Simplify ordering of top-level declarations.

lib/src/compiler/element_loader.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 '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;
 
-typedef void ModuleItemEmitter(AstNode item);
-
 /// Helper that tracks order of elements visited by the compiler, detecting
 /// if the top level item can be loaded eagerly or not.
 class ElementLoader {
-  /// Whether an item has been loaded (emitted) already.
-  final _loaded = new HashSet<Element>();
-
   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;
 
-  final ModuleItemEmitter _emitModuleItem;
-
-  ElementLoader(this._emitModuleItem, this._declarationNodes) {
+  ElementLoader(this._declarationNodes) {
     assert(!_declarationNodes.containsKey(null));
   }
 
   Element get currentElement => _currentElements.last;
 
-  bool isLoaded(Element e) =>
-      !_declarationNodes.containsKey(e) || _loaded.contains(e);
+  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));
@@ skipping 21 matching lines @@
   /// 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.
-  void emitDeclaration(Element e) {
-    var node = _declarationNodes[e];
-    if (node == null) return; // not from this 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.
 
-    // If we already tried to load it, see if we succeeded or not.
-    // Otherwise try and load now.
-    if (_loaded.contains(e)) return;
-
-    _loaded.add(e);
     _currentElements.add(e);
 
-    _emitModuleItem(node);
+    var result = visit(node);
 
     var last = _currentElements.removeLast();
     assert(identical(e, last));
-  }
 
-  /// Used to immediately emit a declaration and return the result.
-  ///
-  /// This will operate regardless of whether the node is currently loaded.
-  /// We use this when we encounter a getter/setter, to immediately emit the
-  /// pair and combine them.
-  /*=T*/ customEmitDeclaration/*<T extends JS.Node>*/(
-      Element e, Func1<AstNode, JS.Node/*=T*/ > visit) {
-    _loaded.add(e);
-    _currentElements.add(e);
-    var result = visit(_declarationNodes[e]);
-    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) {
+  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.
-      emitDeclaration(e);
+      emit(e);
     }
   }
 }