add generics

Author: Warxcell

src/Executor/Promise/Promise.php

@@ -2,13 +2,14 @@
 
 namespace GraphQL\Executor\Promise;
 
-use Amp\Promise as AmpPromise;
 use GraphQL\Error\InvariantViolation;
 use GraphQL\Executor\Promise\Adapter\SyncPromise;
 use React\Promise\PromiseInterface as ReactPromise;
+use Throwable;
 
 /**
  * Convenience wrapper for promises represented by Promise Adapter.
+ * @template T
  */
 class Promise
 {
@@ -30,6 +31,11 @@ public function __construct($adoptedPromise, PromiseAdapter $adapter)
         $this->adapter = $adapter;
     }
 
+    /**
+     * @param Closure(T):mixed $onfulfilled
+     * @param Closure(Throwable):mixed $onRejected
+     * @return Promise<T>
+     */
     public function then(?callable $onFulfilled = null, ?callable $onRejected = null): Promise
     {
         return $this->adapter->then($this, $onFulfilled, $onRejected);