Support user generated custom native JS classes.

pkg/compiler/lib/src/js_backend/backend.dart

Index: pkg/compiler/lib/src/js_backend/backend.dart
diff --git a/pkg/compiler/lib/src/js_backend/backend.dart b/pkg/compiler/lib/src/js_backend/backend.dart
index ce801a9b8414fb83ec11b204a952f63a9ed69dcb..6495dd70d5e82a67dd8aa601a405b4f57dd82817 100644
--- a/pkg/compiler/lib/src/js_backend/backend.dart
+++ b/pkg/compiler/lib/src/js_backend/backend.dart
@@ -233,6 +233,8 @@ class JavaScriptBackend extends Backend {
       new Uri(scheme: 'dart', path: '_js_embedded_names');
   static final Uri DART_ISOLATE_HELPER =
       new Uri(scheme: 'dart', path: '_isolate_helper');
+  static final Uri PACKAGE_JS =
+         new Uri(scheme: 'package', path: 'js/js.dart');
 
   static const String INVOKE_ON = '_getCachedInvocation';
   static const String START_ROOT_ISOLATE = 'startRootIsolate';
@@ -289,6 +291,8 @@ class JavaScriptBackend extends Backend {
   ClassElement jsBoolClass;
   ClassElement jsPlainJavaScriptObjectClass;
   ClassElement jsUnknownJavaScriptObjectClass;
+  ClassElement jsJavaScriptFunctionClass;
+  ClassElement jsJavaScriptObjectClass;
 
   ClassElement jsIndexableClass;
   ClassElement jsMutableIndexableClass;
@@ -326,6 +330,8 @@ class JavaScriptBackend extends Backend {
   ClassElement forceInlineClass;
   ClassElement irRepresentationClass;
 
+  ClassElement jsAnnotationClass;
+
   Element getInterceptorMethod;
 
   ClassElement jsInvocationMirrorClass;
@@ -660,7 +666,7 @@ class JavaScriptBackend extends Backend {
   }
 
   FunctionElement resolveExternalFunction(FunctionElement element) {
-    if (isForeign(element)) return element;
+    if (isForeign(element) || element.isJsInterop) return element;
     return patchResolverTask.measure(() {
       return patchResolverTask.resolveExternalFunction(element);
     });
@@ -888,6 +894,28 @@ class JavaScriptBackend extends Backend {
       ClassElement cls, Enqueuer enqueuer) {
     if (enqueuer.isResolutionQueue) {
       cls.ensureResolved(compiler);
+      if (cls.isJsInterop) {
+        if (!cls.implementsInterface(jsJavaScriptObjectClass)) {
+          compiler.reportError(
+              cls,
+              MessageKind.JS_INTEROP_CLASS_CANNOT_EXTEND_DART_CLASS,
+              {'cls': cls.name});
+          return;
+        }
+
+        cls.forEachMember((ClassElement classElement, Element member) {
+          if (member.isSynthesized) return;
+          if (cls.isJsInterop && member is FunctionElement) {
+            FunctionElement fn = member;
+            if (!fn.isExternal && !fn.isAbstract) {
+              compiler.reportError(
+                  fn,
+                  MessageKind.JS_INTEROP_CLASS_NON_EXTERNAL_MEMBER,
+                  {'cls': cls.name, 'member': member.name});
+            }
+          }
+        });
+      }
       cls.forEachMember((ClassElement classElement, Element member) {
         if (member.name == Identifiers.call) {
           compiler.reportError(
@@ -1038,7 +1066,9 @@ class JavaScriptBackend extends Backend {
       } else if (Elements.isNativeOrExtendsNative(cls)) {
         enqueue(enqueuer, getNativeInterceptorMethod, registry);
         enqueueClass(enqueuer, jsInterceptorClass, compiler.globalDependencies);
+        enqueueClass(enqueuer, jsJavaScriptObjectClass, registry);
         enqueueClass(enqueuer, jsPlainJavaScriptObjectClass, registry);
+        enqueueClass(enqueuer, jsJavaScriptFunctionClass, registry);
       } else if (cls == mapLiteralClass) {
         // For map literals, the dependency between the implementation class
         // and [Map] is not visible, so we have to add it manually.
@@ -1115,10 +1145,14 @@ class JavaScriptBackend extends Backend {
       addInterceptors(jsUInt31Class, enqueuer, registry);
       addInterceptors(jsDoubleClass, enqueuer, registry);
       addInterceptors(jsNumberClass, enqueuer, registry);
+    } else if (cls == jsJavaScriptObjectClass) {
+      addInterceptors(jsJavaScriptObjectClass, enqueuer, registry);
     } else if (cls == jsPlainJavaScriptObjectClass) {
       addInterceptors(jsPlainJavaScriptObjectClass, enqueuer, registry);
     } else if (cls == jsUnknownJavaScriptObjectClass) {
       addInterceptors(jsUnknownJavaScriptObjectClass, enqueuer, registry);
+    } else if (cls == jsJavaScriptFunctionClass) {
+      addInterceptors(jsJavaScriptFunctionClass, enqueuer, registry);
     } else if (Elements.isNativeOrExtendsNative(cls)) {
       addInterceptorsForNativeClassMembers(cls, enqueuer);
     } else if (cls == jsIndexingBehaviorInterface) {
@@ -1136,7 +1170,9 @@ class JavaScriptBackend extends Backend {
     if (!enqueuer.nativeEnqueuer.hasInstantiatedNativeClasses()) return;
     Registry registry = compiler.globalDependencies;
     enqueue(enqueuer, getNativeInterceptorMethod, registry);
+    enqueueClass(enqueuer, jsJavaScriptObjectClass, registry);
     enqueueClass(enqueuer, jsPlainJavaScriptObjectClass, registry);
+    enqueueClass(enqueuer, jsJavaScriptFunctionClass, registry);
     needToInitializeIsolateAffinityTag = true;
     needToInitializeDispatchProperty = true;
   }
@@ -1467,6 +1503,7 @@ class JavaScriptBackend extends Backend {
   }
 
