Add impure method tests to verify type narrowing is not applied

Addresses review feedback: adds test cases with @phpstan-impure methods
to both bug-9455 and bug-5207 regression tests, asserting that impure
method results are correctly NOT narrowed when stored in boolean variables.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: phpstan-bot

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

@@ -22,3 +22,23 @@ public function sayHelloInline(): void {
 		}
 	}
 }
+
+abstract class ImpureWorld {
+	/**
+	 * @phpstan-impure
+	 */
+	abstract public function getChild(): ?ImpureWorld;
+
+	public function sayHello(): void {
+		$foo = null !== $this->getChild();
+		if ($foo) {
+			assertType('Bug5207\ImpureWorld|null', $this->getChild());
+		}
+	}
+
+	public function sayHelloInline(): void {
+		if (null !== $this->getChild()) {
+			assertType('Bug5207\ImpureWorld|null', $this->getChild());
+		}
+	}
+}

tests/PHPStan/Analyser/nsrt/bug-9455.php

@@ -50,3 +50,35 @@ public function testSucceeds(): void
 		}
 	}
 }
+
+class C {
+	/**
+	 * @phpstan-impure
+	 */
+	public function getA(): ?A {
+		return rand(0, 1) ? new A(1) : null;
+	}
+}
+
+class ImpureTest
+{
+	public function testImpureMethodNotNarrowed(): void
+	{
+		$c = new C();
+
+		$hasA = $c->getA() !== null;
+
+		if($hasA) {
+			assertType('Bug9455\A|null', $c->getA());
+		}
+	}
+
+	public function testImpureMethodInline(): void
+	{
+		$c = new C();
+
+		if($c->getA() !== null) {
+			assertType('Bug9455\A|null', $c->getA());
+		}
+	}
+}