Replace Backend with JavaScriptBackend.

pkg/compiler/lib/src/common/backend_api.dart

Index: pkg/compiler/lib/src/common/backend_api.dart
diff --git a/pkg/compiler/lib/src/common/backend_api.dart b/pkg/compiler/lib/src/common/backend_api.dart
index c0c3d0a5fab4d8e0093232a33b46f80932d8a6b7..197df20cee1153748656e8d8a8d6eed9afe081dc 100644
--- a/pkg/compiler/lib/src/common/backend_api.dart
+++ b/pkg/compiler/lib/src/common/backend_api.dart
@@ -45,307 +45,6 @@ import '../world.dart' show ClosedWorld, ClosedWorldRefiner;
 import 'codegen.dart' show CodegenWorkItem;
 import 'tasks.dart' show CompilerTask;
 
-abstract class Backend extends Target {
-  final Compiler compiler;
-
-  Backend(this.compiler);
-
-  /// Returns true if the backend supports reflection.
-  bool get supportsReflection;
-
-  /// The [ConstantSystem] used to interpret compile-time constants for this
-  /// backend.
-  ConstantSystem get constantSystem;
-
-  /// The constant environment for the backend interpretation of compile-time
-  /// constants.
-  BackendConstantEnvironment get constants;
-
-  /// The compiler task responsible for the compilation of constants for both
-  /// the frontend and the backend.
-  ConstantCompilerTask get constantCompilerTask;
-
-  /// Backend transformation methods for the world impacts.
-  ImpactTransformer get impactTransformer;
-
-  /// The strategy used for collecting and emitting source information.
-  SourceInformationStrategy get sourceInformationStrategy {
-    return const SourceInformationStrategy();
-  }
-
-  /// Common classes used by the backend.
-  BackendClasses get backendClasses;
-
-  /// Interface for serialization of backend specific data.
-  BackendSerialization get serialization => const BackendSerialization();
-
-  // TODO(johnniwinther): Move this to the JavaScriptBackend.
-  String get patchVersion => null;
-
-  /// Set of classes that need to be considered for reflection although not
-  /// otherwise visible during resolution.
-  Iterable<ClassElement> classesRequiredForReflection = const [];
-
-  // Given a [FunctionElement], return a buffer with the code generated for it
-  // or null if no code was generated.
-  CodeBuffer codeOf(Element element) => null;
-
-  void initializeHelperClasses() {}
-
-  /// Compute the [WorldImpact] for backend helper methods.
-  WorldImpact computeHelpersImpact();
-
-  /// Creates an [Enqueuer] for code generation specific to this backend.
-  Enqueuer createCodegenEnqueuer(CompilerTask task, Compiler compiler);
-
-  WorldImpact codegen(CodegenWorkItem work);
-
-  // The backend determines the native resolution enqueuer, with a no-op
-  // default, so tools like dart2dart can ignore the native classes.
-  native.NativeEnqueuer nativeResolutionEnqueuer() {
-    return new native.NativeEnqueuer();
-  }
-
-  native.NativeEnqueuer nativeCodegenEnqueuer() {
-    return new native.NativeEnqueuer();
-  }
-
-  /// Generates the output and returns the total size of the generated code.
-  int assembleProgram(ClosedWorld closedWorld);
-
-  List<CompilerTask> get tasks;
-
-  void onResolutionComplete(
-      ClosedWorld closedWorld, ClosedWorldRefiner closedWorldRefiner) {}
-  void onTypeInferenceComplete() {}
-
-  bool classNeedsRti(ClassElement cls);
-  bool methodNeedsRti(FunctionElement function);
-
-  /// Enable compilation of code with compile time errors. Returns `true` if
-  /// supported by the backend.
-  bool enableCodegenWithErrorsIfSupported(Spannable node);
-
-  /// Enable deferred loading. Returns `true` if the backend supports deferred
-  /// loading.
-  bool enableDeferredLoadingIfSupported(Spannable node);
-
-  /// Returns the [WorldImpact] of enabling deferred loading.
-  WorldImpact computeDeferredLoadingImpact() => const WorldImpact();
-
-  /// Called during codegen when [constant] has been used.
-  void computeImpactForCompileTimeConstant(ConstantValue constant,
-      WorldImpactBuilder impactBuilder, bool isForResolution) {}
-
-  /// Called to notify to the backend that a class is being instantiated. Any
-  /// backend specific [WorldImpact] of this is returned.
