Implement fullNameForErrors on all Builders.

pkg/front_end/lib/src/fasta/builder/metadata_builder.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.metadata_builder;
 
 import 'builder.dart' show Builder, TypeBuilder;
 
 import 'constructor_reference_builder.dart' show ConstructorReferenceBuilder;
 
@@ skipping 19 matching lines @@
 
 class ConstructorMetadataBuilder<T extends TypeBuilder>
     extends MetadataBuilder<T> {
   final ConstructorReferenceBuilder constructorReference;
 
   final List arguments;
 
   ConstructorMetadataBuilder(
       this.constructorReference, this.arguments, Builder parent, int charOffset)
       : super(parent, charOffset);
+
+  @override
+  String get fullNameForErrors => constructorReference.fullNameForErrors;
 }
 
 /// Expression metadata (without arguments).
 ///
 /// Matches this grammar rule:
 ///
 ///    '@' qualified (‘.’ identifier)?
 class ExpressionMetadataBuilder<T extends TypeBuilder>
     extends MetadataBuilder<T> {
   final String qualified;
 
   final String identifier;
 
   ExpressionMetadataBuilder(
       this.qualified, this.identifier, Builder parent, int charOffset)
       : super(parent, charOffset);
+
+  @override
+  String get fullNameForErrors {
+    return identifier == null ? qualified : "$qualified.$identifier";
+  }
 }