Allow empty initializer lists

corpus/expressions.txt

@@ -246,7 +246,7 @@ Compound literals
 ============================================
 
 int main() {
-  x = (SomeType) { .f1 = 5, .f2 = 6 };
+  x = (SomeType) { .f1 = 5, .f2 = 6, .f3 = {} };
   y = (struct SomeStruct) { 7, 8 };
 }
 
@@ -263,7 +263,8 @@ int main() {
           (type_name (identifier))
           (initializer_list
             (designator (identifier)) (number_literal)
-            (designator (identifier)) (number_literal)))))
+            (designator (identifier)) (number_literal)
+            (designator (identifier)) (initializer_list)))))
       (expression_statement (assignment_expression
         (identifier)
         (compound_literal_expression

grammar.js

@@ -549,8 +549,10 @@ module.exports = grammar({
 
     initializer_list: $ => seq(
       '{',
-      $._initializer_list_contents,
-      optional(','),
+      optional(seq(
+        $._initializer_list_contents,
+        optional(',')
+      )),
       '}'
     ),
 

src/grammar.json

@@ -2736,16 +2736,29 @@
           "type": "STRING",
           "value": "{"
         },
-        {
-          "type": "SYMBOL",
-          "name": "_initializer_list_contents"
-        },
         {
           "type": "CHOICE",
           "members": [
             {
-              "type": "STRING",
-              "value": ","
+              "type": "SEQ",
+              "members": [
+                {
+                  "type": "SYMBOL",
+                  "name": "_initializer_list_contents"
+                },
+                {
+                  "type": "CHOICE",
+                  "members": [
+                    {
+                      "type": "STRING",
+                      "value": ","
+                    },
+                    {
+                      "type": "BLANK"
+                    }
+                  ]
+                }
+              ]
             },
             {
               "type": "BLANK"