| // 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; |
| |
| import 'package:analyzer/dart/ast/ast.dart'; |
| import 'package:analyzer/dart/element/element.dart'; |
| import 'package:func/func.dart'; |
| import '../js_ast/js_ast.dart' as JS; |
| |
| /// Helper that tracks order of elements visited by the compiler, detecting |
| /// if the top level item can be loaded eagerly or not. |
| class ElementLoader { |
| final HashMap<Element, AstNode> _declarationNodes; |
| |
| /// The stack of currently emitting elements, if generating top-level code |
| /// for them. This is not used when inside method bodies, because order does |
| /// not matter for those. |
| final _topLevelElements = new List<Element>(); |
| |
| /// The current element being loaded. |
| /// We can use this to determine if we're loading top-level code or not: |
| /// |
| /// _currentElements.last == _topLevelElements.last |
| final _currentElements = new List<Element>(); |
| |
| bool _checkReferences; |
| |
| ElementLoader(this._declarationNodes) { |
| assert(!_declarationNodes.containsKey(null)); |
| } |
| |
| Element get currentElement => _currentElements.last; |
| |
| bool isLoaded(Element e) => !_declarationNodes.containsKey(e); |
| |
| /// True if the element is currently being loaded. |
| bool _isLoading(Element e) => _currentElements.contains(e); |
| |
| /// Start generating top-level code for the element [e]. |
| /// |
| /// Subsequent [emitDeclaration] calls will cause those elements to be |
| /// generated before this one, until [finishTopLevel] is called. |
| void startTopLevel(Element e) { |
| assert(identical(e, currentElement)); |
| _topLevelElements.add(e); |
| } |
| |
| /// Finishes the top-level code for the element [e]. |
| void finishTopLevel(Element e) { |
| var last = _topLevelElements.removeLast(); |
| assert(identical(e, last)); |
| } |
| |
| /// Starts recording calls to [declareBeforeUse], until |
| /// [finishCheckingReferences] is called. |
| void startCheckingReferences() { |
| // This function should not be reentrant, and we should not current be |
| // emitting top-level code. |
| assert(_checkReferences == null); |
| assert(_topLevelElements.isEmpty || |
| !identical(currentElement, _topLevelElements.last)); |
| // Assume true until proven otherwise |
| _checkReferences = true; |
| } |
| |
| /// Finishes recording references, and returns `true` if all referenced |
| /// items were loaded (or if no items were referenced). |
| bool finishCheckingReferences() { |
| var result = _checkReferences; |
| _checkReferences = null; |
| return result; |
| } |
| |
| /// Ensures a top-level declaration is generated, and returns `true` if it |
| /// is part of the current module. |
| /*=T*/ emitDeclaration/*<T extends JS.Node>*/( |
| Element e, Func1<AstNode, JS.Node/*=T*/ > visit) { |
| var node = _declarationNodes.remove(e); |
| if (node == null) return null; // not from this module or already loaded. |
| |
| _currentElements.add(e); |
| |
| var result = visit(node); |
| |
| var last = _currentElements.removeLast(); |
| assert(identical(e, last)); |
| |
| return result; |
| } |
| |
| /// To emit top-level module items, we sometimes need to reorder them. |
| /// |
| /// This function takes care of that, and also detects cases where reordering |
| /// failed, and we need to resort to lazy loading, by marking the element as |
| /// lazy. All elements need to be aware of this possibility and generate code |
| /// accordingly. |
| /// |
| /// If we are not emitting top-level code, this does nothing, because all |
| /// declarations are assumed to be available before we start execution. |
| /// See [startTopLevel]. |
| void declareBeforeUse(Element e, VoidFunc1<Element> emit) { |
| if (e == null) return; |
| |
| if (_checkReferences != null) { |
| _checkReferences = _checkReferences && isLoaded(e) && !_isLoading(e); |
| return; |
| } |
| |
| var topLevel = _topLevelElements; |
| if (topLevel.isNotEmpty && identical(currentElement, topLevel.last)) { |
| // If the item is from our library, try to emit it now. |
| emit(e); |
| } |
| } |
| } |