fix list filtering if the filter is a method

pkg/polymer_expressions/lib/eval.dart

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library polymer_expressions.eval;
 
 import 'dart:async';
 import 'dart:collection';
 import 'dart:mirrors';
 
@@ skipping 130 matching lines @@
 }
 
 /**
  * A mapping of names to objects. Scopes contain a set of named [variables] and
  * a single [model] object (which can be thought of as the "this" reference).
  * Names are currently looked up in [variables] first, then the [model].
  *
  * Scopes can be nested by giving them a [parent]. If a name in not found in a
  * Scope, it will look for it in it's parent.
  */
-class Scope extends Object {
+class Scope {
   final Scope parent;
   final Object model;
   // TODO(justinfagnani): disallow adding/removing names
   final ObservableMap<String, Object> _variables;
   InstanceMirror __modelMirror;
 
   Scope({this.model, Map<String, Object> variables: const {}, this.parent})
       : _variables = new ObservableMap.from(variables);
 
   InstanceMirror get _modelMirror {
     if (__modelMirror != null) return __modelMirror;
     __modelMirror = reflect(model);
     return __modelMirror;
   }
 
   Object operator[](String name) {
     if (name == 'this') {
       return model;
     } else if (_variables.containsKey(name)) {
       return _convert(_variables[name]);
     } else if (model != null) {
       var symbol = new Symbol(name);
       var classMirror = _modelMirror.type;
       var memberMirror = getMemberMirror(classMirror, symbol);
+      // TODO(jmesserly): simplify once dartbug.com/13002 is fixed.
+      // This can just be "if memberMirror != null" and delete the Method class.
       if (memberMirror is VariableMirror ||
           (memberMirror is MethodMirror && memberMirror.isGetter)) {
         return _convert(_modelMirror.getField(symbol).reflectee);
       } else if (memberMirror is MethodMirror) {
         return new Method(_modelMirror, symbol);
       }
     }
     if (parent != null) {
       return _convert(parent[name]);
     } else {
@@ skipping 407 matching lines @@
 
     // TODO: make Comprehension observable and update it
     _value = new Comprehension(identifier.value, iterable);
   }
 
   accept(Visitor v) => v.visitInExpression(this);
 }
 
 _toBool(v) => (v == null) ? false : v;
 
-call(dynamic receiver, List args) {
+/** Call a [Function] or a [Method]. */
+// TODO(jmesserly): remove this once dartbug.com/13002 is fixed.
+// Just inline `_convert(Function.apply(...))` to the call site.
+Object call(Object receiver, List args) {
+  var result;
   if (receiver is Method) {
-    return
-        _convert(receiver.mirror.invoke(receiver.symbol, args, null).reflectee);
+    result = receiver.mirror.invoke(receiver.symbol, args, null).reflectee;
   } else {
-    return _convert(Function.apply(receiver, args, null));
+    result = Function.apply(receiver, args, null);
   }
+  return _convert(result);
 }
 
 /**
  * A comprehension declaration ("a in b"). [identifier] is the loop variable
  * that's added to the scope during iteration. [iterable] is the set of
  * objects to iterate over.
  */
 class Comprehension {
   final String identifier;
   final Iterable iterable;
 
   Comprehension(this.identifier, Iterable iterable)
       : iterable = (iterable != null) ? iterable : const [];
 }
 
-/**
- * A method on a model object in a [Scope].
- */
-class Method { //implements _FunctionWrapper {
+/** A method on a model object in a [Scope]. */
+class Method {
   final InstanceMirror mirror;
   final Symbol symbol;
 
   Method(this.mirror, this.symbol);
 
-  dynamic call(List args) => mirror.invoke(symbol, args, null).reflectee;
+  /**
+   * Support for calling single argument methods like [Filter]s.
+   * This does not work for calls that need to pass more than one argument.
+   */
+  call(arg0) => mirror.invoke(symbol, [arg0], null).reflectee;
 }
 
 class EvalException implements Exception {
   final String message;
   EvalException(this.message);
   String toString() => "EvalException: $message";
 }