Avoid duplicated messages.

dart/pkg/compiler/lib/src/scanner/parser.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.
 
 part of scanner;
 
 class FormalParameterType {
   final String type;
   const FormalParameterType(this.type);
   bool get isRequired => this == REQUIRED;
@@ skipping 878 matching lines @@
     }
     Token token = parseIdentifier(name);
 
     token = parseFormalParametersOpt(token);
     bool previousYieldIsKeyword = yieldIsKeyword;
     bool previousAwaitIsKeyword = awaitIsKeyword;
     token = parseAsyncModifier(token);
     token = parseFunctionBody(token, false, externalModifier != null);
     yieldIsKeyword = previousYieldIsKeyword;
     awaitIsKeyword = previousAwaitIsKeyword;
-    listener.endTopLevelMethod(start, getOrSet, token);
-    return token.next;
+    Token endToken = token;
+    token = token.next;
+    if (token.kind == BAD_INPUT_TOKEN) {
+      token = listener.unexpected(token);
+    }
+    listener.endTopLevelMethod(start, getOrSet, endToken);
+    return token;
   }
 
   Link<Token> findMemberName(Token token) {
     Token start = token;
     Link<Token> identifiers = const Link<Token>();
     while (!identical(token.kind, EOF_TOKEN)) {
       String value = token.stringValue;
       if ((identical(value, '(')) || (identical(value, '{'))
           || (identical(value, '=>'))) {
         // A method.
@@ skipping 1682 matching lines @@
     }
     listener.handleContinueStatement(hasTarget, continueKeyword, token);
     return expectSemicolon(token);
   }
 
   Token parseEmptyStatement(Token token) {
     listener.handleEmptyStatement(token);
     return expectSemicolon(token);
   }
 }