Use is_file() instead of file_exists() where possible

Author: nicolas-grekas

Caster/ExceptionCaster.php

@@ -212,15 +212,15 @@ public static function castFrameStub(FrameStub $frame, array $a, Stub $stub, boo
                 $ellipsisTail = isset($ellipsis->attr['ellipsis-tail']) ? $ellipsis->attr['ellipsis-tail'] : 0;
                 $ellipsis = isset($ellipsis->attr['ellipsis']) ? $ellipsis->attr['ellipsis'] : 0;
 
-                if (file_exists($f['file']) && 0 <= self::$srcContext) {
+                if (is_file($f['file']) && 0 <= self::$srcContext) {
                     if (!empty($f['class']) && (is_subclass_of($f['class'], 'Twig\Template') || is_subclass_of($f['class'], 'Twig_Template')) && method_exists($f['class'], 'getDebugInfo')) {
                         $template = isset($f['object']) ? $f['object'] : unserialize(sprintf('O:%d:"%s":0:{}', \strlen($f['class']), $f['class']));
 
                         $ellipsis = 0;
                         $templateSrc = method_exists($template, 'getSourceContext') ? $template->getSourceContext()->getCode() : (method_exists($template, 'getSource') ? $template->getSource() : '');
                         $templateInfo = $template->getDebugInfo();
                         if (isset($templateInfo[$f['line']])) {
-                            if (!method_exists($template, 'getSourceContext') || !file_exists($templatePath = $template->getSourceContext()->getPath())) {
+                            if (!method_exists($template, 'getSourceContext') || !is_file($templatePath = $template->getSourceContext()->getPath())) {
                                 $templatePath = null;
                             }
                             if ($templateSrc) {

Caster/LinkStub.php

@@ -43,7 +43,7 @@ public function __construct($label, int $line = 0, $href = null)
 
             return;
         }
-        if (!file_exists($href)) {
+        if (!is_file($href)) {
             return;
         }
         if ($line) {
@@ -72,7 +72,7 @@ private function getComposerRoot(string $file, bool &$inVendor)
                 if ('C' === $class[0] && 0 === strpos($class, 'ComposerAutoloaderInit')) {
                     $r = new \ReflectionClass($class);
                     $v = \dirname($r->getFileName(), 2);
-                    if (file_exists($v.'/composer/installed.json')) {
+                    if (is_file($v.'/composer/installed.json')) {
                         self::$vendorRoots[] = $v.\DIRECTORY_SEPARATOR;
                     }
                 }
@@ -91,7 +91,7 @@ private function getComposerRoot(string $file, bool &$inVendor)
         }
 
         $parent = $dir;
-        while (!@file_exists($parent.'/composer.json')) {
+        while (!@is_file($parent.'/composer.json')) {
             if (!@file_exists($parent)) {
                 // open_basedir restriction in effect
                 break;