Undeprecate IncompleteError.

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;
 
 import 'package:kernel/ast.dart'
     hide InvalidExpression, InvalidInitializer, InvalidStatement;
 
 import '../../scanner/token.dart' show Token;
@@ skipping 446 matching lines @@
 
   final Name name;
 
   IncompleteSend(this.helper, this.token, this.name);
 
   withReceiver(Object receiver, int operatorOffset, {bool isNullAware});
 
   Arguments get arguments => null;
 }
 
-class deprecated_IncompleteError extends IncompleteSend with ErrorAccessor {
-  final Object error;
+class IncompleteError extends IncompleteSend with ErrorAccessor {
+  final Message message;
 
-  deprecated_IncompleteError(BuilderHelper helper, Token token, this.error)
+  IncompleteError(BuilderHelper helper, Token token, this.message)
       : super(helper, token, null);
 
   @override
   Expression buildError(Arguments arguments,
       {bool isGetter: false, bool isSetter: false, int offset}) {
-    return helper.deprecated_buildCompileTimeError(
-        error, offset ?? offsetForToken(this.token));
+    return helper.buildCompileTimeError(
+        message, offset ?? offsetForToken(this.token));
   }
 
   @override
   doInvocation(int offset, Arguments arguments) => this;
 }
 
 class SendAccessor extends IncompleteSend {
   @override
   final Arguments arguments;
 
@@ skipping 570 matching lines @@
     offset ??= offsetForToken(this.token);
     return helper.throwNoSuchMethodError(new NullLiteral()..fileOffset = offset,
         plainNameForRead, arguments, offset,
         isGetter: isGetter, isSetter: isSetter);
   }
 }
 
 bool isFieldOrGetter(Member member) {
   return member is Field || (member is Procedure && member.isGetter);
 }