Remove direct access to enqueuer through use of WorldImpact

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 2bb7001798d1f93dba50e4768471892cea45ef41..089058ca32bf9c5d80ca95da9b373216c306c72d 100644
--- a/pkg/compiler/lib/src/common/backend_api.dart
+++ b/pkg/compiler/lib/src/common/backend_api.dart
@@ -82,7 +82,8 @@ abstract class Backend extends Target {
 
   void initializeHelperClasses() {}
 
-  void enqueueHelpers(ResolutionEnqueuer world);
+  /// 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);
@@ -116,21 +117,27 @@ abstract class Backend extends Target {
 
   /// Enable deferred loading. Returns `true` if the backend supports deferred
   /// loading.
-  bool enableDeferredLoadingIfSupported(
-      ResolutionEnqueuer enqueuer, Spannable node);
+  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.
-  // TODO(johnniwinther): Remove this. It's only called once for each [cls] and
-  // only with [Compiler.globalDependencies] as [registry].
-  void registerInstantiatedClass(ClassElement cls, Enqueuer enqueuer) {}
+  /// 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.
-  void registerImplementedClass(ClassElement cls, Enqueuer enqueuer) {}
+  /// 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].
@@ -141,40 +148,47 @@ abstract class Backend extends Target {
   void registerTypeVariableBoundsSubtypeCheck(
       DartType typeArgument, DartType bound) {}
 
-  /**
-   * Call this to register that an instantiated generic class has a call
-   * method.
-   */
-  void registerCallMethodWithFreeTypeVariables(
-      Element callMethod, Enqueuer enqueuer) {}
+  /// Called to register that an instantiated generic class has a call method.
+  /// Any backend specific [WorldImpact] of this is returned.
+  ///
+  /// Note: The [callMethod] is registered even thought it doesn't reference
+  /// the type variables.
+  WorldImpact registerCallMethodWithFreeTypeVariables(Element callMethod,
+          {bool forResolution}) =>
+      const WorldImpact();
 
   /// Called to instruct the backend to register that a closure exists for a
-  /// function on an instantiated generic class.
-  void registerClosureWithFreeTypeVariables(
-      Element closure, Enqueuer enqueuer) {}
+  /// function on an instantiated generic class. Any backend specific
+  /// [WorldImpact] of this is returned.
+  WorldImpact registerClosureWithFreeTypeVariables(Element closure,
+          {bool forResolution}) =>
+      const WorldImpact();
 
-  /// Call this to register that a member has been closurized.
-  void registerBoundClosure(Enqueuer enqueuer) {}
+  /// Called to register that a member has been closurized. Any backend specific
+  /// [WorldImpact] of this is returned.
+  WorldImpact registerBoundClosure() => const WorldImpact();
 
-  /// Call this to register that a static function has been closurized.
-  void registerGetOfStaticFunction(Enqueuer enqueuer) {}
+  /// Called to register that a static function has been closurized. Any backend
+  /// specific [WorldImpact] of this is returned.
+  WorldImpact registerGetOfStaticFunction() => const WorldImpact();
 
-  /**
-   * Call this to register that the [:runtimeType:] property has been accessed.
-   */
-  void registerRuntimeType(Enqueuer enqueuer) {}
+  /// Called to register that the `runtimeType` property has been accessed. Any
+  /// backend specific [WorldImpact] of this is returned.
+  WorldImpact registerRuntimeType() => const WorldImpact();
 
-  /// Call this to register a `noSuchMethod` implementation.
+  /// Called to register a `noSuchMethod` implementation.
   void registerNoSuchMethod(FunctionElement noSuchMethodElement) {}
 
-  /// Call this method to enable support for `noSuchMethod`.
-  void enableNoSuchMethod(Enqueuer enqueuer) {}
+  /// Called to enable support for `noSuchMethod`. Any backend specific
+  /// [WorldImpact] of this is returned.
+  WorldImpact enableNoSuchMethod() => const WorldImpact();
 
   /// Returns whether or not `noSuchMethod` support has been enabled.
   bool get enabledNoSuchMethod => false;
 
-  /// Call this method to enable support for isolates.
-  void enableIsolateSupport(Enqueuer enqueuer) {}
+  /// Called to enable support for isolates. Any backend specific [WorldImpact]
+  /// of this is returned.
+  WorldImpact enableIsolateSupport({bool forResolution});
 
   void registerConstSymbol(String name) {}
 
@@ -206,7 +220,10 @@ abstract class Backend extends Target {
     return false;
   }
 
-  void registerStaticUse(Enqueuer enqueuer, Element element) {}
+  /// Called to register that [element] is statically known to be used. Any
+  /// backend specific [WorldImpact] of this is returned.
+  WorldImpact registerStaticUse(Element element, {bool forResolution}) =>
+      const WorldImpact();
 
   /// This method is called immediately after the [LibraryElement] [library] has
   /// been created.
@@ -314,7 +331,9 @@ abstract class Backend extends Target {
   void forgetElement(Element element) {}
 
   /// Computes the [WorldImpact] of calling [mainMethod] as the entry point.
-  WorldImpact computeMainImpact(Enqueuer enqueuer, MethodElement mainMethod) {}
+  WorldImpact computeMainImpact(MethodElement mainMethod,
+          {bool forResolution}) =>
+      const WorldImpact();
 
   /// Returns the location of the patch-file associated with [libraryName]
   /// resolved from [plaformConfigUri].