diff --git a/xilem_core/src/view.rs b/xilem_core/src/view.rs
index 75e491a875..93c1d41f67 100644
--- a/xilem_core/src/view.rs
+++ b/xilem_core/src/view.rs
@@ -164,5 +164,15 @@ pub trait View<State: ViewArgument, Action, Context: ViewPathTracker>:
         crate::map_action(self, f)
     }
 
+    #[doc(hidden)]
+    /// An identity function, that lets us assert that
+    /// the receiver always implements WidgetView<..>
+    fn check_impl_view(self) -> Self
+    where
+        Self: Sized,
+    {
+        self
+    }
+
     // fn debug_name?
 }
diff --git a/xilem_masonry/src/view/button.rs b/xilem_masonry/src/view/button.rs
index a161eaca73..736f8dc4de 100644
--- a/xilem_masonry/src/view/button.rs
+++ b/xilem_masonry/src/view/button.rs
@@ -74,16 +74,19 @@ use crate::{Pod, ViewCtx, WidgetView};
 /// ```
 pub fn button<
     State: ViewArgument,
-    Action,
+    Action: 'static,
     V: WidgetView<State, Action>,
-    F: Fn(Arg<'_, State>) -> Action + Send + 'static,
+    F: Fn(Arg<'_, State>) -> Action + Send + Sync + 'static,
 >(
     child: V,
     callback: F,
 ) -> Button<
     State,
     Action,
-    impl for<'a> Fn(Arg<'_, State>, Option<PointerButton>) -> MessageResult<Action> + Send + 'static,
+    impl for<'a> Fn(Arg<'_, State>, Option<PointerButton>) -> MessageResult<Action>
+    + Send
+    + Sync
+    + 'static,
     V,
 > {
     Button {
@@ -95,6 +98,7 @@ pub fn button<
         disabled: false,
         phantom: PhantomData,
     }
+    .check_impl_widget_view()
 }
 
 /// A button with default styled text.
@@ -102,7 +106,7 @@ pub fn button<
 /// This is equivalent to `button(label(text), callback)`, and is useful for
 /// making buttons quickly from string literals.
 /// For more advanced text styling, prefer [`button`].
-pub fn text_button<State: ViewArgument, Action>(
+pub fn text_button<State: ViewArgument, Action: 'static>(
     text: impl Into<ArcStr>,
     callback: impl Fn(Arg<'_, State>) -> Action + Send + Sync + 'static,
 ) -> Button<
@@ -127,7 +131,7 @@ pub fn text_button<State: ViewArgument, Action>(
 /// Similarly, there is not currently long-press support.
 ///
 /// For more documentation and examples, see [`button`].
-pub fn button_any_pointer<State: ViewArgument, Action, V: WidgetView<State, Action>>(
+pub fn button_any_pointer<State: ViewArgument, Action: 'static, V: WidgetView<State, Action>>(
     child: V,
     callback: impl Fn(Arg<'_, State>, Option<PointerButton>) -> Action + Send + Sync + 'static,
 ) -> Button<
diff --git a/xilem_masonry/src/view/checkbox.rs b/xilem_masonry/src/view/checkbox.rs
index 9983017b6a..c38bfe2612 100644
--- a/xilem_masonry/src/view/checkbox.rs
+++ b/xilem_masonry/src/view/checkbox.rs
@@ -8,6 +8,7 @@ use masonry::parley::StyleProperty;
 use masonry::parley::style::{FontStack, FontWeight};
 use masonry::widgets::{self, CheckboxToggled};
 
+use crate::WidgetView as _;
 use crate::core::{Arg, MessageCtx, MessageResult, Mut, View, ViewArgument, ViewMarker};
 use crate::{Pod, ViewCtx};
 
@@ -30,13 +31,13 @@ use crate::{Pod, ViewCtx};
 /// })
 /// # }
 /// ```
-pub fn checkbox<F, State, Action>(
+pub fn checkbox<F, State, Action: 'static>(
     label: impl Into<ArcStr>,
     checked: bool,
     callback: F,
 ) -> Checkbox<State, Action, F>
 where
-    F: Fn(Arg<'_, State>, bool) -> Action + Send + 'static,
+    F: Fn(Arg<'_, State>, bool) -> Action + Send + Sync + 'static,
     State: ViewArgument,
 {
     Checkbox {
@@ -49,6 +50,7 @@ where
         disabled: false,
         phantom: PhantomData,
     }
+    .check_impl_widget_view()
 }
 
