Add ElementCodegenWorldBuilder

Reusable parts are left in CodegenWorldBuilderImpl and a stub KernelCodegenWorldBuilder is added.

R=sigmund@google.com

Review-Url: https://codereview.chromium.org/2894893002 .

pkg/compiler/lib/src/backend_strategy.dart

@@ -4,8 +4,10 @@
 
 library dart2js.backend_strategy;
 
-import 'compiler.dart';
+import 'enqueue.dart';
+import 'js_backend/native_data.dart';
 import 'js_emitter/sorter.dart';
+import 'universe/world_builder.dart';
 import 'world.dart';
 
 /// Strategy pattern that defines the element model used in type inference
@@ -19,21 +21,13 @@ abstract class BackendStrategy {
 
   /// The [Sorter] used for sorting elements in the generated code.
   Sorter get sorter;
-}
-
-/// Strategy for using the [Element] model from the resolver as the backend
-/// model.
-class ElementBackendStrategy implements BackendStrategy {
-  final Compiler _compiler;
-
-  ElementBackendStrategy(this._compiler);
-
-  ClosedWorldRefiner createClosedWorldRefiner(ClosedWorldImpl closedWorld) =>
-      closedWorld;
-
-  Sorter get sorter => const ElementSorter();
-
-  void convertClosures(ClosedWorldRefiner closedWorldRefiner) {
-    _compiler.closureToClassMapper.createClosureClasses(closedWorldRefiner);
-  }
+
+  /// Creates the [CodegenWorldBuilder] used by the codegen enqueuer.
+  CodegenWorldBuilder createCodegenWorldBuilder(
+      NativeBasicData nativeBasicData,
+      ClosedWorld closedWorld,
+      SelectorConstraintsStrategy selectorConstraintsStrategy);
+
+  /// Creates the [WorkItemBuilder] used by the codegen enqueuer.
+  WorkItemBuilder createCodegenWorkItemBuilder(ClosedWorld closedWorld);
 }

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

@@ -4,23 +4,15 @@
 
 library dart2js.common.codegen;
 
-import '../common.dart';
 import '../elements/elements.dart'
-    show
-        AsyncMarker,
-        ClassElement,
-        LocalFunctionElement,
-        MemberElement,
-        ResolvedAst;
+    show AsyncMarker, ClassElement, LocalFunctionElement, MemberElement;
 import '../elements/entities.dart';
 import '../elements/types.dart' show DartType, InterfaceType;
-import '../js_backend/backend.dart' show JavaScriptBackend;
 import '../universe/use.dart' show ConstantUse, DynamicUse, StaticUse, TypeUse;
 import '../universe/world_impact.dart'
     show WorldImpact, WorldImpactBuilderImpl, WorldImpactVisitor;
 import '../util/enumset.dart';
 import '../util/util.dart' show Pair, Setlet;
-import '../world.dart' show ClosedWorld;
 import 'work.dart' show WorkItem;
 
 class CodegenImpact extends WorldImpact {
@@ -181,32 +173,6 @@ class CodegenRegistry {
 }
 
 /// [WorkItem] used exclusively by the [CodegenEnqueuer].
-class CodegenWorkItem extends WorkItem {
-  CodegenRegistry registry;
-  final ResolvedAst resolvedAst;
-  final JavaScriptBackend _backend;
-  final ClosedWorld _closedWorld;
-
-  factory CodegenWorkItem(JavaScriptBackend backend, ClosedWorld closedWorld,
-      MemberElement element) {
-    // If this assertion fails, the resolution callbacks of the backend may be
-    // missing call of form registry.registerXXX. Alternatively, the code
-    // generation could spuriously be adding dependencies on things we know we
-    // don't need.
-    assert(invariant(element, element.hasResolvedAst,
-        message: "$element has no resolved ast."));
-    ResolvedAst resolvedAst = element.resolvedAst;
-    return new CodegenWorkItem.internal(resolvedAst, backend, closedWorld);
-  }
-
-  CodegenWorkItem.internal(this.resolvedAst, this._backend, this._closedWorld);
-
-  MemberElement get element => resolvedAst.element;
-
-  WorldImpact run() {
-    registry = new CodegenRegistry(element);
-    return _backend.codegen(this, _closedWorld);
-  }
-
-  String toString() => 'CodegenWorkItem(${resolvedAst.element})';
+abstract class CodegenWorkItem extends WorkItem {
+  CodegenRegistry get registry;
 }

pkg/compiler/lib/src/compiler.dart

@@ -40,6 +40,7 @@ import 'frontend_strategy.dart';
 import 'id_generator.dart';
 import 'io/source_information.dart' show SourceInformation;
 import 'js_backend/backend.dart' show JavaScriptBackend;
+import 'js_backend/element_strategy.dart' show ElementBackendStrategy;
 import 'kernel/kernel_strategy.dart';
 import 'library_loader.dart'
     show

pkg/compiler/lib/src/elements/entities.dart

@@ -5,6 +5,7 @@
 library entities;
 
 import '../common.dart';
+import '../universe/call_structure.dart' show CallStructure;
 
 /// Abstract interface for entities.
 ///
@@ -183,4 +184,11 @@ class ParameterStructure {
   /// The number of optional parameters (positional or named).
   int get optionalParameters =>
       positionalParameters - requiredParameters + namedParameters.length;
+
+  /// Returns the [CallStructure] corresponding to a call site passing all
+  /// parameters both required and optional.
+  CallStructure get callStructure {
+    return new CallStructure(
+        positionalParameters + namedParameters.length, namedParameters);
+  }
 }

