sp-std -> core (paritytech#3199)

First in a series of PRs that reduces our use of sp-std with a view to
deprecating it.

This is just looking at /substrate and moving some of the references
from `sp-std` to `core`.
These particular changes should be uncontroversial.

Where macros are used `::core` should be used to remove any ambiguity.

part of paritytech#2101

substrate/frame/alliance/src/benchmarking.rs

@@ -19,13 +19,12 @@
 
 #![cfg(feature = "runtime-benchmarks")]
 
-use sp_runtime::traits::{Bounded, Hash, StaticLookup};
-use sp_std::{
+use core::{
 	cmp,
 	convert::{TryFrom, TryInto},
 	mem::size_of,
-	prelude::*,
 };
+use sp_runtime::traits::{Bounded, Hash, StaticLookup};
 
 use frame_benchmarking::{account, impl_benchmark_test_suite, v2::*, BenchmarkError};
 use frame_support::traits::{EnsureOrigin, Get, UnfilteredDispatchable};

substrate/frame/alliance/src/mock.rs

@@ -17,13 +17,13 @@
 
 //! Test utilities
 
+use core::convert::{TryFrom, TryInto};
 pub use sp_core::H256;
 use sp_runtime::traits::Hash;
 pub use sp_runtime::{
 	traits::{BlakeTwo256, IdentifyAccount, Lazy, Verify},
 	BuildStorage,
 };
-use sp_std::convert::{TryFrom, TryInto};
 
 pub use frame_support::{
 	assert_noop, assert_ok, derive_impl, ord_parameter_types, parameter_types,

substrate/frame/asset-conversion/src/mock.rs

@@ -19,6 +19,7 @@
 
 use super::*;
 use crate as pallet_asset_conversion;
+use core::default::Default;
 use frame_support::{
 	construct_runtime, derive_impl,
 	instances::{Instance1, Instance2},
@@ -39,7 +40,6 @@ use sp_runtime::{
 	traits::{AccountIdConversion, BlakeTwo256, IdentityLookup},
 	BuildStorage,
 };
-use sp_std::default::Default;
 
 type Block = frame_system::mocking::MockBlock<Test>;
 

substrate/frame/asset-conversion/src/types.rs

@@ -17,8 +17,8 @@
 
 use super::*;
 use codec::{Decode, Encode, MaxEncodedLen};
+use core::marker::PhantomData;
 use scale_info::TypeInfo;
-use sp_std::marker::PhantomData;
 
 /// Represents a swap path with associated asset amounts indicating how much of the asset needs to
 /// be deposited to get the following asset's amount withdrawn (this is inclusive of fees).

substrate/frame/assets/src/extra_mutator.rs

@@ -38,7 +38,7 @@ impl<T: Config<I>, I: 'static> Drop for ExtraMutator<T, I> {
 	}
 }
 
-impl<T: Config<I>, I: 'static> sp_std::ops::Deref for ExtraMutator<T, I> {
+impl<T: Config<I>, I: 'static> core::ops::Deref for ExtraMutator<T, I> {
 	type Target = T::Extra;
 	fn deref(&self) -> &T::Extra {
 		match self.pending {
@@ -48,7 +48,7 @@ impl<T: Config<I>, I: 'static> sp_std::ops::Deref for ExtraMutator<T, I> {
 	}
 }
 
-impl<T: Config<I>, I: 'static> sp_std::ops::DerefMut for ExtraMutator<T, I> {
+impl<T: Config<I>, I: 'static> core::ops::DerefMut for ExtraMutator<T, I> {
 	fn deref_mut(&mut self) -> &mut T::Extra {
 		if self.pending.is_none() {
 			self.pending = Some(self.original.clone());
@@ -60,7 +60,7 @@ impl<T: Config<I>, I: 'static> sp_std::ops::DerefMut for ExtraMutator<T, I> {
 impl<T: Config<I>, I: 'static> ExtraMutator<T, I> {
 	pub(super) fn maybe_new(
 		id: T::AssetId,
-		who: impl sp_std::borrow::Borrow<T::AccountId>,
+		who: impl core::borrow::Borrow<T::AccountId>,
 	) -> Option<ExtraMutator<T, I>> {
 		if let Some(a) = Account::<T, I>::get(&id, who.borrow()) {
 			Some(ExtraMutator::<T, I> {

substrate/frame/assets/src/migration.rs

@@ -64,7 +64,7 @@ pub mod v1 {
 		}
 	}
 
-	pub struct MigrateToV1<T>(sp_std::marker::PhantomData<T>);
+	pub struct MigrateToV1<T>(core::marker::PhantomData<T>);
 	impl<T: Config> OnRuntimeUpgrade for MigrateToV1<T> {
 		fn on_runtime_upgrade() -> Weight {
 			let current_version = Pallet::<T>::current_storage_version();