 /// The [`View`] created by [`checkbox`] from a `label`, a bool value and a callback.
diff --git a/xilem_masonry/src/view/flex.rs b/xilem_masonry/src/view/flex.rs
index 330161bf3b..ec70babc97 100644
--- a/xilem_masonry/src/view/flex.rs
+++ b/xilem_masonry/src/view/flex.rs
@@ -82,7 +82,7 @@ use crate::{AnyWidgetView, Pod, ViewCtx, WidgetView};
 ///     .cross_axis_alignment(CrossAxisAlignment::Center)
 /// }
 /// ```
-pub fn flex<State: ViewArgument, Action, Seq: FlexSequence<State, Action>>(
+pub fn flex<State: ViewArgument, Action: 'static, Seq: FlexSequence<State, Action>>(
     axis: Axis,
     sequence: Seq,
 ) -> Flex<Seq, State, Action> {
@@ -94,6 +94,7 @@ pub fn flex<State: ViewArgument, Action, Seq: FlexSequence<State, Action>>(
         fill_major_axis: false,
         phantom: PhantomData,
     }
+    .check_impl_widget_view()
 }
 
 /// A layout where the children are laid out in a row.
@@ -102,7 +103,7 @@ pub fn flex<State: ViewArgument, Action, Seq: FlexSequence<State, Action>>(
 /// [`direction`](Flex::direction).
 /// We recommend reading that type's documentation for a detailed
 /// explanation of this component's layout model.
-pub fn flex_row<State: ViewArgument, Action, Seq: FlexSequence<State, Action>>(
+pub fn flex_row<State: ViewArgument, Action: 'static, Seq: FlexSequence<State, Action>>(
     sequence: Seq,
 ) -> Flex<Seq, State, Action> {
     flex(Axis::Horizontal, sequence)
@@ -114,7 +115,7 @@ pub fn flex_row<State: ViewArgument, Action, Seq: FlexSequence<State, Action>>(
 /// [`direction`](Flex::direction).
 /// We recommend reading that type's documentation for a detailed
 /// explanation of this component's layout model.
-pub fn flex_col<State: ViewArgument, Action, Seq: FlexSequence<State, Action>>(
+pub fn flex_col<State: ViewArgument, Action: 'static, Seq: FlexSequence<State, Action>>(
     sequence: Seq,
 ) -> Flex<Seq, State, Action> {
     flex(Axis::Vertical, sequence)
@@ -451,17 +452,17 @@ impl ElementSplice<FlexElement> for FlexSplice<'_, '_> {
 /// }
 /// ```
 pub trait FlexSequence<State: ViewArgument, Action = ()>:
-    ViewSequence<State, Action, ViewCtx, FlexElement>
+    ViewSequence<State, Action, ViewCtx, FlexElement> + Send + Sync
 {
 }
 
 impl<Seq, State: ViewArgument, Action> FlexSequence<State, Action> for Seq where
-    Seq: ViewSequence<State, Action, ViewCtx, FlexElement>
+    Seq: ViewSequence<State, Action, ViewCtx, FlexElement> + Send + Sync
 {
 }
 
 /// A trait which extends a [`WidgetView`] with methods to provide parameters for a flex item, or being able to use it interchangeably with a spacer.
-pub trait FlexExt<State: ViewArgument, Action>: WidgetView<State, Action> {
+pub trait FlexExt<State: ViewArgument, Action: 'static>: WidgetView<State, Action> {
     /// Applies [`impl Into<FlexParams>`](`FlexParams`) to this view, can be used as child of a [`Flex`] [`View`]
     ///
     /// # Examples
@@ -515,7 +516,10 @@ pub trait FlexExt<State: ViewArgument, Action>: WidgetView<State, Action> {
     }
 }
 
-impl<State: ViewArgument, Action, V: WidgetView<State, Action>> FlexExt<State, Action> for V {}
+impl<State: ViewArgument, Action: 'static, V: WidgetView<State, Action>> FlexExt<State, Action>
+    for V
+{
+}
 
 /// A `WidgetView` that can be used within a [`Flex`] [`View`].
 pub struct FlexItem<V, State, Action> {
diff --git a/xilem_masonry/src/view/grid.rs b/xilem_masonry/src/view/grid.rs
index 35c736eb77..c788f03b05 100644
--- a/xilem_masonry/src/view/grid.rs
+++ b/xilem_masonry/src/view/grid.rs
@@ -46,7 +46,7 @@ pub use masonry::widgets::GridParams;
 /// .gap(GRID_GAP)
 /// ```
 /// Also see Calculator example [here](https://github.com/linebender/xilem/blob/main/xilem/examples/calc.rs) to learn more about grid layout.
-pub fn grid<State: ViewArgument, Action, Seq: GridSequence<State, Action>>(
+pub fn grid<State: ViewArgument, Action: 'static, Seq: GridSequence<State, Action>>(
     sequence: Seq,
     width: i32,
     height: i32,
@@ -57,6 +57,7 @@ pub fn grid<State: ViewArgument, Action, Seq: GridSequence<State, Action>>(
         width,
         phantom: PhantomData,
     }
+    .check_impl_widget_view()
 }
 
