Add TypeBuilder.declaration

Change-Id: Iede4bde8e30bb4ac034c0cb0db49a843ff84d48b
Reviewed-on: https://dart-review.googlesource.com/c/89541
Reviewed-by: Dmitry Stefantsov <dmitryas@google.com>
diff --git a/pkg/front_end/lib/src/fasta/builder/named_type_builder.dart b/pkg/front_end/lib/src/fasta/builder/named_type_builder.dart
index 8baf2e1..1a17041 100644
--- a/pkg/front_end/lib/src/fasta/builder/named_type_builder.dart
+++ b/pkg/front_end/lib/src/fasta/builder/named_type_builder.dart
@@ -38,6 +38,7 @@
 
   List<T> arguments;
 
+  @override
   TypeDeclarationBuilder<T, R> declaration;
 
   NamedTypeBuilder(this.name, this.arguments);
diff --git a/pkg/front_end/lib/src/fasta/builder/type_builder.dart b/pkg/front_end/lib/src/fasta/builder/type_builder.dart
index ceb7a59..bebc060 100644
--- a/pkg/front_end/lib/src/fasta/builder/type_builder.dart
+++ b/pkg/front_end/lib/src/fasta/builder/type_builder.dart
@@ -12,6 +12,8 @@
 abstract class TypeBuilder {
   const TypeBuilder();
 
+  TypeDeclarationBuilder get declaration => null;
+
   void resolveIn(
       Scope scope, int charOffset, Uri fileUri, LibraryBuilder library) {}