Complain about duplicated names.

pkg/front_end/lib/src/fasta/kernel/fasta_accessors.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.fasta_accessors;
 
 export 'frontend_accessors.dart' show wrapInvalid;
 
 import 'package:front_end/src/fasta/kernel/utils.dart' show offsetForToken;
 
@@ skipping 69 matching lines @@
   Expression buildProblemExpression(ProblemBuilder builder, int offset);
 
   Expression throwNoSuchMethodError(
       String name, Arguments arguments, int offset,
       {bool isSuper: false, isGetter: false, isSetter: false});
 
   bool checkArguments(FunctionNode function, Arguments arguments,
       List<TypeParameter> typeParameters);
 
   StaticGet makeStaticGet(Member readTarget, Token token);
+
+  dynamic addCompileTimeError(int charOffset, String message,
+      {bool silent: false});
 }
 
 abstract class FastaAccessor implements Accessor {
   BuilderHelper get helper;
 
   String get plainNameForRead;
 
   Uri get uri => helper.uri;
 
   String get plainNameForWrite => plainNameForRead;
@@ skipping 833 matching lines @@
             new NullLiteral(),
             astFactory.methodInvocation(
                 new VariableGet(variable), name, arguments)
               ..fileOffset = offset,
             const DynamicType()));
   } else {
     return astFactory.methodInvocation(receiver, name, arguments)
       ..fileOffset = offset;
   }
 }