 /// The [`View`] created by [`grid`] from a sequence, which also consumes custom width and height.
@@ -286,19 +287,19 @@ impl ElementSplice<GridElement> for GridSplice<'_, '_> {
 
 /// `GridSequence` is what allows an input to the grid that contains all the grid elements.
 pub trait GridSequence<State: ViewArgument, Action = ()>:
-    ViewSequence<State, Action, ViewCtx, GridElement>
+    ViewSequence<State, Action, ViewCtx, GridElement> + Send + Sync
 {
 }
 
 impl<Seq, State, Action> GridSequence<State, Action> for Seq
 where
-    Seq: ViewSequence<State, Action, ViewCtx, GridElement>,
+    Seq: ViewSequence<State, Action, ViewCtx, GridElement> + Send + Sync,
     State: ViewArgument,
 {
 }
 
 /// A trait which extends a [`WidgetView`] with methods to provide parameters for a grid item
-pub trait GridExt<State: ViewArgument, Action>: WidgetView<State, Action> {
+pub trait GridExt<State: ViewArgument, Action: 'static>: WidgetView<State, Action> {
     /// Applies [`impl Into<GridParams>`](`GridParams`) to this view. This allows the view
     /// to be placed as a child within a [`Grid`] [`View`].
     ///
@@ -352,7 +353,10 @@ pub trait GridExt<State: ViewArgument, Action>: WidgetView<State, Action> {
     }
 }
 
-impl<State: ViewArgument, Action, V: WidgetView<State, Action>> GridExt<State, Action> for V {}
+impl<State: ViewArgument, Action: 'static, V: WidgetView<State, Action>> GridExt<State, Action>
+    for V
+{
+}
 
 /// A child widget within a [`Grid`] view.
 pub struct GridElement {
diff --git a/xilem_masonry/src/view/indexed_stack.rs b/xilem_masonry/src/view/indexed_stack.rs
index 2450aaab19..9f72682823 100644
--- a/xilem_masonry/src/view/indexed_stack.rs
+++ b/xilem_masonry/src/view/indexed_stack.rs
@@ -10,7 +10,7 @@ use crate::core::{
     AppendVec, Arg, ElementSplice, MessageCtx, MessageResult, Mut, SuperElement, View,
     ViewArgument, ViewElement, ViewMarker, ViewSequence,
 };
-use crate::{Pod, ViewCtx};
+use crate::{Pod, ViewCtx, WidgetView};
 
 /// An `IndexedStack` displays one of several children elements at a time.
 ///
@@ -50,7 +50,11 @@ use crate::{Pod, ViewCtx};
 /// )
 /// .active(state.tab);
 /// ```
-pub fn indexed_stack<State: ViewArgument, Action, Seq: IndexedStackSequence<State, Action>>(
+pub fn indexed_stack<
+    State: ViewArgument,
+    Action: 'static,
+    Seq: IndexedStackSequence<State, Action>,
+>(
     sequence: Seq,
 ) -> IndexedStack<Seq, State, Action> {
     IndexedStack {
@@ -58,6 +62,7 @@ pub fn indexed_stack<State: ViewArgument, Action, Seq: IndexedStackSequence<Stat
         active_child: 0,
         phantom: PhantomData,
     }
+    .check_impl_widget_view()
 }
 
 /// The [`View`] created by [`indexed_stack`] from a sequence.
@@ -287,13 +292,13 @@ impl ElementSplice<IndexedStackElement> for IndexedStackSplice<'_, '_> {
 
 /// `IndexedStackSequence` is what allows an input to the indexed stack that contains all the stack elements.
 pub trait IndexedStackSequence<State: ViewArgument, Action = ()>:
-    ViewSequence<State, Action, ViewCtx, IndexedStackElement>
+    ViewSequence<State, Action, ViewCtx, IndexedStackElement> + Send + Sync
 {
 }
 
 impl<Seq, State, Action> IndexedStackSequence<State, Action> for Seq
 where
-    Seq: ViewSequence<State, Action, ViewCtx, IndexedStackElement>,
+    Seq: ViewSequence<State, Action, ViewCtx, IndexedStackElement> + Send + Sync,
     State: ViewArgument,
 {
 }
diff --git a/xilem_masonry/src/view/label.rs b/xilem_masonry/src/view/label.rs
index 42deceb8e0..6cd3d23ac4 100644
--- a/xilem_masonry/src/view/label.rs
+++ b/xilem_masonry/src/view/label.rs
@@ -7,7 +7,7 @@ use masonry::parley::{FontFamily, GenericFamily};
 use masonry::widgets;
 
 use crate::core::{Arg, MessageCtx, MessageResult, Mut, View, ViewArgument, ViewMarker};
-use crate::{Pod, TextAlign, ViewCtx};
+use crate::{Pod, TextAlign, ViewCtx, WidgetView};
 
