Add Send bound to T in Vc<T> to make type error less cryptic (v…

…ercel/turborepo#5871)

### Description

Currently, the diagnostics for `T` in `Vc<T>` not implementing `Send` is
too cryptic.

### Testing Instructions

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  Give a quick description of steps to test your changes.
-->


Closes WEB-1498

crates/turbo-tasks-macros/src/generic_type_macro.rs

@@ -6,7 +6,7 @@ use turbo_tasks_macros_shared::{get_type_ident, GenericTypeInput};
 use crate::value_macro::value_type_and_register;
 
 pub fn generic_type(input: TokenStream) -> TokenStream {
-    let input = parse_macro_input!(input as GenericTypeInput);
+    let mut input = parse_macro_input!(input as GenericTypeInput);
 
     for param in &input.generics.params {
         match param {
@@ -33,6 +33,14 @@ pub fn generic_type(input: TokenStream) -> TokenStream {
         }
     }
 
+    // Add Send bound to input generics.
+
+    for param in &mut input.generics.params {
+        if let GenericParam::Type(param) = param {
+            param.bounds.push(syn::parse_quote! { std::marker::Send });
+        }
+    }
+
     let (impl_generics, _, where_clause) = input.generics.split_for_impl();
 
     let repr = replace_generics_with_unit(input.generics.params.iter(), &input.ty);

crates/turbo-tasks-macros/src/value_impl_macro.rs

@@ -251,7 +251,7 @@ pub fn value_impl(args: TokenStream, input: TokenStream) -> TokenStream {
                     #[doc(hidden)]
                     #[allow(non_camel_case_types)]
                     // #[turbo_tasks::async_trait]
-                    trait #inline_extension_trait_ident {
+                    trait #inline_extension_trait_ident: std::marker::Send {
                         #[allow(declare_interior_mutable_const)]
                         #[doc(hidden)]
                         const #native_function_ident: #native_function_ty;

crates/turbo-tasks-macros/src/value_trait_macro.rs

@@ -129,7 +129,7 @@ pub fn value_trait(args: TokenStream, input: TokenStream) -> TokenStream {
                 #[doc(hidden)]
                 #[allow(non_camel_case_types)]
                 // #[turbo_tasks::async_trait]
-                trait #inline_extension_trait_ident {
+                trait #inline_extension_trait_ident: std::marker::Send {
                     #[allow(declare_interior_mutable_const)]
                     const #native_function_ident: #native_function_ty;
                     #[allow(declare_interior_mutable_const)]
@@ -197,7 +197,7 @@ pub fn value_trait(args: TokenStream, input: TokenStream) -> TokenStream {
     let expanded = quote! {
         #[must_use]
         #(#attrs)*
-        #vis #trait_token #trait_ident: #(#supertraits)+*
+        #vis #trait_token #trait_ident: std::marker::Send + #(#supertraits)+*
         {
             #(#items)*
         }

crates/turbo-tasks/src/generics/index_map.rs

@@ -23,7 +23,11 @@ async fn index_map_is_empty(index_map: Vc<IndexMap<Vc<()>, Vc<()>>>) -> Result<V
     Ok(Vc::cell(index_map.is_empty()))
 }
 
-impl<K, V> Vc<IndexMap<Vc<K>, Vc<V>>> {
+impl<K, V> Vc<IndexMap<Vc<K>, Vc<V>>>
+where
+    K: Send,
+    V: Send,
+{
     /// See [`IndexMap::len`].
     pub fn len(self) -> Vc<usize> {
         index_map_len(Self::to_repr(self))
@@ -40,7 +44,11 @@ fn index_map_default() -> Vc<IndexMap<Vc<()>, Vc<()>>> {
     Vc::cell(Default::default())
 }
 
-impl<K, V> ValueDefault for IndexMap<Vc<K>, Vc<V>> {
+impl<K, V> ValueDefault for IndexMap<Vc<K>, Vc<V>>
+where
+    K: Send,
+    V: Send,
+{
     fn value_default() -> Vc<Self> {
         // Safety: `index_map_default` creates an empty map, which is a valid
         // representation of any index set of `Vc`.
@@ -60,7 +68,11 @@ async fn index_map_dbg_depth(
         .await
 }
 
