incompatible.
+!!! error TS1055:           Types of parameters 'value' and 'value' are incompatible.
+!!! error TS1055:             Type 'T | (T extends PromiseLike<infer U> ? U : T)' is not assignable to type 'T'.
+!!! error TS1055:               'T | (T extends PromiseLike<infer U> ? U : T)' is assignable to the constraint of type 'T', but 'T' could be instantiated with a different subtype of constraint '{}'.
+!!! error TS1055:                 Type 'T extends PromiseLike<infer U> ? U : T' is not assignable to type 'T'.
+!!! error TS1055:                   'T extends PromiseLike<infer U> ? U : T' is assignable to the constraint of type 'T', but 'T' could be instantiated with a different subtype of constraint '{}'.
+!!! error TS1055:                     Type 'unknown' is not assignable to type 'T'.
+!!! error TS1055:                       'unknown' is assignable to the constraint of type 'T', but 'T' could be instantiated with a different subtype of constraint '{}'.
       var v = { [await]: foo }
                       ~
 !!! error TS1109: Expression expected.
diff --git a/tests/baselines/reference/asyncImportedPromise_es5.types b/tests/baselines/reference/asyncImportedPromise_es5.types
index c8ea6bdf61e5d..809b0370b3cf1 100644
--- a/tests/baselines/reference/asyncImportedPromise_es5.types
+++ b/tests/baselines/reference/asyncImportedPromise_es5.types
@@ -1,7 +1,7 @@
 === tests/cases/conformance/async/es5/task.ts ===
 export class Task<T> extends Promise<T> { }
 >Task : Task<T>
->Promise : Promise<T>
+>Promise : Promise<T extends PromiseLike<infer U> ? U : T>
 
 === tests/cases/conformance/async/es5/test.ts ===
 import { Task } from "./task";
diff --git a/tests/baselines/reference/asyncImportedPromise_es6.types b/tests/baselines/reference/asyncImportedPromise_es6.types
index 05411f1dda588..c32f669665337 100644
--- a/tests/baselines/reference/asyncImportedPromise_es6.types
+++ b/tests/baselines/reference/asyncImportedPromise_es6.types
@@ -1,7 +1,7 @@
 === tests/cases/conformance/async/es6/task.ts ===
 export class Task<T> extends Promise<T> { }
 >Task : Task<T>
->Promise : Promise<T>
+>Promise : Promise<T extends PromiseLike<infer U> ? U : T>
 
 === tests/cases/conformance/async/es6/test.ts ===
 import { Task } from "./task";
diff --git a/tests/baselines/reference/asyncQualifiedReturnType_es5.types b/tests/baselines/reference/asyncQualifiedReturnType_es5.types
index 8df2ac42c50c9..9fcfdbba2d63a 100644
--- a/tests/baselines/reference/asyncQualifiedReturnType_es5.types
+++ b/tests/baselines/reference/asyncQualifiedReturnType_es5.types
@@ -4,7 +4,7 @@ namespace X {
 
     export class MyPromise<T> extends Promise<T> {
 >MyPromise : MyPromise<T>
->Promise : Promise<T>
+>Promise : Promise<T extends PromiseLike<infer U> ? U : T>
     }
 }
 
diff --git a/tests/baselines/reference/asyncQualifiedReturnType_es6.types b/tests/baselines/reference/asyncQualifiedReturnType_es6.types
index f1878fed5d80f..a69b7cc0476a0 100644
--- a/tests/baselines/reference/asyncQualifiedReturnType_es6.types
+++ b/tests/baselines/reference/asyncQualifiedReturnType_es6.types
@@ -4,7 +4,7 @@ namespace X {
 
     export class MyPromise<T> extends Promise<T> {
 >MyPromise : MyPromise<T>
->Promise : Promise<T>
+>Promise : Promise<T extends PromiseLike<infer U> ? U : T>
     }
 }
 