-  WorldImpact registerInstantiatedClass(ClassElement cls,
-          {bool forResolution}) =>
-      const WorldImpact();
-
-  /// Called to notify to the backend that a class is implemented by an
-  /// instantiated class. Any backend specific [WorldImpact] of this is
-  /// returned.
-  WorldImpact registerImplementedClass(ClassElement cls,
-          {bool forResolution}) =>
-      const WorldImpact();
-
-  /// Called to instruct to the backend register [type] as instantiated on
-  /// [enqueuer].
-  void registerInstantiatedType(ResolutionInterfaceType type) {}
-
-  /// Register a runtime type variable bound tests between [typeArgument] and
-  /// [bound].
-  void registerTypeVariableBoundsSubtypeCheck(
-      ResolutionDartType typeArgument, ResolutionDartType bound) {}
-
-  /// Called to instruct the backend to register that a closure exists for a
-  /// function on an instantiated generic class. Any backend specific
-  /// [WorldImpact] of this is returned.
-  WorldImpact registerClosureWithFreeTypeVariables(Element closure,
-          {bool forResolution}) =>
-      const WorldImpact();
-
-  /// Called to register that a member has been closurized. Any backend specific
-  /// [WorldImpact] of this is returned.
-  WorldImpact registerBoundClosure() => const WorldImpact();
-
-  /// Called to register that a static function has been closurized. Any backend
-  /// specific [WorldImpact] of this is returned.
-  WorldImpact registerGetOfStaticFunction() => const WorldImpact();
-
-  /// Returns whether or not `noSuchMethod` support has been enabled.
-  bool get enabledNoSuchMethod => false;
-
-  /// Called to enable support for isolates. Any backend specific [WorldImpact]
-  /// of this is returned.
-  WorldImpact enableIsolateSupport({bool forResolution});
-
-  void registerConstSymbol(String name) {}
-
-  ClassElement defaultSuperclass(ClassElement element) {
-    return compiler.commonElements.objectClass;
-  }
-
-  bool isInterceptorClass(ClassElement element) => false;
-
-  /// Returns `true` if [element] is implemented via typed JavaScript interop.
-  // TODO(johnniwinther): Move this to [JavaScriptBackend].
-  bool isJsInterop(Element element) => false;
-
-  /// Returns `true` if the `native` pseudo keyword is supported for [library].
-  bool canLibraryUseNative(LibraryElement library) {
-    // TODO(johnniwinther): Move this to [JavaScriptBackend].
-    return native.maybeEnableNative(compiler, library);
-  }
-
-  @override
-  bool isTargetSpecificLibrary(LibraryElement library) {
-    // TODO(johnniwinther): Remove this when patching is only done by the
-    // JavaScript backend.
-    Uri canonicalUri = library.canonicalUri;
-    if (canonicalUri == js_backend.BackendHelpers.DART_JS_HELPER ||
-        canonicalUri == js_backend.BackendHelpers.DART_INTERCEPTORS) {
-      return true;
-    }
-    return false;
-  }
-
-  /// Called to register that [element] is statically known to be used. Any
-  /// backend specific [WorldImpact] of this is returned.
-  WorldImpact registerUsedElement(MemberElement element,
-          {bool forResolution}) =>
-      const WorldImpact();
-
-  /// This method is called immediately after the [library] and its parts have
-  /// been scanned.
-  Future onLibraryScanned(LibraryElement library, LibraryLoader loader) {
-    // TODO(johnniwinther): Move this to [JavaScriptBackend].
-    if (!compiler.serialization.isDeserialized(library)) {
-      if (canLibraryUseNative(library)) {
-        library.forEachLocalMember((Element element) {
-          if (element.isClass) {
-            checkNativeAnnotation(compiler, element);
-          }
-        });
-      }
-      checkJsInteropAnnotation(compiler, library);
-      library.forEachLocalMember((Element element) {
-        checkJsInteropAnnotation(compiler, element);
-        if (element.isClass && isJsInterop(element)) {
-          ClassElement classElement = element;
-          classElement.forEachMember((_, memberElement) {
-            checkJsInteropAnnotation(compiler, memberElement);
-          });
-        }
-      });
-    }
-    return new Future.value();
-  }
-
-  /// This method is called when all new libraries loaded through
-  /// [LibraryLoader.loadLibrary] has been loaded and their imports/exports
-  /// have been computed.
