Implement more message argument kinds.

pkg/front_end/lib/src/fasta/fasta_codes.dart

Index: pkg/front_end/lib/src/fasta/fasta_codes.dart
diff --git a/pkg/front_end/lib/src/fasta/fasta_codes.dart b/pkg/front_end/lib/src/fasta/fasta_codes.dart
index 67631e6aca2ec22dede2c0f5d669fdf7c84c8f63..f62f6802a98eebf4450dc8afeb1edc5773b89eb7 100644
--- a/pkg/front_end/lib/src/fasta/fasta_codes.dart
+++ b/pkg/front_end/lib/src/fasta/fasta_codes.dart
@@ -4,7 +4,9 @@
 
 library fasta.codes;
 
-import 'package:front_end/src/scanner/token.dart' show Token;
+import '../scanner/token.dart' show Token;
+
+import 'util/relativize.dart' as util show relativizeUri;
 
 part 'fasta_codes_generated.dart';
 
@@ -83,3 +85,13 @@ class LocatedMessage {
 
   Map<String, dynamic> get arguments => messageObject.arguments;
 }
+
+String relativizeUri(Uri uri) {
+  // We have this method here for two reasons:
+  //
+  // 1. It allows us to implement #uri message argument without using it
+  // (otherwise, we might get an `UNUSED_IMPORT` warning).

[Siggi Cherem (dart-lang), 2017/07/11 21:25:27]

Note that for #1 is enough to add a dartdoc reference too :)

/// [relativizeUri] may be used in the generated code.
import 'util/relativize.dart' show relativizeUri;

the alternative could be to switch fasta_code_generates to be a library and not
a part, and include the import if you see a #uri in any message

[ahe, 2017/07/12 12:42:12]

Acknowledged.

+  //
+  // 2. We can change `base` argument here if needed.
+  return util.relativizeUri(uri, base: Uri.base);
+}