Check field overrides

pkg/analyzer/lib/src/task/strong/info.dart

Index: pkg/analyzer/lib/src/task/strong/info.dart
diff --git a/pkg/analyzer/lib/src/task/strong/info.dart b/pkg/analyzer/lib/src/task/strong/info.dart
index 1aa42b2dfd377339e6124e25a37eabbb7b76f223..9d4812f8b9839edc61a1dea5da4431605cf954dc 100644
--- a/pkg/analyzer/lib/src/task/strong/info.dart
+++ b/pkg/analyzer/lib/src/task/strong/info.dart
@@ -452,6 +452,15 @@ class InvalidMethodOverride extends InvalidOverride {
   String get message => _messageHelper('Invalid override');
 }
 
+class InvalidFieldOverride extends InvalidOverride {
+  InvalidFieldOverride(AstNode node, ExecutableElement element,
+      InterfaceType base, DartType subType, DartType baseType)
+      : super(node, element, base, subType, baseType);
+
+  String get message => 'Field declaration {3}.{1} cannot be '
+      'overridden in {0}.';
+}
+
 /// Dart constructors have one weird quirk, illustrated with this example:
 ///
 ///     class Base {