BridgeHubRococo/Wococo nits + updated subtree (#2572)

* Nits (merge before separatelly)

* Small cosmetics for Rococo/Wococo bridge local run

* Squashed 'bridges/' changes from 04b3dda6aa..5fc377ab34

5fc377ab34 Support for kusama-polkadot relaying (#2128)
01f4b7f1ba Fix clippy warnings (#2127)
696ff1c368 BHK/P alignments (#2115)
2a66aa3248 Small fixes (#2126)
7810f1a988 Cosmetics (#2124)
daf250f69c Remove some `expect()` statements (#2123)
1c5fba8274 temporarily remove balance guard (#2121)
3d0e547361 Propagate message receival confirmation errors (#2116)
1c33143f07 Propagate message verification errors (#2114)
b075b00910 Bump time from 0.3.20 to 0.3.21
51a3a51618 Bump serde from 1.0.160 to 1.0.162
da88d044a6 Bump clap from 4.2.5 to 4.2.7
cdca322cd6 Bump sysinfo from 0.28.4 to 0.29.0

git-subtree-dir: bridges
git-subtree-split: 5fc377ab34f7dfd3293099c5feec49255e827812

* Fix

* Allow to change storage constants (DeliveryReward, RequiredStakeForStakeAndSlash) + tests

* Clippy

* New SA for RO/WO

* Squashed 'bridges/' changes from 5fc377ab34..0f6091d481

0f6091d481 Bump polkadot/substrate (#2134)
9233f0a337 Bump tokio from 1.28.0 to 1.28.1
a29c1caa93 Bump serde from 1.0.162 to 1.0.163

git-subtree-dir: bridges
git-subtree-split: 0f6091d48184ebb4f75cb3089befa6b92cf37335

cumulus/bridges/primitives/chain-bridge-hub-kusama/src/lib.rs

@@ -72,12 +72,10 @@ pub type Address = MultiAddress<AccountId, ()>;
 pub const BRIDGE_HUB_KUSAMA_PARACHAIN_ID: u32 = 1002;
 
 /// Name of the With-BridgeHubKusama messages pallet instance that is deployed at bridged chains.
-// TODO: check me (https://github.com/paritytech/parity-bridges-common/issues/1945)
 pub const WITH_BRIDGE_HUB_KUSAMA_MESSAGES_PALLET_NAME: &str = "BridgeKusamaMessages";
 
 /// Name of the With-BridgeHubKusama bridge-relayers pallet instance that is deployed at bridged
 /// chains.
-// TODO: check me (https://github.com/paritytech/parity-bridges-common/issues/1945)
 pub const WITH_BRIDGE_HUB_KUSAMA_RELAYERS_PALLET_NAME: &str = "BridgeRelayers";
 
 decl_bridge_finality_runtime_apis!(bridge_hub_kusama);

cumulus/bridges/primitives/chain-bridge-hub-polkadot/src/lib.rs

@@ -59,16 +59,13 @@ impl Parachain for BridgeHubPolkadot {
 }
 
 /// Identifier of BridgeHubPolkadot in the Polkadot relay chain.
-// TODO: check me (https://github.com/paritytech/parity-bridges-common/issues/1945)
 pub const BRIDGE_HUB_POLKADOT_PARACHAIN_ID: u32 = 1002;
 
 /// Name of the With-BridgeHubPolkadot messages pallet instance that is deployed at bridged chains.
-// TODO: check me (https://github.com/paritytech/parity-bridges-common/issues/1945)
 pub const WITH_BRIDGE_HUB_POLKADOT_MESSAGES_PALLET_NAME: &str = "BridgePolkadotMessages";
 
 /// Name of the With-BridgeHubPolkadot bridge-relayers pallet instance that is deployed at bridged
 /// chains.
-// TODO: check me (https://github.com/paritytech/parity-bridges-common/issues/1945)
 pub const WITH_BRIDGE_HUB_POLKADOT_RELAYERS_PALLET_NAME: &str = "BridgeRelayers";
 
 decl_bridge_finality_runtime_apis!(bridge_hub_polkadot);

cumulus/bridges/primitives/chain-kusama/src/lib.rs

@@ -62,4 +62,11 @@ pub const PARAS_PALLET_NAME: &str = "Paras";
 /// Name of the With-Kusama GRANDPA pallet instance that is deployed at bridged chains.
 pub const WITH_KUSAMA_GRANDPA_PALLET_NAME: &str = "BridgeKusamaGrandpa";
 