 /// A non-interactive text element.
 /// # Example
@@ -33,13 +33,13 @@ use crate::{Pod, TextAlign, ViewCtx};
 /// # }
 /// ```
 pub fn label(label: impl Into<ArcStr>) -> Label {
-    Label {
+    WidgetView::<()>::check_impl_widget_view(Label {
         label: label.into(),
         text_alignment: TextAlign::default(),
         text_size: masonry::theme::TEXT_SIZE_NORMAL,
         weight: FontWeight::NORMAL,
         font: FontStack::Single(FontFamily::Generic(GenericFamily::SystemUi)),
-    }
+    })
 }
 
 /// The [`View`] created by [`label`] from a text which `impl Into<`[`ArcStr`]`>`.
diff --git a/xilem_masonry/src/view/portal.rs b/xilem_masonry/src/view/portal.rs
index dc71bbe172..0b48ba07ac 100644
--- a/xilem_masonry/src/view/portal.rs
+++ b/xilem_masonry/src/view/portal.rs
@@ -11,7 +11,7 @@ use crate::{Pod, ViewCtx, WidgetView};
 /// A view which puts `child` into a scrollable region.
 ///
 /// This corresponds to the Masonry [`Portal`](masonry::widgets::Portal) widget.
-pub fn portal<Child, State, Action>(child: Child) -> Portal<Child, State, Action>
+pub fn portal<Child, State, Action: 'static>(child: Child) -> Portal<Child, State, Action>
 where
     State: ViewArgument,
     Child: WidgetView<State, Action>,
@@ -20,6 +20,7 @@ where
         child,
         phantom: PhantomData,
     }
+    .check_impl_widget_view()
 }
 
 /// The [`View`] created by [`portal`].
diff --git a/xilem_masonry/src/view/progress_bar.rs b/xilem_masonry/src/view/progress_bar.rs
index 9e2c2f5c4a..eb14c40580 100644
--- a/xilem_masonry/src/view/progress_bar.rs
+++ b/xilem_masonry/src/view/progress_bar.rs
@@ -4,13 +4,13 @@
 use masonry::widgets;
 
 use crate::core::{Arg, MessageCtx, MessageResult, Mut, View, ViewArgument, ViewMarker};
-use crate::{Pod, ViewCtx};
+use crate::{Pod, ViewCtx, WidgetView};
 
 /// A view which displays a progress bar.
 ///
 /// This can be for showing progress of a task or a download.
 pub fn progress_bar(progress: Option<f64>) -> ProgressBar {
-    ProgressBar { progress }
+    WidgetView::<()>::check_impl_widget_view(ProgressBar { progress })
 }
 
 /// The [`View`] created by [`progress_bar`].
diff --git a/xilem_masonry/src/view/prose.rs b/xilem_masonry/src/view/prose.rs
index 61ad345a10..c4dee293c4 100644
--- a/xilem_masonry/src/view/prose.rs
+++ b/xilem_masonry/src/view/prose.rs
@@ -9,10 +9,12 @@ use masonry::properties::{ContentColor, DisabledContentColor, LineBreaking};
 use masonry::widgets;
 
 use crate::core::{Arg, MessageCtx, MessageResult, Mut, View, ViewArgument, ViewMarker};
-use crate::{Color, Pod, TextAlign, ViewCtx};
+use crate::{Color, Pod, TextAlign, ViewCtx, WidgetView};
 
 /// A view which displays selectable text.
-pub fn prose<State, Action>(content: impl Into<ArcStr>) -> Prose<State, Action> {
+pub fn prose<State: ViewArgument, Action: 'static>(
+    content: impl Into<ArcStr>,
+) -> Prose<State, Action> {
     Prose {
         content: content.into(),
         text_color: None,
@@ -23,6 +25,7 @@ pub fn prose<State, Action>(content: impl Into<ArcStr>) -> Prose<State, Action>
         weight: FontWeight::NORMAL,
         phantom: PhantomData,
     }
+    .check_impl_widget_view()
 }
 
 /// A version of [`prose`] suitable for including in the same line
@@ -31,7 +34,9 @@ pub fn prose<State, Action>(content: impl Into<ArcStr>) -> Prose<State, Action>
 /// Note that setting [`text_alignment`](Prose::text_alignment) on the result
 /// will be meaningless.
 #[doc(alias = "span")]
-pub fn inline_prose<State, Action>(content: impl Into<ArcStr>) -> Prose<State, Action> {
+pub fn inline_prose<State: ViewArgument, Action: 'static>(
+    content: impl Into<ArcStr>,
+) -> Prose<State, Action> {
     prose(content).line_break_mode(LineBreaking::Overflow)
 }
 
diff --git a/xilem_masonry/src/view/resize_observer.rs b/xilem_masonry/src/view/resize_observer.rs
index 782653aa7f..8c4a05af5c 100644
--- a/xilem_masonry/src/view/resize_observer.rs
+++ b/xilem_masonry/src/view/resize_observer.rs
@@ -72,6 +72,7 @@ where
         on_resize,
         phantom: PhantomData,
     }
+    .check_impl_widget_view()
 }
 
