remove unnessisary use statements due to 2021 core prelude (#4183)

Some traits are already included in the 2021 prelude and so shouldn't be
needed to use explicitly:

use `convert::TryFrom`, `convert::TryInto`, and `iter::FromIterator` are
removed.

( https://doc.rust-lang.org/core/prelude/rust_2021/ )

No breaking changes or change of functionality, so I think no PR doc is
needed in this case.

(Motivation: Removes some references to `sp-std`)

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

@@ -35,7 +35,7 @@ use frame_support::{traits::Get, weights::Weight};
 use hash_db::Hasher;
 use scale_info::TypeInfo;
 use sp_runtime::RuntimeDebug;
-use sp_std::{convert::TryFrom, marker::PhantomData, vec::Vec};
+use sp_std::{marker::PhantomData, vec::Vec};
 
 /// Bidirectional message bridge.
 pub trait MessageBridge {

bridges/modules/grandpa/src/lib.rs

@@ -49,7 +49,7 @@ use sp_runtime::{
 	traits::{Header as HeaderT, Zero},
 	SaturatedConversion,
 };
-use sp_std::{boxed::Box, convert::TryInto, prelude::*};
+use sp_std::{boxed::Box, prelude::*};
 
 mod call_ext;
 #[cfg(test)]

bridges/primitives/runtime/src/chain.rs

@@ -26,7 +26,7 @@ use sp_runtime::{
 	},
 	FixedPointOperand,
 };
-use sp_std::{convert::TryFrom, fmt::Debug, hash::Hash, str::FromStr, vec, vec::Vec};
+use sp_std::{fmt::Debug, hash::Hash, str::FromStr, vec, vec::Vec};
 
 /// Chain call, that is either SCALE-encoded, or decoded.
 #[derive(Debug, Clone, PartialEq)]

bridges/primitives/runtime/src/lib.rs

@@ -31,7 +31,7 @@ use sp_runtime::{
 	traits::{BadOrigin, Header as HeaderT, UniqueSaturatedInto},
 	RuntimeDebug,
 };
-use sp_std::{convert::TryFrom, fmt::Debug, ops::RangeInclusive, vec, vec::Vec};
+use sp_std::{fmt::Debug, ops::RangeInclusive, vec, vec::Vec};
 
 pub use chain::{
 	AccountIdOf, AccountPublicOf, BalanceOf, BlockNumberOf, Chain, EncodedOrDecodedCall, HashOf,

bridges/relays/lib-substrate-relay/src/messages_lane.rs

@@ -46,7 +46,7 @@ use relay_utils::{
 };
 use sp_core::Pair;
 use sp_runtime::traits::Zero;
-use std::{convert::TryFrom, fmt::Debug, marker::PhantomData};
+use std::{fmt::Debug, marker::PhantomData};
 
 /// Substrate -> Substrate messages synchronization pipeline.
 pub trait SubstrateMessageLane: 'static + Clone + Debug + Send + Sync {

bridges/relays/lib-substrate-relay/src/messages_metrics.rs

@@ -32,7 +32,7 @@ use relay_substrate_client::{
 use relay_utils::metrics::{MetricsParams, StandaloneMetric};
 use sp_core::storage::StorageData;
 use sp_runtime::{FixedPointNumber, FixedU128};
-use std::{convert::TryFrom, fmt::Debug, marker::PhantomData};
+use std::{fmt::Debug, marker::PhantomData};
 
 /// Add relay accounts balance metrics.
 pub async fn add_relay_balances_metrics<C: ChainWithBalances, BC: ChainWithMessages>(

bridges/relays/lib-substrate-relay/src/messages_target.rs

@@ -45,7 +45,7 @@ use relay_substrate_client::{
 };
 use relay_utils::relay_loop::Client as RelayClient;
 use sp_core::Pair;
-use std::{convert::TryFrom, ops::RangeInclusive};
+use std::ops::RangeInclusive;
 