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

@@ -893,9 +893,9 @@ class JavaScriptBackend {
         task,
         compiler.options,
         const TreeShakingEnqueuerStrategy(),
-        new CodegenWorldBuilderImpl(
-            nativeBasicData, closedWorld, constants, const TypeMaskStrategy()),
-        new CodegenWorkItemBuilder(this, closedWorld, compiler.options),
+        compiler.backendStrategy.createCodegenWorldBuilder(
+            nativeBasicData, closedWorld, const TypeMaskStrategy()),
+        compiler.backendStrategy.createCodegenWorkItemBuilder(closedWorld),
         new CodegenEnqueuerListener(
             compiler.elementEnvironment,
             commonElements,

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

@@ -105,13 +105,14 @@ class CodegenEnqueuerListener extends EnqueuerListener {
   }
 
   /// Computes the [WorldImpact] of calling [mainMethod] as the entry point.
-  WorldImpact _computeMainImpact(MethodElement mainMethod) {
+  WorldImpact _computeMainImpact(FunctionEntity mainMethod) {
     WorldImpactBuilderImpl mainImpact = new WorldImpactBuilderImpl();
-    if (mainMethod.parameters.isNotEmpty) {
+    CallStructure callStructure = mainMethod.parameterStructure.callStructure;
+    if (callStructure.argumentCount > 0) {
       _impacts.mainWithArguments
           .registerImpact(mainImpact, _elementEnvironment);
       mainImpact.registerStaticUse(
-          new StaticUse.staticInvoke(mainMethod, CallStructure.TWO_ARGS));
+          new StaticUse.staticInvoke(mainMethod, callStructure));
       // If the main method takes arguments, this compilation could be the
       // target of Isolate.spawnUri. Strictly speaking, that can happen also if
       // main takes no arguments, but in this case the spawned isolate can't

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

@@ -0,0 +1,117 @@
+// Copyright (c) 2017, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+library dart2js.js_backend.element_strategy;
+
+import '../backend_strategy.dart';
+import '../common.dart';
+import '../common/codegen.dart';
+import '../common/work.dart';
+import '../compiler.dart';
+import '../elements/elements.dart';
+import '../enqueue.dart';
+import '../js_backend/backend.dart';
+import '../js_backend/native_data.dart';
+import '../js_emitter/sorter.dart';
+import '../options.dart';
+import '../universe/world_builder.dart';
+import '../universe/world_impact.dart';
+import '../world.dart';
+
+/// Strategy for using the [Element] model from the resolver as the backend
+/// model.
+class ElementBackendStrategy implements BackendStrategy {
+  final Compiler _compiler;
+
+  ElementBackendStrategy(this._compiler);
+
+  ClosedWorldRefiner createClosedWorldRefiner(ClosedWorldImpl closedWorld) =>
+      closedWorld;
+
+  Sorter get sorter => const ElementSorter();
+
+  void convertClosures(ClosedWorldRefiner closedWorldRefiner) {
+    _compiler.closureToClassMapper.createClosureClasses(closedWorldRefiner);
+  }
+
+  @override
+  CodegenWorldBuilder createCodegenWorldBuilder(
+      NativeBasicData nativeBasicData,
+      ClosedWorld closedWorld,
+      SelectorConstraintsStrategy selectorConstraintsStrategy) {
+    return new ElementCodegenWorldBuilderImpl(
+        _compiler.elementEnvironment,
+        nativeBasicData,
+        closedWorld,
+        _compiler.backend.constants,
+        selectorConstraintsStrategy);
+  }
+
+  @override
+  WorkItemBuilder createCodegenWorkItemBuilder(ClosedWorld closedWorld) {
+    return new ElementCodegenWorkItemBuilder(
+        _compiler.backend, closedWorld, _compiler.options);
+  }
+}
+
+/// Builder that creates the work item necessary for the code generation of a
+/// [MemberElement].
+class ElementCodegenWorkItemBuilder extends WorkItemBuilder {
+  final JavaScriptBackend _backend;
+  final ClosedWorld _closedWorld;
+  final CompilerOptions _options;
+
+  ElementCodegenWorkItemBuilder(
+      this._backend, this._closedWorld, this._options);
+
+  @override
+  WorkItem createWorkItem(MemberElement element) {
+    assert(invariant(element, element.isDeclaration));
+    // Don't generate code for foreign elements.
+    if (_backend.isForeign(element)) return null;
+    if (element.isAbstract) return null;
+
+    // Codegen inlines field initializers. It only needs to generate
+    // code for checked setters.
+    if (element.isField && element.isInstanceMember) {
+      if (!_options.enableTypeAssertions ||
+          element.enclosingElement.isClosure) {
+        return null;
+      }
+    }
+    return new ElementCodegenWorkItem(_backend, _closedWorld, element);
+  }
+}
+
+class ElementCodegenWorkItem extends CodegenWorkItem {
+  CodegenRegistry registry;
+  final ResolvedAst resolvedAst;
+  final JavaScriptBackend _backend;
+  final ClosedWorld _closedWorld;
+
+  factory ElementCodegenWorkItem(JavaScriptBackend backend,
+      ClosedWorld closedWorld, MemberElement element) {
+    // If this assertion fails, the resolution callbacks of the backend may be
+    // missing call of form registry.registerXXX. Alternatively, the code
+    // generation could spuriously be adding dependencies on things we know we
+    // don't need.
+    assert(invariant(element, element.hasResolvedAst,
+        message: "$element has no resolved ast."));
+    ResolvedAst resolvedAst = element.resolvedAst;
+    return new ElementCodegenWorkItem.internal(
+        resolvedAst, backend, closedWorld);
+  }
+
+  ElementCodegenWorkItem.internal(
+      this.resolvedAst, this._backend, this._closedWorld);
+
+  MemberElement get element => resolvedAst.element;
+
+  WorldImpact run() {
+    registry = new CodegenRegistry(element);
+    return _backend.codegen(this, _closedWorld);
+  }
+
+  String toString() => 'CodegenWorkItem(${resolvedAst.element})';
+}

