Fix BooleanNot false positive for $this-dependent checks in traits

When ImpossibleCheckTypeHelper returns null (uncertain) for trait+$this
function calls, ConstantConditionRuleHelper fell through to scope type
resolution which still gave a definitive answer. This caused
BooleanNotConstantConditionRule to report "always false" for negated
type checks like `! is_string($this->message)` in traits.

The fix skips function calls with $this-dependent arguments in trait
context in ConstantConditionRuleHelper::shouldSkip(), consistent with
how ImpossibleCheckTypeHelper already handles these cases.

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

Author: phpstan-bot

src/Rules/Comparison/ConstantConditionRuleHelper.php

@@ -61,6 +61,14 @@ private function shouldSkip(Scope $scope, Expr $expr): bool
 			if ($isAlways !== null) {
 				return true;
 			}
+
+			if ($scope->isInTrait()) {
+				foreach ($expr->getArgs() as $arg) {
+					if (ImpossibleCheckTypeHelper::isExpressionDependentOnThis($arg->value)) {
+						return true;
+					}
+				}
+			}
 		}
 
 		return false;

src/Rules/Comparison/ImpossibleCheckTypeHelper.php

@@ -391,7 +391,7 @@ private static function isSpecified(Scope $scope, Expr $node, Expr $expr): bool
 		) && $scope->hasExpressionType($expr)->yes();
 	}
 
-	private static function isExpressionDependentOnThis(Expr $expr): bool
+	public static function isExpressionDependentOnThis(Expr $expr): bool
 	{
 		if ($expr instanceof Expr\Variable && $expr->name === 'this') {
 			return true;

tests/PHPStan/Rules/Comparison/BooleanNotConstantConditionRuleTest.php

@@ -236,4 +236,10 @@ public function testBug6702(): void
 		$this->analyse([__DIR__ . '/data/bug-6702.php'], []);
 	}
 
+	public function testBug13023(): void
+	{
+		$this->treatPhpDocTypesAsCertain = true;
+		$this->analyse([__DIR__ . '/data/bug-13023.php'], []);
+	}
+
 }

tests/PHPStan/Rules/Comparison/data/bug-13023.php

@@ -110,3 +110,59 @@ public function getRandom(): int
 		return $value;
 	}
 }
+
+class HelloWorld
+{
+	use SomeTrait;
+
+	public string $message = 'Hello';
+
+	public function foo(): void
+	{
+		$this->bar();
+	}
+}
+
+class EmptyClass {
+	use SomeTrait;
+}
+
+trait SomeTrait {
+	public function bar(): void
+	{
+		if (property_exists($this, 'message')) {
+			if (! is_string($this->message)) {
+				return;
+			}
+
+			echo $this->message . "\n";
+		}
+	}
+}
+
+class SomeClass9
+{
+	use MyTrait5;
+
+	public string $prop = 'foo';
+}
+
+class SomeClass10
+{
+	use MyTrait5;
+
+	public int $prop = 1;
+}
+
+trait MyTrait5
+{
+	public function getRandom(): int
+	{
+		$value = random_int(1, 100);
+		if (!\is_int($this->prop)) {
+			return $value;
+		}
+
+		return $value * $value;
+	}
+}