 /// Message receiving proof returned by the target Substrate node.
 pub type SubstrateMessagesDeliveryProof<C> =

bridges/snowbridge/pallets/inbound-queue/src/envelope.rs

@@ -3,7 +3,7 @@
 use snowbridge_core::{inbound::Log, ChannelId};
 
 use sp_core::{RuntimeDebug, H160, H256};
-use sp_std::{convert::TryFrom, prelude::*};
+use sp_std::prelude::*;
 
 use alloy_primitives::B256;
 use alloy_sol_types::{sol, SolEvent};

bridges/snowbridge/pallets/inbound-queue/src/lib.rs

@@ -50,7 +50,7 @@ use frame_system::ensure_signed;
 use scale_info::TypeInfo;
 use sp_core::{H160, H256};
 use sp_runtime::traits::Zero;
-use sp_std::{convert::TryFrom, vec};
+use sp_std::vec;
 use xcm::prelude::{
 	send_xcm, Instruction::SetTopic, Junction::*, Location, SendError as XcmpSendError, SendXcm,
 	Xcm, XcmContext, XcmHash,

bridges/snowbridge/primitives/beacon/src/bits.rs

@@ -1,6 +1,6 @@
 // SPDX-License-Identifier: Apache-2.0
 // SPDX-FileCopyrightText: 2023 Snowfork <hello@snowfork.com>
-use sp_std::{convert::TryInto, prelude::*};
+use sp_std::prelude::*;
 use ssz_rs::{Bitvector, Deserialize};
 
 pub fn decompress_sync_committee_bits<

bridges/snowbridge/primitives/beacon/src/serde_utils.rs

@@ -7,7 +7,7 @@ use serde::{Deserialize, Deserializer};
 
 // helper to deserialize arbitrary arrays like [T; N]
 pub mod arrays {
-	use std::{convert::TryInto, marker::PhantomData};
+	use std::marker::PhantomData;
 
 	use serde::{
 		de::{SeqAccess, Visitor},

bridges/snowbridge/primitives/ethereum/src/header.rs

@@ -8,7 +8,7 @@ use rlp::RlpStream;
 use scale_info::TypeInfo;
 use sp_io::hashing::keccak_256;
 use sp_runtime::RuntimeDebug;
-use sp_std::{convert::TryInto, prelude::*};
+use sp_std::prelude::*;
 
 #[cfg(feature = "std")]
 use serde::{Deserialize, Serialize};

bridges/snowbridge/primitives/ethereum/src/mpt.rs

@@ -3,7 +3,7 @@
 //! Helper types to work with Ethereum's Merkle Patricia Trie nodes
 
 use ethereum_types::H256;
-use sp_std::{convert::TryFrom, prelude::*};
+use sp_std::prelude::*;
 
 pub trait Node {
 	fn contains_hash(&self, hash: H256) -> bool;

bridges/snowbridge/runtime/test-common/Cargo.toml

@@ -3,7 +3,7 @@ name = "snowbridge-runtime-test-common"
 description = "Snowbridge Runtime Tests"
 version = "0.2.0"
 authors = ["Snowfork <contact@snowfork.com>"]
-edition = "2021"
+edition.workspace = true
 license = "Apache-2.0"
 categories = ["cryptography::cryptocurrencies"]
 

cumulus/client/consensus/aura/src/collator.rs

@@ -55,7 +55,7 @@ use sp_runtime::{
 };
 use sp_state_machine::StorageChanges;
 use sp_timestamp::Timestamp;
-use std::{convert::TryFrom, error::Error, time::Duration};
+use std::{error::Error, time::Duration};
 
 /// Parameters for instantiating a [`Collator`].
 pub struct Params<BI, CIDP, RClient, Proposer, CS> {

cumulus/client/consensus/aura/src/collators/basic.rs

@@ -48,7 +48,7 @@ use sp_inherents::CreateInherentDataProviders;
 use sp_keystore::KeystorePtr;
 use sp_runtime::traits::{Block as BlockT, Header as HeaderT, Member};
 use sp_state_machine::Backend as _;
-use std::{convert::TryFrom, sync::Arc, time::Duration};
+use std::{sync::Arc, time::Duration};
 
 use crate::collator as collator_util;
 

cumulus/client/consensus/aura/src/collators/lookahead.rs

@@ -67,7 +67,7 @@ use sp_inherents::CreateInherentDataProviders;
 use sp_keystore::KeystorePtr;
 use sp_runtime::traits::{Block as BlockT, Header as HeaderT, Member};
 use sp_timestamp::Timestamp;
-use std::{convert::TryFrom, sync::Arc, time::Duration};
+use std::{sync::Arc, time::Duration};
 
 use crate::collator::{self as collator_util, SlotClaim};
 

cumulus/client/network/src/lib.rs

@@ -36,7 +36,7 @@ use polkadot_primitives::{
 
 use codec::{Decode, DecodeAll, Encode};
 use futures::{channel::oneshot, future::FutureExt, Future};
-use std::{convert::TryFrom, fmt, marker::PhantomData, pin::Pin, sync::Arc};
+use std::{fmt, marker::PhantomData, pin::Pin, sync::Arc};
 