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

@@ -6,17 +6,14 @@ library dart2js.js.enqueue;
 
 import 'dart:collection' show Queue;
 
-import '../common/codegen.dart' show CodegenWorkItem;
 import '../common/tasks.dart' show CompilerTask;
 import '../common/work.dart' show WorkItem;
 import '../common.dart';
 import '../common_elements.dart' show ElementEnvironment;
 import '../elements/resolution_types.dart'
     show ResolutionDartType, ResolutionInterfaceType;
-import '../elements/elements.dart' show MemberElement;
 import '../elements/entities.dart';
 import '../enqueue.dart';
-import '../js_backend/backend.dart' show JavaScriptBackend;
 import '../options.dart';
 import '../universe/world_builder.dart';
 import '../universe/use.dart'
@@ -31,7 +28,6 @@ import '../universe/world_impact.dart'
     show ImpactUseCase, WorldImpact, WorldImpactVisitor;
 import '../util/enumset.dart';
 import '../util/util.dart' show Setlet;
-import '../world.dart' show ClosedWorld;
 
 /// [Enqueuer] which is specific to code generation.
 class CodegenEnqueuer extends EnqueuerImpl {
@@ -268,31 +264,3 @@ class CodegenEnqueuer extends EnqueuerImpl {
   @override
   Iterable<ClassEntity> get processedClasses => _worldBuilder.processedClasses;
 }
-
-/// Builder that creates the work item necessary for the code generation of a
-/// [MemberElement].
-class CodegenWorkItemBuilder extends WorkItemBuilder {
-  final JavaScriptBackend _backend;
-  final ClosedWorld _closedWorld;
-  final CompilerOptions _options;
-
-  CodegenWorkItemBuilder(this._backend, this._closedWorld, this._options);
-
-  @override
-  WorkItem createWorkItem(MemberElement element) {
-    assert(invariant(element, element.isDeclaration));
-    // Don't generate code for foreign elements.
-    if (_backend.isForeign(element)) return null;
-    if (element.isAbstract) return null;
-
-    // Codegen inlines field initializers. It only needs to generate
-    // code for checked setters.
-    if (element.isField && element.isInstanceMember) {
-      if (!_options.enableTypeAssertions ||
-          element.enclosingElement.isClosure) {
-        return null;
-      }
-    }
-    return new CodegenWorkItem(_backend, _closedWorld, element);
-  }
-}

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

@@ -153,11 +153,7 @@ class ResolutionEnqueuerListener extends EnqueuerListener {
   /// Computes the [WorldImpact] of calling [mainMethod] as the entry point.
   WorldImpact _computeMainImpact(FunctionEntity mainMethod) {
     WorldImpactBuilderImpl mainImpact = new WorldImpactBuilderImpl();
-    ParameterStructure parameterStructure = mainMethod.parameterStructure;
-    CallStructure callStructure = new CallStructure(
-        parameterStructure.positionalParameters +
-            parameterStructure.namedParameters.length,
-        parameterStructure.namedParameters);
+    CallStructure callStructure = mainMethod.parameterStructure.callStructure;
     if (callStructure.argumentCount > 0) {
       _impacts.mainWithArguments
           .registerImpact(mainImpact, _elementEnvironment);

pkg/compiler/lib/src/js_emitter/program_builder/collector.dart

@@ -203,7 +203,7 @@ class Collector {
         .toList());
 
     // Compute needed classes.
-    Set<ClassElement> instantiatedClasses =
+    Set<ClassEntity> instantiatedClasses =
         // TODO(johnniwinther): This should be accessed from a codegen closed
         // world.
         _worldBuilder.directlyInstantiatedClasses
@@ -219,7 +219,7 @@ class Collector {
       }
     }
 
-    void addClassesWithSuperclasses(Iterable<ClassElement> classes) {
+    void addClassesWithSuperclasses(Iterable<ClassEntity> classes) {
       for (ClassElement cls in classes) {
         addClassWithSuperclasses(cls);
       }

pkg/compiler/lib/src/js_emitter/type_test_registry.dart

@@ -7,7 +7,7 @@ library dart2js.js_emitter.type_test_registry;
 import '../common.dart';
 import '../common_elements.dart';
 import '../elements/elements.dart'
-    show ClassElement, Element, ElementKind, MemberElement, MethodElement;
+    show ClassElement, ElementKind, MemberElement, MethodElement;
 import '../elements/entities.dart';
 import '../elements/resolution_types.dart'
     show
@@ -138,7 +138,7 @@ class TypeTestRegistry {
       }
     }
 