diff --git a/tests/baselines/reference/contextuallyTypeAsyncFunctionAwaitOperand.types b/tests/baselines/reference/contextuallyTypeAsyncFunctionAwaitOperand.types
index 377f7c15ae321..2b8f7e79fcbca 100644
--- a/tests/baselines/reference/contextuallyTypeAsyncFunctionAwaitOperand.types
+++ b/tests/baselines/reference/contextuallyTypeAsyncFunctionAwaitOperand.types
@@ -17,10 +17,10 @@ async function fn1(): Promise<Obj> {
 >await new Promise(resolve => resolve({ key: "value" })) : Obj
 >new Promise(resolve => resolve({ key: "value" })) : Promise<Obj>
 >Promise : PromiseConstructor
->resolve => resolve({ key: "value" }) : (resolve: (value?: Obj | PromiseLike<Obj>) => void) => void
->resolve : (value?: Obj | PromiseLike<Obj>) => void
+>resolve => resolve({ key: "value" }) : (resolve: (value?: Obj) => void) => void
+>resolve : (value?: Obj) => void
 >resolve({ key: "value" }) : void
->resolve : (value?: Obj | PromiseLike<Obj>) => void
+>resolve : (value?: Obj) => void
 >{ key: "value" } : { key: "value"; }
 >key : "value"
 >"value" : "value"
diff --git a/tests/baselines/reference/contextuallyTypeAsyncFunctionReturnType.types b/tests/baselines/reference/contextuallyTypeAsyncFunctionReturnType.types
index d47a623ffc6c3..f9462634dcec0 100644
--- a/tests/baselines/reference/contextuallyTypeAsyncFunctionReturnType.types
+++ b/tests/baselines/reference/contextuallyTypeAsyncFunctionReturnType.types
@@ -17,12 +17,12 @@ async function fn2(): Promise<Obj> {
     return new Promise(resolve => {
 >new Promise(resolve => {        resolve({ key: "value" });    }) : Promise<Obj>
 >Promise : PromiseConstructor
->resolve => {        resolve({ key: "value" });    } : (resolve: (value?: Obj | PromiseLike<Obj>) => void) => void
->resolve : (value?: Obj | PromiseLike<Obj>) => void
+>resolve => {        resolve({ key: "value" });    } : (resolve: (value?: Obj) => void) => void
+>resolve : (value?: Obj) => void
 
         resolve({ key: "value" });
 >resolve({ key: "value" }) : void
->resolve : (value?: Obj | PromiseLike<Obj>) => void
+>resolve : (value?: Obj) => void
 >{ key: "value" } : { key: "value"; }
 >key : "value"
 >"value" : "value"
@@ -47,12 +47,12 @@ async function fn4(): Promise<Obj> {
 >await new Promise(resolve => {        resolve({ key: "value" });    }) : Obj
 >new Promise(resolve => {        resolve({ key: "value" });    }) : Promise<Obj>
 >Promise : PromiseConstructor
->resolve => {        resolve({ key: "value" });    } : (resolve: (value?: Obj | PromiseLike<Obj>) => void) => void
->resolve : (value?: Obj | PromiseLike<Obj>) => void
+>resolve => {        resolve({ key: "value" });    } : (resolve: (value?: Obj) => void) => void
+>resolve : (value?: Obj) => void
 
