Create map for dump_info on demand.

pkg/compiler/lib/src/resolution/tree_elements.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.
 
 library dart2js.resolution.tree_elements;
 
 import '../common.dart';
 import '../constants/expressions.dart';
 import '../dart_types.dart';
 import '../diagnostics/source_span.dart';
@@ skipping 93 matching lines @@
 
   /// `true` if the [analyzedElement]'s source code contains a [TryStatement].
   bool get containsTryStatement;
 }
 
 class TreeElementMapping extends TreeElements {
   final AnalyzableElement analyzedElement;
   Map<Spannable, Selector> _selectors;
   Map<Spannable, TypeMask> _typeMasks;
   Map<Node, DartType> _types;
-  Map<Node, DartType> typesCache = <Node, DartType>{};
+
+  Map<Node, DartType> _typesCache;
+  Map<Node, DartType> get typesCache =>
+      _typesCache ?? _typesCache = <Node, DartType>{};

[Siggi Cherem (dart-lang), 2016/03/09 19:15:03]

replace with `_typesCache ??= <Node, DartType>{}`?

+
   Setlet<SourceSpan> _superUses;
   Map<Node, ConstantExpression> _constants;
   Map<VariableElement, List<Node>> _potentiallyMutated;
   Map<Node, Map<VariableElement, List<Node>>> _potentiallyMutatedIn;
   Map<VariableElement, List<Node>> _potentiallyMutatedInClosure;
   Map<Node, Map<VariableElement, List<Node>>> _accessedByClosureIn;
   Maplet<Send, SendStructure> _sendStructureMap;
   Maplet<NewExpression, NewStructure> _newStructureMap;
   bool containsTryStatement = false;
 
@@ skipping 342 matching lines @@
   }
 
   void setCurrentTypeMask(ForIn node, TypeMask mask) {
     _setTypeMask(node.inToken, mask);
   }
 
   TypeMask getCurrentTypeMask(ForIn node) {
     return _getTypeMask(node.inToken);
   }
 }