Ternary operator support for polymer_expressions

pkg/polymer_expressions/lib/expression.dart

Index: pkg/polymer_expressions/lib/expression.dart
diff --git a/pkg/polymer_expressions/lib/expression.dart b/pkg/polymer_expressions/lib/expression.dart
index c89724fe8232828b3ff828bcdb1783ac7263fba6..5a69ab05891db0e655869bcf7e0295d76520746c 100644
--- a/pkg/polymer_expressions/lib/expression.dart
+++ b/pkg/polymer_expressions/lib/expression.dart
@@ -23,7 +23,8 @@ Index index(Expression e, Expression a) => new Index(e, a);
 Invoke invoke(Expression e, String m, List<Expression> a) =>
     new Invoke(e, m, a);
 InExpression inExpr(Expression l, Expression r) => new InExpression(l, r);
-
+TernaryOperator ternary(Expression c, Expression t, Expression f) =>
+    new TernaryOperator(c, t, f);
 
 class AstFactory {
   EmptyExpression empty() => const EmptyExpression();
@@ -46,6 +47,9 @@ class AstFactory {
   BinaryOperator binary(Expression l, String op, Expression r) =>
       new BinaryOperator(l, op, r);
 
+  TernaryOperator ternary(Expression c, Expression t, Expression f) =>
+      new TernaryOperator(c, t, f);
+
   Getter getter(Expression g, String n) => new Getter(g, n);
 
   Index index(Expression e, Expression a) => new Index(e, a);
@@ -173,6 +177,26 @@ class BinaryOperator extends Expression {
       right.hashCode);
 }
 
+class TernaryOperator extends Expression {
+  final Expression condition;
+  final Expression trueExpr;
+  final Expression falseExpr;
+
+  TernaryOperator(this.condition, this.trueExpr, this.falseExpr);
+
+  accept(Visitor v) => v.visitTernaryOperator(this);
+
+  String toString() => '($condition ? $trueExpr : $falseExpr)';
+
+  bool operator ==(o) => o is TernaryOperator
+      && o.condition == condition
+      && o.trueExpr == trueExpr
+      && o.falseExpr == falseExpr;
+
+  int get hashCode => _JenkinsSmiHash.hash3(condition.hashCode,
+      trueExpr.hashCode, falseExpr.hashCode);
+}
+
 class InExpression extends Expression {
   final Expression left;
   final Expression right;