microsoft · rbuckton · Oct 6, 2015 · Oct 6, 2015
diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
@@ -2209,7 +2209,7 @@ namespace ts {
 
         /**
          * Push an entry on the type resolution stack. If an entry with the given target and the given property name
-         * is already on the stack, and no entries in between already have a type, then a circularity has occurred. 
+         * is already on the stack, and no entries in between already have a type, then a circularity has occurred.
          * In this case, the result values of the existing entry and all entries pushed after it are changed to false,
          * and the value false is returned. Otherwise, the new entry is just pushed onto the stack, and true is returned.
          * In order to see if the same query has already been done before, the target object and the propertyName both
@@ -5243,7 +5243,7 @@ namespace ts {
                     // Only want to compare the construct signatures for abstractness guarantees.
 
                     // Because the "abstractness" of a class is the same across all construct signatures
-                    // (internally we are checking the corresponding declaration), it is enough to perform 
+                    // (internally we are checking the corresponding declaration), it is enough to perform
                     // the check and report an error once over all pairs of source and target construct signatures.
                     //
                     // sourceSig and targetSig are (possibly) undefined.
@@ -6642,7 +6642,7 @@ namespace ts {
             let needToCaptureLexicalThis = false;
 
             if (!isCallExpression) {
-                // adjust the container reference in case if super is used inside arrow functions with arbitrary deep nesting                                    
+                // adjust the container reference in case if super is used inside arrow functions with arbitrary deep nesting
                 while (container && container.kind === SyntaxKind.ArrowFunction) {
                     container = getSuperContainer(container, /*includeFunctions*/ true);
                     needToCaptureLexicalThis = languageVersion < ScriptTarget.ES6;
@@ -6652,7 +6652,7 @@ namespace ts {
             let canUseSuperExpression = isLegalUsageOfSuperExpression(container);
             let nodeCheckFlag: NodeCheckFlags = 0;
 
-            // always set NodeCheckFlags for 'super' expression node            
+            // always set NodeCheckFlags for 'super' expression node
             if (canUseSuperExpression) {
                 if ((container.flags & NodeFlags.Static) || isCallExpression) {
                     nodeCheckFlag = NodeCheckFlags.SuperStatic;
@@ -8568,7 +8568,7 @@ namespace ts {
                         // A method or accessor declaration decorator will have two or three arguments (see
                         // `PropertyDecorator` and `MethodDecorator` in core.d.ts)
 
-                        // If we are emitting decorators for ES3, we will only pass two arguments. 
+                        // If we are emitting decorators for ES3, we will only pass two arguments.
                         if (languageVersion === ScriptTarget.ES3) {
                             return 2;
                         }
@@ -11306,7 +11306,8 @@ namespace ts {
         }
 
