Draft time-travel debugging feature

src/application.rs

@@ -75,7 +75,7 @@ pub fn application<State, Message, Theme, Renderer>(
 ) -> Application<impl Program<State = State, Message = Message, Theme = Theme>>
 where
     State: 'static,
-    Message: Send + std::fmt::Debug + 'static,
+    Message: program::Message + 'static,
     Theme: Default + theme::Base,
     Renderer: program::Renderer,
 {
@@ -94,7 +94,7 @@ where
     impl<State, Message, Theme, Renderer, Boot, Update, View> Program
         for Instance<State, Message, Theme, Renderer, Boot, Update, View>
     where
-        Message: Send + std::fmt::Debug + 'static,
+        Message: program::Message + 'static,
         Theme: Default + theme::Base,
         Renderer: program::Renderer,
         Boot: self::Boot<State, Message>,

src/daemon.rs

@@ -25,7 +25,7 @@ pub fn daemon<State, Message, Theme, Renderer>(
 ) -> Daemon<impl Program<State = State, Message = Message, Theme = Theme>>
 where
     State: 'static,
-    Message: Send + std::fmt::Debug + 'static,
+    Message: program::Message + 'static,
     Theme: Default + theme::Base,
     Renderer: program::Renderer,
 {
@@ -44,7 +44,7 @@ where
     impl<State, Message, Theme, Renderer, Boot, Update, View> Program
         for Instance<State, Message, Theme, Renderer, Boot, Update, View>
     where
-        Message: Send + std::fmt::Debug + 'static,
+        Message: program::Message + 'static,
         Theme: Default + theme::Base,
         Renderer: program::Renderer,
         Boot: application::Boot<State, Message>,

src/lib.rs

@@ -343,7 +343,7 @@
 //! use iced::window;
 //! use iced::{Size, Subscription};
 //!
-//! #[derive(Debug)]
+//! #[derive(Debug, Clone)]
 //! enum Message {
 //!     WindowResized(Size),
 //! }
@@ -387,7 +387,7 @@
 //! #         pub fn update(&mut self, message: Message) -> Action { unimplemented!() }
 //! #         pub fn view(&self) -> Element<Message> { unimplemented!() }
 //! #     }
-//! #     #[derive(Debug)]
+//! #     #[derive(Debug, Clone)]
 //! #     pub enum Message {}
 //! #     pub enum Action { None, Run(Task<Message>), Chat(()) }
 //! # }
@@ -399,7 +399,7 @@
 //! #         pub fn update(&mut self, message: Message) -> Task<Message> { unimplemented!() }
 //! #         pub fn view(&self) -> Element<Message> { unimplemented!() }
 //! #     }
-//! #     #[derive(Debug)]
+//! #     #[derive(Debug, Clone)]
 //! #     pub enum Message {}
 //! # }
 //! use contacts::Contacts;
@@ -697,7 +697,7 @@ pub fn run<State, Message, Theme, Renderer>(
 ) -> Result
 where
     State: Default + 'static,
-    Message: std::fmt::Debug + Send + 'static,
+    Message: program::Message + 'static,
     Theme: Default + theme::Base + 'static,
     Renderer: program::Renderer + 'static,
 {