gpui: Reduce amount of monomorphizations taking place (#48014)

Re-lands #3266 after recent scheduler changes

Back-of-napkin calculation: editor tests (build) went from 32s to 17s.

Release Notes:

- N/A

crates/gpui/src/app.rs

@@ -1462,29 +1462,33 @@ impl App {
 
             cx.window_update_stack.push(window.handle.id);
             let result = update(root_view, &mut window, cx);
-            cx.window_update_stack.pop();
+            fn trail(id: WindowId, window: Box<Window>, cx: &mut App) -> Option<()> {
+                cx.window_update_stack.pop();
 
-            if window.removed {
-                cx.window_handles.remove(&id);
-                cx.windows.remove(id);
+                if window.removed {
+                    cx.window_handles.remove(&id);
+                    cx.windows.remove(id);
 
-                cx.window_closed_observers.clone().retain(&(), |callback| {
-                    callback(cx);
-                    true
-                });
+                    cx.window_closed_observers.clone().retain(&(), |callback| {
+                        callback(cx);
+                        true
+                    });
 
-                let quit_on_empty = match cx.quit_mode {
-                    QuitMode::Explicit => false,
-                    QuitMode::LastWindowClosed => true,
-                    QuitMode::Default => cfg!(not(target_os = "macos")),
-                };
+                    let quit_on_empty = match cx.quit_mode {
+                        QuitMode::Explicit => false,
+                        QuitMode::LastWindowClosed => true,
+                        QuitMode::Default => cfg!(not(target_os = "macos")),
+                    };
 
-                if quit_on_empty && cx.windows.is_empty() {
-                    cx.quit();
+                    if quit_on_empty && cx.windows.is_empty() {
+                        cx.quit();
+                    }
+                } else {
+                    cx.windows.get_mut(id)?.replace(window);
                 }
-            } else {
-                cx.windows.get_mut(id)?.replace(window);
+                Some(())
             }
+            trail(id, window, cx)?;
 
             Some(result)
         })
@@ -1529,7 +1533,7 @@ impl App {
         let mut cx = self.to_async();
 
         self.foreground_executor
-            .spawn(async move { f(&mut cx).await })
+            .spawn(async move { f(&mut cx).await }.boxed_local())
     }
 
     /// Spawns the future returned by the given function on the main thread with
@@ -1547,7 +1551,7 @@ impl App {
         let mut cx = self.to_async();
 
         self.foreground_executor
-            .spawn_with_priority(priority, async move { f(&mut cx).await })
+            .spawn_with_priority(priority, async move { f(&mut cx).await }.boxed_local())
     }
 
     /// Schedules the given function to be run at the end of the current effect cycle, allowing entities

crates/gpui/src/app/async_context.rs

@@ -7,6 +7,7 @@ use crate::{
 use anyhow::Context as _;
 use derive_more::{Deref, DerefMut};
 use futures::channel::oneshot;
+use smol::future::FutureExt;
 use std::{future::Future, rc::Weak};
 
 use super::{Context, WeakEntity};
@@ -184,7 +185,7 @@ impl AsyncApp {
     {
         let mut cx = self.clone();
         self.foreground_executor
-            .spawn(async move { f(&mut cx).await })
+            .spawn(async move { f(&mut cx).await }.boxed_local())
     }
 
     /// Determine whether global state of the specified type has been assigned.
@@ -322,7 +323,7 @@ impl AsyncWindowContext {
     {
         let mut cx = self.clone();
         self.foreground_executor
-            .spawn(async move { f(&mut cx).await })
+            .spawn(async move { f(&mut cx).await }.boxed_local())
     }
 
     /// Present a platform dialog.

crates/gpui/src/executor.rs

@@ -145,7 +145,7 @@ impl BackgroundExecutor {
     where
         R: Send + 'static,
     {
-        self.spawn_with_priority(Priority::default(), future)
+        self.spawn_with_priority(Priority::default(), future.boxed())
     }
 
     /// Enqueues the given future to be run to completion on a background thread with the given priority.
@@ -409,7 +409,7 @@ impl ForegroundExecutor {
     where
         R: 'static,
     {
-        Task::from_scheduler(self.inner.spawn(future))
+        Task::from_scheduler(self.inner.spawn(future.boxed_local()))
     }
 
     /// Enqueues the given Task to run on the main thread with the given priority.