Make Xilem Views `must_use` (#742)

Also fixes `unused_qualifications` as an easy fix.

---------

Co-authored-by: Kaur Kuut <strom@nevermore.ee>

xilem/src/driver.rs

@@ -33,12 +33,10 @@ type MessagePackage = (Arc<[ViewId]>, DynMessage);
 
 impl RawProxy for MasonryProxy {
     fn send_message(&self, path: Arc<[ViewId]>, message: DynMessage) -> Result<(), ProxyError> {
-        match self
-            .0
-            .send_event(event_loop_runner::MasonryUserEvent::Action(
-                async_action(path, message),
-                ASYNC_MARKER_WIDGET,
-            )) {
+        match self.0.send_event(MasonryUserEvent::Action(
+            async_action(path, message),
+            ASYNC_MARKER_WIDGET,
+        )) {
             Ok(()) => Ok(()),
             Err(err) => {
                 let MasonryUserEvent::Action(masonry::Action::Other(res), _) = err.0 else {
@@ -74,7 +72,7 @@ where
     fn on_action(
         &mut self,
         masonry_ctx: &mut masonry::DriverCtx<'_>,
-        widget_id: masonry::WidgetId,
+        widget_id: WidgetId,
         action: masonry::Action,
     ) {
         let message_result = if widget_id == ASYNC_MARKER_WIDGET {

xilem/src/lib.rs

@@ -18,12 +18,13 @@
 )]
 // TODO: Remove any items listed as "Deferred"
 #![cfg_attr(not(debug_assertions), allow(unused))]
-#![expect(missing_debug_implementations, reason = "Deferred: Noisy")]
-#![expect(unused_qualifications, reason = "Deferred: Noisy")]
+#![expect(
+    missing_debug_implementations,
+    reason = "Deferred: Noisy. Requires same lint to be addressed in Masonry"
+)]
 #![expect(clippy::exhaustive_enums, reason = "Deferred: Noisy")]
 #![expect(clippy::match_same_arms, reason = "Deferred: Noisy")]
 #![expect(clippy::missing_assert_message, reason = "Deferred: Noisy")]
-#![expect(clippy::return_self_not_must_use, reason = "Deferred: Noisy")]
 #![expect(elided_lifetimes_in_paths, reason = "Deferred: Noisy")]
 #![expect(clippy::use_self, reason = "Deferred: Noisy")]
 // https://github.com/rust-lang/rust/pull/130025
@@ -65,6 +66,7 @@ pub mod view;
 pub use any_view::AnyWidgetView;
 pub use driver::{async_action, MasonryDriver, MasonryProxy, ASYNC_MARKER_WIDGET};
 
+#[must_use = "A Xilem app does nothing unless ran."]
 pub struct Xilem<State, Logic> {
     state: State,
     logic: Logic,

xilem/src/view/button.rs

@@ -35,6 +35,7 @@ pub fn button_any_pointer<State, Action>(
     }
 }
 
+#[must_use = "View values do nothing unless provided to Xilem."]
 pub struct Button<F> {
     label: ArcStr,
     callback: F,

xilem/src/view/checkbox.rs

@@ -22,6 +22,7 @@ where
     }
 }
 
+#[must_use = "View values do nothing unless provided to Xilem."]
 pub struct Checkbox<F> {
     label: ArcStr,
     checked: bool,
@@ -38,10 +39,7 @@ where
 
     fn build(&self, ctx: &mut ViewCtx) -> (Self::Element, Self::ViewState) {
         ctx.with_leaf_action_widget(|ctx| {
-            ctx.new_pod(masonry::widget::Checkbox::new(
-                self.checked,
-                self.label.clone(),
-            ))
+            ctx.new_pod(widget::Checkbox::new(self.checked, self.label.clone()))
         })
     }
 

xilem/src/view/flex.rs

@@ -27,6 +27,7 @@ pub fn flex<State, Action, Seq: FlexSequence<State, Action>>(
     }
 }
 
+#[must_use = "View values do nothing unless provided to Xilem."]
 pub struct Flex<Seq, State, Action = ()> {
     sequence: Seq,
     axis: Axis,

xilem/src/view/grid.rs

@@ -26,6 +26,7 @@ pub fn grid<State, Action, Seq: GridSequence<State, Action>>(
     }
 }
 
