The storage runtime interface should not enforce a hash type (#4231)

* The storage runtime interface should not enforce a hash type

Currently the runtime interface enforces `H256` as hash type, but in the
future people could use whatever they want as hash type. The hash type
always needs to match between the runtime and the node, but that is
already required.

* Update primitives/externalities/src/lib.rs

Co-Authored-By: thiolliere <gui.thiolliere@gmail.com>

substrate/client/src/cht.rs

@@ -92,7 +92,7 @@ pub fn build_proof<Header, Hasher, BlocksI, HashesI>(
 	where
 		Header: HeaderT,
 		Hasher: hash_db::Hasher,
-		Hasher::Out: Ord,
+		Hasher::Out: Ord + codec::Codec,
 		BlocksI: IntoIterator<Item=Header::Number>,
 		HashesI: IntoIterator<Item=ClientResult<Option<Header::Hash>>>,
 {
@@ -119,7 +119,7 @@ pub fn check_proof<Header, Hasher>(
 	where
 		Header: HeaderT,
 		Hasher: hash_db::Hasher,
-		Hasher::Out: Ord,
+		Hasher::Out: Ord + codec::Codec,
 {
 	do_check_proof::<Header, Hasher, _>(
 		local_root,
@@ -148,7 +148,7 @@ pub fn check_proof_on_proving_backend<Header, Hasher>(
 	where
 		Header: HeaderT,
 		Hasher: hash_db::Hasher,
-		Hasher::Out: Ord,
+		Hasher::Out: Ord + codec::Codec,
 {
 	do_check_proof::<Header, Hasher, _>(
 		local_root,

substrate/client/src/light/backend.rs

@@ -21,7 +21,9 @@ use std::collections::HashMap;
 use std::sync::Arc;
 use parking_lot::RwLock;
 
-use state_machine::{Backend as StateBackend, TrieBackend, backend::InMemory as InMemoryState, ChangesTrieTransaction};
+use state_machine::{
+	Backend as StateBackend, TrieBackend, backend::InMemory as InMemoryState, ChangesTrieTransaction
+};
 use primitives::offchain::storage::InMemOffchainStorage;
 use sr_primitives::{generic::BlockId, Justification, StorageOverlay, ChildrenStorageOverlay};
 use sr_primitives::traits::{Block as BlockT, NumberFor, Zero, Header};
@@ -341,7 +343,7 @@ impl<H: Hasher> std::fmt::Debug for GenesisOrUnavailableState<H> {
 
 impl<H: Hasher> StateBackend<H> for GenesisOrUnavailableState<H>
 	where
-		H::Out: Ord,
+		H::Out: Ord + codec::Codec,
 {
 	type Error = ClientError;
 	type Transaction = ();
@@ -409,7 +411,7 @@ impl<H: Hasher> StateBackend<H> for GenesisOrUnavailableState<H>
 		}
 	}
 
-	fn child_storage_root<I>(&self, key: &[u8], delta: I) -> (Vec<u8>, bool, Self::Transaction)
+	fn child_storage_root<I>(&self, key: &[u8], delta: I) -> (H::Out, bool, Self::Transaction)
 	where
 		I: IntoIterator<Item=(Vec<u8>, Option<Vec<u8>>)>
 	{
@@ -418,7 +420,7 @@ impl<H: Hasher> StateBackend<H> for GenesisOrUnavailableState<H>
 				let (root, is_equal, _) = state.child_storage_root(key, delta);
 				(root, is_equal, ())
 			},
-			GenesisOrUnavailableState::Unavailable => (H::Out::default().as_ref().to_vec(), true, ()),
+			GenesisOrUnavailableState::Unavailable => (H::Out::default(), true, ()),
 		}
 	}
 

substrate/client/src/light/fetcher.rs

@@ -70,7 +70,7 @@ impl<E, H, B: BlockT, S: BlockchainStorage<B>> LightDataChecker<E, H, B, S> {
 	) -> ClientResult<Vec<(NumberFor<B>, u32)>>
 		where
 			H: Hasher,
-			H::Out: Ord,
+			H::Out: Ord + codec::Codec,
 	{
 		// since we need roots of all changes tries for the range begin..max
 		// => remote node can't use max block greater that one that we have passed
@@ -148,7 +148,7 @@ impl<E, H, B: BlockT, S: BlockchainStorage<B>> LightDataChecker<E, H, B, S> {
 	) -> ClientResult<()>
 		where
 			H: Hasher,
-			H::Out: Ord,
+			H::Out: Ord + codec::Codec,
 	{
 		// all the checks are sharing the same storage
 		let storage = create_proof_check_backend_storage(remote_roots_proof);