-impl<K, V> ValueDebug for IndexMap<Vc<K>, Vc<V>> {
+impl<K, V> ValueDebug for IndexMap<Vc<K>, Vc<V>>
+where
+    K: Send,
+    V: Send,
+{
     fn dbg(self: Vc<Self>) -> Vc<ValueDebugString> {
         index_map_dbg_depth(Vc::<Self>::to_repr(self), usize::MAX)
     }

crates/turbo-tasks/src/generics/index_set.rs

@@ -23,7 +23,10 @@ async fn index_set_is_empty(index_set: Vc<IndexSet<Vc<()>>>) -> Result<Vc<bool>>
     Ok(Vc::cell(index_set.is_empty()))
 }
 
-impl<T> Vc<IndexSet<Vc<T>>> {
+impl<T> Vc<IndexSet<Vc<T>>>
+where
+    T: Send,
+{
     /// See [`IndexSet::len`].
     pub fn len(self) -> Vc<usize> {
         index_set_len(Self::to_repr(self))
@@ -40,7 +43,10 @@ fn index_set_default() -> Vc<IndexSet<Vc<()>>> {
     Vc::cell(Default::default())
 }
 
-impl<T> ValueDefault for IndexSet<Vc<T>> {
+impl<T> ValueDefault for IndexSet<Vc<T>>
+where
+    T: Send,
+{
     fn value_default() -> Vc<Self> {
         // Safety: `index_set_default` creates an empty set, which is a valid
         // representation of any index set of `Vc`.
@@ -60,7 +66,10 @@ async fn index_set_dbg_depth(
         .await
 }
 
-impl<T> ValueDebug for IndexSet<Vc<T>> {
+impl<T> ValueDebug for IndexSet<Vc<T>>
+where
+    T: Send,
+{
     fn dbg(self: Vc<Self>) -> Vc<ValueDebugString> {
         index_set_dbg_depth(Vc::<Self>::to_repr(self), usize::MAX)
     }

crates/turbo-tasks/src/generics/option.rs

@@ -22,7 +22,10 @@ async fn option_is_some(option: Vc<Option<Vc<()>>>) -> Result<Vc<bool>> {
     Ok(Vc::cell(option.is_some()))
 }
 
-impl<T> Vc<Option<Vc<T>>> {
+impl<T> Vc<Option<Vc<T>>>
+where
+    T: Send,
+{
     /// See [`Option::is_none`].
     pub fn is_none(self) -> Vc<bool> {
         option_is_none(Self::to_repr(self))
@@ -39,7 +42,10 @@ fn option_default() -> Vc<Option<Vc<()>>> {
     Vc::cell(Default::default())
 }
 
-impl<T> ValueDefault for Option<Vc<T>> {
+impl<T> ValueDefault for Option<Vc<T>>
+where
+    T: Send,
+{
     fn value_default() -> Vc<Self> {
         // Safety: `option_default` creates a None variant, which is a valid
         // representation of any option of `Vc`.
@@ -59,7 +65,10 @@ async fn option_dbg_depth(
         .await
 }
 
-impl<T> ValueDebug for Option<Vc<T>> {
+impl<T> ValueDebug for Option<Vc<T>>
+where
+    T: Send,
+{
     fn dbg(self: Vc<Self>) -> Vc<ValueDebugString> {
         option_dbg_depth(Vc::<Self>::to_repr(self), usize::MAX)
     }

crates/turbo-tasks/src/generics/vec.rs

@@ -22,7 +22,10 @@ async fn vec_is_empty(vec: Vc<Vec<Vc<()>>>) -> Result<Vc<bool>> {
     Ok(Vc::cell(vec.is_empty()))
 }
 
-impl<T> Vc<Vec<Vc<T>>> {
+impl<T> Vc<Vec<Vc<T>>>
+where
+    T: Send,
+{
     /// See [`Vec::len`].
     pub fn len(self) -> Vc<usize> {
         vec_len(Self::to_repr(self))
@@ -39,7 +42,10 @@ fn vec_default() -> Vc<Vec<Vc<()>>> {
     Vc::cell(Default::default())
 }
 