-    bool canTearOff(Element function) {
+    bool canTearOff(MemberElement function) {
       if (!function.isFunction ||
           function.isConstructor ||
           function.isAccessor) {

pkg/compiler/lib/src/kernel/kernel_strategy.dart

@@ -9,6 +9,7 @@ import '../backend_strategy.dart';
 import '../common.dart';
 import '../common_elements.dart';
 import '../common/backend_api.dart';
+import '../common/codegen.dart' show CodegenWorkItem;
 import '../common/resolution.dart';
 import '../common/tasks.dart';
 import '../common/work.dart';
@@ -256,4 +257,25 @@ class KernelBackendStrategy implements BackendStrategy {
     // elements.
     throw new UnimplementedError('KernelBackendStrategy.createClosureClasses');
   }
+
+  @override
+  WorkItemBuilder createCodegenWorkItemBuilder(ClosedWorld closedWorld) {
+    return new KernelCodegenWorkItemBuilder();
+  }
+
+  @override
+  CodegenWorldBuilder createCodegenWorldBuilder(
+      NativeBasicData nativeBasicData,
+      ClosedWorld closedWorld,
+      SelectorConstraintsStrategy selectorConstraintsStrategy) {
+    return new KernelCodegenWorldBuilder(
+        null, nativeBasicData, closedWorld, selectorConstraintsStrategy);
+  }
+}
+
+class KernelCodegenWorkItemBuilder implements WorkItemBuilder {
+  @override
+  CodegenWorkItem createWorkItem(MemberEntity entity) {
+    throw new UnimplementedError('KernelCodegenWorkItemBuilder.createWorkItem');
+  }
 }

pkg/compiler/lib/src/native/enqueue.dart

@@ -246,7 +246,7 @@ class NativeCodegenEnqueuer extends NativeEnqueuerBase {
       this._nativeData)
       : super(options, elementEnvironment, commonElements, dartTypes);
 
-  WorldImpact processNativeClasses(Iterable<LibraryElement> libraries) {
+  WorldImpact processNativeClasses(Iterable<LibraryEntity> libraries) {
     WorldImpactBuilderImpl impactBuilder = new WorldImpactBuilderImpl();
     _unusedClasses.addAll(_resolutionEnqueuer._nativeClasses);
 

pkg/compiler/lib/src/ssa/builder.dart

@@ -8,7 +8,7 @@ import 'package:js_runtime/shared/embedded_names.dart';
 
 import '../closure.dart';
 import '../common.dart';
-import '../common/codegen.dart' show CodegenRegistry, CodegenWorkItem;
+import '../common/codegen.dart' show CodegenRegistry;
 import '../common/names.dart' show Identifiers, Selectors;
 import '../common/tasks.dart' show CompilerTask;
 import '../compiler.dart';
@@ -27,6 +27,7 @@ import '../elements/types.dart';
 import '../io/source_information.dart';
 import '../js/js.dart' as js;
 import '../js_backend/backend.dart' show JavaScriptBackend;
+import '../js_backend/element_strategy.dart' show ElementCodegenWorkItem;
 import '../js_backend/runtime_types.dart';
 import '../js_emitter/js_emitter.dart' show CodeEmitterTask, NativeEmitter;
 import '../native/native.dart' as native;
@@ -65,7 +66,7 @@ class SsaBuilderTask extends CompilerTask {
 
   DiagnosticReporter get reporter => backend.reporter;
 
-  HGraph build(CodegenWorkItem work, ClosedWorld closedWorld) {
+  HGraph build(ElementCodegenWorkItem work, ClosedWorld closedWorld) {
     return measure(() {
       MemberElement element = work.element.implementation;
       return reporter.withCurrentElement(element, () {

pkg/compiler/lib/src/ssa/builder_kernel.dart

@@ -6,7 +6,7 @@ import 'package:kernel/ast.dart' as ir;
 
 import '../closure.dart';
 import '../common.dart';
-import '../common/codegen.dart' show CodegenRegistry, CodegenWorkItem;
+import '../common/codegen.dart' show CodegenRegistry;
 import '../common/names.dart';
 import '../common/tasks.dart' show CompilerTask;
 import '../compiler.dart';
@@ -22,6 +22,7 @@ import '../elements/resolution_types.dart';
 import '../io/source_information.dart';
 import '../js/js.dart' as js;
 import '../js_backend/backend.dart' show JavaScriptBackend;
+import '../js_backend/element_strategy.dart' show ElementCodegenWorkItem;
 import '../kernel/kernel.dart';
 import '../native/native.dart' as native;
 import '../resolution/tree_elements.dart';
@@ -53,7 +54,7 @@ class SsaKernelBuilderTask extends CompilerTask {
       : backend = backend,
         super(backend.compiler.measurer);
 
-  HGraph build(CodegenWorkItem work, ClosedWorld closedWorld) {
+  HGraph build(ElementCodegenWorkItem work, ClosedWorld closedWorld) {
     return measure(() {
       MemberElement element = work.element.implementation;
       Kernel kernel = backend.kernelTask.kernel;

pkg/compiler/lib/src/ssa/codegen.dart

@@ -19,6 +19,7 @@ import '../js/js.dart' as js;
 import '../js_backend/interceptor_data.dart';
 import '../js_backend/backend.dart';
 import '../js_backend/checked_mode_helpers.dart';
+import '../js_backend/element_strategy.dart' show ElementCodegenWorkItem;
 import '../js_backend/native_data.dart';
 import '../js_backend/namer.dart';
 import '../js_backend/runtime_types.dart';
@@ -63,7 +64,7 @@ class SsaCodeGeneratorTask extends CompilerTask {
   }
 
