fix list filtering if the filter is a method

pkg/polymer_expressions/lib/eval.dart

Index: pkg/polymer_expressions/lib/eval.dart
diff --git a/pkg/polymer_expressions/lib/eval.dart b/pkg/polymer_expressions/lib/eval.dart
index c191bd9cf79311452379d03db3e393432f02109f..26a0ca47150b720e69fd118cb048981de407cffd 100644
--- a/pkg/polymer_expressions/lib/eval.dart
+++ b/pkg/polymer_expressions/lib/eval.dart
@@ -148,7 +148,7 @@ void assign(Expression expr, Object value, Scope scope) {
  * 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 {

[Jennifer Messerly, 2013/10/04 02:18:19]

trivial style fix: remove "extends Object" which is implied.

   final Scope parent;
   final Object model;
   // TODO(justinfagnani): disallow adding/removing names
@@ -600,13 +600,15 @@ class InObserver extends ExpressionObserver<InExpression>
 
 _toBool(v) => (v == null) ? false : v;
 
-call(dynamic receiver, List args) {
+/** Call a [Function] or a [Method]. */
+Object call(Object receiver, List args) {

[Jennifer Messerly, 2013/10/04 02:18:19]

trivial style fix: avoid "dynamic" except as type parameter.
factor out the _convert

[justinfagnani, 2013/10/04 20:46:08]

if InstanceMirror.getField() properly closurizes, we can replace call() with
Function.apply()

+  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);
 }
 
 /**
@@ -622,16 +624,18 @@ class Comprehension {
       : 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;

[Jennifer Messerly, 2013/10/04 02:18:19]

the actual bug fix. "call" is different from Function.apply; it's expected to
match the method signature.

[justinfagnani, 2013/10/04 20:41:47]

I think this fix could be different, because InstanceMirror.getField() is
supposed to correctly closurize methods now.

Background on Method: I think that this call() originally wasn't intended to be
the Function-emulating call(), but was used to invoke the method from within
polymer expression code consistently where there used to be a FunctionWrapper
class. Unfortunate naming, that's why the signature took a list.

Right now the invoke ast node takes care of invoking most methods, and only
those that are method directly on the model object get wrapped in Method. Other
methods reached via expressions won't be wrapped, but should be closurized by
mirrors. I think we might just want to remove call() altogether.

[Jennifer Messerly, 2013/10/04 20:44:28]

Alright, I'll take a shot at removing "Method" instead. Fingers crossed it
actually works in all impls now.

 }
 
 class EvalException implements Exception {