bug #34091 [Debug] work around failing chdir() on Darwin (mary2501)

This PR was merged into the 4.3 branch.

Discussion
----------

[Debug] work around failing chdir() on Darwin

| Q             | A
| ------------- | ---
| Branch?       |  4.3 for bug fixes <!-- see below -->
| Bug fix?      | yes
| New feature?  | no <!-- please update src/**/CHANGELOG.md files -->
| Deprecations? | no <!-- please update UPGRADE-*.md and src/**/CHANGELOG.md files -->
| Tickets       | Fix https://github.com/happybottoms/coverd/issues/15 <!-- prefix each issue number with "Fix #", if any -->
| License       | MIT
| Doc PR        | symfony/symfony-docs#... <!-- required for new features -->
<!--
Replace this notice by a short README for your feature/bugfix. This will help people
understand your PR and can be used as a start for the documentation.

Additionally (see https://symfony.com/roadmap):
 - Always add tests and ensure they pass.
 - Never break backward compatibility (see https://symfony.com/bc).
 - Bug fixes must be submitted against the lowest maintained branch where they apply
   (lowest branches are regularly merged to upper ones so they get the fixes too.)
 - Features and deprecations must be submitted against branch 4.4.
 - Legacy code removals go to the master branch.
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Commits
-------

f40373eb7c [Debug] work around failing chdir() on Darwin

DebugClassLoader.php

@@ -455,7 +455,11 @@ class DebugClassLoader
                 $real = self::$darwinCache[$kDir][0];
             } else {
                 $dir = getcwd();
-                chdir($real);
+
+                if (!@chdir($real)) {
+                    return $real.$file;
+                }
+
                 $real = getcwd().'/';
                 chdir($dir);
 
@@ -482,7 +486,7 @@ class DebugClassLoader
         }
 
         if (isset($dirFiles[$file])) {
-            return $real .= $dirFiles[$file];
+            return $real.$dirFiles[$file];
         }
 
         $kFile = strtolower($file);
@@ -501,7 +505,7 @@ class DebugClassLoader
             self::$darwinCache[$kDir][1] = $dirFiles;
         }
 
-        return $real .= $dirFiles[$kFile];
+        return $real.$dirFiles[$kFile];
     }
 
     /**

Tests/Exception/FlattenExceptionTest.php

@@ -294,7 +294,7 @@ class FlattenExceptionTest extends TestCase
 
         // assertEquals() does not like NAN values.
         $this->assertEquals($array[$i][0], 'float');
-        $this->assertNan($array[$i++][1]);
+        $this->assertNan($array[$i][1]);
     }
 
     public function testRecursionInArguments()