Return impl IntoElement from RenderOnce::render

This makes it a bit more approachable to implement.

This required converting the state of Component to AnyElement, which
costs an allocation. I'm hoping this will be ok performance-wise now
that AnyElements use bump allocation, but I need to benchmark still.

crates/ui2/src/components/avatar.rs

@@ -1,5 +1,5 @@
 use crate::prelude::*;
-use gpui::{img, Div, Hsla, ImageSource, Img, IntoElement, Styled};
+use gpui::{img, Hsla, ImageSource, Img, IntoElement, Styled};
 
 #[derive(Debug, Default, PartialEq, Clone)]
 pub enum Shape {
@@ -16,9 +16,7 @@ pub struct Avatar {
 }
 
 impl RenderOnce for Avatar {
-    type Output = Div;
-
-    fn render(mut self, cx: &mut WindowContext) -> Self::Output {
+    fn render(mut self, cx: &mut WindowContext) -> impl IntoElement {
         if self.image.style().corner_radii.top_left.is_none() {
             self = self.shape(Shape::Circle);
         }

crates/ui2/src/components/button/button.rs

@@ -136,9 +136,8 @@ impl ButtonCommon for Button {
 }
 
 impl RenderOnce for Button {
-    type Output = ButtonLike;
-
-    fn render(self, _cx: &mut WindowContext) -> Self::Output {
+    #[allow(refining_impl_trait)]
+    fn render(self, _cx: &mut WindowContext) -> ButtonLike {
         let is_disabled = self.base.disabled;
         let is_selected = self.base.selected;
 

crates/ui2/src/components/button/button_icon.rs

@@ -63,9 +63,7 @@ impl Selectable for ButtonIcon {
 }
 
 impl RenderOnce for ButtonIcon {
-    type Output = IconElement;
-
-    fn render(self, _cx: &mut WindowContext) -> Self::Output {
+    fn render(self, _cx: &mut WindowContext) -> impl IntoElement {
         let icon = self
             .selected_icon
             .filter(|_| self.selected)

crates/ui2/src/components/button/button_like.rs

@@ -1,5 +1,5 @@
 use gpui::{relative, DefiniteLength, MouseButton};
-use gpui::{rems, transparent_black, AnyElement, AnyView, ClickEvent, Div, Hsla, Rems, Stateful};
+use gpui::{rems, transparent_black, AnyElement, AnyView, ClickEvent, Hsla, Rems};
 use smallvec::SmallVec;
 
 use crate::prelude::*;
@@ -363,9 +363,7 @@ impl ParentElement for ButtonLike {
 }
 
 impl RenderOnce for ButtonLike {
-    type Output = Stateful<Div>;
-
-    fn render(self, cx: &mut WindowContext) -> Self::Output {
+    fn render(self, cx: &mut WindowContext) -> impl IntoElement {
         self.base
             .h_flex()
             .id(self.id.clone())

crates/ui2/src/components/button/icon_button.rs

@@ -106,9 +106,7 @@ impl VisibleOnHover for IconButton {
 }
 
 impl RenderOnce for IconButton {
-    type Output = ButtonLike;
-
-    fn render(self, _cx: &mut WindowContext) -> Self::Output {
+    fn render(self, _cx: &mut WindowContext) -> impl IntoElement {
         let is_disabled = self.base.disabled;
         let is_selected = self.base.selected;
 

crates/ui2/src/components/button/toggle_button.rs

@@ -99,9 +99,7 @@ impl ButtonCommon for ToggleButton {
 }
 
 impl RenderOnce for ToggleButton {
-    type Output = ButtonLike;
-
-    fn render(self, _cx: &mut WindowContext) -> Self::Output {
+    fn render(self, _cx: &mut WindowContext) -> impl IntoElement {
         let is_disabled = self.base.disabled;
         let is_selected = self.base.selected;
 

crates/ui2/src/components/checkbox.rs

@@ -1,4 +1,4 @@
-use gpui::{div, prelude::*, Div, Element, ElementId, IntoElement, Styled, WindowContext};
+use gpui::{div, prelude::*, Element, ElementId, IntoElement, Styled, WindowContext};
 
 use crate::prelude::*;
 use crate::{Color, Icon, IconElement, Selection};
@@ -19,9 +19,7 @@ pub struct Checkbox {
 }
 
