Read Intl.message examples argument as a map, not a string

pkg/intl/lib/extract_messages.dart

 // Copyright (c) 2013, 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.
 
 /**
  * This is for use in extracting messages from a Dart program
  * using the Intl.message() mechanism and writing them to a file for
  * translation. This provides only the stub of a mechanism, because it
  * doesn't define how the file should be written. It provides an
  * [IntlMessage] class that holds the extracted data and [parseString]
@@ skipping 211 matching lines @@
     var message = new MainMessage();
     message.name = name;
     message.arguments = parameters.parameters.map(
         (x) => x.identifier.name).toList();
     var arguments = node.argumentList.arguments;
     extract(message, arguments);
 
     for (var namedArgument in arguments.where((x) => x is NamedExpression)) {
       var name = namedArgument.name.label.name;
       var exp = namedArgument.expression;
-      var string = exp is SimpleStringLiteral ? exp.value : exp.toString();
-      setAttribute(message, name, string);
+      var evaluator = new ConstantEvaluator();
+      var basicValue = exp.accept(evaluator);
+      var value = basicValue == ConstantEvaluator.NOT_A_CONSTANT ?
+          exp.toString() : basicValue;
+      setAttribute(message, name, value);
     }
     return message;
   }
 
   /**
    * Create a MainMessage from [node] using the name and
    * parameters of the last function/method declaration we encountered
    * and the parameters to the Intl.message call.
    */
   MainMessage messageFromIntlMessageCall(MethodInvocation node) {
 
     void extractFromIntlCall(MainMessage message, List arguments) {
       try {
         var interpolation = new InterpolationVisitor(message);
         arguments.first.accept(interpolation);
         message.messagePieces.addAll(interpolation.pieces);
       } on IntlMessageExtractionException catch (e) {
         message = null;
         var err = new StringBuffer();
         err.write("Error $e\n");
         err.write("Processing <$node>\n");
         err.write(_reportErrorLocation(node));
         print(err);
         warnings.add(err);
       }
     }
 
-    void setValue(MainMessage message, String fieldName, String fieldValue) {
+    void setValue(MainMessage message, String fieldName, Object fieldValue) {
       message[fieldName] = fieldValue;
     }
 
     return _messageFromNode(node, extractFromIntlCall, setValue);
   }
 
   /**
    * Create a MainMessage from [node] using the name and
    * parameters of the last function/method declaration we encountered
    * and the parameters to the Intl.plural or Intl.gender call.
@@ skipping 198 matching lines @@
    */
   final String message;
 
   /**
    * Creates a new exception with an optional error [message].
    */
   const IntlMessageExtractionException([this.message = ""]);
 
   String toString() => "IntlMessageExtractionException: $message";
 }