Debug for Gd includes refcount, if available

Author: Bromeon

godot-core/src/classes/class_runtime.rs

@@ -23,10 +23,13 @@ pub(crate) fn debug_string<T: GodotClass>(
 ) -> std::fmt::Result {
     if let Some(id) = obj.instance_id_or_none() {
         let class: StringName = obj.dynamic_class_string();
-        f.debug_struct(ty)
-            .field("id", &id)
-            .field("class", &class)
-            .finish()
+
+        let mut builder = f.debug_struct(ty);
+        builder.field("id", &id).field("class", &class);
+        if let Some(refcount) = obj.maybe_refcount() {
+            builder.field("refc", &refcount);
+        }
+        builder.finish()
     } else {
         write!(f, "{ty} {{ freed obj }}")
     }
@@ -57,11 +60,16 @@ pub(crate) fn debug_string_with_trait<T: GodotClass>(
 ) -> std::fmt::Result {
     if let Some(id) = obj.instance_id_or_none() {
         let class: StringName = obj.dynamic_class_string();
-        f.debug_struct(ty)
+
+        let mut builder = f.debug_struct(ty);
+        builder
             .field("id", &id)
             .field("class", &class)
-            .field("trait", &trt)
-            .finish()
+            .field("trait", &trt);
+        if let Some(refcount) = obj.maybe_refcount() {
+            builder.field("refc", &refcount);
+        }
+        builder.finish()
     } else {
         write!(f, "{ty} {{ freed obj }}")
     }

godot-core/src/obj/gd.rs

@@ -302,6 +302,15 @@ impl<T: GodotClass> Gd<T> {
         }
     }
 
+    /// Returns the reference count, if the dynamic object inherits `RefCounted`; and `None` otherwise.
+    pub(crate) fn maybe_refcount(&self) -> Option<usize> {
+        // Fast check if ref-counted without downcast.
+        self.instance_id_unchecked().is_ref_counted().then(|| {
+            let rc = self.raw.with_ref_counted(|refc| refc.get_reference_count());
+            rc as usize
+        })
+    }
+
     /// **Upcast:** convert into a smart pointer to a base class. Always succeeds.
     ///
     /// Moves out of this value. If you want to create _another_ smart pointer instance,