 impl RenderOnce for Checkbox {
-    type Output = gpui::Stateful<Div>;
-
-    fn render(self, cx: &mut WindowContext) -> Self::Output {
+    fn render(self, cx: &mut WindowContext) -> impl IntoElement {
         let group_id = format!("checkbox_group_{:?}", self.id);
 
         let icon = match self.checked {

crates/ui2/src/components/disclosure.rs

@@ -28,9 +28,7 @@ impl Disclosure {
 }
 
 impl RenderOnce for Disclosure {
-    type Output = IconButton;
-
-    fn render(self, _cx: &mut WindowContext) -> Self::Output {
+    fn render(self, _cx: &mut WindowContext) -> impl IntoElement {
         IconButton::new(
             self.id,
             match self.is_open {

crates/ui2/src/components/divider.rs

@@ -1,4 +1,4 @@
-use gpui::{Div, Hsla, IntoElement};
+use gpui::{Hsla, IntoElement};
 
 use crate::prelude::*;
 
@@ -31,9 +31,7 @@ pub struct Divider {
 }
 
 impl RenderOnce for Divider {
-    type Output = Div;
-
-    fn render(self, cx: &mut WindowContext) -> Self::Output {
+    fn render(self, cx: &mut WindowContext) -> impl IntoElement {
         div()
             .map(|this| match self.direction {
                 DividerDirection::Horizontal => {

crates/ui2/src/components/icon.rs

@@ -1,4 +1,4 @@
-use gpui::{rems, svg, IntoElement, Rems, Svg};
+use gpui::{rems, svg, IntoElement, Rems};
 use strum::EnumIter;
 
 use crate::prelude::*;
@@ -200,9 +200,7 @@ pub struct IconElement {
 }
 
 impl RenderOnce for IconElement {
-    type Output = Svg;
-
-    fn render(self, cx: &mut WindowContext) -> Self::Output {
+    fn render(self, cx: &mut WindowContext) -> impl IntoElement {
         svg()
             .size(self.size.rems())
             .flex_none()

crates/ui2/src/components/indicator.rs

@@ -1,4 +1,4 @@
-use gpui::{Div, Position};
+use gpui::Position;
 
 use crate::prelude::*;
 
@@ -45,9 +45,7 @@ impl Indicator {
 }
 
 impl RenderOnce for Indicator {
-    type Output = Div;
-
-    fn render(self, cx: &mut WindowContext) -> Self::Output {
+    fn render(self, cx: &mut WindowContext) -> impl IntoElement {
         div()
             .flex_none()
             .map(|this| match self.style {

crates/ui2/src/components/keybinding.rs

@@ -1,5 +1,5 @@
 use crate::{h_stack, prelude::*, Icon, IconElement, IconSize};
-use gpui::{relative, rems, Action, Div, FocusHandle, IntoElement, Keystroke};
+use gpui::{relative, rems, Action, FocusHandle, IntoElement, Keystroke};
 
 #[derive(IntoElement, Clone)]
 pub struct KeyBinding {
@@ -11,9 +11,7 @@ pub struct KeyBinding {
 }
 
 impl RenderOnce for KeyBinding {
-    type Output = Div;
-
-    fn render(self, cx: &mut WindowContext) -> Self::Output {
+    fn render(self, cx: &mut WindowContext) -> impl IntoElement {
         h_stack()
             .flex_none()
             .gap_2()
@@ -87,9 +85,7 @@ pub struct Key {
 }
 
 impl RenderOnce for Key {
-    type Output = Div;
-
-    fn render(self, cx: &mut WindowContext) -> Self::Output {
+    fn render(self, cx: &mut WindowContext) -> impl IntoElement {
         let single_char = self.key.len() == 1;
 
         div()
@@ -121,9 +117,7 @@ pub struct KeyIcon {
 }
 
 impl RenderOnce for KeyIcon {
-    type Output = Div;
-
-    fn render(self, _cx: &mut WindowContext) -> Self::Output {
+    fn render(self, _cx: &mut WindowContext) -> impl IntoElement {
         div()
             .w(rems(14. / 16.))
             .child(IconElement::new(self.icon).size(IconSize::Small))