 /// The [`View`] created by [`resize_observer`].
diff --git a/xilem_masonry/src/view/sized_box.rs b/xilem_masonry/src/view/sized_box.rs
index cccf1d746d..3fa84492bf 100644
--- a/xilem_masonry/src/view/sized_box.rs
+++ b/xilem_masonry/src/view/sized_box.rs
@@ -43,6 +43,7 @@ where
         width: None,
         phantom: PhantomData,
     }
+    .check_impl_widget_view()
 }
 
 /// The [`View`] created by [`sized_box`].
diff --git a/xilem_masonry/src/view/slider.rs b/xilem_masonry/src/view/slider.rs
index 3d8500551f..b40895de8f 100644
--- a/xilem_masonry/src/view/slider.rs
+++ b/xilem_masonry/src/view/slider.rs
@@ -42,6 +42,7 @@ where
         disabled: false,
         phantom: PhantomData,
     }
+    .check_impl_widget_view()
 }
 
 impl<State, Action, F> Slider<State, Action, F> {
diff --git a/xilem_masonry/src/view/spinner.rs b/xilem_masonry/src/view/spinner.rs
index 09ab656f7f..b8c11ea4ae 100644
--- a/xilem_masonry/src/view/spinner.rs
+++ b/xilem_masonry/src/view/spinner.rs
@@ -4,7 +4,7 @@
 use masonry::widgets;
 
 use crate::core::{Arg, MessageCtx, MessageResult, Mut, View, ViewArgument, ViewMarker};
-use crate::{Pod, ViewCtx};
+use crate::{Pod, ViewCtx, WidgetView};
 
 /// An indefinite spinner.
 ///
@@ -34,7 +34,7 @@ use crate::{Pod, ViewCtx};
 /// }
 /// ```
 pub fn spinner() -> Spinner {
-    Spinner
+    WidgetView::<()>::check_impl_widget_view(Spinner)
 }
 
 /// The [`View`] created by [`spinner`].
diff --git a/xilem_masonry/src/view/split.rs b/xilem_masonry/src/view/split.rs
index 346863e1ce..e3f3c42e82 100644
--- a/xilem_masonry/src/view/split.rs
+++ b/xilem_masonry/src/view/split.rs
@@ -42,7 +42,7 @@ use crate::{Pod, ViewCtx, WidgetView};
 ///     .split_point(0.25)
 /// ```
 ///
-pub fn split<State, Action, ChildA, ChildB>(
+pub fn split<State, Action: 'static, ChildA, ChildB>(
     child1: ChildA,
     child2: ChildB,
 ) -> Split<ChildA, ChildB, State, Action>
@@ -63,6 +63,7 @@ where
         child2,
         phantom: PhantomData,
     }
+    .check_impl_widget_view()
 }
 
 /// The [`View`] created by [`split`].
diff --git a/xilem_masonry/src/view/task.rs b/xilem_masonry/src/view/task.rs
index c40f3c6581..9dc0fa84e0 100644
--- a/xilem_masonry/src/view/task.rs
+++ b/xilem_masonry/src/view/task.rs
@@ -32,11 +32,12 @@ pub fn task<M, F, H, State, Action, Fut>(
     on_event: H,
 ) -> Task<State, Action, F, H, M>
 where
-    F: Fn(MessageProxy<M>, Arg<'_, State>) -> Fut,
+    F: Fn(MessageProxy<M>, Arg<'_, State>) -> Fut + 'static,
     Fut: Future<Output = ()> + Send + 'static,
     H: Fn(Arg<'_, State>, M) -> Action + 'static,
     M: AnyDebug + Send + 'static,
     State: ViewArgument,
+    Action: 'static,
 {
     const {
         assert!(
@@ -50,6 +51,7 @@ where
         on_event,
         message: PhantomData,
     }
+    .check_impl_view()
 }
 