-  Future onLibrariesLoaded(LoadedLibraries loadedLibraries) {
-    return new Future.value();
-  }
-
-  /// Called by [MirrorUsageAnalyzerTask] after it has merged all @MirrorsUsed
-  /// annotations. The arguments corresponds to the unions of the corresponding
-  /// fields of the annotations.
-  void registerMirrorUsage(
-      Set<String> symbols, Set<Element> targets, Set<Element> metaTargets) {}
-
-  /// Returns true if this element needs reflection information at runtime.
-  bool isAccessibleByReflection(Element element) => true;
-
-  /// Returns true if this member element needs reflection information at
-  /// runtime.
-  bool isMemberAccessibleByReflection(MemberElement element) => true;
-
-  /// Returns true if this element is covered by a mirrorsUsed annotation.
-  ///
-  /// Note that it might still be ok to tree shake the element away if no
-  /// reflection is used in the program (and thus [isTreeShakingDisabled] is
-  /// still false). Therefore _do not_ use this predicate to decide inclusion
-  /// in the tree, use [requiredByMirrorSystem] instead.
-  bool referencedFromMirrorSystem(Element element, [recursive]) => false;
-
-  /// Returns true if this element has to be enqueued due to
-  /// mirror usage. Might be a subset of [referencedFromMirrorSystem] if
-  /// normal tree shaking is still active ([isTreeShakingDisabled] is false).
-  bool requiredByMirrorSystem(Element element) => false;
-
-  /// Returns true if global optimizations such as type inferencing
-  /// can apply to this element. One category of elements that do not
-  /// apply is runtime helpers that the backend calls, but the
-  /// optimizations don't see those calls.
-  bool canBeUsedForGlobalOptimizations(Element element) => true;
-
-  /// Called when [enqueuer]'s queue is empty, but before it is closed.
-  /// This is used, for example, by the JS backend to enqueue additional
-  /// elements needed for reflection. [recentClasses] is a collection of
-  /// all classes seen for the first time by the [enqueuer] since the last call
-  /// to [onQueueEmpty].
-  ///
-  /// A return value of [:true:] indicates that [recentClasses] has been
-  /// processed and its elements do not need to be seen in the next round. When
-  /// [:false:] is returned, [onQueueEmpty] will be called again once the
-  /// resolution queue has drained and [recentClasses] will be a superset of the
-  /// current value.
-  ///
-  /// There is no guarantee that a class is only present once in
-  /// [recentClasses], but every class seen by the [enqueuer] will be present in
-  /// [recentClasses] at least once.
-  bool onQueueEmpty(Enqueuer enqueuer, Iterable<ClassEntity> recentClasses) {
-    return true;
-  }
-
-  /// Called after the queue is closed. [onQueueEmpty] may be called multiple
-  /// times, but [onQueueClosed] is only called once.
-  void onQueueClosed() {}
-
-  /// Called when the compiler starts running the codegen enqueuer. The
-  /// [WorldImpact] of enabled backend features is returned.
-  WorldImpact onCodegenStart(ClosedWorld closedWorld) => const WorldImpact();
-
-  /// Called when code generation has been completed.
-  void onCodegenEnd() {}
-
-  // Does this element belong in the output
-  bool shouldOutput(Element element) => true;
-
-  MethodElement helperForBadMain() => null;
-
-  MethodElement helperForMissingMain() => null;
-
-  MethodElement helperForMainArity() => null;
-
-  /// Computes the [WorldImpact] of calling [mainMethod] as the entry point.
-  WorldImpact computeMainImpact(MethodElement mainMethod,
-          {bool forResolution}) =>
-      const WorldImpact();
-
-  /// Returns the location of the patch-file associated with [libraryName]
-  /// resolved from [plaformConfigUri].
-  ///
-  /// Returns null if there is none.
-  Uri resolvePatchUri(String libraryName, Uri plaformConfigUri);
-
-  /// Creates an impact strategy to use for compilation.
-  ImpactStrategy createImpactStrategy(
-      {bool supportDeferredLoad: true,
-      bool supportDumpInfo: true,
-      bool supportSerialization: true}) {
-    return const ImpactStrategy();
-  }
-
-  /// Backend access to the front-end.
-  Frontend get frontend => compiler.resolution;
-
-  EnqueueTask makeEnqueuer() => new EnqueueTask(compiler);
-}
-
 /// Interface for resolving native data for a target specific element.
 abstract class NativeRegistry {
   /// Registers [nativeData] as part of the resolution impact.