Mark 'expression_statement' as a supertype

Author: wetneb

grammar.js

@@ -60,6 +60,7 @@ module.exports = grammar({
   supertypes: $ => [
     $._simple_statement,
     $._compound_statement,
+    $.expression_statement,
     $.expression,
     $.primary_expression,
     $.pattern,
@@ -227,12 +228,15 @@ module.exports = grammar({
 
     expression_statement: $ => choice(
       $.expression,
-      seq(commaSep1($.expression), optional(',')),
+      $.comma_separated_expressions,
       $.assignment,
       $.augmented_assignment,
       $.yield,
     ),
 
+    comma_separated_expressions: $ => 
+      seq(seq($.expression, ',', commaSep1($.expression)), optional(',')),
+
     named_expression: $ => seq(
       field('name', $._named_expression_lhs),
       ':=',