Weaken the definition of PromiseLike to allow 'T | awaited T'

Author: rbuckton

src/lib/es5.d.ts

@@ -1378,20 +1378,25 @@ 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> | awaited T) => void, reject: (reason?: any) => void) => void) => PromiseLike<T>;
+declare type PromiseConstructorLike = new <T>(executor: (resolve: (value?: T | PromiseLike<T>) => void, reject: (reason?: any) => void) => void) => PromiseLike<T>;
 
+/**
+ * A "Promise-like" is an object that has a callable `then` method that accepts fulfillment and rejection handlers.
+ * A "Promise-like" implementation may or may not be compatible with native ES2015 or Promise/A+, but provides a similar-
+ * enough implementation that a native of Promise/A+ -compatible promise implementation could adopt its result.
+ */
 interface PromiseLike<T> {
     /**
      * Attaches callbacks for the resolution and/or rejection of the Promise.
      * @param onfulfilled The callback to execute when the Promise is resolved.
      * @param onrejected The callback to execute when the Promise is rejected.
      * @returns A Promise for the completion of which ever callback is executed.
      */
-    then<TResult1 = T, TResult2 = never>(onfulfilled?: ((value: awaited T) => TResult1 | PromiseLike<TResult1>) | undefined | null, onrejected?: ((reason: any) => TResult2 | PromiseLike<TResult2>) | undefined | null): PromiseLike<awaited TResult1 | awaited TResult2>;
+    then<TResult1 = T, TResult2 = never>(onfulfilled?: ((value: T | awaited T) => TResult1 | PromiseLike<TResult1>) | undefined | null, onrejected?: ((reason: any) => TResult2 | PromiseLike<TResult2>) | undefined | null): PromiseLike<TResult1 | TResult2>;
 }
 
 /**
- * Represents the completion of an asynchronous operation
+ * Represents the completion of an asynchronous operation.
  */
 interface Promise<T> {
     /**

tests/baselines/reference/asyncFunctionDeclaration15_es5.errors.txt

@@ -7,7 +7,7 @@ tests/cases/conformance/async/es5/functionDeclarations/asyncFunctionDeclaration1
 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.
     The types returned by 'then(...)' are incompatible between these types.
-      Type 'void' is not assignable to type 'PromiseLike<awaited TResult1 | awaited TResult2>'.
+      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.
 tests/cases/conformance/async/es5/functionDeclarations/asyncFunctionDeclaration15_es5.ts(23,25): error TS1320: Type of 'await' operand must either be a valid promise or must not contain a callable 'then' member.
 
@@ -39,7 +39,7 @@ tests/cases/conformance/async/es5/functionDeclarations/asyncFunctionDeclaration1
 !!! 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:     The types returned by 'then(...)' are incompatible between these types.
-!!! error TS1055:       Type 'void' is not assignable to type 'PromiseLike<awaited TResult1 | awaited TResult2>'.
+!!! error TS1055:       Type 'void' is not assignable to type 'PromiseLike<TResult1 | TResult2>'.
     async function fn7() { return; } // valid: Promise<void>
     async function fn8() { return 1; } // valid: Promise<number>
     async function fn9() { return null; } // valid: Promise<any>

tests/baselines/reference/awaitedVariance.errors.txt

@@ -1,8 +1,8 @@
-tests/cases/conformance/types/awaited/awaitedVariance.ts(74,1): error TS2322: Type 'C<Promise<number>>' is not assignable to type 'C<number>'.
+tests/cases/conformance/types/awaited/awaitedVariance.ts(58,1): error TS2322: Type 'C<Promise<number>>' is not assignable to type 'C<number>'.
   Types of property 'x' are incompatible.
     Type 'number' is not assignable to type '{ _tag: string; } & number'.
       Type 'number' is not assignable to type '{ _tag: string; }'.
-tests/cases/conformance/types/awaited/awaitedVariance.ts(84,1): error TS2322: Type 'D<Promise<number>>' is not assignable to type 'D<number>'.
+tests/cases/conformance/types/awaited/awaitedVariance.ts(68,1): error TS2322: Type 'D<Promise<number>>' is not assignable to type 'D<number>'.
   Types of property 'a' are incompatible.
     Type 'C<Promise<number>>' is not assignable to type 'C<number>'.
 
@@ -30,22 +30,6 @@ tests/cases/conformance/types/awaited/awaitedVariance.ts(84,1): error TS2322: Ty
     declare let pl0: PromiseLike<number>;
     declare let pl1: PromiseLike<PromiseLike<number>>;
     declare let pl2: PromiseLike<awaited number>;
-    pl0 = pl1;
-    pl0 = pl2;
-    pl1 = pl0;
-    pl1 = pl2;
-    pl2 = pl0;
-    pl2 = pl1;
-    
-    function fn2<T>(pl0: PromiseLike<T>, pl1: PromiseLike<PromiseLike<T>>, pl2: PromiseLike<awaited T>) {
-        pl0 = pl1;
-        pl0 = pl2;
-        pl1 = pl0;
-        pl1 = pl2;
-        pl2 = pl0;
-        pl2 = pl1;
-    }
-    
     pl0 = p0;
     pl0 = p1;
     pl0 = p2;

tests/baselines/reference/awaitedVariance.js

@@ -21,22 +21,6 @@ function fn1<T>(p0: Promise<T>, p1: Promise<Promise<T>>, p2: Promise<awaited T>)
 declare let pl0: PromiseLike<number>;
 declare let pl1: PromiseLike<PromiseLike<number>>;
 declare let pl2: PromiseLike<awaited number>;
-pl0 = pl1;
-pl0 = pl2;
-pl1 = pl0;
-pl1 = pl2;
-pl2 = pl0;
-pl2 = pl1;
-
-function fn2<T>(pl0: PromiseLike<T>, pl1: PromiseLike<PromiseLike<T>>, pl2: PromiseLike<awaited T>) {
-    pl0 = pl1;
-    pl0 = pl2;
-    pl1 = pl0;
-    pl1 = pl2;
-    pl2 = pl0;
-    pl2 = pl1;
-}
-
 pl0 = p0;
 pl0 = p1;
 pl0 = p2;
@@ -136,20 +120,6 @@ function fn1(p0, p1, p2) {
     p2 = p0;
     p2 = p1;
 }
-pl0 = pl1;
-pl0 = pl2;
-pl1 = pl0;
-pl1 = pl2;
-pl2 = pl0;
-pl2 = pl1;
-function fn2(pl0, pl1, pl2) {
-    pl0 = pl1;
-    pl0 = pl2;
-    pl1 = pl0;
-    pl1 = pl2;
-    pl2 = pl0;
-    pl2 = pl1;
-}
 pl0 = p0;
 pl0 = p1;
 pl0 = p2;