         function checkNonThenableType(type: Type, location?: Node, message?: DiagnosticMessage) {
-            if (!(type.flags & TypeFlags.Any) && isTypeAssignableTo(type, getGlobalThenableType())) {
+            type = getWidenedType(type);
+            if (!isTypeAny(type) && isTypeAssignableTo(type, getGlobalThenableType())) {
                 if (location) {
                     if (!message) {
                         message = Diagnostics.Operand_for_await_does_not_have_a_valid_callable_then_member;
@@ -12544,7 +12545,12 @@ namespace ts {
                         if (isAsyncFunctionLike(func)) {
                             let promisedType = getPromisedType(returnType);
                             let awaitedType = checkAwaitedType(exprType, node.expression, Diagnostics.Return_expression_in_async_function_does_not_have_a_valid_callable_then_member);
-                            checkTypeAssignableTo(awaitedType, promisedType, node.expression);
+                            if (promisedType) {
+                                // If the function has a return type, but promisedType is
+                                // undefined, an error will be reported in checkAsyncFunctionReturnType
+                                // so we don't need to report one here.
+                                checkTypeAssignableTo(awaitedType, promisedType, node.expression);
+                            }
                         }
                         else {
                             checkTypeAssignableTo(exprType, returnType, node.expression);
@@ -13154,13 +13160,13 @@ namespace ts {
                         autoValue = computeConstantValueForEnumMemberInitializer(initializer, enumType, enumIsConst, ambient);
                     }
                     else if (ambient && !enumIsConst) {
-                        // In ambient enum declarations that specify no const modifier, enum member declarations 
+                        // In ambient enum declarations that specify no const modifier, enum member declarations
                         // that omit a value are considered computed members (as opposed to having auto-incremented values assigned).
                         autoValue = undefined;
                     }
                     else if (previousEnumMemberIsNonConstant) {
-                        // If the member declaration specifies no value, the member is considered a constant enum member. 
-                        // If the member is the first member in the enum declaration, it is assigned the value zero. 
+                        // If the member declaration specifies no value, the member is considered a constant enum member.
+                        // If the member is the first member in the enum declaration, it is assigned the value zero.
                         // Otherwise, it is assigned the value of the immediately preceding member plus one,
                         // and an error occurs if the immediately preceding member is not a constant enum member
                         error(member.name, Diagnostics.Enum_member_must_have_initializer);
@@ -14100,7 +14106,7 @@ namespace ts {
                         case SyntaxKind.ClassDeclaration:
                         case SyntaxKind.InterfaceDeclaration:
                             // If we didn't come from static member of class or interface,
-                            // add the type parameters into the symbol table 
+                            // add the type parameters into the symbol table
                             // (type parameters of classDeclaration/classExpression and interface are in member property of the symbol.
                             // Note: that the memberFlags come from previous iteration.
                             if (!(memberFlags & NodeFlags.Static)) {

