Remove WorldImpact from caches when no longer needed.

pkg/compiler/lib/src/deferred_load.dart

 // Copyright (c) 2014, 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 deferred_load;
 
 import 'common.dart';
 import 'common/backend_api.dart' show
     Backend;
 import 'common/tasks.dart' show
@@ skipping 10 matching lines @@
     AccessorElement,
     AstElement,
     ClassElement,
     Element,
     ElementKind,
     Elements,
     ExportElement,
     FunctionElement,
     ImportElement,
     LibraryElement,
+    LocalFunctionElement,
     MetadataAnnotation,
     PrefixElement,
     ScopeContainerElement,
     TypedefElement;
 import 'js_backend/js_backend.dart' show
     JavaScriptBackend;
 import 'resolution/resolution.dart' show
     AnalyzableElementX;
 import 'resolution/tree_elements.dart' show
     TreeElements;
 import 'tree/tree.dart' as ast;
 import 'tree/tree.dart' show
     Import,
     LibraryTag,
     LibraryDependency,
     LiteralDartString,
     LiteralString,
     NewExpression,
     Node;
 import 'universe/use.dart' show
+    DynamicUse,
     StaticUse,
     TypeUse,
     TypeUseKind;
 import 'universe/world_impact.dart' show
-    WorldImpact;
+    ImpactUseCase,
+    WorldImpact,
+    WorldImpactVisitorImpl;
 import 'util/setlet.dart' show
     Setlet;
 import 'util/uri_extras.dart' as uri_extras;
 import 'util/util.dart' show
     Link, makeUnique;
 
 /// A "hunk" of the program that will be loaded whenever one of its [imports]
 /// are loaded.
 ///
 /// Elements that are only used in one deferred import, is in an OutputUnit with
@@ skipping 49 matching lines @@
   /// The OutputUnit that will be loaded when the program starts.
   final OutputUnit mainOutputUnit = new OutputUnit(isMainOutput: true);
 
   /// A set containing (eventually) all output units that will result from the
   /// program.
   final Set<OutputUnit> allOutputUnits = new Set<OutputUnit>();
 
   /// Will be `true` if the program contains deferred libraries.
   bool isProgramSplit = false;
 
+  static const ImpactUseCase IMPACT_USE = const ImpactUseCase('Deferred load');
+
   /// A mapping from the name of a defer import to all the output units it
   /// depends on in a list of lists to be loaded in the order they appear.
   ///
   /// For example {"lib1": [[lib1_lib2_lib3], [lib1_lib2, lib1_lib3],
   /// [lib1]]} would mean that in order to load "lib1" first the hunk
   /// lib1_lib2_lib2 should be loaded, then the hunks lib1_lib2 and lib1_lib3
   /// can be loaded in parallel. And finally lib1 can be loaded.
   final Map<String, List<OutputUnit>> hunksToLoad =
       new Map<String, List<OutputUnit>>();
 
@@ skipping 176 matching lines @@
       } else {
         // TODO(sigurdm): We want to be more specific about this - need a better
         // way to query "liveness".
         AstElement analyzableElement = element.analyzableElement.declaration;
         if (!compiler.enqueuer.resolution.hasBeenProcessed(analyzableElement)) {
           return;
         }
 
         WorldImpact worldImpact =
             compiler.resolution.getWorldImpact(analyzableElement);
-        worldImpact.staticUses.forEach((StaticUse staticUse) {
-          elements.add(staticUse.element);
-        });
-        for (TypeUse typeUse in worldImpact.typeUses) {
-          DartType type = typeUse.type;
-          switch (typeUse.kind) {
-            case TypeUseKind.TYPE_LITERAL:
-              if (type.isTypedef || type.isInterfaceType) {
-                elements.add(type.element);
-              }
-              break;
-            case TypeUseKind.INSTANTIATION:
-            case TypeUseKind.IS_CHECK:
-            case TypeUseKind.AS_CAST:
-            case TypeUseKind.CATCH_TYPE:
-              collectTypeDependencies(type);
-              break;
-            case TypeUseKind.CHECKED_MODE_CHECK:
-              if (compiler.enableTypeAssertions) {
-                collectTypeDependencies(type);
-              }
-              break;
-          }
-        }
+        compiler.impactStrategy.visitImpact(
+            analyzableElement,
+            worldImpact,
+            new WorldImpactVisitorImpl(
+                visitStaticUse: (StaticUse staticUse) {
+                  elements.add(staticUse.element);
+                },
+                visitTypeUse: (TypeUse typeUse) {
+                  DartType type = typeUse.type;
+                  switch (typeUse.kind) {
+                    case TypeUseKind.TYPE_LITERAL:
+                      if (type.isTypedef || type.isInterfaceType) {
+                        elements.add(type.element);
+                      }
+                      break;
+                    case TypeUseKind.INSTANTIATION:
+                    case TypeUseKind.IS_CHECK:
+                    case TypeUseKind.AS_CAST:
+                    case TypeUseKind.CATCH_TYPE:
+                      collectTypeDependencies(type);
+                      break;
+                    case TypeUseKind.CHECKED_MODE_CHECK:
+                      if (compiler.enableTypeAssertions) {
+                        collectTypeDependencies(type);
+                      }
+                      break;
+                  }
+                }),
+             IMPACT_USE);
 
         TreeElements treeElements = analyzableElement.resolvedAst.elements;
         assert(treeElements != null);
 
         treeElements.forEachConstantNode((Node node, _) {
           // Explicitly depend on the backend constants.
           ConstantValue value =
               backend.constants.getConstantValueForNode(node, treeElements);
           if (value != null) {
             // TODO(johnniwinther): Assert that all constants have values when
@@ skipping 349 matching lines @@
         if (representative == null) {
           representative = outputUnit;
           allOutputUnits.add(representative);
         }
         _constantToOutputUnit[constant] = representative;
       });
 
       // Generate a unique name for each OutputUnit.
       _assignNamesToOutputUnits(allOutputUnits);
     });
+    // Notify the impact strategy impacts are no longer needed for deferred
+    // load.
+    compiler.impactStrategy.onImpactUsed(IMPACT_USE);
   }
 
   void beforeResolution(Compiler compiler) {
     if (compiler.mainApp == null) return;
     _allDeferredImports[_fakeMainImport] = compiler.mainApp;
     var lastDeferred;
     // When detecting duplicate prefixes of deferred libraries there are 4
     // cases of duplicate prefixes:
     // 1.
     // import "lib.dart" deferred as a;
@@ skipping 274 matching lines @@
     return result;
   }
 
   bool operator ==(other) {
     if (other is! _DeclaredDeferredImport) return false;
     return declaration == other.declaration;
   }
 
   int get hashCode => declaration.hashCode * 17;
 }