 #[cfg(test)]
 mod tests;

cumulus/parachains/pallets/collective-content/Cargo.toml

@@ -2,7 +2,7 @@
 name = "pallet-collective-content"
 version = "0.6.0"
 authors = ["Parity Technologies <admin@parity.io>"]
-edition = "2021"
+edition.workspace = true
 description = "Managed content"
 license = "Apache-2.0"
 

polkadot/node/core/bitfield-signing/src/lib.rs

@@ -38,7 +38,7 @@ use polkadot_node_subsystem::{
 use polkadot_node_subsystem_util::{self as util, Validator};
 use polkadot_primitives::{AvailabilityBitfield, CoreState, Hash, ValidatorIndex};
 use sp_keystore::{Error as KeystoreError, KeystorePtr};
-use std::{collections::HashMap, iter::FromIterator, time::Duration};
+use std::{collections::HashMap, time::Duration};
 use wasm_timer::{Delay, Instant};
 
 mod metrics;

polkadot/node/network/bitfield-distribution/src/tests.rs

@@ -40,7 +40,7 @@ use sp_core::Pair as PairT;
 use sp_keyring::Sr25519Keyring;
 use sp_keystore::{testing::MemoryKeystore, Keystore, KeystorePtr};
 
-use std::{iter::FromIterator as _, sync::Arc, time::Duration};
+use std::{sync::Arc, time::Duration};
 
 const TIMEOUT: Duration = Duration::from_millis(50);
 macro_rules! launch {

polkadot/node/network/collator-protocol/src/collator_side/mod.rs

@@ -16,7 +16,6 @@
 
 use std::{
 	collections::{HashMap, HashSet},
-	convert::TryInto,
 	time::Duration,
 };
 

polkadot/node/network/collator-protocol/src/validator_side/mod.rs

@@ -20,9 +20,7 @@ use futures::{
 use futures_timer::Delay;
 use std::{
 	collections::{hash_map::Entry, HashMap, HashSet},
-	convert::TryInto,
 	future::Future,
-	iter::FromIterator,
 	time::{Duration, Instant},
 };
 use tokio_util::sync::CancellationToken;

polkadot/node/network/statement-distribution/src/legacy_v1/tests.rs

@@ -55,7 +55,7 @@ use sp_application_crypto::{sr25519::Pair, AppCrypto, Pair as TraitPair};
 use sp_authority_discovery::AuthorityPair;
 use sp_keyring::Sr25519Keyring;
 use sp_keystore::{Keystore, KeystorePtr};
-use std::{iter::FromIterator as _, sync::Arc, time::Duration};
+use std::{sync::Arc, time::Duration};
 use util::reputation::add_reputation;
 
 // Some deterministic genesis hash for protocol names

polkadot/node/subsystem-types/src/messages/network_bridge_event.rs

@@ -14,7 +14,7 @@
 // You should have received a copy of the GNU General Public License
 // along with Polkadot.  If not, see <http://www.gnu.org/licenses/>.
 
-use std::{collections::HashSet, convert::TryFrom};
+use std::collections::HashSet;
 
 pub use sc_network::ReputationChange;
 pub use sc_network_types::PeerId;

polkadot/xcm/src/v3/junction.rs

@@ -26,7 +26,6 @@ use crate::{
 	VersionedLocation,
 };
 use bounded_collections::{BoundedSlice, BoundedVec, ConstU32};
-use core::convert::{TryFrom, TryInto};
 use parity_scale_codec::{self, Decode, Encode, MaxEncodedLen};
 use scale_info::TypeInfo;
 use serde::{Deserialize, Serialize};

polkadot/xcm/src/v3/junctions.rs

@@ -17,7 +17,7 @@
 //! XCM `Junctions`/`InteriorMultiLocation` datatype.
 