   js.Expression generateCode(
-      CodegenWorkItem work, HGraph graph, ClosedWorld closedWorld) {
+      ElementCodegenWorkItem work, HGraph graph, ClosedWorld closedWorld) {
     if (work.element.isField) {
       return generateLazyInitializer(work, graph, closedWorld);
     } else {
@@ -72,7 +73,7 @@ class SsaCodeGeneratorTask extends CompilerTask {
   }
 
   js.Expression generateLazyInitializer(
-      CodegenWorkItem work, HGraph graph, ClosedWorld closedWorld) {
+      ElementCodegenWorkItem work, HGraph graph, ClosedWorld closedWorld) {
     return measure(() {
       backend.tracer.traceGraph("codegen", graph);
       SourceInformation sourceInformation = sourceInformationFactory
@@ -97,7 +98,7 @@ class SsaCodeGeneratorTask extends CompilerTask {
   }
 
   js.Expression generateMethod(
-      CodegenWorkItem work, HGraph graph, ClosedWorld closedWorld) {
+      ElementCodegenWorkItem work, HGraph graph, ClosedWorld closedWorld) {
     return measure(() {
       MethodElement element = work.element;
       if (element.asyncMarker != AsyncMarker.SYNC) {

pkg/compiler/lib/src/ssa/ssa.dart

@@ -4,12 +4,12 @@
 
 library ssa;
 
-import '../common/codegen.dart' show CodegenWorkItem;
 import '../common/tasks.dart' show CompilerTask;
 import '../elements/elements.dart' show Element, FunctionElement;
 import '../io/source_information.dart';
 import '../js/js.dart' as js;
 import '../js_backend/backend.dart' show JavaScriptBackend, FunctionCompiler;
+import '../js_backend/element_strategy.dart' show ElementCodegenWorkItem;
 import '../world.dart' show ClosedWorld;
 
 import 'builder.dart';
@@ -37,7 +37,7 @@ class SsaFunctionCompiler implements FunctionCompiler {
 
   /// Generates JavaScript code for `work.element`.
   /// Using the ssa builder, optimizer and codegenerator.
-  js.Fun compile(CodegenWorkItem work, ClosedWorld closedWorld) {
+  js.Fun compile(ElementCodegenWorkItem work, ClosedWorld closedWorld) {
     HGraph graph = useKernel
         ? builderKernel.build(work, closedWorld)
         : builder.build(work, closedWorld);

pkg/compiler/lib/src/universe/codegen_world_builder.dart

@@ -28,9 +28,9 @@ abstract class CodegenWorldBuilder implements WorldBuilder {
       f(String name, Map<Selector, SelectorConstraints> selectors));
 
   /// Returns `true` if [member] is invoked as a setter.
-  bool hasInvokedSetter(Element member, ClosedWorld world);
+  bool hasInvokedSetter(MemberEntity member, ClosedWorld world);
 
-  bool hasInvokedGetter(Element member, ClosedWorld world);
+  bool hasInvokedGetter(MemberEntity member, ClosedWorld world);
 
   Map<Selector, SelectorConstraints> invocationsByName(String name);
 
@@ -50,10 +50,10 @@ abstract class CodegenWorldBuilder implements WorldBuilder {
   Iterable<FunctionEntity> get closurizedMembers;
 }
 
-class CodegenWorldBuilderImpl implements CodegenWorldBuilder {
-  final NativeBasicData _nativeData;
+abstract class CodegenWorldBuilderImpl implements CodegenWorldBuilder {
+  final ElementEnvironment _elementEnvironment;
+  final NativeBasicData _nativeBasicData;
   final ClosedWorld _world;
-  final JavaScriptConstantCompiler _constants;
 
   /// The set of all directly instantiated classes, that is, classes with a
   /// generative constructor that has been called directly and not only through
@@ -62,8 +62,7 @@ class CodegenWorldBuilderImpl implements CodegenWorldBuilder {
   /// Invariant: Elements are declaration elements.
   // TODO(johnniwinther): [_directlyInstantiatedClasses] and
   // [_instantiatedTypes] sets should be merged.
-  final Set<ClassElement> _directlyInstantiatedClasses =
-      new Set<ClassElement>();
+  final Set<ClassEntity> _directlyInstantiatedClasses = new Set<ClassEntity>();
 
   /// The set of all directly instantiated types, that is, the types of the
   /// directly instantiated classes.
@@ -72,12 +71,12 @@ class CodegenWorldBuilderImpl implements CodegenWorldBuilder {
   final Set<InterfaceType> _instantiatedTypes = new Set<InterfaceType>();
 
   /// Classes implemented by directly instantiated classes.
-  final Set<ClassElement> _implementedClasses = new Set<ClassElement>();
+  final Set<ClassEntity> _implementedClasses = new Set<ClassEntity>();
 
   /// The set of all referenced static fields.
   ///
   /// Invariant: Elements are declaration elements.
-  final Set<FieldElement> allReferencedStaticFields = new Set<FieldElement>();
+  final Set<FieldEntity> allReferencedStaticFields = new Set<FieldEntity>();
 
   /**
    * Documentation wanted -- johnniwinther
@@ -95,8 +94,8 @@ class CodegenWorldBuilderImpl implements CodegenWorldBuilder {
   final Map<String, Map<Selector, SelectorConstraints>> _invokedSetters =
       <String, Map<Selector, SelectorConstraints>>{};
 
