Consistently use $this->filter->isFile().

Author: sebastianbergmann

PHP/CodeCoverage.php

@@ -538,7 +538,7 @@ protected function applyListsFilter(&$data)
     protected function applyIgnoredLinesFilter(&$data)
     {
         foreach (array_keys($data) as $filename) {
-            if (!is_file($filename)) {
+            if (!$this->filter->isFile($filename)) {
                 continue;
             }