-impl<T> ValueDefault for Vec<Vc<T>> {
+impl<T> ValueDefault for Vec<Vc<T>>
+where
+    T: Send,
+{
     fn value_default() -> Vc<Self> {
         // Safety: `vec_default` creates an empty vector, which is a valid
         // representation of any vector of `Vc`s.
@@ -55,7 +61,10 @@ async fn vec_dbg_depth(vec: Vc<Vec<Vc<()>>>, depth: usize) -> Result<Vc<ValueDeb
         .await
 }
 
-impl<T> ValueDebug for Vec<Vc<T>> {
+impl<T> ValueDebug for Vec<Vc<T>>
+where
+    T: Send,
+{
     fn dbg(self: Vc<Self>) -> Vc<ValueDebugString> {
         vec_dbg_depth(Vc::<Self>::to_repr(self), usize::MAX)
     }

crates/turbo-tasks/src/manager.rs

@@ -341,6 +341,7 @@ impl<B: Backend + 'static> TurboTasks<B> {
     /// Creates a new root task
     pub fn spawn_root_task<T, F, Fut>(&self, functor: F) -> TaskId
     where
+        T: Send,
         F: Fn() -> Fut + Send + Sync + Clone + 'static,
         Fut: Future<Output = Result<Vc<T>>> + Send,
     {
@@ -361,6 +362,7 @@ impl<B: Backend + 'static> TurboTasks<B> {
     #[track_caller]
     pub fn spawn_once_task<T, Fut>(&self, future: Fut) -> TaskId
     where
+        T: Send,
         Fut: Future<Output = Result<Vc<T>>> + Send + 'static,
     {
         let id = self.backend.create_transient_task(
@@ -1398,7 +1400,7 @@ pub fn notify_scheduled_tasks() {
     with_turbo_tasks(|tt| tt.notify_scheduled_tasks())
 }
 
-pub fn emit<T: VcValueTrait>(collectible: Vc<T>) {
+pub fn emit<T: VcValueTrait + Send>(collectible: Vc<T>) {
     with_turbo_tasks(|tt| tt.emit_collectible(T::get_trait_type_id(), collectible.node))
 }
 

crates/turbo-tasks/src/raw_vc.rs

@@ -436,7 +436,7 @@ impl<T: VcValueTrait> CollectiblesFuture<T> {
     }
 }
 
-impl<T: VcValueTrait> Future for CollectiblesFuture<T> {
+impl<T: VcValueTrait + Send> Future for CollectiblesFuture<T> {
     type Output = Result<AutoSet<Vc<T>>>;
 
     fn poll(self: Pin<&mut Self>, cx: &mut std::task::Context<'_>) -> Poll<Self::Output> {

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

@@ -167,7 +167,10 @@ where
     }
 }
 
-impl<T> TaskInput for Vc<T> {
+impl<T> TaskInput for Vc<T>
+where
+    T: Send,
+{
     fn try_from_concrete(input: &ConcreteTaskInput) -> Result<Self> {
         match input {
             ConcreteTaskInput::TaskCell(task, index) => Ok(Vc {

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

@@ -15,7 +15,7 @@ pub trait TaskOutput {
 
 impl<T> TaskOutput for Vc<T>
 where
-    T: ?Sized,
+    T: ?Sized + Send,
 {
     type Return = Vc<T>;
 

crates/turbo-tasks/src/trait_ref.rs

@@ -104,7 +104,7 @@ where
 
 impl<T> TraitRef<T>
 where
-    T: VcValueTrait + ?Sized,
+    T: VcValueTrait + ?Sized + Send,
 {
     /// Returns a new cell that points to a value that implements the value
     /// trait `T`.
@@ -136,7 +136,7 @@ pub trait IntoTraitRef {
 
 impl<T> IntoTraitRef for Vc<T>
 where
-    T: VcValueTrait + ?Sized,
+    T: VcValueTrait + ?Sized + Send,
 {
     type ValueTrait = T;