more repro

frb_example/dart_minimal/rust/src/api/minimal.rs

@@ -9,10 +9,21 @@ pub fn minimal_adder(a: i32, b: i32) -> i32 {
     a + b
 }
 
-pub trait MyTraitToBeUsedAsBoxDyn {
-    fn my_method_twin_normal(&self);
+use std::fmt;
+use std::fmt::Debug;
+
+/// Trait that logs at level INFO every update received (if any).
+pub trait Progress: Send + Sync + 'static {
+    /// Send a new progress update. The progress value should be in the range 0.0 - 100.0, and the message value is an
+    /// optional text message that can be displayed to the user.
+    fn update(&self, progress: f32, message: Option<String>);
 }
 
-fn function_with_box_dyn_trait(arg: Box<dyn MyTraitToBeUsedAsBoxDyn>) {
-    let _ = arg;
+pub struct ProgressHolder {
+    pub progress: Box<dyn Progress>,
+}
+impl Debug for ProgressHolder {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.debug_struct("ProgressHolder").finish_non_exhaustive()
+    }
 }