Implement fullNameForErrors on all Builders.

pkg/front_end/lib/src/fasta/kernel/kernel_variable_builder.dart

Index: pkg/front_end/lib/src/fasta/kernel/kernel_variable_builder.dart
diff --git a/pkg/front_end/lib/src/fasta/kernel/kernel_variable_builder.dart b/pkg/front_end/lib/src/fasta/kernel/kernel_variable_builder.dart
index a6c29f5244b138d0fdd9cfd3cf2d0db83a4be340..de696cbdff2eab1ea1711c4e79a8ec26a767c997 100644
--- a/pkg/front_end/lib/src/fasta/kernel/kernel_variable_builder.dart
+++ b/pkg/front_end/lib/src/fasta/kernel/kernel_variable_builder.dart
@@ -19,4 +19,7 @@ class KernelVariableBuilder extends Builder {
   bool get isLocal => true;
 
   VariableDeclaration get target => variable;
+
+  @override
+  String get fullNameForErrors => variable.name ?? "";

[Paul Berry, 2017/03/21 18:09:56]

It seems like this might lead to user confusion.  How about something like:

String get fullNameForErrors => variable.name ?? "<unnamed>";

[ahe, 2017/03/21 18:22:18]

Yes. Will do.

 }