+#[must_use = "View values do nothing unless provided to Xilem."]
 pub struct Grid<Seq, State, Action = ()> {
     sequence: Seq,
     spacing: f64,

xilem/src/view/image.rs

@@ -31,6 +31,7 @@ pub fn image(image: &vello::peniko::Image) -> Image {
 /// The [`View`] created by [`image`].
 ///
 /// See `image`'s docs for more details.
+#[must_use = "View values do nothing unless provided to Xilem."]
 pub struct Image {
     image: vello::peniko::Image,
     object_fit: ObjectFit,

xilem/src/view/label.rs

@@ -17,6 +17,7 @@ pub fn label(label: impl Into<ArcStr>) -> Label {
     }
 }
 
+#[must_use = "View values do nothing unless provided to Xilem."]
 pub struct Label {
     label: ArcStr,
 
@@ -99,7 +100,7 @@ impl<State, Action> View<State, Action, ViewCtx> for Label {
         _id_path: &[ViewId],
         message: DynMessage,
         _app_state: &mut State,
-    ) -> crate::MessageResult<Action> {
+    ) -> MessageResult<Action> {
         tracing::error!("Message arrived in Label::message, but Label doesn't consume any messages, this is a bug");
         MessageResult::Stale(message)
     }

xilem/src/view/portal.rs

@@ -21,6 +21,7 @@ where
     }
 }
 
+#[must_use = "View values do nothing unless provided to Xilem."]
 pub struct Portal<V, State, Action> {
     child: V,
     phantom: PhantomData<(State, Action)>,

xilem/src/view/progress_bar.rs

@@ -20,9 +20,7 @@ impl<State, Action> View<State, Action, ViewCtx> for ProgressBar {
     type ViewState = ();
 
     fn build(&self, ctx: &mut ViewCtx) -> (Self::Element, Self::ViewState) {
-        ctx.with_leaf_action_widget(|ctx| {
-            ctx.new_pod(masonry::widget::ProgressBar::new(self.progress))
-        })
+        ctx.with_leaf_action_widget(|ctx| ctx.new_pod(widget::ProgressBar::new(self.progress)))
     }
 
     fn rebuild(

xilem/src/view/prose.rs

@@ -27,6 +27,7 @@ pub fn inline_prose(content: impl Into<ArcStr>) -> Prose {
     prose(content).line_break_mode(LineBreaking::Overflow)
 }
 
+#[must_use = "View values do nothing unless provided to Xilem."]
 pub struct Prose {
     content: ArcStr,
 
@@ -109,7 +110,7 @@ impl<State, Action> View<State, Action, ViewCtx> for Prose {
         _id_path: &[ViewId],
         message: DynMessage,
         _app_state: &mut State,
-    ) -> crate::MessageResult<Action> {
+    ) -> MessageResult<Action> {
         tracing::error!("Message arrived in Prose::message, but Prose doesn't consume any messages, this is a bug");
         MessageResult::Stale(message)
     }

xilem/src/view/sized_box.rs

@@ -30,6 +30,7 @@ where
     }
 }
 
+#[must_use = "View values do nothing unless provided to Xilem."]
 pub struct SizedBox<V, State, Action = ()> {
     inner: V,
     width: Option<f64>,

xilem/src/view/spinner.rs

@@ -38,6 +38,7 @@ pub fn spinner() -> Spinner {
 /// The [`View`] created by [`spinner`].
 ///
 /// See `spinner`'s docs for more details.
+#[must_use = "View values do nothing unless provided to Xilem."]
 pub struct Spinner {
     color: Option<Color>,
 }

xilem/src/view/task.rs

@@ -33,7 +33,7 @@ where
 {
     const {
         assert!(
-            core::mem::size_of::<F>() == 0,
+            size_of::<F>() == 0,
             "`task` will not be ran again when its captured variables are updated.\n\
             To ignore this warning, use `task_raw`."
         );

xilem/src/view/textbox.rs

@@ -28,6 +28,7 @@ where
     }
 }
 
+#[must_use = "View values do nothing unless provided to Xilem."]
 pub struct Textbox<State, Action> {
     contents: String,
     on_changed: Callback<State, Action>,
@@ -72,7 +73,7 @@ impl<State: 'static, Action: 'static> View<State, Action, ViewCtx> for Textbox<S
     fn build(&self, ctx: &mut ViewCtx) -> (Self::Element, Self::ViewState) {
         ctx.with_leaf_action_widget(|ctx| {
             ctx.new_pod(
-                masonry::widget::Textbox::new(self.contents.clone())
+                widget::Textbox::new(self.contents.clone())
                     .with_text_brush(self.text_brush.clone())
                     .with_text_alignment(self.alignment),
             )

xilem/src/view/variable_label.rs

@@ -22,6 +22,7 @@ pub fn variable_label(label: impl Into<ArcStr>) -> VariableLabel {
     }
 }
 
