Remove unnecessary Promise.resolve and Promise.reject (#3290)

Author: IvanGoncharov

src/execution/execute.ts

@@ -368,7 +368,7 @@ function executeOperation(
     if (isPromise(result)) {
       return result.then(undefined, (error) => {
         exeContext.errors.push(error);
-        return Promise.resolve(null);
+        return null;
       });
     }
     return result;

src/execution/mapAsyncIterator.ts

@@ -43,9 +43,10 @@ export function mapAsyncIterator<T, U, R = undefined>(
         : { value: undefined as any, done: true };
     },
     async throw(error?: unknown) {
-      return typeof iterator.throw === 'function'
-        ? mapResult(await iterator.throw(error))
-        : Promise.reject(error);
+      if (typeof iterator.throw === 'function') {
+        return mapResult(await iterator.throw(error));
+      }
+      throw error;
     },
     [Symbol.asyncIterator]() {
       return this;