box Scheduled task state to save memory (vercel/turborepo#8807)

### Description

This makes the enum smaller for the Done state, which is the common one

### Testing Instructions

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Author: sokra

crates/turbo-tasks-memory/src/task.rs

@@ -187,7 +187,7 @@ impl TaskState {
         let description2 = description.clone();
         Self {
             aggregation_node: TaskAggregationNode::new(),
-            state_type: Scheduled {
+            state_type: Scheduled(Box::new(ScheduledState {
                 start_event: Event::new(move || {
                     format!("TaskState({})::start_event", description())
                 }),
@@ -196,7 +196,7 @@ impl TaskState {
                 }),
                 outdated_edges: Default::default(),
                 clean: true,
-            },
+            })),
             collectibles: Default::default(),
             output: Default::default(),
             cells: Default::default(),
@@ -326,8 +326,8 @@ struct InProgressState {
     /// true, when the task was invalidated while executing. It will be
     /// scheduled again.
     stale: bool,
-    /// Dependencies and children that need to be disconnected once leaving
-    /// this state.
+    /// Dependencies and children that need to be disconnected once entering
+    /// Done.
     outdated_edges: TaskEdgesSet,
     /// Children that are connected during execution. These children are already
     /// removed from `outdated_edges`.
@@ -336,6 +336,18 @@ struct InProgressState {
     outdated_collectibles: MaybeCollectibles,
 }
 
+struct ScheduledState {
+    /// Event is fired when the task is IsProgress.
+    start_event: Event,
+    /// Event is fired when the task is Done.
+    done_event: Event,
+    /// Dependencies and children that need to be disconnected once entering
+    /// Done.
+    outdated_edges: Box<TaskEdgesSet>,
+    /// true, when the task wasn't changed since the last execution
+    clean: bool,
+}
+
 enum TaskStateType {
     /// Ready
     ///
@@ -362,15 +374,7 @@ enum TaskStateType {
     /// Execution is invalid and scheduled
     ///
     /// on start this will move to InProgress or Dirty depending on active flag
-    Scheduled {
-        /// Event is fired when the task is IsProgress.
-        start_event: Event,
-        /// Event is fired when the task is Done.
-        done_event: Event,
-        outdated_edges: Box<TaskEdgesSet>,
-        /// true, when the task wasn't changed since the last execution
-        clean: bool,
-    },
+    Scheduled(Box<ScheduledState>),
 
     /// Execution is happening
     ///
@@ -396,7 +400,7 @@ impl TaskStateType {
             TaskStateType::Dirty { outdated_edges, .. } => {
                 Either::Right(Either::Right(outdated_edges.children()))
             }
-            TaskStateType::Scheduled { outdated_edges, .. } => {
+            TaskStateType::Scheduled(box ScheduledState { outdated_edges, .. }) => {
                 Either::Right(Either::Right(outdated_edges.children()))
             }
         }
@@ -420,7 +424,7 @@ impl TaskStateType {
                 (edges, children)
             }
             TaskStateType::Dirty { outdated_edges, .. }
-            | TaskStateType::Scheduled { outdated_edges, .. } => {
+            | TaskStateType::Scheduled(box ScheduledState { outdated_edges, .. }) => {
                 let mut edges = *outdated_edges;
                 let children = edges.drain_children();
                 (edges, children)
@@ -718,12 +722,12 @@ impl Task {
                     // should not start in this state
                     return None;
                 }
-                Scheduled {
+                Scheduled(box ScheduledState {
                     ref mut done_event,
                     ref mut start_event,
                     ref mut outdated_edges,
                     clean,
-                } => {
+                }) => {
                     start_event.notify(usize::MAX);
                     let done_event = done_event.take();
                     let outdated_edges = *take(outdated_edges);
@@ -997,12 +1001,12 @@ impl Task {
                     let description = self.get_event_description();
                     let start_event =
                         Event::new(move || format!("TaskState({})::start_event", description()));
-                    state.state_type = Scheduled {
+                    state.state_type = Scheduled(Box::new(ScheduledState {
                         start_event,
                         done_event,
                         outdated_edges: Box::new(outdated_edges),
                         clean: false,
-                    };
+                    }));
                     drop(state);
                     schedule_task = true;
                 } else {
@@ -1088,7 +1092,7 @@ impl Task {
 
         if let TaskMetaStateWriteGuard::Full(mut state) = self.state_mut() {
             match state.state_type {
-                Scheduled { ref mut clean, .. } => {
+                Scheduled(box ScheduledState { ref mut clean, .. }) => {
                     *clean = false;
 