 /// Launch a task which will run until the view is no longer in the tree.
diff --git a/xilem_masonry/src/view/text_input.rs b/xilem_masonry/src/view/text_input.rs
index 674cae0001..50cdb708d5 100644
--- a/xilem_masonry/src/view/text_input.rs
+++ b/xilem_masonry/src/view/text_input.rs
@@ -80,7 +80,10 @@ type Callback<State, Action> =
 /// .insert_newline(InsertNewline::OnEnter)
 /// # }
 /// ```
-pub fn text_input<F, State, Action>(contents: String, on_changed: F) -> TextInput<State, Action>
+pub fn text_input<F, State, Action: 'static>(
+    contents: String,
+    on_changed: F,
+) -> TextInput<State, Action>
 where
     F: Fn(Arg<'_, State>, String) -> Action + Send + Sync + 'static,
     State: ViewArgument,
@@ -102,6 +105,7 @@ where
         // not clipping
         clip: true,
     }
+    .check_impl_widget_view()
 }
 
 /// The [`View`] created by [`text_input`].
diff --git a/xilem_masonry/src/view/transform.rs b/xilem_masonry/src/view/transform.rs
index 3bb2f5446d..53bb019e69 100644
--- a/xilem_masonry/src/view/transform.rs
+++ b/xilem_masonry/src/view/transform.rs
@@ -19,7 +19,7 @@ use crate::{Pod, ViewCtx, WidgetView};
 /// Transformations apply in order.
 /// That is, calling [`rotate`](Transformed::rotate) then [`translate`](Transformed::translate)
 /// will move the rotated widget.
-pub fn transformed<Child, State, Action>(child: Child) -> Transformed<Child, State, Action>
+pub fn transformed<Child, State, Action: 'static>(child: Child) -> Transformed<Child, State, Action>
 where
     Child: WidgetView<State, Action>,
     State: ViewArgument,
@@ -29,13 +29,14 @@ where
         transform: Affine::IDENTITY,
         phantom: PhantomData,
     }
+    .check_impl_widget_view()
 }
 
 /// The view for [`transformed`].
 pub struct Transformed<V, State, Action> {
     child: V,
     transform: Affine,
-    phantom: PhantomData<(State, Action)>,
+    phantom: PhantomData<fn(State) -> Action>,
 }
 
 impl<V, State, Action> Transformed<V, State, Action> {
diff --git a/xilem_masonry/src/view/variable_label.rs b/xilem_masonry/src/view/variable_label.rs
index c73a5279b6..c29ccd3db7 100644
--- a/xilem_masonry/src/view/variable_label.rs
+++ b/xilem_masonry/src/view/variable_label.rs
@@ -9,15 +9,15 @@ use crate::core::{
     Arg, MessageCtx, MessageResult, Mut, View, ViewArgument, ViewId, ViewMarker, ViewPathTracker,
 };
 use crate::view::{Label, label};
-use crate::{Pod, TextAlign, ViewCtx};
+use crate::{Pod, TextAlign, ViewCtx, WidgetView};
 
 /// A view for displaying non-editable text, with a variable [weight](masonry::parley::style::FontWeight).
 pub fn variable_label(text: impl Into<ArcStr>) -> VariableLabel {
-    VariableLabel {
+    WidgetView::<()>::check_impl_widget_view(VariableLabel {
         label: label(text),
         target_weight: FontWeight::NORMAL,
         over_millis: 0.,
-    }
+    })
 }
 
 /// The [`View`] created by [`variable_label`].
diff --git a/xilem_masonry/src/view/virtual_scroll.rs b/xilem_masonry/src/view/virtual_scroll.rs
index 34f5092b23..311eb37dd7 100644
--- a/xilem_masonry/src/view/virtual_scroll.rs
+++ b/xilem_masonry/src/view/virtual_scroll.rs
@@ -5,7 +5,6 @@ use std::collections::HashMap;
 use std::marker::PhantomData;
 use std::ops::Range;
 
-use masonry::core::{Widget, WidgetPod};
 use masonry::util::debug_panic;
 use masonry::widgets::{self, VirtualScrollAction};
 use private::VirtualScrollState;
@@ -19,7 +18,7 @@ use crate::{Pod, ViewCtx, WidgetView};
 ///
 /// See its documentation for details.
 pub struct VirtualScroll<State, Action, ChildrenViews, F> {
-    phantom: PhantomData<fn() -> (WidgetPod<dyn Widget>, State, Action, ChildrenViews)>,
+    phantom: PhantomData<fn() -> (State, Action, ChildrenViews)>,
     func: F,
     valid_range: Range<i64>,
 }
@@ -56,14 +55,16 @@ pub fn virtual_scroll<State, Action, ChildrenViews, F>(
 ) -> VirtualScroll<State, Action, ChildrenViews, F>
 where
     ChildrenViews: WidgetView<State, Action>,
-    F: Fn(Arg<'_, State>, i64) -> ChildrenViews + 'static,
+    F: Fn(Arg<'_, State>, i64) -> ChildrenViews + Send + Sync + 'static,
     State: ViewArgument,
+    Action: 'static,
 {
     VirtualScroll {
         phantom: PhantomData,
         func,
         valid_range,
     }
+    .check_impl_widget_view()
 }
 
