Add a test for invokable objects.

Author: Crell

Zend/tests/closure_composition/invokable.phpt

@@ -0,0 +1,27 @@
+--TEST--
+Invokable objects may be composed
+--FILE--
+<?php
+
+class Times {
+    public function __construct(private int $x) {}
+
+    public function __invoke(int $y): int
+    {
+        return $this->x * $y;
+    }
+}
+
+function double(int $x): int {
+    return $x * 2;
+}
+
+$cb1 = double(...) + new Times(3);
+var_dump($cb1(4));
+
+$cb2 = new Times(3) + double(...);
+var_dump($cb2(4));
+
+--EXPECT--
+int(24)
+int(24)