Add test for trait behavior

Author: nikic

Zend/tests/constexpr/trait_evaluation.phpt

@@ -0,0 +1,29 @@
+--TEST--
+Initializers in traits should not be eagerly evaluated
+--FILE--
+<?php
+
+class Order {
+    public function __construct(string $class, int $i) {
+        echo "Creating $class($i)\n";
+    }
+}
+
+trait T {
+    public static $s = new Order(self::class, 1);
+    public $p = new Order(self::class, 2);
+}
+
+class C {
+    use T;
+}
+new C;
+
+// Lazy-evaluate illegal direct trait access.
+T::$s;
+
+?>
+--EXPECT--
+Creating C(1)
+Creating C(2)
+Creating T(1)