Use Pin<Box<>> for collation future (#1792)

polkadot/node/collation-generation/src/lib.rs

@@ -407,7 +407,7 @@ mod tests {
 			Arc::new(CollationGenerationConfig {
 				key: CollatorPair::generate().0,
 				collator: Box::new(|_: Hash, _vd: &ValidationData| {
-					Box::new(TestCollator)
+					TestCollator.boxed()
 				}),
 				para_id: para_id.into(),
 			})

polkadot/node/overseer/src/lib.rs

@@ -1876,7 +1876,7 @@ mod tests {
 	fn test_collator_generation_msg() -> CollationGenerationMessage {
 		CollationGenerationMessage::Initialize(CollationGenerationConfig {
 			key: CollatorPair::generate().0,
-			collator: Box::new(|_, _| Box::new(TestCollator)),
+			collator: Box::new(|_, _| TestCollator.boxed()),
 			para_id: Default::default(),
 		})
 	}

polkadot/node/primitives/src/lib.rs

@@ -35,6 +35,7 @@ use polkadot_statement_table::{
 	},
 	v1::Misbehavior as TableMisbehavior,
 };
+use std::pin::Pin;
 
 pub use sp_core::traits::SpawnNamed;
 
@@ -289,7 +290,7 @@ pub struct CollationGenerationConfig {
 	/// Will be called with the hash of the relay chain block the parachain
 	/// block should be build on and the [`ValidationData`] that provides
 	/// information about the state of the parachain on the relay chain.
-	pub collator: Box<dyn Fn(Hash, &ValidationData) -> Box<dyn Future<Output = Option<Collation>> + Unpin + Send> + Send + Sync>,
+	pub collator: Box<dyn Fn(Hash, &ValidationData) -> Pin<Box<dyn Future<Output = Option<Collation>> + Send>> + Send + Sync>,
 	/// The parachain that this collator collates for
 	pub para_id: ParaId,
 }

polkadot/roadmap/implementers-guide/src/node/collators/collation-generation.md

@@ -39,7 +39,7 @@ struct CollationGenerationConfig {
   /// Collate will be called with the relay chain hash the parachain should build 
   /// a block on and the `ValidationData` that provides information about the state
   /// of the parachain on the relay chain.
-  collator: Box<dyn Fn(Hash, &ValidationData) -> Box<dyn Future<Output = Option<Collation>>>>
+  collator: Box<dyn Fn(Hash, &ValidationData) -> Pin<Box<dyn Future<Output = Option<Collation>>>>>
   para_id: ParaId,
 }
 ```