                     // already scheduled
@@ -1113,7 +1117,7 @@ impl Task {
                         );
                         let description = self.get_event_description();
                         let description2 = description.clone();
-                        state.state_type = Scheduled {
+                        state.state_type = Scheduled(Box::new(ScheduledState {
                             done_event: Event::new(move || {
                                 format!("TaskState({})::done_event", description())
                             }),
@@ -1122,7 +1126,7 @@ impl Task {
                             }),
                             outdated_edges: Box::new(outdated_edges),
                             clean: false,
-                        };
+                        }));
                         drop(state);
                         change_job.apply(&aggregation_context);
 
@@ -1210,7 +1214,7 @@ impl Task {
             } => {
                 let description = self.get_event_description();
                 let description2 = description.clone();
-                state.state_type = Scheduled {
+                state.state_type = Scheduled(Box::new(ScheduledState {
                     start_event: Event::new(move || {
                         format!("TaskState({})::start_event", description())
                     }),
@@ -1219,7 +1223,7 @@ impl Task {
                     }),
                     outdated_edges: take(outdated_edges),
                     clean: false,
-                };
+                }));
                 let change_job = state.aggregation_node.apply_change(
                     &aggregation_context,
                     TaskChange {
@@ -1245,7 +1249,7 @@ impl Task {
                 );
                 let description = self.get_event_description();
                 let description2 = description.clone();
-                state.state_type = Scheduled {
+                state.state_type = Scheduled(Box::new(ScheduledState {
                     start_event: Event::new(move || {
                         format!("TaskState({})::start_event", description())
                     }),
@@ -1254,7 +1258,7 @@ impl Task {
                     }),
                     outdated_edges: Box::new(outdated_edges),
                     clean: true,
-                };
+                }));
                 drop(state);
                 change_job.apply(&aggregation_context);
 
@@ -1277,7 +1281,7 @@ impl Task {
             let mut aggregation_context = TaskAggregationContext::new(turbo_tasks, backend);
             let description = self.get_event_description();
             let description2 = description.clone();
-            state.state_type = Scheduled {
+            state.state_type = Scheduled(Box::new(ScheduledState {
                 start_event: Event::new(move || {
                     format!("TaskState({})::start_event", description())
                 }),
@@ -1286,7 +1290,7 @@ impl Task {
                 }),
                 outdated_edges: take(outdated_edges),
                 clean: false,
-            };
+            }));
             let job = state.aggregation_node.apply_change(
                 &aggregation_context,
                 TaskChange {
@@ -1390,14 +1394,14 @@ impl Task {
                 let start_event =
                     Event::new(move || format!("TaskState({})::start_event", description()));
                 let listener = start_event.listen_with_note(note);
-                state.state_type = Scheduled {
+                state.state_type = Scheduled(Box::new(ScheduledState {
                     start_event,
                     done_event: Event::new(move || {
                         format!("TaskState({})::done_event", description2())
                     }),
                     outdated_edges: take(outdated_edges),
                     clean: false,
-                };
+                }));
                 let change_job = state.aggregation_node.apply_change(
                     &aggregation_context,
                     TaskChange {
@@ -1411,9 +1415,9 @@ impl Task {
                 aggregation_context.apply_queued_updates();
                 Err(ReadCellError::Recomputing(listener))
             }
-            Scheduled {
+            Scheduled(box ScheduledState {
                 ref start_event, ..
-            } => Err(ReadCellError::Recomputing(
+            }) => Err(ReadCellError::Recomputing(
                 start_event.listen_with_note(note),
             )),
         }
@@ -1630,14 +1634,14 @@ impl Task {
                 let done_event =
                     Event::new(move || format!("TaskState({})::done_event", description()));
                 let listener = done_event.listen_with_note(note);
-                state.state_type = Scheduled {
+                state.state_type = Scheduled(Box::new(ScheduledState {
                     start_event: Event::new(move || {
                         format!("TaskState({})::start_event", description2())
                     }),
                     done_event,
                     outdated_edges: take(outdated_edges),
                     clean: false,
-                };
+                }));
                 let change_job = state.aggregation_node.apply_change(
                     &aggregation_context,
                     TaskChange {
@@ -1649,15 +1653,9 @@ impl Task {
                 change_job.apply(&aggregation_context);
                 Ok(Err(listener))
             }
-            Scheduled {
-                done_event: ref event,
-                ..
-            }
-            | InProgress(box InProgressState {
-                done_event: ref event,
-                ..
-            }) => {
-                let listener = event.listen_with_note(note);
+            Scheduled(box ScheduledState { ref done_event, .. })
+            | InProgress(box InProgressState { ref done_event, .. }) => {
+                let listener = done_event.listen_with_note(note);
                 drop(state);
                 Ok(Err(listener))
             }