small refactor to move JsPeer code out of _finishClassDef

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 6635ad69c937c2e70a19e52c9a9c449c6e9a6c8c..f5844c65761728921a3bf47a68cca07f49f1f8e7 100644
--- a/lib/src/codegen/js_codegen.dart
+++ b/lib/src/codegen/js_codegen.dart
@@ -277,7 +277,7 @@ class JSCodegenVisitor extends GeneralizingAstVisitor with ConversionVisitor {
       _emitTypeName(node.element.type, lowerTypedef: true)
     ]);
 
-    return _finishClassDef(type, result, null);
+    return _finishClassDef(type, result);
   }
 
   @override
@@ -295,7 +295,7 @@ class JSCodegenVisitor extends GeneralizingAstVisitor with ConversionVisitor {
     var classDecl = new JS.ClassDeclaration(
         new JS.ClassExpression(new JS.Identifier(name), heritage, []));
 
-    return _finishClassDef(type, classDecl, null);
+    return _finishClassDef(type, classDecl);
   }
 
   JS.Statement _emitJsType(String dartClassName, DartObjectImpl jsName) {
@@ -340,13 +340,25 @@ class JSCodegenVisitor extends GeneralizingAstVisitor with ConversionVisitor {
     var body =
         _finishClassMembers(classElem, classExpr, ctors, fields, staticFields);
 
+    var result = _finishClassDef(type, body);
+
     var jsPeer = getAnnotationValue(node, _isJsPeerInterface);
-    String jsPeerName = null;
     if (jsPeer != null) {
-      jsPeerName = getConstantField(jsPeer, 'name', types.stringType);
+      var jsPeerName = getConstantField(jsPeer, 'name', types.stringType);
+      if (jsPeerName != null) {
+        // TODO(jmesserly): this copies the dynamic members.
+        // Probably fine for objects coming from JS, but not if we actually
+        // want to support construction of instances with generic types other
+        // than dynamic. See issue #154 for Array and List<E> related bug.
+        var copyMembers = js.statement(
+          'dart.copyProperties(dart.global.#.prototype, #.prototype);', [

[Jennifer Messerly, 2015/04/23 17:05:43]

hmmm, it occurs to me we should assert !_lazyClass if we reach this point, as
this will cause the type name to be evaluated eagerly.

[Jacob, 2015/04/23 17:09:14]

make it so.

+          _propertyName(jsPeerName),
+          classElem.name
+        ]);
+        return _statement([result, copyMembers]);
+      }
     }
-
-    return _finishClassDef(type, body, jsPeerName);
+    return result;
   }
 
   @override
@@ -356,8 +368,7 @@ class JSCodegenVisitor extends GeneralizingAstVisitor with ConversionVisitor {
   /// Given a class element and body, complete the class declaration.
   /// This handles generic type parameters, laziness (in library-cycle cases),
   /// and ensuring dependencies are loaded first.
-  JS.Statement _finishClassDef(
-      ParameterizedType type, JS.Statement body, String jsPeerName) {
+  JS.Statement _finishClassDef(ParameterizedType type, JS.Statement body) {
     var name = type.name;
     var genericName = '$name\$';
 
@@ -416,13 +427,6 @@ class JSCodegenVisitor extends GeneralizingAstVisitor with ConversionVisitor {
       _emitClassIfNeeded(classDefs, types.functionType);
     }
     classDefs.add(body);
-    if (jsPeerName != null) {
-      classDefs.add(js.statement(
-          'dart.copyProperties(dart.global.#.prototype, #.prototype);', [
-        _propertyName(jsPeerName),
-        name
-      ]));
-    }
     return _statement(classDefs);
   }
 
@@ -642,7 +646,6 @@ class JSCodegenVisitor extends GeneralizingAstVisitor with ConversionVisitor {
     }
     var lazy = _emitLazyFields(new JS.Identifier(name), lazyStatics);
     if (lazy != null) body.add(lazy);
-
     return _statement(body);
   }