fix #29182, generate top level const fields lazily

pkg/dev_compiler/lib/src/compiler/element_loader.dart

Index: pkg/dev_compiler/lib/src/compiler/element_loader.dart
diff --git a/pkg/dev_compiler/lib/src/compiler/element_loader.dart b/pkg/dev_compiler/lib/src/compiler/element_loader.dart
deleted file mode 100644
index a2635eb26e6dcb34a7e4d6ed319e0d192a1bfb08..0000000000000000000000000000000000000000
--- a/pkg/dev_compiler/lib/src/compiler/element_loader.dart
+++ /dev/null
@@ -1,117 +0,0 @@
-// 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);
-    }
-  }
-}