| // Copyright (c) 2016, 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, Queue; |
| |
| import 'package:analyzer/dart/ast/ast.dart' show Identifier; |
| import 'package:analyzer/dart/element/element.dart'; |
| import 'package:analyzer/src/dart/element/element.dart' show FieldElementImpl; |
| |
| import '../js_ast/js_ast.dart' as JS; |
| import 'element_helpers.dart'; |
| import 'js_names.dart' as JS; |
| |
| /// Dart allows all fields to be overridden. |
| /// |
| /// To prevent a performance/code size penalty for allowing this, we analyze |
| /// private classes within each library that is being compiled to determine |
| /// if those fields should be virtual or not. In effect, we devirtualize fields |
| /// when possible by analyzing the class hierarchy and using knowledge of |
| /// which members are private and thus, could not be overridden outside of the |
| /// current library. |
| class VirtualFieldModel { |
| final _modelForLibrary = |
| new HashMap<LibraryElement, _LibraryVirtualFieldModel>(); |
| |
| _LibraryVirtualFieldModel _getModel(LibraryElement library) => |
| _modelForLibrary.putIfAbsent( |
| library, () => new _LibraryVirtualFieldModel.build(library)); |
| |
| /// Returns true if a field is virtual. |
| bool isVirtual(FieldElement field) => |
| _getModel(field.library).isVirtual(field); |
| } |
| |
| /// This is a building block of [VirtualFieldModel], used to track information |
| /// about a single library that has been analyzed. |
| class _LibraryVirtualFieldModel { |
| /// Fields that are private (or public fields of a private class) and |
| /// overridden in this library. |
| /// |
| /// This means we must generate them as virtual fields using a property pair |
| /// in JavaScript. |
| final _overriddenPrivateFields = new HashSet<FieldElement>(); |
| |
| /// Private classes that can be extended outside of this library. |
| /// |
| /// Normally private classes cannot be accessed outside this library, however, |
| /// this can happen if they are extended by a public class, for example: |
| /// |
| /// class _A { int x = 42; } |
| /// class _B { int x = 42; } |
| /// |
| /// // _A is now effectively public for the purpose of overrides. |
| /// class C extends _A {} |
| /// |
| /// The class _A must treat is "x" as virtual, however _B does not. |
| final _extensiblePrivateClasses = new HashSet<ClassElement>(); |
| |
| _LibraryVirtualFieldModel.build(LibraryElement library) { |
| var allTypes = library.units.expand((u) => u.types).toList(); |
| |
| // The set of public types is our initial extensible type set. |
| // From there, visit all immediate private types in this library, and so on |
| // from those private types, marking them as extensible. |
| var typesToVisit = |
| new Queue<ClassElement>.from(allTypes.where((t) => t.isPublic)); |
| while (typesToVisit.isNotEmpty) { |
| var extensibleType = typesToVisit.removeFirst(); |
| |
| // For each supertype of a public type in this library, |
| // if we encounter a private class, we mark it as being extended, and |
| // add it to our work set if this is the first time we've visited it. |
| for (var type in getImmediateSuperclasses(extensibleType)) { |
| if (!type.isPublic && type.library == library) { |
| if (_extensiblePrivateClasses.add(type)) typesToVisit.add(type); |
| } |
| } |
| } |
| |
| // ClassElement can only look up inherited members with an O(N) scan through |
| // the class, so we build up a mapping of all fields in the library ahead of |
| // time. |
| var allFields = |
| new HashMap<ClassElement, HashMap<String, FieldElement>>.fromIterable( |
| allTypes, |
| value: (t) => new HashMap.fromIterable( |
| t.fields.where((f) => !f.isStatic), |
| key: (f) => f.name)); |
| |
| for (var type in allTypes) { |
| Set<ClassElement> supertypes = null; |
| |
| // Visit accessors in the current class, and see if they override an |
| // otherwise private field. |
| for (var accessor in type.accessors) { |
| // For getter/setter pairs only process them once. |
| if (accessor.correspondingGetter != null) continue; |
| // Ignore abstract or static accessors. |
| if (accessor.isAbstract || accessor.isStatic) continue; |
| // Ignore public accessors in extensible classes. |
| if (accessor.isPublic && |
| (type.isPublic || _extensiblePrivateClasses.contains(type))) { |
| continue; |
| } |
| |
| if (supertypes == null) { |
| supertypes = new Set(); |
| void collectSupertypes(ClassElement cls) { |
| if (!supertypes.add(cls)) return; |
| var s = cls.supertype?.element; |
| if (s != null) collectSupertypes(s); |
