Refactor of PolymerExpressions. Adds "as" expressions.

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 7b925a724cac8f21b9c04427bfc9def3fa3466cd..597fe44f77dafee9b811b6fd39ee618c5801e63e 100644
--- a/pkg/polymer_expressions/lib/eval.dart
+++ b/pkg/polymer_expressions/lib/eval.dart
@@ -65,7 +65,7 @@ Object eval(Expression expr, Scope scope) {
  * [ExpressionObsserver].
  */
 ExpressionObserver observe(Expression expr, Scope scope) {
-  var observer = new ObserverBuilder(scope).visit(expr);
+  var observer = new ObserverBuilder(/*scope*/).visit(expr);

[Jennifer Messerly, 2014/03/17 23:10:08]

did you mean to remove the scope argument to "observe"?

[justinfagnani, 2014/04/24 00:26:13]

yep

   return observer;
 }
 
@@ -164,6 +164,8 @@ class Scope {
   Scope({this.model, Map<String, Object> variables, this.parent})
       : _variables = new ObservableMap.from(variables == null ? {} : variables);
 
+  get variables => _variables;

[Jennifer Messerly, 2014/03/17 23:10:08]

another option is just to make _variables public. Since it's already "final" it
won't have a setter :)

[justinfagnani, 2014/04/24 00:26:13]

Done.

+
   Object operator[](String name) {
     if (name == 'this') {
       return model;
@@ -196,18 +198,11 @@ class Scope {
     if (parent != null) {
       return parent.ownerOf(name);
     }
+    return null;
   }
 
-  bool contains(String name) {
-    if (_variables.containsKey(name) ||
-        smoke.hasGetter(model.runtimeType, smoke.nameToSymbol(name))) {
-      return true;
-    }
-    if (parent != null) {
-      return parent.contains(name);
-    }
-    return false;
-  }
+  String toString() => 'Scope(parent: $parent, model: $model, '
+      'variables: $variables)';
 }
 
 Object _convert(v) {
@@ -270,18 +265,13 @@ class Updater extends RecursiveVisitor {
   visitExpression(ExpressionObserver e) {
     e._observe(scope);
   }
-
-  visitInExpression(InObserver c) {
-    visit(c.right);
-    visitExpression(c);
-  }
 }
 
 class ObserverBuilder extends Visitor {
-  final Scope scope;
+//  final Scope scope;
   final Queue parents = new Queue();
 
-  ObserverBuilder(this.scope);
+  ObserverBuilder(/*this.scope*/);
 
   visitEmptyExpression(EmptyExpression e) => new EmptyObserver(e);
 
@@ -369,14 +359,13 @@ class ObserverBuilder extends Visitor {
   }
 
   visitInExpression(InExpression i) {
-    // don't visit the left. It's an identifier, but we don't want to evaluate
-    // it, we just want to add it to the comprehension object
-    var left = visit(i.left);
-    var right = visit(i.right);
-    var inexpr = new InObserver(i, left, right);
-    right._parent = inexpr;
-    return inexpr;
+    throw new UnsupportedError("can't eval an 'in' expression");
+  }
+
+  visitAsExpression(AsExpression i) {
+    throw new UnsupportedError("can't eval an 'as' expression");
   }
+
 }
 
 class EmptyObserver extends ExpressionObserver<EmptyExpression>
@@ -654,47 +643,8 @@ class InvokeObserver extends ExpressionObserver<Invoke> implements Invoke {
   accept(Visitor v) => v.visitInvoke(this);
 }
 
-class InObserver extends ExpressionObserver<InExpression>
-    implements InExpression {
-  IdentifierObserver left;
-  ExpressionObserver right;
-
-  InObserver(Expression expr, this.left, this.right) : super(expr);
-
-  _updateSelf(Scope scope) {
-    Identifier identifier = left;
-    var iterable = right._value;
-
-    if (iterable is! Iterable && iterable != null) {
-      throw new EvalException("right side of 'in' is not an iterator");
-    }
-
-    if (iterable is ObservableList) {
-      _subscription = iterable.listChanges.listen((_) => _invalidate(scope));
-    }
-
-    // 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;
 
-/**
- * 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 [];
-}
-
 class EvalException implements Exception {
   final String message;
   EvalException(this.message);