Added regression test

Author: staabm

tests/PHPStan/Analyser/nsrt/bug-5207b.php

@@ -0,0 +1,20 @@
+<?php // lint >= 8.0
+
+declare(strict_types = 1);
+
+namespace Bug5207b;
+
+use function PHPStan\Testing\assertType;
+
+abstract class HelloWorld {
+	abstract public function getChild(): ?HelloWorld;
+
+	public function sayHello(): void {
+		$foo = null !== $this->getChild()->getChild();
+		if ($foo) {
+			assertType('Bug5207\HelloWorld', $this->getChild());
+			assertType('Bug5207\HelloWorld', $this->getChild()->getChild());
+			assertType('Bug5207b\HelloWorld|null', $this->getChild()->getChild()->getChild());
+		}
+	}
+}