| cls.mixins.forEach((m) => collectSupertypes(m.element)); |
| } |
| |
| collectSupertypes(type); |
| supertypes.remove(type); |
| supertypes.removeWhere((c) => c.library != type.library); |
| } |
| |
| // Look in all super classes to see if we're overriding a field in our |
| // library, if so mark that field as overridden. |
| var name = accessor.variable.name; |
| _overriddenPrivateFields.addAll( |
| supertypes.map((c) => allFields[c][name]).where((f) => f != null)); |
| } |
| } |
| } |
| |
| /// Returns true if a field inside this library is virtual. |
| bool isVirtual(FieldElement field) { |
| // If the field was marked non-virtual, we know for sure. |
| if (!field.isVirtual) return false; |
| if (field.isStatic) return false; |
| |
| var type = field.enclosingElement; |
| var library = type.library; |
| if (library.isInSdk && library.source.uri.toString().startsWith('dart:_')) { |
| // There should be no extensible fields in private SDK libraries. |
| return false; |
| } |
| |
| if (field.isPublic) { |
| // Public fields in public classes (or extensible private classes) |
| // are always virtual. |
| // They could be overridden by someone using our library. |
| if (type.isPublic) return true; |
| if (_extensiblePrivateClasses.contains(type)) return true; |
| } |
| |
| // Otherwise, the field is effectively private and we only need to make it |
| // virtual if it's overridden. |
| return _overriddenPrivateFields.contains(field); |
| } |
| } |
| |
| /// Tracks how fields, getters and setters are represented when emitting JS. |
| /// |
| /// Dart classes have implicit features that must be made explicit: |
| /// |
| /// - virtual fields induce a getter and setter pair. |
| /// - getters and setters are independent. |
| /// - getters and setters can be overridden. |
| /// |
| class ClassPropertyModel { |
| /// Fields that are virtual, that is, they must be generated as a property |
| /// pair in JavaScript. |
| /// |
| /// The value property stores the symbol used for the field's storage slot. |
| final virtualFields = <FieldElement, JS.TemporaryId>{}; |
| |
| /// Static fields that are overridden, this does not matter for Dart but in |
| /// JS we need to take care initializing these because JS classes inherit |
| /// statics. |
| final staticFieldOverrides = new HashSet<FieldElement>(); |
| |
| /// The set of inherited getters, used because JS getters/setters are paired, |
| /// so if we're generating a setter we may need to emit a getter that calls |
| /// super. |
| final inheritedGetters = new HashSet<String>(); |
| |
| /// The set of inherited setters, used because JS getters/setters are paired, |
| /// so if we're generating a getter we may need to emit a setter that calls |
| /// super. |
| final inheritedSetters = new HashSet<String>(); |
| |
| ClassPropertyModel.build(VirtualFieldModel fieldModel, ClassElement classElem, |
| Iterable<ExecutableElement> extensionMembers) { |
| // Visit superclasses to collect information about their fields/accessors. |
| // This is expensive so we try to collect everything in one pass. |
| for (var base in getSuperclasses(classElem)) { |
| for (var accessor in base.accessors) { |
| // For getter/setter pairs only process them once. |
| if (accessor.correspondingGetter != null) continue; |
| |
| var field = accessor.variable; |
| var name = field.name; |
| // Ignore private names from other libraries. |
| if (Identifier.isPrivateName(name) && |
| accessor.library != classElem.library) { |
| continue; |
| } |
| |
| if (field.getter?.isAbstract == false) inheritedGetters.add(name); |
| if (field.setter?.isAbstract == false) inheritedSetters.add(name); |
| } |
| } |
| |
| var extensionNames = |
| new HashSet<String>.from(extensionMembers.map((e) => e.name)); |
| |
| // Visit accessors in the current class, and see if they need to be |
| // generated differently based on the inherited fields/accessors. |
| for (var accessor in classElem.accessors) { |
| // For getter/setter pairs only process them once. |
| if (accessor.correspondingGetter != null) continue; |
| // Also ignore abstract fields. |
| if (accessor.isAbstract) continue; |
| |
| var field = accessor.variable; |
| var name = field.name; |
| // Is it a field? |
| if (!field.isSynthetic && field is FieldElementImpl) { |
| if (inheritedGetters.contains(name) || |
| inheritedSetters.contains(name) || |
| extensionNames.contains(name) || |
| fieldModel.isVirtual(field)) { |
| if (field.isStatic) { |
| staticFieldOverrides.add(field); |
| } else { |
| virtualFields[field] = new JS.TemporaryId(name); |
| } |
| } |
| } |
| } |
| } |
| } |