         resolve({ key: "value" });
 >resolve({ key: "value" }) : void
->resolve : (value?: Obj | PromiseLike<Obj>) => void
+>resolve : (value?: Obj) => void
 >{ key: "value" } : { key: "value"; }
 >key : "value"
 >"value" : "value"
diff --git a/tests/baselines/reference/inferenceLimit.types b/tests/baselines/reference/inferenceLimit.types
index 6aa7ab501ea16..3b6973bc9030f 100644
--- a/tests/baselines/reference/inferenceLimit.types
+++ b/tests/baselines/reference/inferenceLimit.types
@@ -19,8 +19,8 @@ export class BrokenClass {
 >new Promise<Array<MyModule.MyModel>>((resolve, reject) => {    let result: Array<MyModule.MyModel> = [];    let populateItems = (order) => {      return new Promise((resolve, reject) => {        this.doStuff(order.id)          .then((items) => {            order.items = items;            resolve(order);          });      });    };    return Promise.all(result.map(populateItems))      .then((orders: Array<MyModule.MyModel>) => {        resolve(orders);      });    }) : Promise<MyModule.MyModel[]>
 >Promise : PromiseConstructor
 >MyModule : any
->(resolve, reject) => {    let result: Array<MyModule.MyModel> = [];    let populateItems = (order) => {      return new Promise((resolve, reject) => {        this.doStuff(order.id)          .then((items) => {            order.items = items;            resolve(order);          });      });    };    return Promise.all(result.map(populateItems))      .then((orders: Array<MyModule.MyModel>) => {        resolve(orders);      });    } : (resolve: (value?: MyModule.MyModel[] | PromiseLike<MyModule.MyModel[]>) => void, reject: (reason?: any) => void) => Promise<void>
->resolve : (value?: MyModule.MyModel[] | PromiseLike<MyModule.MyModel[]>) => void
+>(resolve, reject) => {    let result: Array<MyModule.MyModel> = [];    let populateItems = (order) => {      return new Promise((resolve, reject) => {        this.doStuff(order.id)          .then((items) => {            order.items = items;            resolve(order);          });      });    };    return Promise.all(result.map(populateItems))      .then((orders: Array<MyModule.MyModel>) => {        resolve(orders);      });    } : (resolve: (value?: MyModule.MyModel[]) => void, reject: (reason?: any) => void) => Promise<void>
+>resolve : (value?: MyModule.MyModel[]) => void
 >reject : (reason?: any) => void
 
     let result: Array<MyModule.MyModel> = [];
@@ -93,7 +93,7 @@ export class BrokenClass {
 
         resolve(orders);
 >resolve(orders) : void
->resolve : (value?: MyModule.MyModel[] | PromiseLike<MyModule.MyModel[]>) => void
+>resolve : (value?: MyModule.MyModel[]) => void
 >orders : MyModule.MyModel[]
 
       });
diff --git a/tests/baselines/reference/tsbuild/moduleSpecifiers/initial-build/resolves-correctly.js b/tests/baselines/reference/tsbuild/moduleSpecifiers/initial-build/resolves-correctly.js
index 2ba8fa808170b..01b6d2e05b696 100644
--- a/tests/baselines/reference/tsbuild/moduleSpecifiers/initial-build/resolves-correctly.js
+++ b/tests/baselines/reference/tsbuild/moduleSpecifiers/initial-build/resolves-correctly.js
@@ -42,8 +42,8 @@ exports.__esModule = true;
         "signature": "232404497324"
       },
       "../../../.ts/lib.es2015.promise.d.ts": {
-        "version": "235321148269",
-        "signature": "235321148269"
+        "version": "17314103363",
+        "signature": "17314103363"
       },
       "../../../.ts/lib.es2015.proxy.d.ts": {
         "version": "55479865087",
@@ -142,8 +142,8 @@ exports.__esModule = true;
         "signature": "232404497324"
       },
       "../../../.ts/lib.es2015.promise.d.ts": {
-        "version": "235321148269",
-        "signature": "235321148269"
+        "version": "17314103363",
+        "signature": "17314103363"
       },
       "../../../.ts/lib.es2015.proxy.d.ts": {
         "version": "55479865087",
@@ -265,8 +265,8 @@ exports.getVar = getVar;
         "signature": "232404497324"
       },
       "../../../.ts/lib.es2015.promise.d.ts": {
-        "version": "235321148269",
-        "signature": "235321148269"
+        "version": "17314103363",
+        "signature": "17314103363"
       },
       "../../../.ts/lib.es2015.proxy.d.ts": {
         "version": "55479865087",