Better typings for Promise.all(), etc. like #31117

Author: jablko

src/lib/es2015.promise.d.ts

@@ -1,3 +1,5 @@
+type Awaited<T> = T extends PromiseLike<infer U> ? U : T;
+
 interface PromiseConstructor {
     /**
      * A reference to the prototype.
@@ -10,103 +12,95 @@ 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<Awaited<T>>;
 
     /**
      * Creates a Promise that is resolved with an array of results when all of the provided Promises
      * resolve, or rejected when any Promise is rejected.
      * @param values An array of Promises.
      * @returns A new Promise.
      */
-    all<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10>(values: readonly [T1 | PromiseLike<T1>, T2 | PromiseLike<T2>, T3 | PromiseLike<T3>, T4 | PromiseLike <T4>, T5 | PromiseLike<T5>, T6 | PromiseLike<T6>, T7 | PromiseLike<T7>, T8 | PromiseLike<T8>, T9 | PromiseLike<T9>, T10 | PromiseLike<T10>]): Promise<[T1, T2, T3, T4, T5, T6, T7, T8, T9, T10]>;
+    all<T extends [any, any, any, any, any, any, any, any, any, any]>(values: T): Promise<{ -readonly [P in keyof T]: Awaited<T[P]> }>;
 
     /**
      * Creates a Promise that is resolved with an array of results when all of the provided Promises
      * resolve, or rejected when any Promise is rejected.
      * @param values An array of Promises.
      * @returns A new Promise.
      */
-    all<T1, T2, T3, T4, T5, T6, T7, T8, T9>(values: readonly [T1 | PromiseLike<T1>, T2 | PromiseLike<T2>, T3 | PromiseLike<T3>, T4 | PromiseLike <T4>, T5 | PromiseLike<T5>, T6 | PromiseLike<T6>, T7 | PromiseLike<T7>, T8 | PromiseLike<T8>, T9 | PromiseLike<T9>]): Promise<[T1, T2, T3, T4, T5, T6, T7, T8, T9]>;
+    all<T extends [any, any, any, any, any, any, any, any, any]>(values: T): Promise<{ -readonly [P in keyof T]: Awaited<T[P]> }>;
 
     /**
      * Creates a Promise that is resolved with an array of results when all of the provided Promises
      * resolve, or rejected when any Promise is rejected.
      * @param values An array of Promises.
      * @returns A new Promise.
      */
-    all<T1, T2, T3, T4, T5, T6, T7, T8>(values: readonly [T1 | PromiseLike<T1>, T2 | PromiseLike<T2>, T3 | PromiseLike<T3>, T4 | PromiseLike <T4>, T5 | PromiseLike<T5>, T6 | PromiseLike<T6>, T7 | PromiseLike<T7>, T8 | PromiseLike<T8>]): Promise<[T1, T2, T3, T4, T5, T6, T7, T8]>;
+    all<T extends [any, any, any, any, any, any, any, any]>(values: T): Promise<{ -readonly [P in keyof T]: Awaited<T[P]> }>;
 
     /**
      * Creates a Promise that is resolved with an array of results when all of the provided Promises
      * resolve, or rejected when any Promise is rejected.
      * @param values An array of Promises.
      * @returns A new Promise.
      */
-    all<T1, T2, T3, T4, T5, T6, T7>(values: readonly [T1 | PromiseLike<T1>, T2 | PromiseLike<T2>, T3 | PromiseLike<T3>, T4 | PromiseLike <T4>, T5 | PromiseLike<T5>, T6 | PromiseLike<T6>, T7 | PromiseLike<T7>]): Promise<[T1, T2, T3, T4, T5, T6, T7]>;
+    all<T extends [any, any, any, any, any, any, any]>(values: T): Promise<{ -readonly [P in keyof T]: Awaited<T[P]> }>;
 
     /**
      * Creates a Promise that is resolved with an array of results when all of the provided Promises
      * resolve, or rejected when any Promise is rejected.
      * @param values An array of Promises.
      * @returns A new Promise.
      */
-    all<T1, T2, T3, T4, T5, T6>(values: readonly [T1 | PromiseLike<T1>, T2 | PromiseLike<T2>, T3 | PromiseLike<T3>, T4 | PromiseLike <T4>, T5 | PromiseLike<T5>, T6 | PromiseLike<T6>]): Promise<[T1, T2, T3, T4, T5, T6]>;
+    all<T extends [any, any, any, any, any, any]>(values: T): Promise<{ -readonly [P in keyof T]: Awaited<T[P]> }>;
 
