Add integrity check for signed extensions (#1780)

* Add integrity check for signed extensions

* Remove unneeded type specification

bridges/bin/runtime-common/src/integrity.rs

@@ -26,6 +26,7 @@ use bp_runtime::{Chain, ChainId};
 use codec::Encode;
 use frame_support::{storage::generator::StorageValue, traits::Get};
 use frame_system::limits;
+use sp_runtime::traits::SignedExtension;
 
 /// Macro that ensures that the runtime configuration and chain primitives crate are sharing
 /// the same types (index, block number, hash, hasher, account id and header).
@@ -319,3 +320,15 @@ pub fn check_message_lane_weights<C: Chain, T: frame_system::Config>(
 		this_chain_max_unconfirmed_messages,
 	);
 }
+
+/// Check that the `AdditionalSigned` type of a wrapped runtime is the same as the one of the
+/// corresponding actual runtime.
+///
+/// This method doesn't perform any `assert`. If the condition is not true it will generate a
+/// compile-time error.
+pub fn check_additional_signed<SignedExt, IndirectSignedExt: SignedExtension>()
+where
+	SignedExt: SignedExtension,
+	IndirectSignedExt: SignedExtension<AdditionalSigned = SignedExt::AdditionalSigned>,
+{
+}