Improve error messages.

pkg/front_end/lib/src/fasta/kernel/body_builder.dart

 // Copyright (c) 2016, 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 fasta.body_builder;
 
 import '../fasta_codes.dart'
     show FastaMessage, codeExpectedButGot, codeExpectedFunctionBody;
 
 import '../parser/parser.dart'
@@ skipping 2906 matching lines @@
   void handleSymbolVoid(Token token) {
     debugEvent("SymbolVoid");
     push(new Identifier(token));
   }
 
   @override
   dynamic addCompileTimeError(int charOffset, String message,
       {bool silent: false}) {
     // TODO(ahe): If constantExpressionRequired is set, set it to false to
     // avoid a long list of errors.
-    return library.addCompileTimeError(charOffset, message, fileUri: uri);
+    return library.addCompileTimeError(charOffset, message,
+        fileUri: uri, silent: silent);
   }
 
   @override
   void handleInvalidFunctionBody(Token token) {
     if (member.isNative) {
       push(NullValue.FunctionBody);
     } else {
       push(new Block(<Statement>[
         buildCompileTimeErrorStatement("Expected '{'.", token.charOffset)
       ]));
@@ skipping 536 matching lines @@
     if (starToken == null) {
       return AsyncMarker.Async;
     } else {
       assert(identical(starToken.stringValue, "*"));
       return AsyncMarker.AsyncStar;
     }
   } else {
     return internalError("Unknown async modifier: $asyncToken");
   }
 }