crates/ui2/src/components/label/highlighted_label.rs

@@ -46,9 +46,7 @@ impl LabelCommon for HighlightedLabel {
 }
 
 impl RenderOnce for HighlightedLabel {
-    type Output = LabelLike;
-
-    fn render(self, cx: &mut WindowContext) -> Self::Output {
+    fn render(self, cx: &mut WindowContext) -> impl IntoElement {
         let highlight_color = cx.theme().colors().text_accent;
 
         let mut highlight_indices = self.highlight_indices.iter().copied().peekable();

crates/ui2/src/components/label/label.rs

@@ -40,9 +40,7 @@ impl LabelCommon for Label {
 }
 
 impl RenderOnce for Label {
-    type Output = LabelLike;
-
-    fn render(self, _cx: &mut WindowContext) -> Self::Output {
+    fn render(self, _cx: &mut WindowContext) -> impl IntoElement {
         self.base.child(self.label)
     }
 }

crates/ui2/src/components/label/label_like.rs

@@ -1,4 +1,4 @@
-use gpui::{relative, AnyElement, Div, Styled};
+use gpui::{relative, AnyElement, Styled};
 use smallvec::SmallVec;
 
 use crate::prelude::*;
@@ -76,9 +76,7 @@ impl ParentElement for LabelLike {
 }
 
 impl RenderOnce for LabelLike {
-    type Output = Div;
-
-    fn render(self, cx: &mut WindowContext) -> Self::Output {
+    fn render(self, cx: &mut WindowContext) -> impl IntoElement {
         div()
             .when(self.strikethrough, |this| {
                 this.relative().child(

crates/ui2/src/components/list/list.rs

@@ -1,4 +1,4 @@
-use gpui::{AnyElement, Div};
+use gpui::AnyElement;
 use smallvec::SmallVec;
 
 use crate::{prelude::*, v_stack, Label, ListHeader};
@@ -46,9 +46,7 @@ impl ParentElement for List {
 }
 
 impl RenderOnce for List {
-    type Output = Div;
-
-    fn render(self, _cx: &mut WindowContext) -> Self::Output {
+    fn render(self, _cx: &mut WindowContext) -> impl IntoElement {
         v_stack().w_full().py_1().children(self.header).map(|this| {
             match (self.children.is_empty(), self.toggle) {
                 (false, _) => this.children(self.children),

crates/ui2/src/components/list/list_header.rs

@@ -1,6 +1,5 @@
-use gpui::{AnyElement, ClickEvent, Div, Stateful};
-
 use crate::{h_stack, prelude::*, Disclosure, Label};
+use gpui::{AnyElement, ClickEvent};
 
 #[derive(IntoElement)]
 pub struct ListHeader {
@@ -76,9 +75,7 @@ impl Selectable for ListHeader {
 }
 
 impl RenderOnce for ListHeader {
-    type Output = Stateful<Div>;
-
-    fn render(self, cx: &mut WindowContext) -> Self::Output {
+    fn render(self, cx: &mut WindowContext) -> impl IntoElement {
         h_stack()
             .id(self.label.clone())
             .w_full()

crates/ui2/src/components/list/list_item.rs

@@ -1,6 +1,4 @@
-use gpui::{
-    px, AnyElement, AnyView, ClickEvent, Div, MouseButton, MouseDownEvent, Pixels, Stateful,
-};
+use gpui::{px, AnyElement, AnyView, ClickEvent, MouseButton, MouseDownEvent, Pixels};
 use smallvec::SmallVec;
 
 use crate::{prelude::*, Disclosure};
@@ -147,9 +145,7 @@ impl ParentElement for ListItem {
 }
 
 impl RenderOnce for ListItem {
-    type Output = Stateful<Div>;
-
-    fn render(self, cx: &mut WindowContext) -> Self::Output {
+    fn render(self, cx: &mut WindowContext) -> impl IntoElement {
         h_stack()
             .id(self.id)
             .w_full()

crates/ui2/src/components/list/list_separator.rs

@@ -1,14 +1,10 @@
-use gpui::Div;
-
 use crate::prelude::*;
 
