Move ExecutionExtensions comment around

client/api/src/execution_extensions.rs

@@ -84,6 +84,10 @@ pub struct ExecutionExtensions<Block: traits::Block> {
 	keystore: Option<BareCryptoStorePtr>,
 	// FIXME: these two are only RwLock because of https://github.com/paritytech/substrate/issues/4587
 	//        remove when fixed.
+	// To break retain cycle between `Client` and `TransactionPool` we require this
+	// extension to be a `Weak` reference.
+	// That's also the reason why it's being registered lazily instead of
+	// during initialization.
 	transaction_pool: RwLock<Option<Weak<dyn sp_transaction_pool::OffchainSubmitTransaction<Block>>>>,
 	extensions_factory: RwLock<Box<dyn ExtensionsFactory>>,
 }
@@ -121,11 +125,6 @@ impl<Block: traits::Block> ExecutionExtensions<Block> {
 	}
 
 	/// Register transaction pool extension.
-	///
-	/// To break retain cycle between `Client` and `TransactionPool` we require this
-	/// extension to be a `Weak` reference.
-	/// That's also the reason why it's being registered lazily instead of
-	/// during initialization.
 	pub fn register_transaction_pool<T>(&self, pool: &Arc<T>)
 		where T: sp_transaction_pool::OffchainSubmitTransaction<Block> + 'static
 	{