diff --git a/tests/baselines/reference/asyncFunctionDeclaration15_es6.errors.txt b/tests/baselines/reference/asyncFunctionDeclaration15_es6.errors.txt
@@ -0,0 +1,56 @@
+tests/cases/conformance/async/es6/functionDeclarations/asyncFunctionDeclaration15_es6.ts(6,16): error TS1055: Type '{}' is not a valid async function return type.
+tests/cases/conformance/async/es6/functionDeclarations/asyncFunctionDeclaration15_es6.ts(7,16): error TS1055: Type 'any' is not a valid async function return type.
+tests/cases/conformance/async/es6/functionDeclarations/asyncFunctionDeclaration15_es6.ts(8,16): error TS1055: Type 'number' is not a valid async function return type.
+tests/cases/conformance/async/es6/functionDeclarations/asyncFunctionDeclaration15_es6.ts(9,16): error TS1055: Type 'PromiseLike<void>' is not a valid async function return type.
+tests/cases/conformance/async/es6/functionDeclarations/asyncFunctionDeclaration15_es6.ts(10,16): error TS1055: Type 'typeof Thenable' is not a valid async function return type.
+  Type 'Thenable' is not assignable to type 'PromiseLike<any>'.
+    Types of property 'then' are incompatible.
+      Type '() => void' is not assignable to type '{ <TResult>(onfulfilled?: (value: any) => TResult | PromiseLike<TResult>, onrejected?: (reason: any) => TResult | PromiseLike<TResult>): PromiseLike<TResult>; <TResult>(onfulfilled?: (value: any) => TResult | PromiseLike<TResult>, onrejected?: (reason: any) => void): PromiseLike<TResult>; }'.
+        Type 'void' is not assignable to type 'PromiseLike<any>'.
+tests/cases/conformance/async/es6/functionDeclarations/asyncFunctionDeclaration15_es6.ts(17,16): error TS1059: Return expression in async function does not have a valid callable 'then' member.
+tests/cases/conformance/async/es6/functionDeclarations/asyncFunctionDeclaration15_es6.ts(23,25): error TS1058: Operand for 'await' does not have a valid callable 'then' member.
+
+
+==== tests/cases/conformance/async/es6/functionDeclarations/asyncFunctionDeclaration15_es6.ts (7 errors) ====
+    declare class Thenable { then(): void; }
+    declare let a: any;
+    declare let obj: { then: string; };
+    declare let thenable: Thenable;
+    async function fn1() { } // valid: Promise<void>
+    async function fn2(): { } { } // error
+                   ~~~
+!!! error TS1055: Type '{}' is not a valid async function return type.
+    async function fn3(): any { } // error
+                   ~~~
+!!! error TS1055: Type 'any' is not a valid async function return type.
+    async function fn4(): number { } // error
+                   ~~~
+!!! error TS1055: Type 'number' is not a valid async function return type.
+    async function fn5(): PromiseLike<void> { } // error
+                   ~~~
+!!! error TS1055: Type 'PromiseLike<void>' is not a valid async function return type.
+    async function fn6(): Thenable { } // error
+                   ~~~
+!!! error TS1055: Type 'typeof Thenable' is not a valid async function return type.
+!!! error TS1055:   Type 'Thenable' is not assignable to type 'PromiseLike<any>'.
+!!! error TS1055:     Types of property 'then' are incompatible.
+!!! error TS1055:       Type '() => void' is not assignable to type '{ <TResult>(onfulfilled?: (value: any) => TResult | PromiseLike<TResult>, onrejected?: (reason: any) => TResult | PromiseLike<TResult>): PromiseLike<TResult>; <TResult>(onfulfilled?: (value: any) => TResult | PromiseLike<TResult>, onrejected?: (reason: any) => void): PromiseLike<TResult>; }'.
+!!! error TS1055:         Type 'void' is not assignable to type 'PromiseLike<any>'.
+    async function fn7() { return; } // valid: Promise<void>
+    async function fn8() { return 1; } // valid: Promise<number>
+    async function fn9() { return null; } // valid: Promise<any>
+    async function fn10() { return undefined; } // valid: Promise<any>
+    async function fn11() { return a; } // valid: Promise<any>
+    async function fn12() { return obj; } // valid: Promise<{ then: string; }>
+    async function fn13() { return thenable; } // error
+                   ~~~~
+!!! error TS1059: Return expression in async function does not have a valid callable 'then' member.
+    async function fn14() { await 1; } // valid: Promise<void>
+    async function fn15() { await null; } // valid: Promise<void>
+    async function fn16() { await undefined; } // valid: Promise<void>
+    async function fn17() { await a; } // valid: Promise<void>
+    async function fn18() { await obj; } // valid: Promise<void>
+    async function fn19() { await thenable; } // error
+                            ~~~~~~~~~~~~~~
+!!! error TS1058: Operand for 'await' does not have a valid callable 'then' member.
+
diff --git a/tests/baselines/reference/asyncFunctionDeclaration15_es6.js b/tests/baselines/reference/asyncFunctionDeclaration15_es6.js
@@ -0,0 +1,84 @@
+//// [asyncFunctionDeclaration15_es6.ts]
