From c7bb207dd099442aa22e99537d904bc79212f36c Mon Sep 17 00:00:00 2001
From: Gino Valente <gino.valente.code@gmail.com>
Date: Fri, 5 May 2023 11:09:53 -0700
Subject: [PATCH] Account for field-less structs

---
 crates/bevy_derive/src/derefs.rs | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/crates/bevy_derive/src/derefs.rs b/crates/bevy_derive/src/derefs.rs
index 3f2ed0278c3c6..9f4cd951f213e 100644
--- a/crates/bevy_derive/src/derefs.rs
+++ b/crates/bevy_derive/src/derefs.rs
@@ -55,6 +55,10 @@ fn get_deref_field(ast: &DeriveInput, is_mut: bool) -> syn::Result<(Member, &Typ
     let deref_attr_str = format!("`#[{DEREF_ATTR}]`");
 
     match &ast.data {
+        Data::Struct(data_struct) if data_struct.fields.len() == 0 => Err(syn::Error::new(
+            Span::call_site().into(),
+            format!("{deref_kind} cannot be derived on field-less structs"),
+        )),
         Data::Struct(data_struct) if data_struct.fields.len() == 1 => {
             let field = data_struct.fields.iter().next().unwrap();
             let member = to_member(field, 0);