Fix error reporting on member declarations.

lib/compiler/implementation/scanner/listener.dart

Index: lib/compiler/implementation/scanner/listener.dart
diff --git a/lib/compiler/implementation/scanner/listener.dart b/lib/compiler/implementation/scanner/listener.dart
index b2514370e8904ffc6a3a2b5e5da39dfb8c156939..2017961c5a8ed5f4ebd4e522d21fd37284dceb12 100644
--- a/lib/compiler/implementation/scanner/listener.dart
+++ b/lib/compiler/implementation/scanner/listener.dart
@@ -553,6 +553,11 @@ class Listener {
     return skipToEof(token);
   }
 
+  Link<Token> expectedDeclaration(Token token) {
+    error("expected a declaration, but got '${token.slowToString()}'", token);
+    return const EmptyLink<Token>();
+  }
+
   Token unmatched(Token token) {
     error("unmatched '${token.slowToString()}'", token);
     return skipToEof(token);
@@ -950,6 +955,12 @@ class ElementListener extends Listener {
     }
   }
 
+  Link<Token> expectedDeclaration(Token token) {
+    listener.cancel("expected a declaration, but got '${token.slowToString()}'",
+                    token: token);
+    return const EmptyLink<Token>();
+  }
+
   Token unmatched(Token token) {
     listener.cancel("unmatched '${token.slowToString()}'", token: token);
     return skipToEof(token);