Update MutatingScope.php

Author: staabm

Diff for: src/Analyser/MutatingScope.php

@@ -4382,7 +4382,7 @@ private function shouldInvalidateExpression(string $exprStringToInvalidate, Expr
 			if (
 				$exprStringToInvalidate === '$this'
 				&& $node instanceof Name
-				&& in_array($node->name, ['self', 'static', 'parent'], true)
+				&& in_array($node->toLowerString(), ['self', 'static', 'parent'], true)
 			) {
 				return true;
 			}