 use super::{Junction, MultiLocation, NetworkId};
-use core::{convert::TryFrom, mem, result};
+use core::{mem, result};
 use parity_scale_codec::{Decode, Encode, MaxEncodedLen};
 use scale_info::TypeInfo;
 

polkadot/xcm/src/v3/mod.rs

@@ -29,11 +29,7 @@ use super::{
 use crate::DoubleEncoded;
 use alloc::{vec, vec::Vec};
 use bounded_collections::{parameter_types, BoundedVec};
-use core::{
-	convert::{TryFrom, TryInto},
-	fmt::Debug,
-	result,
-};
+use core::{fmt::Debug, result};
 use derivative::Derivative;
 use parity_scale_codec::{
 	self, decode_vec_with_len, Compact, Decode, Encode, Error as CodecError, Input as CodecInput,

polkadot/xcm/src/v3/multiasset.rs

@@ -42,10 +42,7 @@ use crate::{
 };
 use alloc::{vec, vec::Vec};
 use bounded_collections::{BoundedVec, ConstU32};
-use core::{
-	cmp::Ordering,
-	convert::{TryFrom, TryInto},
-};
+use core::cmp::Ordering;
 use parity_scale_codec::{self as codec, Decode, Encode, MaxEncodedLen};
 use scale_info::TypeInfo;
 

polkadot/xcm/src/v3/multilocation.rs

@@ -20,10 +20,7 @@ use super::{Junction, Junctions};
 use crate::{
 	v2::MultiLocation as OldMultiLocation, v4::Location as NewMultiLocation, VersionedLocation,
 };
-use core::{
-	convert::{TryFrom, TryInto},
-	result,
-};
+use core::result;
 use parity_scale_codec::{Decode, Encode, MaxEncodedLen};
 use scale_info::TypeInfo;
 
@@ -766,7 +763,6 @@ mod tests {
 	#[test]
 	fn conversion_from_other_types_works() {
 		use crate::v2;
-		use core::convert::TryInto;
 
 		fn takes_multilocation<Arg: Into<MultiLocation>>(_arg: Arg) {}
 

polkadot/xcm/src/v4/asset.rs

@@ -34,10 +34,7 @@ use crate::v3::{
 };
 use alloc::{vec, vec::Vec};
 use bounded_collections::{BoundedVec, ConstU32};
-use core::{
-	cmp::Ordering,
-	convert::{TryFrom, TryInto},
-};
+use core::cmp::Ordering;
 use parity_scale_codec::{self as codec, Decode, Encode, MaxEncodedLen};
 use scale_info::TypeInfo;
 

polkadot/xcm/src/v4/junction.rs

@@ -23,7 +23,6 @@ use crate::{
 	VersionedLocation,
 };
 use bounded_collections::{BoundedSlice, BoundedVec, ConstU32};
-use core::convert::TryFrom;
 use parity_scale_codec::{self, Decode, Encode, MaxEncodedLen};
 use scale_info::TypeInfo;
 use serde::{Deserialize, Serialize};

polkadot/xcm/src/v4/junctions.rs

@@ -18,7 +18,7 @@
 
 use super::{Junction, Location, NetworkId};
 use alloc::sync::Arc;
-use core::{convert::TryFrom, mem, ops::Range, result};
+use core::{mem, ops::Range, result};
 use parity_scale_codec::{Decode, Encode, MaxEncodedLen};
 use scale_info::TypeInfo;
 

polkadot/xcm/src/v4/location.rs

@@ -18,10 +18,7 @@
 
 use super::{traits::Reanchorable, Junction, Junctions};
 use crate::{v3::MultiLocation as OldLocation, VersionedLocation};
-use core::{
-	convert::{TryFrom, TryInto},
-	result,
-};
+use core::result;
 use parity_scale_codec::{Decode, Encode, MaxEncodedLen};
 use scale_info::TypeInfo;
 