+/// Maximal size of encoded `bp_parachains::ParaStoredHeaderData` structure among all Polkadot
+/// parachains.
+///
+/// It includes the block number and state root, so it shall be near 40 bytes, but let's have some
+/// reserve.
+pub const MAX_NESTED_PARACHAIN_HEAD_DATA_SIZE: u32 = 128;
+
 decl_bridge_finality_runtime_apis!(kusama);

cumulus/bridges/primitives/chain-polkadot/src/lib.rs

@@ -62,4 +62,11 @@ pub const PARAS_PALLET_NAME: &str = "Paras";
 /// Name of the With-Polkadot GRANDPA pallet instance that is deployed at bridged chains.
 pub const WITH_POLKADOT_GRANDPA_PALLET_NAME: &str = "BridgePolkadotGrandpa";
 
+/// Maximal size of encoded `bp_parachains::ParaStoredHeaderData` structure among all Polkadot
+/// parachains.
+///
+/// It includes the block number and state root, so it shall be near 40 bytes, but let's have some
+/// reserve.
+pub const MAX_NESTED_PARACHAIN_HEAD_DATA_SIZE: u32 = 128;
+
 decl_bridge_finality_runtime_apis!(polkadot);

cumulus/bridges/primitives/header-chain/src/justification.rs

@@ -49,6 +49,7 @@ pub struct GrandpaJustification<Header: HeaderT> {
 	pub votes_ancestries: Vec<Header>,
 }
 
+// TODO: remove and use `RuntimeDebug` (https://github.com/paritytech/parity-bridges-common/issues/2136)
 impl<Header: HeaderT> sp_std::fmt::Debug for GrandpaJustification<Header> {
 	fn fmt(&self, fmt: &mut sp_std::fmt::Formatter) -> sp_std::fmt::Result {
 		#[cfg(feature = "std")]

cumulus/bridges/primitives/header-chain/src/lib.rs

@@ -73,18 +73,14 @@ impl<H: HeaderT> StoredHeaderDataBuilder<H::Number, H::Hash> for H {
 pub trait HeaderChain<C: Chain> {
 	/// Returns state (storage) root of given finalized header.
 	fn finalized_header_state_root(header_hash: HashOf<C>) -> Option<HashOf<C>>;
-	/// Parse storage proof using finalized header.
-	fn parse_finalized_storage_proof<R>(
+	/// Get storage proof checker using finalized header.
+	fn storage_proof_checker(
 		header_hash: HashOf<C>,
 		storage_proof: RawStorageProof,
-		parse: impl FnOnce(StorageProofChecker<HasherOf<C>>) -> R,
-	) -> Result<R, HeaderChainError> {
+	) -> Result<StorageProofChecker<HasherOf<C>>, HeaderChainError> {
 		let state_root = Self::finalized_header_state_root(header_hash)
 			.ok_or(HeaderChainError::UnknownHeader)?;
-		let storage_proof_checker = bp_runtime::StorageProofChecker::new(state_root, storage_proof)
-			.map_err(HeaderChainError::StorageProof)?;
-
-		Ok(parse(storage_proof_checker))
+		StorageProofChecker::new(state_root, storage_proof).map_err(HeaderChainError::StorageProof)
 	}
 }
 

cumulus/bridges/primitives/messages/Cargo.toml

@@ -14,6 +14,7 @@ serde = { version = "1.0", optional = true, features = ["derive"] }
 # Bridge dependencies
 
 bp-runtime = { path = "../runtime", default-features = false }
+bp-header-chain = { path = "../header-chain", default-features = false }
 
 # Substrate Dependencies
 
@@ -29,6 +30,7 @@ hex-literal = "0.4"
 default = ["std"]
 std = [
 	"bp-runtime/std",
+	"bp-header-chain/std",
 	"codec/std",
 	"frame-support/std",
 	"scale-info/std",

cumulus/bridges/primitives/messages/src/lib.rs

@@ -20,9 +20,15 @@
 // RuntimeApi generated functions
 #![allow(clippy::too_many_arguments)]
 
-use bp_runtime::{BasicOperatingMode, OperatingMode, RangeInclusiveExt};
+use bp_header_chain::HeaderChainError;
+use bp_runtime::{
+	messages::MessageDispatchResult, BasicOperatingMode, OperatingMode, RangeInclusiveExt,
+	StorageProofError,
+};
 use codec::{Decode, Encode, MaxEncodedLen};
-use frame_support::RuntimeDebug;
+use frame_support::{PalletError, RuntimeDebug};
+// Weight is reexported to avoid additional frame-support dependencies in related crates.
+pub use frame_support::weights::Weight;
 use scale_info::TypeInfo;
 use source_chain::RelayersRewards;
 use sp_core::TypeId;
@@ -32,10 +38,6 @@ pub mod source_chain;
 pub mod storage_keys;
 pub mod target_chain;
 
