Support for extending native classes

sdk/lib/_internal/compiler/implementation/js_backend/emitter.dart

Index: sdk/lib/_internal/compiler/implementation/js_backend/emitter.dart
diff --git a/sdk/lib/_internal/compiler/implementation/js_backend/emitter.dart b/sdk/lib/_internal/compiler/implementation/js_backend/emitter.dart
index 21e7b5ca20fb720a8661c077e3daa58b0f9b5429..0c1c3d40acfd11cb0c93fbc969b5f621c21723d2 100644
--- a/sdk/lib/_internal/compiler/implementation/js_backend/emitter.dart
+++ b/sdk/lib/_internal/compiler/implementation/js_backend/emitter.dart
@@ -2627,6 +2627,8 @@ class CodeEmitterTask extends CompilerTask {
     for (Element element in Elements.sortedByPosition(staticNonFinalFields)) {
       // [:interceptedNames:] is handled in [emitInterceptedNames].
       if (element == backend.interceptedNames) continue;
+      // `mapTypeToInterceptor` is handled in [emitMapTypeToInterceptor].
+      if (element == backend.mapTypeToInterceptor) continue;
       compiler.withCurrentElement(element, () {
         Constant initialValue = handler.getInitialValueFor(element);
         jsAst.Expression init =
@@ -3040,9 +3042,8 @@ if (typeof document !== "undefined" && document.readyState !== "complete") {
       else if (cls == backend.jsStringClass) hasString = true;
       else {
         // TODO(sra): The set of classes includes classes mixed-in to
-        // interceptor classes.
-        // assert(cls == compiler.objectClass || cls.isNative());
-        if (cls.isNative()) hasNative = true;
+        // interceptor classes and user extensions of native classes.
+        if (Elements.isNativeOrExtendsNative(cls)) hasNative = true;
       }
     }
     if (hasDouble) {
@@ -3216,9 +3217,13 @@ if (typeof document !== "undefined" && document.readyState !== "complete") {
     for (ClassElement element in sortedClasses) {
       if (rtiNeededClasses.contains(element)) {
         regularClasses.add(element);
-      } else if (element.isNative()) {
-        // For now, native classes cannot be deferred.
+      } else if (Elements.isNativeOrExtendsNative(element)) {
+        // For now, native classes and related classes cannot be deferred.
         nativeClasses.add(element);
+        if (!element.isNative()) {
+          assert(!isDeferred(element));
+          regularClasses.add(element);
+        }
       } else if (isDeferred(element)) {
         deferredClasses.add(element);
       } else {
@@ -3482,6 +3487,36 @@ if (typeof document !== "undefined" && document.readyState !== "complete") {
     buffer.write(N);
   }
 
+  /**
+   * Emit initializer for [mapTypeToInterceptor] data structure used by
+   * [findInterceptorForType].

[ahe, 2013/08/12 20:47:35]

I'd like more documentation here, could you answer these questions:

* What is the data structure used for?

* What are the components of the data structure?

[sra1, 2013/08/12 23:06:14]

This is described where the variable is declared.
I'll add a comment to look there, so there is one comment answering your
questions.

+   */
+  void emitMapTypeToInterceptor(CodeBuffer buffer) {
+    // TODO(sra): Perhaps inject a constant instead?
+    // TODO(sra): Filter by subclasses of native types.
+    List<jsAst.Expression> elements = <jsAst.Expression>[];
+    ConstantHandler handler = compiler.constantHandler;
+    List<Constant> constants = handler.getConstantsForEmission();
+    for (Constant constant in constants) {
+      if (constant is TypeConstant) {
+        TypeConstant typeConstant = constant;
+        Element element = typeConstant.representedType.element;
+        if (element is ClassElement) {
+          ClassElement classElement = element;
+          elements.add(backend.emitter.constantReference(constant));
+          elements.add(js(namer.isolateAccess(classElement)));
+        }
+      }
+    }
+
+    jsAst.ArrayInitializer array = new jsAst.ArrayInitializer.from(elements);
+    String name = backend.namer.getName(backend.mapTypeToInterceptor);
+    jsAst.Expression assignment = js('$isolateProperties.$name = #', array);
+
+    buffer.write(jsAst.prettyPrint(assignment, compiler));
+    buffer.write(N);
+  }
+
   void emitInitFunction(CodeBuffer buffer) {
     jsAst.Fun fun = js.fun([], [
       js('$isolateProperties = {}'),
@@ -3814,6 +3849,7 @@ if (typeof document !== "undefined" && document.readyState !== "complete") {
       emitStaticNonFinalFieldInitializations(mainBuffer);
       emitOneShotInterceptors(mainBuffer);
       emitInterceptedNames(mainBuffer);
+      emitMapTypeToInterceptor(mainBuffer);
       emitLazilyInitializedStaticFields(mainBuffer);
 
       mainBuffer.add(nativeBuffer);