   ClassElement defaultSuperclass(ClassElement element) {
+    if (element.isJsInterop) return jsJavaScriptObjectClass;
     // Native classes inherit from Interceptor.
     return element.isNative ? jsInterceptorClass : compiler.objectClass;
   }
@@ -2099,6 +2136,8 @@ class JavaScriptBackend extends Backend {
         jsExtendableArrayClass = findClass('JSExtendableArray');
         jsUnmodifiableArrayClass = findClass('JSUnmodifiableArray');
         jsPlainJavaScriptObjectClass = findClass('PlainJavaScriptObject');
+        jsJavaScriptObjectClass = findClass('JavaScriptObject');
+        jsJavaScriptFunctionClass = findClass('JavaScriptFunction');
         jsUnknownJavaScriptObjectClass = findClass('UnknownJavaScriptObject');
         jsIndexableClass = findClass('JSIndexable');
         jsMutableIndexableClass = findClass('JSMutableIndexable');
@@ -2133,6 +2172,8 @@ class JavaScriptBackend extends Backend {
         jsBuiltinEnum = find(library, 'JsBuiltin');
       } else if (uri == Uris.dart_html) {
         htmlLibraryIsLoaded = true;
+      } else if (uri == PACKAGE_JS) {
+        jsAnnotationClass = find(library, 'Js');
       }
       annotations.onLibraryScanned(library);
     });
@@ -2528,6 +2569,11 @@ class JavaScriptBackend extends Backend {
     customElementsAnalysis.onQueueEmpty(enqueuer);
     if (!enqueuer.queueIsEmpty) return false;
 
+    // XXXX this is a bad hack.
+    // We are validating way too many times.
+    compiler.libraryLoader.libraries.forEach(processJsInteropAnnotationsInLibrary);
+
+
     noSuchMethodRegistry.onQueueEmpty();
     if (!enabledNoSuchMethod &&
         (noSuchMethodRegistry.hasThrowingNoSuchMethod ||
@@ -2577,6 +2623,13 @@ class JavaScriptBackend extends Backend {
     return true;
   }
 
+  void processJsInteropAnnotationsInLibrary(LibraryElement library) {
+    checkJsInteropAnnotation(compiler, library);
+    library.implementation.forEachLocalMember((Element element) {
+      checkJsInteropAnnotation(compiler, element);
+    });
+  }
+
   void onElementResolved(Element element, TreeElements elements) {
     if ((element.isFunction || element.isGenerativeConstructor) &&
         annotations.noInline(element)) {