     /**
      * Creates a Promise that is resolved with an array of results when all of the provided Promises
      * resolve, or rejected when any Promise is rejected.
      * @param values An array of Promises.
      * @returns A new Promise.
      */
-    all<T1, T2, T3, T4, T5>(values: readonly [T1 | PromiseLike<T1>, T2 | PromiseLike<T2>, T3 | PromiseLike<T3>, T4 | PromiseLike <T4>, T5 | PromiseLike<T5>]): Promise<[T1, T2, T3, T4, T5]>;
+    all<T extends [any, any, any, any, any]>(values: T): Promise<{ -readonly [P in keyof T]: Awaited<T[P]> }>;
 
     /**
      * Creates a Promise that is resolved with an array of results when all of the provided Promises
      * resolve, or rejected when any Promise is rejected.
      * @param values An array of Promises.
      * @returns A new Promise.
      */
-    all<T1, T2, T3, T4>(values: readonly [T1 | PromiseLike<T1>, T2 | PromiseLike<T2>, T3 | PromiseLike<T3>, T4 | PromiseLike <T4>]): Promise<[T1, T2, T3, T4]>;
+    all<T extends [any, any, any, any]>(values: T): Promise<{ -readonly [P in keyof T]: Awaited<T[P]> }>;
 
     /**
      * Creates a Promise that is resolved with an array of results when all of the provided Promises
      * resolve, or rejected when any Promise is rejected.
      * @param values An array of Promises.
      * @returns A new Promise.
      */
-    all<T1, T2, T3>(values: readonly [T1 | PromiseLike<T1>, T2 | PromiseLike<T2>, T3 | PromiseLike<T3>]): Promise<[T1, T2, T3]>;
+    all<T extends [any, any, any]>(values: T): Promise<{ -readonly [P in keyof T]: Awaited<T[P]> }>;
 
     /**
      * Creates a Promise that is resolved with an array of results when all of the provided Promises
      * resolve, or rejected when any Promise is rejected.
      * @param values An array of Promises.
      * @returns A new Promise.
      */
-    all<T1, T2>(values: readonly [T1 | PromiseLike<T1>, T2 | PromiseLike<T2>]): Promise<[T1, T2]>;
+    all<T extends [any, any]>(values: T): Promise<{ -readonly [P in keyof T]: Awaited<T[P]> }>;
 
     /**
      * Creates a Promise that is resolved with an array of results when all of the provided Promises
      * resolve, or rejected when any Promise is rejected.
      * @param values An array of Promises.
      * @returns A new Promise.
      */
-    all<T>(values: readonly (T | PromiseLike<T>)[]): Promise<T[]>;
-
-    /**
-     * Creates a Promise that is resolved or rejected when any of the provided Promises are resolved
-     * or rejected.
-     * @param values An array of Promises.
-     * @returns A new Promise.
-     */
-    race<T>(values: readonly T[]): Promise<T extends PromiseLike<infer U> ? U : T>;
+    all<T extends readonly any[]>(values: T): Promise<{ -readonly [P in keyof T]: Awaited<T[P]> }>;
 
     /**
      * Creates a Promise that is resolved or rejected when any of the provided Promises are resolved
      * or rejected.
      * @param values An iterable of Promises.
      * @returns A new Promise.
      */
-    race<T>(values: Iterable<T>): Promise<T extends PromiseLike<infer U> ? U : T>;
+    race<T>(values: Iterable<T>): Promise<Awaited<T>>;
 
     /**
      * Creates a new rejected promise for the provided reason.
@@ -120,10 +114,10 @@ interface PromiseConstructor {
      * @param value A promise.
      * @returns A promise whose internal state matches the provided promise.
      */
-    resolve<T>(value: T | PromiseLike<T>): Promise<T>;
+    resolve<T>(value: T): Promise<Awaited<T>>;
 
     /**
-     * Creates a new resolved promise .
+     * Creates a new resolved promise.
      * @returns A resolved promise.
      */
     resolve(): Promise<void>;