Implement literal maps.

dart/frog/leg/resolver.dart

 // Copyright (c) 2012, 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.
 
 interface TreeElements {
   Element operator[](Node node);
   Selector getSelector(Send send);
 }
 
 class TreeElementMapping implements TreeElements {
@@ skipping 1107 matching lines @@
       mapping[node.label] = element;
     } else {
       warning(node.label, MessageKind.UNUSED_LABEL, [labelName]);
     }
     if (!statementElement.isBreakTarget) {
       mapping.map.remove(body);
     }
   }
 
   visitLiteralMap(LiteralMap node) {
-    warning(node, MessageKind.GENERIC, ['map literals are not implemented']);
+    node.visitChildren(this);
   }
 
   visitLiteralMapEntry(LiteralMapEntry node) {
-    unimplemented(node, 'map entry');
+    node.visitChildren(this);
   }
 
   visitNamedArgument(NamedArgument node) {
     visit(node.expression);
   }
 
   visitSwitchStatement(SwitchStatement node) {
     warning(node, MessageKind.GENERIC, ['switch statement is not implemented']);
   }
 
@@ skipping 318 matching lines @@
 class TopScope extends Scope {
   LibraryElement get library() => element;
 
   TopScope(LibraryElement library) : super(null, library);
   Element lookup(SourceString name) => library.find(name);
 
   Element add(Element element) {
     throw "Cannot add an element in the top scope";
   }
 }