-  final Map<ClassElement, _ClassUsage> _processedClasses =
-      <ClassElement, _ClassUsage>{};
+  final Map<ClassEntity, _ClassUsage> _processedClasses =
+      <ClassEntity, _ClassUsage>{};
 
   /// Map of registered usage of static members of live classes.
   final Map<Entity, _StaticMemberUsage> _staticMemberUsage =
@@ -116,7 +115,7 @@ class CodegenWorldBuilderImpl implements CodegenWorldBuilder {
   final Map<String, Set<_MemberUsage>> _instanceFunctionsByName =
       <String, Set<_MemberUsage>>{};
 
-  final Set<ResolutionDartType> isChecks = new Set<ResolutionDartType>();
+  final Set<DartType> isChecks = new Set<DartType>();
 
   final SelectorConstraintsStrategy selectorConstraintsStrategy;
 
@@ -125,34 +124,17 @@ class CodegenWorldBuilderImpl implements CodegenWorldBuilder {
   /// Set of methods in instantiated classes that are potentially closurized.
   final Set<FunctionEntity> closurizedMembers = new Set<FunctionEntity>();
 
-  CodegenWorldBuilderImpl(this._nativeData, this._world, this._constants,
-      this.selectorConstraintsStrategy);
+  CodegenWorldBuilderImpl(this._elementEnvironment, this._nativeBasicData,
+      this._world, this.selectorConstraintsStrategy);
 
-  /// Calls [f] with every instance field, together with its declarer, in an
-  /// instance of [cls].
-  void forEachInstanceField(
-      ClassElement cls, void f(ClassEntity declarer, FieldEntity field)) {
-    cls.implementation
-        .forEachInstanceField(f, includeSuperAndInjectedMembers: true);
-  }
-
-  @override
-  void forEachParameter(
-      MethodElement function, void f(DartType type, String name)) {
-    FunctionSignature parameters = function.functionSignature;
-    parameters.forEachParameter((ParameterElement parameter) {
-      f(parameter.type, parameter.name);
-    });
-  }
-
-  Iterable<ClassElement> get processedClasses => _processedClasses.keys
+  Iterable<ClassEntity> get processedClasses => _processedClasses.keys
       .where((cls) => _processedClasses[cls].isInstantiated);
 
   /// All directly instantiated classes, that is, classes with a generative
   /// constructor that has been called directly and not only through a
   /// super-call.
   // TODO(johnniwinther): Improve semantic precision.
-  Iterable<ClassElement> get directlyInstantiatedClasses {
+  Iterable<ClassEntity> get directlyInstantiatedClasses {
     return _directlyInstantiatedClasses;
   }
 
@@ -170,10 +152,10 @@ class CodegenWorldBuilderImpl implements CodegenWorldBuilder {
   // subclass and through subtype instantiated types/classes.
   // TODO(johnniwinther): Support unknown type arguments for generic types.
   void registerTypeInstantiation(
-      ResolutionInterfaceType type, ClassUsedCallback classUsed,
+      InterfaceType type, ClassUsedCallback classUsed,
       {bool byMirrors: false}) {
-    ClassElement cls = type.element;
-    bool isNative = _nativeData.isNativeClass(cls);
+    ClassEntity cls = type.element;
+    bool isNative = _nativeBasicData.isNativeClass(cls);
     _instantiatedTypes.add(type);
     if (!cls.isAbstract
         // We can't use the closed-world assumption with native abstract
@@ -195,7 +177,7 @@ class CodegenWorldBuilderImpl implements CodegenWorldBuilder {
     // include the type arguments.
     if (_implementedClasses.add(cls)) {
       classUsed(cls, _getClassUsage(cls).implement());
-      cls.allSupertypes.forEach((ResolutionInterfaceType supertype) {
+      _elementEnvironment.forEachSupertype(cls, (InterfaceType supertype) {
         if (_implementedClasses.add(supertype.element)) {
           classUsed(
               supertype.element, _getClassUsage(supertype.element).implement());
@@ -205,7 +187,7 @@ class CodegenWorldBuilderImpl implements CodegenWorldBuilder {
   }
 
   bool _hasMatchingSelector(Map<Selector, SelectorConstraints> selectors,
-      MemberElement member, ClosedWorld world) {
+      MemberEntity member, ClosedWorld world) {
     if (selectors == null) return false;
     for (Selector selector in selectors.keys) {
       if (selector.appliesUnnamed(member)) {
@@ -218,16 +200,16 @@ class CodegenWorldBuilderImpl implements CodegenWorldBuilder {
     return false;
   }
 
-  bool hasInvocation(Element member, ClosedWorld world) {
+  bool hasInvocation(MemberEntity member, ClosedWorld world) {
     return _hasMatchingSelector(_invokedNames[member.name], member, world);
   }
 
-  bool hasInvokedGetter(Element member, ClosedWorld world) {
+  bool hasInvokedGetter(MemberEntity member, ClosedWorld world) {
     return _hasMatchingSelector(_invokedGetters[member.name], member, world) ||
         member.isFunction && methodsNeedingSuperGetter.contains(member);
   }
 
-  bool hasInvokedSetter(Element member, ClosedWorld world) {
+  bool hasInvokedSetter(MemberEntity member, ClosedWorld world) {
     return _hasMatchingSelector(_invokedSetters[member.name], member, world);
   }
 
