Update ConstructorNamedArgumentTest to use the 'runtime-error' directive

tools/testing/dart/multitest.dart

 // Copyright (c) 2011, 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("multitest");
 
 #import("dart:io");
 
 // Multitests are Dart test scripts containing lines of the form
 // " [some dart code] /// [key]: [error type]"
@@ skipping 63 matching lines @@
   List<String> testTemplate = new List<String>();
   testTemplate.add('// Test created from multitest named $filename.');
   // Create the set of multitests, which will have a new test added each
   // time we see a multitest line with a new key.
   Map<String, List<String>> testsAsLines = new Map<String, List<String>>();
 
   // Matches #import( or #source( followed by " or ' followed by anything
   // except dart: or /, at the beginning of a line.
   RegExp relativeImportRegExp =
       const RegExp('^#(import|source)[(]["\'](?!(dart:|/))');
+  int lineCount = 0;
   for (String line in lines) {
+    lineCount++;
     if (line.contains('///')) {
       var parts = line.split('///')[1].split(':');
       var key = parts[0].trim();
       var rest = parts[1].trim();
       if (testsAsLines.containsKey(key)) {
         Expect.equals('continued', rest);
         testsAsLines[key].add(line);
       } else {
         (testsAsLines[key] = new List<String>.from(testTemplate)).add(line);
         outcomes[key] = rest;
-        Expect.isTrue(validMultitestOutcomes.contains(rest));
+        if (!validMultitestOutcomes.contains(rest)) {
+          Expect.fail("Invalid test directive on line ${lineCount}: $rest ");
+        }
       }
     } else {
       testTemplate.add(line);
       for (var test in testsAsLines.getValues()) test.add(line);
     }
     // Warn if any import or source tags have relative paths.
     if (relativeImportRegExp.hasMatch(line)) {
       print('Warning: Multitest cannot contain relative imports:');
       print('    $filename: $line');
     }
@@ skipping 66 matching lines @@
   var split = testDir.split('/');
   var lastComponent = split.removeLast();
   Expect.isTrue(lastComponent == 'src');
   String path = '${generatedTestDir.path}/${split.last()}';
   Directory dir = new Directory(path);
   if (!dir.existsSync()) {
     dir.createSync();
   }
   return path;
 }