frog: allow optional arguments in implicit method closures.

frog/gen.dart

Index: frog/gen.dart
diff --git a/frog/gen.dart b/frog/gen.dart
index bcb4fd0bdd59bb9217e093e2a12ef5f2874e09ca..d68f7b2b669731e6296f6338bd3864a901461a39 100644
--- a/frog/gen.dart
+++ b/frog/gen.dart
@@ -975,7 +975,13 @@ class MethodGenerator implements TreeVisitor, CallingContext {
     if (m._provideGetter) {
       String suffix = world.gen._writePrototypePatch(m.declaringType,
           'get\$${m.jsname}', 'function() {', defWriter, false);
-      defWriter.writeln('return this.${m.jsname}.bind(this);');
+      if (m.parameters.some((p) => p.isOptional)) {
+        defWriter.writeln('var \$bound = this.${m.jsname}.bind(this);');

[sra1, 2012/04/21 03:33:14]

nit.
$bound could be any name (e.g. 'f') since there are no free vars here.
no need for $.

+        defWriter.writeln('\$bound.\$optional = this.${m.jsname}.\$optional;');
+        defWriter.writeln('return \$bound;');
+      } else {
+        defWriter.writeln('return this.${m.jsname}.bind(this);');
+      }
       defWriter.exitBlock(suffix);
       return true;
     }