Better typings for Promise executor, like #31117

Author: jablko

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

src/lib/es5.d.ts

@@ -1378,7 +1378,7 @@ declare type PropertyDecorator = (target: Object, propertyKey: string | symbol)
 declare type MethodDecorator = <T>(target: Object, propertyKey: string | symbol, descriptor: TypedPropertyDescriptor<T>) => TypedPropertyDescriptor<T> | void;
 declare type ParameterDecorator = (target: Object, propertyKey: string | symbol, parameterIndex: number) => void;
 
-declare type PromiseConstructorLike = new <T>(executor: (resolve: (value?: T | PromiseLike<T>) => void, reject: (reason?: any) => void) => void) => PromiseLike<T>;
+declare type PromiseConstructorLike = new <T>(executor: (resolve: (value?: T) => void, reject: (reason?: any) => void) => void) => PromiseLike<T extends PromiseLike<infer U> ? U : T>;
 
 interface PromiseLike<T> {
     /**

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 {

tests/baselines/reference/asyncFunctionDeclaration15_es5.errors.txt

@@ -5,7 +5,7 @@ tests/cases/conformance/async/es5/functionDeclarations/asyncFunctionDeclaration1
 tests/cases/conformance/async/es5/functionDeclarations/asyncFunctionDeclaration15_es5.ts(8,23): error TS2355: A function whose declared type is neither 'void' nor 'any' must return a value.
 tests/cases/conformance/async/es5/functionDeclarations/asyncFunctionDeclaration15_es5.ts(9,23): error TS1055: Type 'PromiseLike' 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/asyncFunctionDeclaration15_es5.ts(10,23): error TS1055: Type 'typeof Thenable' is not a valid async function return type in ES5/ES3 because it does not refer to a Promise-compatible constructor value.
-  Construct signature return types 'Thenable' and 'PromiseLike<T>' are incompatible.
+  Construct signature return types 'Thenable' and 'PromiseLike<T extends PromiseLike<infer U> ? U : T>' are incompatible.
     The types returned by 'then(...)' are incompatible between these types.
       Type 'void' is not assignable to type 'PromiseLike<TResult1 | TResult2>'.
 tests/cases/conformance/async/es5/functionDeclarations/asyncFunctionDeclaration15_es5.ts(17,16): error TS1058: The return type of an async function must either be a valid promise or must not contain a callable 'then' member.
@@ -37,7 +37,7 @@ tests/cases/conformance/async/es5/functionDeclarations/asyncFunctionDeclaration1
     async function fn6(): Thenable { } // error
                           ~~~~~~~~
 !!! error TS1055: Type 'typeof Thenable' is not a valid async function return type in ES5/ES3 because it does not refer to a Promise-compatible constructor value.
-!!! error TS1055:   Construct signature return types 'Thenable' and 'PromiseLike<T>' are incompatible.
+!!! error TS1055:   Construct signature return types 'Thenable' and 'PromiseLike<T extends PromiseLike<infer U> ? U : T>' are incompatible.
 !!! error TS1055:     The types returned by 'then(...)' are incompatible between these types.
 !!! error TS1055:       Type 'void' is not assignable to type 'PromiseLike<TResult1 | TResult2>'.
     async function fn7() { return; } // valid: Promise<void>

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";

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";

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>
     }
 }
 

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>
     }
 }
 

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"

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"

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[]
 
       });