 #[derive(IntoElement)]
 pub struct ListSeparator;
 
 impl RenderOnce for ListSeparator {
-    type Output = Div;
-
-    fn render(self, cx: &mut WindowContext) -> Self::Output {
+    fn render(self, cx: &mut WindowContext) -> impl IntoElement {
         div()
             .h_px()
             .w_full()

crates/ui2/src/components/list/list_sub_header.rs

@@ -1,5 +1,3 @@
-use gpui::Div;
-
 use crate::prelude::*;
 use crate::{h_stack, Icon, IconElement, IconSize, Label};
 
@@ -26,9 +24,7 @@ impl ListSubHeader {
 }
 
 impl RenderOnce for ListSubHeader {
-    type Output = Div;
-
-    fn render(self, _cx: &mut WindowContext) -> Self::Output {
+    fn render(self, _cx: &mut WindowContext) -> impl IntoElement {
         h_stack().flex_1().w_full().relative().py_1().child(
             div()
                 .h_6()

crates/ui2/src/components/popover.rs

@@ -1,5 +1,5 @@
 use gpui::{
-    div, AnyElement, Div, Element, ElementId, IntoElement, ParentElement, RenderOnce, Styled,
+    div, AnyElement, Element, ElementId, IntoElement, ParentElement, RenderOnce, Styled,
     WindowContext,
 };
 use smallvec::SmallVec;
@@ -41,9 +41,7 @@ pub struct Popover {
 }
 
 impl RenderOnce for Popover {
-    type Output = Div;
-
-    fn render(self, cx: &mut WindowContext) -> Self::Output {
+    fn render(self, cx: &mut WindowContext) -> impl IntoElement {
         div()
             .flex()
             .gap_1()

crates/ui2/src/components/popover_menu.rs

@@ -153,7 +153,7 @@ impl<M: ManagedView> Element for PopoverMenu<M> {
             }
 
             let mut element = overlay.child(menu.clone()).into_any();
-            menu_layout_id = Some(element.layout(cx));
+            menu_layout_id = Some(element.request_layout(cx));
             element
         });
 
@@ -164,7 +164,7 @@ impl<M: ManagedView> Element for PopoverMenu<M> {
 
         let child_layout_id = child_element
             .as_mut()
-            .map(|child_element| child_element.layout(cx));
+            .map(|child_element| child_element.request_layout(cx));
 
         let layout_id = cx.request_layout(
             &gpui::Style::default(),

crates/ui2/src/components/right_click_menu.rs

@@ -81,7 +81,7 @@ impl<M: ManagedView> Element for RightClickMenu<M> {
             overlay = overlay.position(*position.borrow());
 
             let mut element = overlay.child(menu.clone()).into_any();
-            menu_layout_id = Some(element.layout(cx));
+            menu_layout_id = Some(element.request_layout(cx));
             element
         });
 
@@ -92,7 +92,7 @@ impl<M: ManagedView> Element for RightClickMenu<M> {
 
         let child_layout_id = child_element
             .as_mut()
-            .map(|child_element| child_element.layout(cx));
+            .map(|child_element| child_element.request_layout(cx));
 
         let layout_id = cx.request_layout(
             &gpui::Style::default(),

crates/ui2/src/components/tab.rs

@@ -93,9 +93,8 @@ impl ParentElement for Tab {
 }
 
 impl RenderOnce for Tab {
-    type Output = Stateful<Div>;
-
-    fn render(self, cx: &mut WindowContext) -> Self::Output {
+    #[allow(refining_impl_trait)]
+    fn render(self, cx: &mut WindowContext) -> Stateful<Div> {
         let (text_color, tab_bg, _tab_hover_bg, _tab_active_bg) = match self.selected {
             false => (
                 cx.theme().colors().text_muted,

crates/ui2/src/components/tab_bar.rs

@@ -1,4 +1,4 @@
-use gpui::{AnyElement, ScrollHandle, Stateful};
+use gpui::{AnyElement, ScrollHandle};
 use smallvec::SmallVec;
 
 use crate::prelude::*;
@@ -89,9 +89,7 @@ impl ParentElement for TabBar {
 }
 
 impl RenderOnce for TabBar {
-    type Output = Stateful<Div>;
-
-    fn render(self, cx: &mut WindowContext) -> Self::Output {
+    fn render(self, cx: &mut WindowContext) -> impl IntoElement {
         const HEIGHT_IN_REMS: f32 = 30. / 16.;
 
         div()