+declare class Thenable { then(): void; }
+declare let a: any;
+declare let obj: { then: string; };
+declare let thenable: Thenable;
+async function fn1() { } // valid: Promise<void>
+async function fn2(): { } { } // error
+async function fn3(): any { } // error
+async function fn4(): number { } // error
+async function fn5(): PromiseLike<void> { } // error
+async function fn6(): Thenable { } // error
+async function fn7() { return; } // valid: Promise<void>
+async function fn8() { return 1; } // valid: Promise<number>
+async function fn9() { return null; } // valid: Promise<any>
+async function fn10() { return undefined; } // valid: Promise<any>
+async function fn11() { return a; } // valid: Promise<any>
+async function fn12() { return obj; } // valid: Promise<{ then: string; }>
+async function fn13() { return thenable; } // error
+async function fn14() { await 1; } // valid: Promise<void>
+async function fn15() { await null; } // valid: Promise<void>
+async function fn16() { await undefined; } // valid: Promise<void>
+async function fn17() { await a; } // valid: Promise<void>
+async function fn18() { await obj; } // valid: Promise<void>
+async function fn19() { await thenable; } // error
+
+
+//// [asyncFunctionDeclaration15_es6.js]
+function fn1() {
+    return __awaiter(this, void 0, Promise, function* () { });
+} // valid: Promise<void>
+function fn2() {
+    return __awaiter(this, void 0, Promise, function* () { });
+} // error
+function fn3() {
+    return __awaiter(this, void 0, Promise, function* () { });
+} // error
+function fn4() {
+    return __awaiter(this, void 0, Promise, function* () { });
+} // error
+function fn5() {
+    return __awaiter(this, void 0, PromiseLike, function* () { });
+} // error
+function fn6() {
+    return __awaiter(this, void 0, Thenable, function* () { });
+} // error
+function fn7() {
+    return __awaiter(this, void 0, Promise, function* () { return; });
+} // valid: Promise<void>
+function fn8() {
+    return __awaiter(this, void 0, Promise, function* () { return 1; });
+} // valid: Promise<number>
+function fn9() {
+    return __awaiter(this, void 0, Promise, function* () { return null; });
+} // valid: Promise<any>
+function fn10() {
+    return __awaiter(this, void 0, Promise, function* () { return undefined; });
+} // valid: Promise<any>
+function fn11() {
+    return __awaiter(this, void 0, Promise, function* () { return a; });
+} // valid: Promise<any>
+function fn12() {
+    return __awaiter(this, void 0, Promise, function* () { return obj; });
+} // valid: Promise<{ then: string; }>
+function fn13() {
+    return __awaiter(this, void 0, Promise, function* () { return thenable; });
+} // error
+function fn14() {
+    return __awaiter(this, void 0, Promise, function* () { yield 1; });
+} // valid: Promise<void>
+function fn15() {
+    return __awaiter(this, void 0, Promise, function* () { yield null; });
+} // valid: Promise<void>
+function fn16() {
+    return __awaiter(this, void 0, Promise, function* () { yield undefined; });
+} // valid: Promise<void>
+function fn17() {
+    return __awaiter(this, void 0, Promise, function* () { yield a; });
+} // valid: Promise<void>
+function fn18() {
+    return __awaiter(this, void 0, Promise, function* () { yield obj; });
+} // valid: Promise<void>
+function fn19() {
+    return __awaiter(this, void 0, Promise, function* () { yield thenable; });
+} // error
diff --git a/tests/cases/conformance/async/es6/functionDeclarations/asyncFunctionDeclaration15_es6.ts b/tests/cases/conformance/async/es6/functionDeclarations/asyncFunctionDeclaration15_es6.ts
@@ -0,0 +1,26 @@
+// @target: ES6
+// @noEmitHelpers: true
+// @experimentalAsyncFunctions: true
+declare class Thenable { then(): void; }
+declare let a: any;
+declare let obj: { then: string; };
+declare let thenable: Thenable;
+async function fn1() { } // valid: Promise<void>
+async function fn2(): { } { } // error
+async function fn3(): any { } // error
+async function fn4(): number { } // error
+async function fn5(): PromiseLike<void> { } // error
+async function fn6(): Thenable { } // error
+async function fn7() { return; } // valid: Promise<void>
+async function fn8() { return 1; } // valid: Promise<number>
+async function fn9() { return null; } // valid: Promise<any>
+async function fn10() { return undefined; } // valid: Promise<any>
+async function fn11() { return a; } // valid: Promise<any>
+async function fn12() { return obj; } // valid: Promise<{ then: string; }>
+async function fn13() { return thenable; } // error
+async function fn14() { await 1; } // valid: Promise<void>
+async function fn15() { await null; } // valid: Promise<void>
+async function fn16() { await undefined; } // valid: Promise<void>
+async function fn17() { await a; } // valid: Promise<void>
+async function fn18() { await obj; } // valid: Promise<void>
+async function fn19() { await thenable; } // error