@@ -318,28 +300,23 @@ class CodegenWorldBuilderImpl implements CodegenWorldBuilder {
     _invokedSetters.forEach(f);
   }
 
-  void registerIsCheck(ResolutionDartType type) {
-    type = type.unaliased;
-    // Even in checked mode, type annotations for return type and argument
-    // types do not imply type checks, so there should never be a check
-    // against the type variable of a typedef.
-    assert(!type.isTypeVariable || !type.element.enclosingElement.isTypedef);
-    isChecks.add(type);
+  void registerIsCheck(DartType type) {
+    isChecks.add(type.unaliased);
   }
 
   void _registerStaticUse(StaticUse staticUse) {
-    Element element = staticUse.element;
-    if (Elements.isStaticOrTopLevel(element) && element.isField) {
-      allReferencedStaticFields.add(element);
+    if (staticUse.element is FieldEntity) {
+      FieldEntity field = staticUse.element;
+      if (field.isTopLevel || field.isStatic) {
+        allReferencedStaticFields.add(field);
+      }
     }
     switch (staticUse.kind) {
       case StaticUseKind.STATIC_TEAR_OFF:
-        MethodElement method = element;
-        staticFunctionsNeedingGetter.add(method);
+        staticFunctionsNeedingGetter.add(staticUse.element);
         break;
       case StaticUseKind.SUPER_TEAR_OFF:
-        MethodElement method = element;
-        methodsNeedingSuperGetter.add(method);
+        methodsNeedingSuperGetter.add(staticUse.element);
         break;
       case StaticUseKind.SUPER_FIELD_SET:
       case StaticUseKind.FIELD_SET:
@@ -357,12 +334,12 @@ class CodegenWorldBuilderImpl implements CodegenWorldBuilder {
   }
 
   void registerStaticUse(StaticUse staticUse, MemberUsedCallback memberUsed) {
-    Element element = staticUse.element;
-    assert(invariant(element, element.isDeclaration,
-        message: "Element ${element} is not the declaration."));
+    Entity element = staticUse.element;
     _registerStaticUse(staticUse);
     _StaticMemberUsage usage = _staticMemberUsage.putIfAbsent(element, () {
-      if ((element.isStatic || element.isTopLevel) && element.isFunction) {
+      if (element is MemberEntity &&
+          (element.isStatic || element.isTopLevel) &&
+          element.isFunction) {
         return new _StaticFunctionUsage(element);
       } else {
         return new _GeneralStaticMemberUsage(element);
@@ -413,22 +390,25 @@ class CodegenWorldBuilderImpl implements CodegenWorldBuilder {
     closurizedMembers.add(element);
   }
 
-  void processClassMembers(ClassElement cls, MemberUsedCallback memberUsed) {
-    cls.implementation.forEachMember((_, MemberElement member) {
-      assert(invariant(member, member.isDeclaration));
-      if (!member.isInstanceMember) return;
-      if (member.isMalformed) return;
-      _getMemberUsage(member, memberUsed);
+  void processClassMembers(ClassEntity cls, MemberUsedCallback memberUsed) {
+    _elementEnvironment.forEachClassMember(cls,
+        (ClassEntity cls, MemberEntity member) {
+      _processInstantiatedClassMember(cls, member, memberUsed);
     });
   }
 
+  void _processInstantiatedClassMember(
+      ClassEntity cls, MemberEntity member, MemberUsedCallback memberUsed) {
+    if (!member.isInstanceMember) return;
+    _getMemberUsage(member, memberUsed);
+  }
+
   _MemberUsage _getMemberUsage(
-      MemberElement member, MemberUsedCallback memberUsed) {
-    assert(invariant(member, member.isDeclaration));
+      MemberEntity member, MemberUsedCallback memberUsed) {
     return _instanceMemberUsage.putIfAbsent(member, () {
       String memberName = member.name;
-      ClassElement cls = member.enclosingClass;
-      bool isNative = _nativeData.isNativeClass(cls);
+      ClassEntity cls = member.enclosingClass;
+      bool isNative = _nativeBasicData.isNativeClass(cls);
       _MemberUsage usage = new _MemberUsage(member, isNative: isNative);
       EnumSet<MemberUse> useSet = new EnumSet<MemberUse>();
       useSet.addAll(usage.appliedUse);
@@ -477,16 +457,15 @@ class CodegenWorldBuilderImpl implements CodegenWorldBuilder {
   }
 
   /// Return the canonical [_ClassUsage] for [cls].
-  _ClassUsage _getClassUsage(ClassElement cls) {
+  _ClassUsage _getClassUsage(ClassEntity cls) {
     return _processedClasses.putIfAbsent(cls, () => new _ClassUsage(cls));
   }
 
-  void _processInstantiatedClass(
-      ClassElement cls, ClassUsedCallback classUsed) {
+  void _processInstantiatedClass(ClassEntity cls, ClassUsedCallback classUsed) {
     // Registers [superclass] as instantiated. Returns `true` if it wasn't
     // already instantiated and we therefore have to process its superclass as
     // well.
-    bool processClass(ClassElement superclass) {
+    bool processClass(ClassEntity superclass) {
       _ClassUsage usage = _getClassUsage(superclass);
       if (!usage.isInstantiated) {
         classUsed(usage.cls, usage.instantiate());
@@ -496,16 +475,108 @@ class CodegenWorldBuilderImpl implements CodegenWorldBuilder {
     }
 
     while (cls != null && processClass(cls)) {
-      cls = cls.superclass;
+      cls = _elementEnvironment.getSuperClass(cls);
     }
   }
 