 /// Component for a [`VirtualScroll`] with unlimited children.
@@ -80,6 +81,7 @@ where
     ChildrenViews: WidgetView<State, Action>,
     F: Fn(Arg<'_, State>, i64) -> ChildrenViews + 'static,
     State: ViewArgument,
+    Action: 'static,
 {
     VirtualScroll {
         phantom: PhantomData,
diff --git a/xilem_masonry/src/view/worker.rs b/xilem_masonry/src/view/worker.rs
index 934286687f..0cfb0e9a61 100644
--- a/xilem_masonry/src/view/worker.rs
+++ b/xilem_masonry/src/view/worker.rs
@@ -45,12 +45,14 @@ pub fn worker<F, H, M, S, V, State, Action, Fut>(
     Dummy,
 >
 where
-    F: Fn(MessageProxy<M>, UnboundedReceiver<V>) -> Fut,
+    F: Fn(MessageProxy<M>, UnboundedReceiver<V>) -> Fut + 'static,
+    V: Send + 'static,
     Fut: Future<Output = ()> + Send + 'static,
     S: Fn(Arg<'_, State>, UnboundedSender<V>) + 'static,
     H: Fn(Arg<'_, State>, M) -> Action + 'static,
     M: AnyDebug + Send + 'static,
     State: ViewArgument,
+    Action: 'static,
 {
     const {
         assert!(
@@ -69,6 +71,7 @@ where
         on_response,
         message: PhantomData,
     }
+    .check_impl_view()
 }
 
 /// A version of [`worker`] which can store its message sender in the environment.
@@ -81,13 +84,15 @@ pub fn env_worker<F, H, M, S, V, Res, State, Action, Fut>(
     on_response: H,
 ) -> Worker<State, Action, F, H, M, S, V, Res>
 where
-    F: Fn(MessageProxy<M>, UnboundedReceiver<V>) -> Fut,
+    F: Fn(MessageProxy<M>, UnboundedReceiver<V>) -> Fut + 'static,
+    V: Send + 'static,
     Fut: Future<Output = ()> + Send + 'static,
-    S: Fn(Arg<'_, State>, &mut Res, UnboundedSender<V>),
+    S: Fn(Arg<'_, State>, &mut Res, UnboundedSender<V>) + 'static,
     H: Fn(Arg<'_, State>, M) -> Action + 'static,
     M: AnyDebug + Send + 'static,
     Res: Resource,
     State: ViewArgument,
+    Action: 'static,
 {
     const {
         assert!(
@@ -102,6 +107,7 @@ where
         on_response,
         message: PhantomData,
     }
+    .check_impl_view()
 }
 
 /// An internal struct used to make [`env_worker`]/[`worker`] work.
@@ -133,12 +139,14 @@ pub fn worker_raw<M, V, S, F, H, State, Action, Fut>(
 >
 where
     // TODO(DJMcNab): Accept app_state here
-    F: Fn(MessageProxy<M>, UnboundedReceiver<V>) -> Fut,
+    F: Fn(MessageProxy<M>, UnboundedReceiver<V>) -> Fut + 'static,
+    V: Send + 'static,
     Fut: Future<Output = ()> + Send + 'static,
     S: Fn(Arg<'_, State>, UnboundedSender<V>) + 'static,
     H: Fn(Arg<'_, State>, M) -> Action + 'static,
     M: AnyDebug + Send + 'static,
     State: ViewArgument,
+    Action: 'static,
 {
     Worker {
         init_future,
@@ -150,6 +158,7 @@ where
         },
         message: PhantomData,
     }
+    .check_impl_view()
 }
 
 /// The View type for [`worker`], [`env_worker`] and [`worker_raw`]. See its documentation for details.
@@ -166,7 +175,6 @@ impl<State, Action, F, H, M, Fut, S, V, Res> View<State, Action, ViewCtx>
     for Worker<State, Action, F, H, M, S, V, Res>
 where
     Res: Resource,
-    Action: 'static,
     F: Fn(MessageProxy<M>, UnboundedReceiver<V>) -> Fut + 'static,
     V: Send + 'static,
     Fut: Future<Output = ()> + Send + 'static,
@@ -174,6 +182,7 @@ where
     H: Fn(Arg<'_, State>, M) -> Action + 'static,
     M: AnyDebug + Send + 'static,
     State: ViewArgument,
+    Action: 'static,
 {
     type Element = NoElement;
 
diff --git a/xilem_masonry/src/view/zstack.rs b/xilem_masonry/src/view/zstack.rs
index df259c6640..486bc5224c 100644
--- a/xilem_masonry/src/view/zstack.rs
+++ b/xilem_masonry/src/view/zstack.rs
@@ -34,13 +34,14 @@ use crate::{Pod, ViewCtx, WidgetView};
 ///     ))
 /// }
 /// ```
-pub fn zstack<State: ViewArgument, Action, Seq: ZStackSequence<State, Action>>(
+pub fn zstack<State: ViewArgument, Action: 'static, Seq: ZStackSequence<State, Action>>(
     sequence: Seq,
 ) -> ZStack<Seq> {
     ZStack {
         sequence,
         alignment: UnitPoint::CENTER,
     }
+    .check_impl_widget_view()
 }
 