@@ -723,7 +720,6 @@ mod tests {
 	#[test]
 	fn conversion_from_other_types_works() {
 		use crate::v3;
-		use core::convert::TryInto;
 
 		fn takes_location<Arg: Into<Location>>(_arg: Arg) {}
 

polkadot/xcm/src/v4/mod.rs

@@ -24,11 +24,7 @@ use super::v3::{
 use crate::DoubleEncoded;
 use alloc::{vec, vec::Vec};
 use bounded_collections::{parameter_types, BoundedVec};
-use core::{
-	convert::{TryFrom, TryInto},
-	fmt::Debug,
-	result,
-};
+use core::{fmt::Debug, result};
 use derivative::Derivative;
 use parity_scale_codec::{
 	self, decode_vec_with_len, Compact, Decode, Encode, Error as CodecError, Input as CodecInput,

polkadot/xcm/xcm-builder/src/tests/mod.rs

@@ -15,7 +15,6 @@
 // along with Polkadot.  If not, see <http://www.gnu.org/licenses/>.
 
 use super::{test_utils::*, *};
-use core::convert::TryInto;
 use frame_support::{
 	assert_err,
 	traits::{ConstU32, ContainsPair, ProcessMessageError},

substrate/client/consensus/grandpa/rpc/src/lib.rs

@@ -125,7 +125,7 @@ where
 #[cfg(test)]
 mod tests {
 	use super::*;
-	use std::{collections::HashSet, convert::TryInto, sync::Arc};
+	use std::{collections::HashSet, sync::Arc};
 
 	use jsonrpsee::{core::EmptyServerParams as EmptyParams, types::SubscriptionId, RpcModule};
 	use parity_scale_codec::{Decode, Encode};

substrate/client/consensus/grandpa/src/environment.rs

@@ -18,7 +18,6 @@
 
 use std::{
 	collections::{BTreeMap, HashMap},
-	iter::FromIterator,
 	marker::PhantomData,
 	pin::Pin,
 	sync::Arc,

substrate/client/mixnet/Cargo.toml

@@ -4,7 +4,7 @@ name = "sc-mixnet"
 version = "0.4.0"
 license = "GPL-3.0-or-later WITH Classpath-exception-2.0"
 authors = ["Parity Technologies <admin@parity.io>"]
-edition = "2021"
+edition.workspace = true
 homepage = "https://substrate.io"
 repository = "https://github.com/paritytech/substrate/"
 readme = "README.md"

substrate/client/network/src/protocol/notifications/upgrade/collec.rs

@@ -19,7 +19,6 @@
 use futures::prelude::*;
 use libp2p::core::upgrade::{InboundUpgrade, ProtocolName, UpgradeInfo};
 use std::{
-	iter::FromIterator,
 	pin::Pin,
 	task::{Context, Poll},
 	vec,

substrate/frame/Cargo.toml

@@ -2,7 +2,7 @@
 name = "polkadot-sdk-frame"
 version = "0.1.0"
 authors = ["Parity Technologies <admin@parity.io>"]
-edition = "2021"
+edition.workspace = true
 license = "Apache-2.0"
 homepage = "paritytech.github.io"
 repository.workspace = true

substrate/frame/alliance/src/benchmarking.rs

@@ -19,11 +19,7 @@
 
 #![cfg(feature = "runtime-benchmarks")]
 
-use core::{
-	cmp,
-	convert::{TryFrom, TryInto},
-	mem::size_of,
-};
+use core::{cmp, mem::size_of};
 use sp_runtime::traits::{Bounded, Hash, StaticLookup};
 
 use frame_benchmarking::{account, v2::*, BenchmarkError};

substrate/frame/alliance/src/lib.rs

@@ -101,7 +101,7 @@ use sp_runtime::{
 	traits::{Dispatchable, Saturating, StaticLookup, Zero},
 	DispatchError, RuntimeDebug,
 };
-use sp_std::{convert::TryInto, prelude::*};
+use sp_std::prelude::*;
 
 use frame_support::{
 	dispatch::{DispatchResult, DispatchResultWithPostInfo, GetDispatchInfo, PostDispatchInfo},

substrate/frame/alliance/src/mock.rs

@@ -17,7 +17,6 @@
 
 //! Test utilities
 
-use core::convert::{TryFrom, TryInto};
 pub use sp_core::H256;
 use sp_runtime::traits::Hash;
 pub use sp_runtime::{

substrate/frame/alliance/src/types.rs

@@ -19,7 +19,7 @@ use codec::{Decode, Encode, MaxEncodedLen};
 use frame_support::{traits::ConstU32, BoundedVec};
 use scale_info::TypeInfo;
 use sp_runtime::RuntimeDebug;
-use sp_std::{convert::TryInto, prelude::*};
+use sp_std::prelude::*;
 
