Implement modular compilation

lib/src/codegen/js_field_storage.dart

-// Copyright (c) 2015, 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.
-
-import 'dart:collection' show HashMap, HashSet;
-import 'package:analyzer/dart/ast/ast.dart' show Identifier;
-import 'package:analyzer/dart/element/element.dart';
-
-import 'js_codegen.dart' show ExtensionTypeSet;
-
-/// We use a storage slot for fields that override or can be overridden by
-/// getter/setter pairs.
-HashSet<FieldElement> findFieldsNeedingStorage(
-    Iterable<CompilationUnitElement> units, ExtensionTypeSet extensionTypes) {
-  var overrides = new HashSet<FieldElement>();
-  for (var unit in units) {
-    for (var cls in unit.types) {
-      var superclasses = getSuperclasses(cls);
-      for (var field in cls.fields) {
-        if (!field.isSynthetic && !overrides.contains(field)) {
-          checkForPropertyOverride(
-              field, superclasses, overrides, extensionTypes);
-        }
-      }
-    }
-  }
-
-  return overrides;
-}
-
-void checkForPropertyOverride(
-    FieldElement field,
-    List<ClassElement> superclasses,
-    HashSet<FieldElement> overrides,
-    ExtensionTypeSet extensionTypes) {
-  assert(!field.isSynthetic);
-
-  var library = field.library;
-
-  bool found = false;
-  for (var superclass in superclasses) {
-    var superprop = getProperty(superclass, library, field.name);
-    if (superprop != null) {
-      // If we find an abstract getter/setter pair, stop the search.
-      var getter = superprop.getter;
-      var setter = superprop.setter;
-      if (!extensionTypes.contains(superclass) &&
-          (getter == null || getter.isAbstract) &&
-          (setter == null || setter.isAbstract)) {
-        break;
-      }
-
-      found = true;
-      // Record that the super property is overridden.
-      if (superprop.library == library) overrides.add(superprop);
-    }
-  }
-
-  // If this we found a super property, then this property overrides it.
-  if (found) overrides.add(field);
-}
-
-FieldElement getProperty(
-    ClassElement cls, LibraryElement fromLibrary, String name) {
-  // Properties from a different library are not accessible.
-  if (Identifier.isPrivateName(name) && cls.library != fromLibrary) {
-    return null;
-  }
-  for (var accessor in cls.accessors) {
-    var prop = accessor.variable;
-    if (prop.name == name) return prop;
-  }
-  return null;
-}
-
-List<ClassElement> getSuperclasses(ClassElement cls) {
-  var result = <ClassElement>[];
-  var visited = new HashSet<ClassElement>();
-  while (cls != null && visited.add(cls)) {
-    for (var mixinType in cls.mixins.reversed) {
-      var mixin = mixinType.element;
-      if (mixin != null) result.add(mixin);
-    }
-    var supertype = cls.supertype;
-    if (supertype == null) break;
-
-    cls = supertype.element;
-    result.add(cls);
-  }
-  return result;
-}