Fix bug that could corrupt the index cache

Author: Joris-van-der-Wel

lib/SymbolTree.js

@@ -265,12 +265,13 @@ class SymbolTree {
                 const filter  = (options && options.filter ) || returnTrue;
                 const thisArg = (options && options.thisArg) || undefined;
 
-                let object = this._node(parent).firstChild;
+                const parentNode = this._node(parent);
+                let object = parentNode.firstChild;
                 let index = 0;
 
                 while (object) {
                         const node = this._node(object);
-                        node.setCachedIndex(parent, index);
+                        node.setCachedIndex(parentNode, index);
 
                         if (filter.call(thisArg, object)) {
                                 array.push(object);

test/SymbolTree.js

@@ -1095,6 +1095,11 @@ test('cached index warmed up by childrenToArray', function(t) {
         t.equal(1, tree.index(ab));
         t.equal(2, tree.index(ac));
 
+        tree.appendChild(a, {});
+        t.equal(2, tree.index(ac));
+        tree.childrenToArray(a);
+        t.equal(2, tree.index(ac));
+
         t.end();
 });