Reintroduce msg dispatch status reporting (#2027)

* Use an actual Result inside MessageDispatchResult

We need this in order to distinguish between Ok and Err

* Revert #1660

* Fixes + simplifications

* Implement review suggestions

bridges/modules/messages/src/mock.rs

@@ -19,6 +19,7 @@
 
 use crate::Config;
 
+use bitvec::prelude::*;
 use bp_messages::{
 	calc_relayers_rewards,
 	source_chain::{DeliveryConfirmationPayments, LaneMessageVerifier, TargetHeaderChain},
@@ -62,13 +63,13 @@ pub struct TestPayload {
 	///
 	/// Note: in correct code `dispatch_result.unspent_weight` will always be <= `declared_weight`,
 	/// but for test purposes we'll be making it larger than `declared_weight` sometimes.
-	pub dispatch_result: MessageDispatchResult<TestDispatchLevelResult>,
+	pub dispatch_result: MessageDispatchResult<TestDispatchError>,
 	/// Extra bytes that affect payload size.
 	pub extra: Vec<u8>,
 }
 pub type TestMessageFee = u64;
 pub type TestRelayer = u64;
-pub type TestDispatchLevelResult = ();
+pub type TestDispatchError = ();
 
 type Block = frame_system::mocking::MockBlock<TestRuntime>;
 type UncheckedExtrinsic = frame_system::mocking::MockUncheckedExtrinsic<TestRuntime>;
@@ -412,7 +413,7 @@ pub struct TestMessageDispatch;
 
 impl MessageDispatch<AccountId> for TestMessageDispatch {
 	type DispatchPayload = TestPayload;
-	type DispatchLevelResult = TestDispatchLevelResult;
+	type DispatchError = TestDispatchError;
 
 	fn dispatch_weight(message: &mut DispatchMessage<TestPayload>) -> Weight {
 		match message.data.payload.as_ref() {
@@ -424,7 +425,7 @@ impl MessageDispatch<AccountId> for TestMessageDispatch {
 	fn dispatch(
 		_relayer_account: &AccountId,
 		message: DispatchMessage<TestPayload>,
-	) -> MessageDispatchResult<TestDispatchLevelResult> {
+	) -> MessageDispatchResult<TestDispatchError> {
 		match message.data.payload.as_ref() {
 			Ok(payload) => payload.dispatch_result.clone(),
 			Err(_) => dispatch_result(0),
@@ -459,12 +460,10 @@ pub const fn message_payload(id: u64, declared_weight: u64) -> TestPayload {
 }
 
 /// Returns message dispatch result with given unspent weight.
-pub const fn dispatch_result(
-	unspent_weight: u64,
-) -> MessageDispatchResult<TestDispatchLevelResult> {
+pub const fn dispatch_result(unspent_weight: u64) -> MessageDispatchResult<TestDispatchError> {
 	MessageDispatchResult {
 		unspent_weight: Weight::from_parts(unspent_weight, 0),
-		dispatch_level_result: (),
+		dispatch_result: Ok(()),
 	}
 }
 
@@ -474,7 +473,14 @@ pub fn unrewarded_relayer(
 	end: MessageNonce,
 	relayer: TestRelayer,
 ) -> UnrewardedRelayer<TestRelayer> {
-	UnrewardedRelayer { relayer, messages: DeliveredMessages { begin, end } }
+	UnrewardedRelayer {
+		relayer,
+		messages: DeliveredMessages {
+			begin,
+			end,
+			dispatch_results: bitvec![u8, Msb0; 1; (end + 1).saturating_sub(begin) as _],
+		},
+	}
 }
 
 /// Return test externalities to use in tests.