Regression test

Closes phpstan/phpstan#7789

Author: ondrejmirtes

tests/PHPStan/Rules/Properties/TypesAssignedToPropertiesRuleTest.php

@@ -514,4 +514,10 @@ public function testBug3311b(): void
 		]);
 	}
 
+	public function testBug7789(): void
+	{
+		$this->checkExplicitMixed = true;
+		$this->analyse([__DIR__ . '/data/bug-7789.php'], []);
+	}
+
 }

tests/PHPStan/Rules/Properties/data/bug-7789.php

@@ -0,0 +1,14 @@
+<?php
+
+namespace Bug7789;
+
+class HelloWorld
+{
+	/** @var '"'|'\'' */
+	public static $u;
+}
+
+function (): void {
+	HelloWorld::$u = '"';
+	HelloWorld::$u = '\'';
+};