Backport official GLib iterator safety fix for Linux desktop

apps/desktop/src-tauri/vendor/glib/tests/derive.rs

@@ -0,0 +1,33 @@
+use std::marker::PhantomData;
+
+use glib::{Downgrade, Object};
+
+#[test]
+fn derive_downgrade() {
+    #[derive(Downgrade)]
+    pub struct NewType(Object);
+
+    #[derive(Downgrade)]
+    pub struct Struct {
+        o1: Object,
+        o2: std::rc::Rc<u32>,
+    }
+
+    #[derive(Downgrade)]
+    pub enum Enum {
+        None,
+        Pair { x: Object, y: Object },
+        Unit(),
+        SingleUnnamed(Object),
+        MultipleUnnamed(Object, Object, Object),
+    }
+
+    #[derive(Downgrade)]
+    pub struct TypedWrapper<T>(Object, PhantomData<T>);
+
+    #[derive(Downgrade)]
+    pub enum TypedEnum<T> {
+        This(Object, PhantomData<T>),
+        That(Object, PhantomData<T>),
+    }
+}