 /// A view container that lays the child widgets on top of each other.
@@ -157,7 +158,7 @@ where
 // --- MARK: ZStackExt
 
 /// A trait that extends a [`WidgetView`] with methods to provide parameters for a parent [`ZStack`].
-pub trait ZStackExt<State: ViewArgument, Action>: WidgetView<State, Action> {
+pub trait ZStackExt<State: ViewArgument, Action: 'static>: WidgetView<State, Action> {
     /// Applies [`ChildAlignment`] to this view.
     /// This allows the view to override the default alignment of the parent [`ZStack`].
     /// This can only be used on views that are direct children of a [`ZStack`].
@@ -171,7 +172,10 @@ pub trait ZStackExt<State: ViewArgument, Action>: WidgetView<State, Action> {
     }
 }
 
-impl<State: ViewArgument, Action, V: WidgetView<State, Action>> ZStackExt<State, Action> for V {}
+impl<State: ViewArgument, Action: 'static, V: WidgetView<State, Action>> ZStackExt<State, Action>
+    for V
+{
+}
 
 /// A wrapper around a [`WidgetView`], with a specified [`ChildAlignment`].
 /// This struct is most often constructed indirectly using [`ZStackExt::alignment`].
@@ -329,13 +333,13 @@ impl<W: Widget + FromDynWidget + ?Sized> SuperElement<Pod<W>, ViewCtx> for ZStac
 
 /// A trait implementing `ViewSequence` for `ZStackElement`.
 pub trait ZStackSequence<State: ViewArgument, Action = ()>:
-    ViewSequence<State, Action, ViewCtx, ZStackElement>
+    ViewSequence<State, Action, ViewCtx, ZStackElement> + Send + Sync
 {
 }
 
 impl<Seq, State, Action> ZStackSequence<State, Action> for Seq
 where
-    Seq: ViewSequence<State, Action, ViewCtx, ZStackElement>,
+    Seq: ViewSequence<State, Action, ViewCtx, ZStackElement> + Send + Sync,
     State: ViewArgument,
 {
 }
diff --git a/xilem_masonry/src/widget_view.rs b/xilem_masonry/src/widget_view.rs
index ea0ee45374..e3b2e9ad7f 100644
--- a/xilem_masonry/src/widget_view.rs
+++ b/xilem_masonry/src/widget_view.rs
@@ -9,7 +9,7 @@ use crate::view::{Prop, Transformed, transformed};
 use crate::{AnyWidgetView, Pod, ViewCtx};
 
 #[expect(missing_docs, reason = "TODO - Document these items")]
-pub trait WidgetView<State: ViewArgument, Action = ()>:
+pub trait WidgetView<State: ViewArgument, Action: 'static = ()>:
     View<State, Action, ViewCtx, Element = Pod<Self::Widget>> + Send + Sync
 {
     type Widget: Widget + FromDynWidget + ?Sized;
@@ -79,9 +79,19 @@ pub trait WidgetView<State: ViewArgument, Action = ()>:
             phantom: std::marker::PhantomData,
         }
     }
+
+    #[doc(hidden)]
+    /// An identity function, that lets us assert that
+    /// the receiver always implements WidgetView<..>
+    fn check_impl_widget_view(self) -> Self
+    where
+        Self: Sized,
+    {
+        self
+    }
 }
 
-impl<V, State, Action, W> WidgetView<State, Action> for V
+impl<V, State, Action: 'static, W> WidgetView<State, Action> for V
 where
     V: View<State, Action, ViewCtx, Element = Pod<W>> + Send + Sync,
     W: Widget + FromDynWidget + ?Sized,
@@ -108,6 +118,15 @@ where
 pub trait WidgetViewSequence<State: ViewArgument, Action = ()>:
     ViewSequence<State, Action, ViewCtx, Pod<dyn Widget>>
 {
+    #[doc(hidden)]
+    /// An identity function, that lets us assert that
+    /// the receiver always implements WidgetViewSequence<..>
+    fn check_impl_widget_view_seq(self) -> Self
+    where
+        Self: Sized,
+    {
+        self
+    }
 }
 
 impl<Seq, State, Action> WidgetViewSequence<State, Action> for Seq