Fixed various parser bugs, implemented unary operators

app/imports/parser/parseTree/IndexNode.js

@@ -12,13 +12,12 @@ export default class IndexNode extends ParseNode {
       let selection = this.array.values[index.value - 1];
       if (selection){
         let result = selection[fn](scope, context);
-        result.inheritDetails([index, this]);
         return result;
       }
     }
     return new IndexNode({
+      index,
       array: this.array[fn](scope, context),
-      index: this.index[fn](scope, context),
       previousNodes: [this],
     });
   }