-use bp_runtime::messages::MessageDispatchResult;
-// Weight is reexported to avoid additional frame-support dependencies in related crates.
-pub use frame_support::weights::Weight;
-
 /// Messages pallet operating mode.
 #[derive(Encode, Decode, Clone, Copy, PartialEq, Eq, RuntimeDebug, TypeInfo, MaxEncodedLen)]
 #[cfg_attr(feature = "std", derive(serde::Serialize, serde::Deserialize))]
@@ -189,6 +191,17 @@ impl<RelayerId> InboundLaneData<RelayerId> {
 			.map(|entry| entry.messages.end)
 			.unwrap_or(self.last_confirmed_nonce)
 	}
+
+	/// Returns the total number of messages in the `relayers` vector,
+	/// saturating in case of underflow or overflow.
+	pub fn total_unrewarded_messages(&self) -> MessageNonce {
+		let relayers = &self.relayers;
+		match (relayers.front(), relayers.back()) {
+			(Some(front), Some(back)) =>
+				(front.messages.begin..=back.messages.end).saturating_len(),
+			_ => 0,
+		}
+	}
 }
 
 /// Outbound message details, returned by runtime APIs.
@@ -285,7 +298,7 @@ impl DeliveredMessages {
 
 	/// Return total count of delivered messages.
 	pub fn total_messages(&self) -> MessageNonce {
-		(self.begin..=self.end).checked_len().unwrap_or(0)
+		(self.begin..=self.end).saturating_len()
 	}
 
 	/// Note new dispatched message.
@@ -316,6 +329,13 @@ pub struct UnrewardedRelayersState {
 	pub last_delivered_nonce: MessageNonce,
 }
 
+impl UnrewardedRelayersState {
+	// Verify that the relayers state corresponds with the `InboundLaneData`.
+	pub fn is_valid<RelayerId>(&self, lane_data: &InboundLaneData<RelayerId>) -> bool {
+		self == &lane_data.into()
+	}
+}
+
 impl<RelayerId> From<&InboundLaneData<RelayerId>> for UnrewardedRelayersState {
 	fn from(lane: &InboundLaneData<RelayerId>) -> UnrewardedRelayersState {
 		UnrewardedRelayersState {
@@ -323,9 +343,9 @@ impl<RelayerId> From<&InboundLaneData<RelayerId>> for UnrewardedRelayersState {
 			messages_in_oldest_entry: lane
 				.relayers
 				.front()
-				.and_then(|entry| (entry.messages.begin..=entry.messages.end).checked_len())
+				.map(|entry| entry.messages.total_messages())
 				.unwrap_or(0),
-			total_messages: total_unrewarded_messages(&lane.relayers).unwrap_or(MessageNonce::MAX),
+			total_messages: lane.total_unrewarded_messages(),
 			last_delivered_nonce: lane.last_delivered_nonce(),
 		}
 	}
@@ -355,24 +375,6 @@ impl Default for OutboundLaneData {
 	}
 }
 
-/// Returns total number of messages in the `InboundLaneData::relayers` vector.
-///
-/// Returns `None` if there are more messages that `MessageNonce` may fit (i.e. `MessageNonce + 1`).
-pub fn total_unrewarded_messages<RelayerId>(
-	relayers: &VecDeque<UnrewardedRelayer<RelayerId>>,
-) -> Option<MessageNonce> {
-	match (relayers.front(), relayers.back()) {
-		(Some(front), Some(back)) => {
-			if let Some(difference) = back.messages.end.checked_sub(front.messages.begin) {
-				difference.checked_add(1)
-			} else {
-				Some(0)
-			}
-		},
-		_ => Some(0),
-	}
-}
-
 /// Calculate the number of messages that the relayers have delivered.
 pub fn calc_relayers_rewards<AccountId>(
 	messages_relayers: VecDeque<UnrewardedRelayer<AccountId>>,
@@ -414,26 +416,50 @@ pub enum BridgeMessagesCall<AccountId, MessagesProof, MessagesDeliveryProof> {
 	},
 }
 
