implement Reflect for Input<T>, some misc improvements to reflect value derive (bevyengine#5676)

# Objective

- I'm currently working on being able to call methods on reflect types (https://github.com/jakobhellermann/bevy_reflect_fns)
- for that, I'd like to add methods to the `Input<KeyCode>` resource (which I'm doing by registering type data)
- implementing `Reflect` is currently a requirement for having type data in the `TypeRegistry`

## Solution

- derive `Reflect` for `KeyCode` and `Input`
- uses `#[reflect_value]` for `Input`, since it's fields aren't supposed to be observable
- using reflect_value would need `Clone` bounds on `T`, but since all the methods (`.pressed` etc) already require `T: Copy`, I unified everything to requiring `Copy`
- add `Send + Sync + 'static` bounds, also required by reflect derive

## Unrelated improvements 
I can extract into a separate PR if needed.

- the `Reflect` derive would previously ignore `#[reflect_value]` and only accept `#[reflect_value()]` which was a bit confusing
- the generated code used `val.clone()` on a reference, which is fine if `val` impls `Clone`, but otherwise also compiles with a worse error message. Change to `std::clone::Clone::clone(val)` instead which gives a neat `T does not implement Clone` error

Author: jakobhellermann

crates/bevy_input/src/input.rs

@@ -1,4 +1,5 @@
 use bevy_ecs::system::Resource;
+use bevy_reflect::Reflect;
 use bevy_utils::HashSet;
 use std::hash::Hash;
 
@@ -33,8 +34,9 @@ use bevy_ecs::schedule::State;
 /// * Call the [`Input::press`] method for each press event.
 /// * Call the [`Input::release`] method for each release event.
 /// * Call the [`Input::clear`] method at each frame start, before processing events.
-#[derive(Debug, Clone, Resource)]
-pub struct Input<T: Eq + Hash> {
+#[derive(Debug, Clone, Resource, Reflect)]
+#[reflect_value]
+pub struct Input<T: Copy + Eq + Hash + Send + Sync + 'static> {
     /// A collection of every button that is currently being pressed.
     pressed: HashSet<T>,
     /// A collection of every button that has just been pressed.
@@ -43,7 +45,7 @@ pub struct Input<T: Eq + Hash> {
     just_released: HashSet<T>,
 }
 
-impl<T: Eq + Hash> Default for Input<T> {
+impl<T: Copy + Eq + Hash + Send + Sync + 'static> Default for Input<T> {
     fn default() -> Self {
         Self {
             pressed: Default::default(),
@@ -55,7 +57,7 @@ impl<T: Eq + Hash> Default for Input<T> {
 
 impl<T> Input<T>
 where
-    T: Copy + Eq + Hash,
+    T: Copy + Eq + Hash + Send + Sync + 'static,
 {
     /// Registers a press for the given `input`.
     pub fn press(&mut self, input: T) {

crates/bevy_input/src/keyboard.rs

@@ -1,5 +1,6 @@
 use crate::{ButtonState, Input};
 use bevy_ecs::{event::EventReader, system::ResMut};
+use bevy_reflect::{FromReflect, Reflect};
 
 /// A keyboard input event.
 ///
@@ -60,8 +61,9 @@ pub fn keyboard_input_system(
 /// ## Updating
 ///
 /// The resource is updated inside of the [`keyboard_input_system`](crate::keyboard::keyboard_input_system).
-#[derive(Debug, Hash, Ord, PartialOrd, PartialEq, Eq, Clone, Copy)]
+#[derive(Reflect, FromReflect, Debug, Hash, Ord, PartialOrd, PartialEq, Eq, Clone, Copy)]
 #[cfg_attr(feature = "serialize", derive(serde::Serialize, serde::Deserialize))]
+#[reflect(Hash, PartialEq)]
 #[repr(u32)]
 pub enum KeyCode {
     /// The `1` key over the letters.
@@ -422,6 +424,7 @@ pub enum KeyCode {
 /// ## Updating
 ///
 /// The resource is updated inside of the [`keyboard_input_system`](crate::keyboard::keyboard_input_system).
-#[derive(Debug, Hash, Ord, PartialOrd, PartialEq, Eq, Clone, Copy)]
+#[derive(Reflect, FromReflect, Debug, Hash, Ord, PartialOrd, PartialEq, Eq, Clone, Copy)]
+#[reflect(Hash, PartialEq)]
 #[cfg_attr(feature = "serialize", derive(serde::Serialize, serde::Deserialize))]
 pub struct ScanCode(pub u32);

crates/bevy_reflect/bevy_reflect_derive/src/derive_data.rs

@@ -111,19 +111,18 @@ impl<'a> ReflectDerive<'a> {
         let mut force_reflect_value = false;
 
         for attribute in input.attrs.iter().filter_map(|attr| attr.parse_meta().ok()) {
-            let meta_list = if let Meta::List(meta_list) = attribute {
-                meta_list
-            } else {
-                continue;
-            };
-
-            if let Some(ident) = meta_list.path.get_ident() {
-                if ident == REFLECT_ATTRIBUTE_NAME {
+            match attribute {
+                Meta::List(meta_list) if meta_list.path.is_ident(REFLECT_ATTRIBUTE_NAME) => {
                     traits = ReflectTraits::from_nested_metas(&meta_list.nested);
-                } else if ident == REFLECT_VALUE_ATTRIBUTE_NAME {
+                }
+                Meta::List(meta_list) if meta_list.path.is_ident(REFLECT_VALUE_ATTRIBUTE_NAME) => {
                     force_reflect_value = true;
                     traits = ReflectTraits::from_nested_metas(&meta_list.nested);
                 }
+                Meta::Path(path) if path.is_ident(REFLECT_VALUE_ATTRIBUTE_NAME) => {
+                    force_reflect_value = true;
+                }
+                _ => continue,
             }
         }
 

crates/bevy_reflect/bevy_reflect_derive/src/impls/values.rs

@@ -68,14 +68,14 @@ pub(crate) fn impl_value(meta: &ReflectMeta) -> TokenStream {
 
             #[inline]
             fn clone_value(&self) -> Box<dyn #bevy_reflect_path::Reflect> {
-                Box::new(self.clone())
+                Box::new(std::clone::Clone::clone(self))
             }
 
             #[inline]
             fn apply(&mut self, value: &dyn #bevy_reflect_path::Reflect) {
                 let value = value.as_any();
                 if let Some(value) = value.downcast_ref::<Self>() {
-                    *self = value.clone();
+                    *self = std::clone::Clone::clone(value);
                 } else {
                     panic!("Value is not {}.", std::any::type_name::<Self>());
                 }