Add class order test cases

The autoload case is supposed to work, but doesn't actually :(

Author: nikic

Zend/tests/type_declarations/variance/class_order.phpt

@@ -0,0 +1,19 @@
+--TEST--
+Returns are covariant, but we don't allow the code due to class ordering
+--FILE--
+<?php
+
+class A {
+    public function method() : B {}
+}
+class B extends A {
+    public function method() : C {}
+}
+class C extends B {
+}
+
+new C;
+
+?>
+--EXPECTF--
+Fatal error: Declaration of B::method(): C must be compatible with A::method(): B in %s on line %d

Zend/tests/type_declarations/variance/class_order_autoload.phpt

@@ -0,0 +1,25 @@
+--TEST--
+Returns are covariant, but we don't allow the code due to class ordering (autoload variation)
+--FILE--
+<?php
+
+spl_autoload_register(function($class) {
+    if ($class === 'A') {
+        class A {
+            public function method() : B {}
+        }
+    } else if ($class == 'B') {
+        class B extends A {
+            public function method() : C {}
+        }
+    } else {
+        class C extends B {
+        }
+    }
+});
+
+$c = new C;
+
+?>
+--EXPECTF--
+Fatal error: Declaration of B::method(): C must be compatible with A::method(): B in %s on line %d