Regression test

Closes phpstan/phpstan#10353

Author: ondrejmirtes

tests/PHPStan/Rules/Classes/ImpossibleInstanceOfRuleTest.php

@@ -546,6 +546,12 @@ public function testBug10036(): void
 		]);
 	}
 
+	public function testBug10353(): void
+	{
+		$this->treatPhpDocTypesAsCertain = true;
+		$this->analyse([__DIR__ . '/data/bug-10353.php'], []);
+	}
+
 	public function testBug12267(): void
 	{
 		$this->treatPhpDocTypesAsCertain = true;

tests/PHPStan/Rules/Classes/data/bug-10353.php

@@ -0,0 +1,37 @@
+<?php declare(strict_types = 1);
+
+namespace Bug10353;
+
+trait Foo
+{
+	public function test(): string
+	{
+		if ($this instanceof HelloWorld) {
+			return 'hello world';
+		}
+		if ($this instanceof OtherClass) {
+			return 'other class';
+		}
+		throw new \Error();
+	}
+}
+
+class HelloWorld
+{
+	use Foo;
+
+	function bar(): string
+	{
+		return $this->test();
+	}
+}
+
+class OtherClass
+{
+	use Foo;
+
+	function bar(): string
+	{
+		return $this->test();
+	}
+}