+  bool registerConstantUse(ConstantUse use);
+}
+
+class ElementCodegenWorldBuilderImpl extends CodegenWorldBuilderImpl {
+  final JavaScriptConstantCompiler _constants;
+
+  ElementCodegenWorldBuilderImpl(
+      ElementEnvironment elementEnvironment,
+      NativeBasicData nativeBasicData,
+      ClosedWorld world,
+      this._constants,
+      SelectorConstraintsStrategy selectorConstraintsStrategy)
+      : super(elementEnvironment, nativeBasicData, world,
+            selectorConstraintsStrategy);
+
+  /// Calls [f] with every instance field, together with its declarer, in an
+  /// instance of [cls].
+  void forEachInstanceField(
+      ClassElement cls, void f(ClassEntity declarer, FieldEntity field)) {
+    cls.implementation
+        .forEachInstanceField(f, includeSuperAndInjectedMembers: true);
+  }
+
+  @override
+  void forEachParameter(
+      MethodElement function, void f(DartType type, String name)) {
+    FunctionSignature parameters = function.functionSignature;
+    parameters.forEachParameter((ParameterElement parameter) {
+      f(parameter.type, parameter.name);
+    });
+  }
+
+  @override
+  void _processInstantiatedClassMember(
+      ClassEntity cls, MemberElement member, MemberUsedCallback memberUsed) {
+    assert(invariant(member, member.isDeclaration));
+    if (member.isMalformed) return;
+    super._processInstantiatedClassMember(cls, member, memberUsed);
+  }
+
+  @override
+  _MemberUsage _getMemberUsage(
+      MemberElement member, MemberUsedCallback memberUsed) {
+    assert(invariant(member, member.isDeclaration));
+    return super._getMemberUsage(member, memberUsed);
+  }
+
+  void registerStaticUse(StaticUse staticUse, MemberUsedCallback memberUsed) {
+    Element element = staticUse.element;
+    assert(invariant(element, element.isDeclaration,
+        message: "Element ${element} is not the declaration."));
+    super.registerStaticUse(staticUse, memberUsed);
+  }
+
   /// Register the constant [use] with this world builder. Returns `true` if
   /// the constant use was new to the world.
+  @override
   bool registerConstantUse(ConstantUse use) {
     if (use.kind == ConstantUseKind.DIRECT) {
       _constants.addCompileTimeConstantForEmission(use.value);
     }
     return _constantValues.add(use.value);
   }
+
+  void registerIsCheck(ResolutionDartType type) {
+    // Even in checked mode, type annotations for return type and argument
+    // types do not imply type checks, so there should never be a check
+    // against the type variable of a typedef.
+    assert(!type.isTypeVariable || !type.element.enclosingElement.isTypedef);
+    super.registerIsCheck(type);
+  }
+}
+
+class KernelCodegenWorldBuilder extends CodegenWorldBuilderImpl {
+  KernelCodegenWorldBuilder(
+      ElementEnvironment elementEnvironment,
+      NativeBasicData nativeBasicData,
+      ClosedWorld world,
+      SelectorConstraintsStrategy selectorConstraintsStrategy)
+      : super(elementEnvironment, nativeBasicData, world,
+            selectorConstraintsStrategy);
+
+  @override
+  bool registerConstantUse(ConstantUse use) {
+    throw new UnimplementedError(
+        'KernelCodegenWorldBuilder.registerConstantUse');
+  }
+
+  @override
+  void forEachParameter(
+      FunctionEntity function, void f(DartType type, String name)) {
+    throw new UnimplementedError('KernelCodegenWorldBuilder.forEachParameter');
+  }
+
+  @override
+  void forEachInstanceField(
+      ClassEntity cls, void f(ClassEntity declarer, FieldEntity field)) {
+    throw new UnimplementedError(
+        'KernelCodegenWorldBuilder.forEachInstanceField');
+  }
 }

tests/compiler/dart2js/compiler_helper.dart

@@ -13,6 +13,8 @@ import 'package:compiler/src/elements/elements.dart';
 export 'package:compiler/src/elements/elements.dart';
 
 import 'package:compiler/src/js_backend/js_backend.dart' as js;
+import 'package:compiler/src/js_backend/element_strategy.dart'
+    show ElementCodegenWorkItem;
 
 import 'package:compiler/src/commandline_options.dart';
 import 'package:compiler/src/common/codegen.dart';
@@ -83,7 +85,7 @@ Future<String> compile(String code,
     resolutionWork.run();
     ClosedWorld closedWorld = compiler.closeResolution().closedWorld;
     CodegenWorkItem work =
-        new CodegenWorkItem(compiler.backend, closedWorld, element);
+        new ElementCodegenWorkItem(compiler.backend, closedWorld, element);
     compiler.phase = Compiler.PHASE_COMPILING;
     work.run();
     js.JavaScriptBackend backend = compiler.backend;

tests/compiler/dart2js/type_representation_test.dart

@@ -49,7 +49,8 @@ void testTypeRepresentations() {
         env.compiler.enqueuer.createCodegenEnqueuer(closedWorld);
         env.compiler.backend.onCodegenStart(
             closedWorld,
-            new CodegenWorldBuilderImpl(
+            new ElementCodegenWorldBuilderImpl(
+                env.compiler.elementEnvironment,
                 env.compiler.backend.nativeBasicData,
                 closedWorld,
                 env.compiler.backend.constants,