+/// Error that happens during message verification.
+#[derive(Encode, Decode, RuntimeDebug, PartialEq, Eq, PalletError, TypeInfo)]
+pub enum VerificationError {
+	/// The message proof is empty.
+	EmptyMessageProof,
+	/// Error returned by the bridged header chain.
+	HeaderChain(HeaderChainError),
+	/// Error returned while reading/decoding inbound lane data from the storage proof.
+	InboundLaneStorage(StorageProofError),
+	/// The declared message weight is incorrect.
+	InvalidMessageWeight,
+	/// Declared messages count doesn't match actual value.
+	MessagesCountMismatch,
+	/// Error returned while reading/decoding message data from the storage proof.
+	MessageStorage(StorageProofError),
+	/// The message is too large.
+	MessageTooLarge,
+	/// Error returned while reading/decoding outbound lane data from the storage proof.
+	OutboundLaneStorage(StorageProofError),
+	/// Storage proof related error.
+	StorageProof(StorageProofError),
+	/// Custom error
+	Other(#[codec(skip)] &'static str),
+}
+
 #[cfg(test)]
 mod tests {
 	use super::*;
 
 	#[test]
 	fn total_unrewarded_messages_does_not_overflow() {
-		assert_eq!(
-			total_unrewarded_messages(
-				&vec![
-					UnrewardedRelayer { relayer: 1, messages: DeliveredMessages::new(0) },
-					UnrewardedRelayer {
-						relayer: 2,
-						messages: DeliveredMessages::new(MessageNonce::MAX)
-					},
-				]
-				.into_iter()
-				.collect()
-			),
-			None,
-		);
+		let lane_data = InboundLaneData {
+			relayers: vec![
+				UnrewardedRelayer { relayer: 1, messages: DeliveredMessages::new(0) },
+				UnrewardedRelayer {
+					relayer: 2,
+					messages: DeliveredMessages::new(MessageNonce::MAX),
+				},
+			]
+			.into_iter()
+			.collect(),
+			last_confirmed_nonce: 0,
+		};
+		assert_eq!(lane_data.total_unrewarded_messages(), MessageNonce::MAX);
 	}
 
 	#[test]

cumulus/bridges/primitives/messages/src/source_chain.rs

@@ -16,7 +16,7 @@
 
 //! Primitives of messages module, that are used on the source chain.
 
-use crate::{InboundLaneData, LaneId, MessageNonce, OutboundLaneData};
+use crate::{InboundLaneData, LaneId, MessageNonce, OutboundLaneData, VerificationError};
 
 use crate::UnrewardedRelayer;
 use bp_runtime::Size;
@@ -40,9 +40,6 @@ pub type RelayersRewards<AccountId> = BTreeMap<AccountId, MessageNonce>;
 /// source chain to the target chain. The `AccountId` type here means the account
 /// type used by the source chain.
 pub trait TargetHeaderChain<Payload, AccountId> {
-	/// Error type.
-	type Error: Debug;
-
 	/// Proof that messages have been received by target chain.
 	type MessagesDeliveryProof: Parameter + Size;
 
@@ -58,12 +55,12 @@ pub trait TargetHeaderChain<Payload, AccountId> {
 	/// 1MB. BTC nodes aren't accepting transactions that are larger than 1MB, so relayer
 	/// will be unable to craft valid transaction => this (and all subsequent) messages will
 	/// never be delivered.
-	fn verify_message(payload: &Payload) -> Result<(), Self::Error>;
+	fn verify_message(payload: &Payload) -> Result<(), VerificationError>;
 
 	/// Verify messages delivery proof and return lane && nonce of the latest received message.
 	fn verify_messages_delivery_proof(
 		proof: Self::MessagesDeliveryProof,
-	) -> Result<(LaneId, InboundLaneData<AccountId>), Self::Error>;
+	) -> Result<(LaneId, InboundLaneData<AccountId>), VerificationError>;
 }
 
 /// Lane message verifier.
@@ -75,9 +72,6 @@ pub trait TargetHeaderChain<Payload, AccountId> {
 ///
 /// Any fee requirements should also be enforced here.
 pub trait LaneMessageVerifier<SenderOrigin, Payload> {
-	/// Error type.
-	type Error: Debug + Into<&'static str>;
-
 	/// Verify message payload and return Ok(()) if message is valid and allowed to be sent over the
 	/// lane.
 	fn verify_message(
@@ -85,7 +79,7 @@ pub trait LaneMessageVerifier<SenderOrigin, Payload> {
 		lane: &LaneId,
 		outbound_data: &OutboundLaneData,
 		payload: &Payload,
-	) -> Result<(), Self::Error>;
+	) -> Result<(), VerificationError>;
 }
 
