Add support for Enums

lib/src/codegen/js_codegen.dart

Index: lib/src/codegen/js_codegen.dart
diff --git a/lib/src/codegen/js_codegen.dart b/lib/src/codegen/js_codegen.dart
index 1eab31a1d0a5ac6acd9e24d86159018afcde097b..41d48cc08023a463b9219aca730e7b3367c57b76 100644
--- a/lib/src/codegen/js_codegen.dart
+++ b/lib/src/codegen/js_codegen.dart
@@ -420,8 +420,52 @@ class JSCodegenVisitor extends GeneralizingAstVisitor {
   }
 
   @override
-  JS.Statement visitEnumDeclaration(EnumDeclaration node) =>
-      _unimplementedCall("Unimplemented enum: $node").toStatement();
+  JS.Statement visitEnumDeclaration(EnumDeclaration node) {
+    var element = node.element;
+    var type = element.type;
+    var name = js.string(type.name);
+
+    // Generate a class per section 13 of the spec.
+    // TODO(vsm): Generate any accompanying metadata
+
+    // Create constructor and initialize index
+    var constructor =
+        new JS.Method(name, js.call('function(index) { this.index = index; }'));
+    var fields = new List<ConstFieldElementImpl>.from(
+        element.fields.where((f) => f.type == type));
+
+    // Create toString() method
+    var properties = new List<JS.Property>();
+    for (var i = 0; i < fields.length; ++i) {
+      properties.add(new JS.Property(
+          js.number(i), js.string('${type.name}.${fields[i].name}')));
+    }
+    var nameMap = new JS.ObjectInitializer(properties, multiline: true);
+    var toStringF = new JS.Method(js.string('toString'),
+        js.call('function () { return #[this.index]; }', nameMap));
+
+    // Create enum class
+    var classExpr = new JS.ClassExpression(new JS.Identifier(type.name),
+        _classHeritage(element), [constructor, toStringF]);
+    var result = [js.statement('#', classExpr)];
+
+    // Create static fields for each enum value
+    for (var i = 0; i < fields.length; ++i) {
+      result.add(js.statement(
+          '${type.name}.${fields[i].name} = dart.const(new ${type.name}($i));'));

[Jennifer Messerly, 2015/07/14 23:57:02]

long line ... I think long strings confuse dartfmt ... BUT, this should probably
be rewritten to use js_ast's interpolation, otherwise it defeats the caching
mechanism. So like this:

result.add(js.statement('#.# = dart.const(new #(#));', [type.name,
js.string(fields[i].name), type.name, i]));

(if we had tagged templates in Dart, like JS does, we wouldn't need these
tricks, FWIW)

[vsm, 2015/07/15 00:34:03]

Done.

+    }
+
+    // Create static values list
+    var values = new JS.ArrayInitializer(
+        fields.map((f) => js.call('${type.name}.${f.name}')).toList());

[Jennifer Messerly, 2015/07/14 23:57:02]

here too: js.call('#.#', type.name, js.string(f.name))

(I'm not 100% sure js.string is needed for second arg ... I forgot if it will
implicitly convert a String to a string literal in the JS AST)

[vsm, 2015/07/15 00:34:03]

Done.

+    result.add(js.statement(
+        '${type.name}.values = dart.const(dart.list(#, #));', [

[Jennifer Messerly, 2015/07/14 23:57:02]

here too. Use #

[vsm, 2015/07/15 00:34:03]

Done.

+      values,
+      _emitTypeName(type)
+    ]));
+
+    return _statement(result);
+  }
 
   /// Given a class element and body, complete the class declaration.
   /// This handles generic type parameters, laziness (in library-cycle cases),