 /// A Multihash instance that only supports the basic functionality and no hashing.
 #[derive(

substrate/frame/examples/frame-crate/Cargo.toml

@@ -2,7 +2,7 @@
 name = "pallet-example-frame-crate"
 version = "0.0.1"
 authors = ["Parity Technologies <admin@parity.io>"]
-edition = "2021"
+edition.workspace = true
 license = "MIT-0"
 homepage = "https://substrate.io"
 repository.workspace = true

substrate/frame/mixnet/Cargo.toml

@@ -4,7 +4,7 @@ name = "pallet-mixnet"
 version = "0.4.0"
 license = "Apache-2.0"
 authors = ["Parity Technologies <admin@parity.io>"]
-edition = "2021"
+edition.workspace = true
 homepage = "https://substrate.io"
 repository = "https://github.com/paritytech/substrate/"
 readme = "README.md"

substrate/frame/node-authorization/src/lib.rs

@@ -47,7 +47,7 @@ pub mod weights;
 pub use pallet::*;
 use sp_core::OpaquePeerId as PeerId;
 use sp_runtime::traits::StaticLookup;
-use sp_std::{collections::btree_set::BTreeSet, iter::FromIterator, prelude::*};
+use sp_std::{collections::btree_set::BTreeSet, prelude::*};
 pub use weights::WeightInfo;
 
 type AccountIdLookupOf<T> = <<T as frame_system::Config>::Lookup as StaticLookup>::Source;

substrate/frame/safe-mode/src/lib.rs

@@ -79,7 +79,6 @@ pub mod mock;
 mod tests;
 pub mod weights;
 
-use core::convert::TryInto;
 use frame_support::{
 	defensive_assert,
 	pallet_prelude::*,

substrate/frame/sassafras/Cargo.toml

@@ -2,7 +2,7 @@
 name = "pallet-sassafras"
 version = "0.3.5-dev"
 authors = ["Parity Technologies <admin@parity.io>"]
-edition = "2021"
+edition.workspace = true
 license = "Apache-2.0"
 homepage = "https://substrate.io"
 repository = "https://github.com/paritytech/substrate/"

substrate/frame/transaction-payment/rpc/src/lib.rs

@@ -17,7 +17,7 @@
 
 //! RPC interface for the transaction payment pallet.
 
-use std::{convert::TryInto, sync::Arc};
+use std::sync::Arc;
 
 use codec::{Codec, Decode};
 use jsonrpsee::{

substrate/frame/tx-pause/src/lib.rs

@@ -87,7 +87,7 @@ use frame_support::{
 };
 use frame_system::pallet_prelude::*;
 use sp_runtime::{traits::Dispatchable, DispatchResult};
-use sp_std::{convert::TryInto, prelude::*};
+use sp_std::prelude::*;
 
 pub use pallet::*;
 pub use weights::*;

substrate/primitives/consensus/sassafras/Cargo.toml

@@ -3,7 +3,7 @@ name = "sp-consensus-sassafras"
 version = "0.3.4-dev"
 authors.workspace = true
 description = "Primitives for Sassafras consensus"
-edition = "2021"
+edition.workspace = true
 license = "Apache-2.0"
 homepage = "https://substrate.io"
 repository = "https://github.com/paritytech/polkadot-sdk/"

substrate/primitives/core/fuzz/Cargo.toml

@@ -2,6 +2,7 @@
 name = "sp-core-fuzz"
 version = "0.0.0"
 publish = false
+edition.workspace = true
 
 [lints]
 workspace = true

substrate/primitives/mixnet/Cargo.toml

@@ -4,7 +4,7 @@ name = "sp-mixnet"
 version = "0.4.0"
 license = "Apache-2.0"
 authors = ["Parity Technologies <admin@parity.io>"]
-edition = "2021"
+edition.workspace = true
 homepage = "https://substrate.io"
 repository = "https://github.com/paritytech/substrate/"
 readme = "README.md"

substrate/primitives/state-machine/src/basic.rs

@@ -33,7 +33,6 @@ use sp_trie::{empty_child_trie_root, LayoutV0, LayoutV1, TrieConfiguration};
 use std::{
 	any::{Any, TypeId},
 	collections::BTreeMap,
-	iter::FromIterator,
 };
 
 /// Simple Map-based Externalities impl.