+#[must_use = "View values do nothing unless provided to Xilem."]
 pub struct VariableLabel {
     label: ArcStr,
 
@@ -149,7 +150,7 @@ impl<State, Action> View<State, Action, ViewCtx> for VariableLabel {
         _id_path: &[ViewId],
         message: DynMessage,
         _app_state: &mut State,
-    ) -> crate::MessageResult<Action> {
+    ) -> MessageResult<Action> {
         tracing::error!("Message arrived in Label::message, but Label doesn't consume any messages, this is a bug");
         MessageResult::Stale(message)
     }

xilem/src/view/worker.rs

@@ -39,7 +39,7 @@ where
 {
     const {
         assert!(
-            core::mem::size_of::<F>() == 0,
+            size_of::<F>() == 0,
             "`worker` will not be ran again when its captured variables are updated.\n\
             To ignore this warning, use `worker_raw`.
             To provide an updating value to this task, use the "

xilem_core/src/views/adapt.rs

@@ -7,6 +7,7 @@ use crate::{MessageResult, Mut, View, ViewId, ViewMarker, ViewPathTracker};
 
 /// A view that wraps a child view and modifies the state that callbacks have access to.
 #[derive(Debug)]
+#[must_use = "View values do nothing unless provided to Xilem."]
 pub struct Adapt<
     ParentState,
     ParentAction,

xilem_core/src/views/fork.rs

@@ -21,6 +21,7 @@ pub fn fork<Active, Alongside>(
 
 /// The view for [`fork`].
 #[derive(Debug)]
+#[must_use = "View values do nothing unless provided to Xilem."]
 pub struct Fork<Active, Alongside> {
     active_view: Active,
     alongside_view: Alongside,

xilem_core/src/views/map_action.rs

@@ -8,6 +8,7 @@ use crate::{Mut, View, ViewId, ViewMarker, ViewPathTracker};
 /// A view that maps a child [`View<State,ChildAction,_>`] to [`View<State,ParentAction,_>`] while providing mutable access to `State` in the map function.
 ///
 /// This is very similar to the Elm architecture, where the parent view can update state based on the action message from the child view
+#[must_use = "View values do nothing unless provided to Xilem."]
 pub struct MapAction<
     V,
     State,

xilem_core/src/views/map_state.rs

@@ -8,6 +8,7 @@ use crate::{MessageResult, Mut, View, ViewId, ViewMarker, ViewPathTracker};
 /// The View for [`map_state`] and [`lens`].
 ///
 /// See their documentation for more context.
+#[must_use = "View values do nothing unless provided to Xilem."]
 pub struct MapState<V, F, ParentState, ChildState, Action, Context, Message> {
     map_state: F,
     child: V,

xilem_core/src/views/memoize.rs

@@ -10,6 +10,7 @@ use crate::{MessageResult, Mut, View, ViewId, ViewMarker, ViewPathTracker};
 ///
 /// The story of Memoization in Xilem is still being worked out,
 /// so the details of this view might change.
+#[must_use = "View values do nothing unless provided to Xilem."]
 pub struct Memoize<Data, InitView, State, Action, Context, Message> {
     data: Data,
     init_view: InitView,

xilem_core/src/views/one_of.rs

@@ -23,6 +23,7 @@ pub trait PhantomElementCtx: ViewPathTracker {
 /// A [`View`] which can be one of nine inner view types.
 #[allow(missing_docs)] // On variants
 #[derive(Debug)]
+#[must_use = "View values do nothing unless provided to Xilem."]
 pub enum OneOf<A = (), B = (), C = (), D = (), E = (), F = (), G = (), H = (), I = ()> {
     A(A),
     B(B),

xilem_core/src/views/run_once.rs

@@ -71,6 +71,7 @@ where
 /// The view type for [`run_once`].
 ///
 /// This is a [`NoElement`] view.
+#[must_use = "View values do nothing unless provided to Xilem."]
 pub struct RunOnce<F> {
     once: F,
 }