use correct class for RecursiveDirectoryIterator

That was one hell of a bug. They overwrote a subclass and expected the overwriting to stay when it created a new copy.

hphp/system/php/spl/iterators/RecursiveDirectoryIterator.php

@@ -75,7 +75,7 @@ class RecursiveDirectoryIterator extends FilesystemIterator
     if ($this->getFlags() & FilesystemIterator::CURRENT_AS_PATHNAME) {
       return $this->current();
     }
-    $child = new self($this->getPathname(), $this->getFlags());
+    $child = new static($this->getPathname(), $this->getFlags());
     $child->subPath = $this->subPath;
     if ($child->subPath) {
       $child->subPath .= DIRECTORY_SEPARATOR;

hphp/test/slow/ext_iterator/RecursiveDirectoryIterator_keep_class.php

@@ -0,0 +1,19 @@
+<?php
+
+class A extends RecursiveDirectoryIterator {
+  public function current() {
+    return 'a';
+  }
+}
+
+function main() {
+
+  $it = new RecursiveIteratorIterator(
+    new A(__DIR__.'/../../sample_dir/'), RecursiveIteratorIterator::SELF_FIRST
+  );
+
+  foreach ($it as $a) {
+    var_dump($a);
+  }
+}
+main();

hphp/test/slow/ext_iterator/RecursiveDirectoryIterator_keep_class.php.expect

@@ -0,0 +1,6 @@
+string(1) "a"
+string(1) "a"
+string(1) "a"
+string(1) "a"
+string(1) "a"
+string(1) "a"