 /// Manages payments that are happening at the source chain during delivery confirmation
@@ -169,31 +163,27 @@ const ALL_OUTBOUND_MESSAGES_REJECTED: &str =
 	"This chain is configured to reject all outbound messages";
 
 impl<Payload, AccountId> TargetHeaderChain<Payload, AccountId> for ForbidOutboundMessages {
-	type Error = &'static str;
-
 	type MessagesDeliveryProof = ();
 
-	fn verify_message(_payload: &Payload) -> Result<(), Self::Error> {
-		Err(ALL_OUTBOUND_MESSAGES_REJECTED)
+	fn verify_message(_payload: &Payload) -> Result<(), VerificationError> {
+		Err(VerificationError::Other(ALL_OUTBOUND_MESSAGES_REJECTED))
 	}
 
 	fn verify_messages_delivery_proof(
 		_proof: Self::MessagesDeliveryProof,
-	) -> Result<(LaneId, InboundLaneData<AccountId>), Self::Error> {
-		Err(ALL_OUTBOUND_MESSAGES_REJECTED)
+	) -> Result<(LaneId, InboundLaneData<AccountId>), VerificationError> {
+		Err(VerificationError::Other(ALL_OUTBOUND_MESSAGES_REJECTED))
 	}
 }
 
 impl<SenderOrigin, Payload> LaneMessageVerifier<SenderOrigin, Payload> for ForbidOutboundMessages {
-	type Error = &'static str;
-
 	fn verify_message(
 		_submitter: &SenderOrigin,
 		_lane: &LaneId,
 		_outbound_data: &OutboundLaneData,
 		_payload: &Payload,
-	) -> Result<(), Self::Error> {
-		Err(ALL_OUTBOUND_MESSAGES_REJECTED)
+	) -> Result<(), VerificationError> {
+		Err(VerificationError::Other(ALL_OUTBOUND_MESSAGES_REJECTED))
 	}
 }
 

cumulus/bridges/primitives/messages/src/target_chain.rs

@@ -16,7 +16,9 @@
 
 //! Primitives of messages module, that are used on the target chain.
 
-use crate::{LaneId, Message, MessageKey, MessageNonce, MessagePayload, OutboundLaneData};
+use crate::{
+	LaneId, Message, MessageKey, MessageNonce, MessagePayload, OutboundLaneData, VerificationError,
+};
 
 use bp_runtime::{messages::MessageDispatchResult, Size};
 use codec::{Decode, Encode, Error as CodecError};
@@ -58,9 +60,6 @@ pub struct DispatchMessage<DispatchPayload> {
 /// can't change. Wrong implementation may lead to invalid lane states (i.e. lane
 /// that's stuck) and/or processing messages without paying fees.
 pub trait SourceHeaderChain {
-	/// Error type.
-	type Error: Debug;
-
 	/// Proof that messages are sent from source chain. This may also include proof
 	/// of corresponding outbound lane states.
 	type MessagesProof: Parameter + Size;
@@ -79,7 +78,7 @@ pub trait SourceHeaderChain {
 	fn verify_messages_proof(
 		proof: Self::MessagesProof,
 		messages_count: u32,
-	) -> Result<ProvedMessages<Message>, Self::Error>;
+	) -> Result<ProvedMessages<Message>, VerificationError>;
 }
 
 /// Called when inbound message is received.
@@ -164,21 +163,20 @@ pub struct ForbidInboundMessages<MessagesProof, DispatchPayload>(
 	PhantomData<(MessagesProof, DispatchPayload)>,
 );
 
-/// Error message that is used in `ForbidOutboundMessages` implementation.
+/// Error message that is used in `ForbidInboundMessages` implementation.
 const ALL_INBOUND_MESSAGES_REJECTED: &str =
 	"This chain is configured to reject all inbound messages";
 
 impl<MessagesProof: Parameter + Size, DispatchPayload> SourceHeaderChain
 	for ForbidInboundMessages<MessagesProof, DispatchPayload>
 {
-	type Error = &'static str;
 	type MessagesProof = MessagesProof;
 
 	fn verify_messages_proof(
 		_proof: Self::MessagesProof,
 		_messages_count: u32,
-	) -> Result<ProvedMessages<Message>, Self::Error> {
-		Err(ALL_INBOUND_MESSAGES_REJECTED)
+	) -> Result<ProvedMessages<Message>, VerificationError> {
+		Err(VerificationError::Other(ALL_INBOUND_MESSAGES_REJECTED))
 	}
 }
 

