Forward compatibility with react/promise 3

Author: WyriHaximus

composer.json

@@ -36,7 +36,7 @@
     "require": {
         "php": ">=5.3",
         "react/stream": "^1.0 || ^0.7 || ^0.6 || ^0.5 || ^0.4.6",
-        "react/promise": "^2.1 || ^1.2"
+        "react/promise": "^3 || ^2.1 || ^1.2"
     },
     "require-dev": {
         "react/event-loop": "^1.0 || ^0.5 || ^0.4 || ^0.3",

src/UnwrapReadableStream.php

@@ -126,7 +126,7 @@ public function close()
         $this->closed = true;
 
         // try to cancel promise once the stream closes
-        if ($this->promise instanceof CancellablePromiseInterface) {
+        if ($this->promise instanceof CancellablePromiseInterface  || ($this->promise !== null && method_exists($this->promise, 'cancel') && $this->promise instanceof PromiseInterface)) {
             $this->promise->cancel();
         }
         $this->promise = null;

src/UnwrapWritableStream.php

@@ -153,7 +153,7 @@ public function close()
         $this->closed = true;
 
         // try to cancel promise once the stream closes
-        if ($this->promise instanceof CancellablePromiseInterface) {
+        if ($this->promise instanceof CancellablePromiseInterface  || (method_exists($this->promise, 'cancel') && $this->promise instanceof PromiseInterface)) {
             $this->promise->cancel();
         }
         $this->promise = $this->stream = null;