diff --git a/src/parser/aast/api/AASTNodeList.php b/src/parser/aast/api/AASTNodeList.php
index 22c0d31..92f76f2 100644
--- a/src/parser/aast/api/AASTNodeList.php
+++ b/src/parser/aast/api/AASTNodeList.php
@@ -1,109 +1,110 @@
 <?php
 
 final class AASTNodeList
   extends Phobject
   implements Countable, Iterator {
 
   protected $list;
   protected $tree;
   protected $ids;
   protected $pos;
 
   protected function __construct() {}
 
   protected function newList(array $nodes) {
     return self::newFromTreeAndNodes($this->tree, $nodes);
   }
 
   public function selectDescendantsOfType($type_name) {
     return $this->selectDescendantsOfTypes(array($type_name));
   }
 
   public function selectDescendantsOfTypes(array $type_names) {
     $results = array();
     foreach ($type_names as $type_name) {
       foreach ($this->list as $id => $node) {
         $results += $node->selectDescendantsOfType($type_name)->getRawNodes();
       }
     }
     return $this->newList($results);
   }
 
   public function getChildrenByIndex($index) {
     $results = array();
     foreach ($this->list as $id => $node) {
       $child = $node->getChildByIndex($index);
       $results[$child->getID()] = $child;
     }
     return $this->newList($results);
   }
 
   public function add(AASTNodeList $list) {
     foreach ($list->list as $id => $node) {
       $this->list[$id] = $node;
     }
     $this->ids = array_keys($this->list);
     return $this;
   }
 
   public function getTokens() {
     $tokens = array();
     foreach ($this->list as $node) {
       $tokens += $node->getTokens();
     }
     return $tokens;
   }
 
   public function getRawNodes() {
     return $this->list;
   }
 
   public static function newFromTreeAndNodes(AASTTree $tree, array $nodes) {
-    assert_instances_of($nodes, 'AASTNode');
+    // We could do `assert_instances_of($nodes, 'AASTNode')` here, but doing
+    // so imposes an observable performance penalty for linting.
 
     $obj = new AASTNodeList();
     $obj->tree = $tree;
     $obj->list = $nodes;
     $obj->ids  = array_keys($nodes);
     return $obj;
   }
 
   public static function newFromTree(AASTTree $tree) {
     $obj = new AASTNodeList();
     $obj->tree = $tree;
     $obj->list = array(0 => $tree->getRootNode());
     $obj->ids = array(0 => 0);
     return $obj;
   }
 
 
 /* -(  Countable  )---------------------------------------------------------- */
 
   public function count() {
     return count($this->ids);
   }
 
 
 /* -(  Iterator  )----------------------------------------------------------- */
 
   public function current() {
     return $this->list[$this->key()];
   }
 
   public function key() {
     return $this->ids[$this->pos];
   }
 
   public function next() {
     $this->pos++;
   }
 
   public function rewind() {
     $this->pos = 0;
   }
 
   public function valid() {
     return $this->pos < count($this->ids);
   }
 
 }