Add optionals

1 files changed, 9 insertions, 1 deletions

diff --git a/grammar.js b/grammar.js
index e74c27b..db1219d 100644
--- a/grammar.js
+++ b/grammar.js
@@ -83,12 +83,20 @@ module.exports = grammar({
       )
     ),
     identifier: $ => prec.left(seq(
-      $._label,
+      choice(
+        $.optional_value,
+        $._label,
+      ),
       optional($.type_annotation),
       optional($.parameter_list),
       optional($.return_statement),
       optional($.throw_statement),
     )),
+    optional_value: $ => seq(
+      '[',
+      $._label,
+      ']'
+    ),
     type_annotation: $ => seq(
       '<',
       $._entry_list,