cumulus/bridges/primitives/polkadot-core/src/parachains.rs

@@ -18,8 +18,8 @@
 //!
 //! Even though this (bridges) repository references polkadot repository, we can't
 //! reference polkadot crates from pallets. That's because bridges repository is
-//! included in the polkadot repository and included pallets are used by polkadot
-//! chains. Having pallets that are referencing polkadot, would mean that there may
+//! included in the Cumulus repository and included pallets are used by Cumulus
+//! parachains. Having pallets that are referencing polkadot, would mean that there may
 //! be two versions of polkadot crates included in the runtime. Which is bad.
 
 use bp_runtime::{RawStorageProof, Size};

cumulus/bridges/primitives/runtime/src/chain.rs

@@ -232,6 +232,14 @@ where
 	const PARACHAIN_ID: u32 = <<T as UnderlyingChainProvider>::Chain as Parachain>::PARACHAIN_ID;
 }
 
+/// Adapter for `Get<u32>` to access `PARACHAIN_ID` from `trait Parachain`
+pub struct ParachainIdOf<Para>(sp_std::marker::PhantomData<Para>);
+impl<Para: Parachain> frame_support::traits::Get<u32> for ParachainIdOf<Para> {
+	fn get() -> u32 {
+		Para::PARACHAIN_ID
+	}
+}
+
 /// Underlying chain type.
 pub type UnderlyingChainOf<C> = <C as UnderlyingChainProvider>::Chain;
 

cumulus/bridges/primitives/runtime/src/lib.rs

@@ -31,11 +31,11 @@ use sp_std::{convert::TryFrom, fmt::Debug, ops::RangeInclusive, vec, vec::Vec};
 
 pub use chain::{
 	AccountIdOf, AccountPublicOf, BalanceOf, BlockNumberOf, Chain, EncodedOrDecodedCall, HashOf,
-	HasherOf, HeaderOf, IndexOf, Parachain, SignatureOf, TransactionEraOf, UnderlyingChainOf,
-	UnderlyingChainProvider,
+	HasherOf, HeaderOf, IndexOf, Parachain, ParachainIdOf, SignatureOf, TransactionEraOf,
+	UnderlyingChainOf, UnderlyingChainProvider,
 };
 pub use frame_support::storage::storage_prefix as storage_value_final_key;
-use num_traits::{CheckedAdd, CheckedSub, One};
+use num_traits::{CheckedAdd, CheckedSub, One, SaturatingAdd, Zero};
 pub use storage_proof::{
 	record_all_keys as record_all_trie_keys, Error as StorageProofError,
 	ProofSize as StorageProofSize, RawStorageProof, StorageProofChecker,
@@ -95,7 +95,7 @@ pub const BRIDGE_HUB_WOCOCO_CHAIN_ID: ChainId = *b"bhwo";
 pub const BRIDGE_HUB_KUSAMA_CHAIN_ID: ChainId = *b"bhks";
 
 /// BridgeHubPolkadot chain id.
-pub const BRIDGE_HUB_POLKADOT_CHAIN_ID: ChainId = *b"bhwo";
+pub const BRIDGE_HUB_POLKADOT_CHAIN_ID: ChainId = *b"bhpd";
 
 /// Generic header Id.
 #[derive(
@@ -527,17 +527,27 @@ impl<T> Debug for StrippableError<T> {
 pub trait RangeInclusiveExt<Idx> {
 	/// Computes the length of the `RangeInclusive`, checking for underflow and overflow.
 	fn checked_len(&self) -> Option<Idx>;
+	/// Computes the length of the `RangeInclusive`, saturating in case of underflow or overflow.
+	fn saturating_len(&self) -> Idx;
 }
 
 impl<Idx> RangeInclusiveExt<Idx> for RangeInclusive<Idx>
 where
-	Idx: CheckedSub + CheckedAdd + One,
+	Idx: CheckedSub + CheckedAdd + SaturatingAdd + One + Zero,
 {
 	fn checked_len(&self) -> Option<Idx> {
 		self.end()
 			.checked_sub(self.start())
 			.and_then(|len| len.checked_add(&Idx::one()))
 	}
+
+	fn saturating_len(&self) -> Idx {
+		let len = match self.end().checked_sub(self.start()) {
+			Some(len) => len,
+			None => return Idx::zero(),
+		};
+		len.saturating_add(&Idx::one())
+	}
 }
 
 #[cfg(test)]