From 14ee2181cbf270863d0aa7e1be36814c1ded1354 Mon Sep 17 00:00:00 2001
From: blob1807 <12388588+blob1807@users.noreply.github.com>
Date: Wed, 21 Feb 2024 00:42:11 +1000
Subject: [PATCH] Fix bug https://github.com/odin-lang/Odin/issues/3173

---
 core/encoding/json/marshal.odin | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/core/encoding/json/marshal.odin b/core/encoding/json/marshal.odin
index e9285364b..da250dc01 100644
--- a/core/encoding/json/marshal.odin
+++ b/core/encoding/json/marshal.odin
@@ -377,6 +377,15 @@ marshal_to_writer :: proc(w: io.Writer, v: any, opt: ^Marshal_Options) -> (err:
 		opt_write_end(w, opt, '}') or_return
 
 	case runtime.Type_Info_Union:
+        // check for empty unions
+        if len(info.variants) == 0 {
+            io.write_string(w, "null") or_return
+            return
+        }
+        if info.tag_type == nil {
+            panic("Union tag type is nil.")
+        }
+
 		tag_ptr := uintptr(v.data) + info.tag_offset
 		tag_any := any{rawptr(tag_ptr), info.tag_type.id}