substrate/frame/assets/src/types.rs

@@ -123,7 +123,7 @@ where
 			return None
 		}
 		if let ExistenceReason::DepositHeld(deposit) =
-			sp_std::mem::replace(self, ExistenceReason::DepositRefunded)
+			core::mem::replace(self, ExistenceReason::DepositRefunded)
 		{
 			Some(deposit)
 		} else {
@@ -136,7 +136,7 @@ where
 			return None
 		}
 		if let ExistenceReason::DepositFrom(depositor, deposit) =
-			sp_std::mem::replace(self, ExistenceReason::DepositRefunded)
+			core::mem::replace(self, ExistenceReason::DepositRefunded)
 		{
 			Some((depositor, deposit))
 		} else {

substrate/frame/atomic-swap/src/lib.rs

@@ -43,6 +43,10 @@
 mod tests;
 
 use codec::{Decode, Encode};
+use core::{
+	marker::PhantomData,
+	ops::{Deref, DerefMut},
+};
 use frame_support::{
 	dispatch::DispatchResult,
 	pallet_prelude::MaxEncodedLen,
@@ -54,11 +58,6 @@ use frame_system::pallet_prelude::BlockNumberFor;
 use scale_info::TypeInfo;
 use sp_io::hashing::blake2_256;
 use sp_runtime::RuntimeDebug;
-use sp_std::{
-	marker::PhantomData,
-	ops::{Deref, DerefMut},
-	prelude::*,
-};
 
 /// Pending atomic swap operation.
 #[derive(Clone, Eq, PartialEq, RuntimeDebugNoBound, Encode, Decode, TypeInfo, MaxEncodedLen)]

substrate/frame/aura/src/migrations.rs

@@ -19,7 +19,7 @@
 
 use frame_support::{pallet_prelude::*, traits::Get, weights::Weight};
 
-struct __LastTimestamp<T>(sp_std::marker::PhantomData<T>);
+struct __LastTimestamp<T>(core::marker::PhantomData<T>);
 impl<T: RemoveLastTimestamp> frame_support::traits::StorageInstance for __LastTimestamp<T> {
 	fn pallet_prefix() -> &'static str {
 		T::PalletPrefix::get()

substrate/frame/babe/src/randomness.rs

@@ -51,7 +51,7 @@ use sp_runtime::traits::{Hash, One, Saturating};
 ///
 /// Adversaries should not possess many block production slots towards the beginning or
 /// end of every epoch, but they possess some influence over when they possess more slots.
-pub struct RandomnessFromTwoEpochsAgo<T>(sp_std::marker::PhantomData<T>);
+pub struct RandomnessFromTwoEpochsAgo<T>(core::marker::PhantomData<T>);
 
 /// Randomness usable by on-chain code that **does not depend** upon finality and takes
 /// action based upon on-chain commitments made during the previous epoch.
@@ -79,7 +79,7 @@ pub struct RandomnessFromTwoEpochsAgo<T>(sp_std::marker::PhantomData<T>);
 /// As an example usage, we determine parachain auctions ending times in Polkadot using
 /// `RandomnessFromOneEpochAgo` because it reduces bias from `ParentBlockRandomness` and
 /// does not require the extra finality delay of `RandomnessFromTwoEpochsAgo`.
-pub struct RandomnessFromOneEpochAgo<T>(sp_std::marker::PhantomData<T>);
+pub struct RandomnessFromOneEpochAgo<T>(core::marker::PhantomData<T>);
 
 /// Randomness produced semi-freshly with each block, but inherits limitations of
 /// `RandomnessFromTwoEpochsAgo` from which it derives.
@@ -119,7 +119,7 @@ pub struct RandomnessFromOneEpochAgo<T>(sp_std::marker::PhantomData<T>);
 /// instead you are using this randomness externally, i.e. after block execution, then
 /// this randomness will be provided by the "current" block (this stems from the fact that
 /// we process VRF outputs on block execution finalization, i.e. `on_finalize`).
-pub struct ParentBlockRandomness<T>(sp_std::marker::PhantomData<T>);
+pub struct ParentBlockRandomness<T>(core::marker::PhantomData<T>);
 
 /// Randomness produced semi-freshly with each block, but inherits limitations of
 /// `RandomnessFromTwoEpochsAgo` from which it derives.
@@ -128,7 +128,7 @@ pub struct ParentBlockRandomness<T>(sp_std::marker::PhantomData<T>);
 #[deprecated(note = "Should not be relied upon for correctness, \
 					 will not provide fresh randomness for the current block. \
 					 Please use `ParentBlockRandomness` instead.")]
-pub struct CurrentBlockRandomness<T>(sp_std::marker::PhantomData<T>);
+pub struct CurrentBlockRandomness<T>(core::marker::PhantomData<T>);
 
 impl<T: Config> RandomnessT<T::Hash, BlockNumberFor<T>> for RandomnessFromTwoEpochsAgo<T> {
 	fn random(subject: &[u8]) -> (T::Hash, BlockNumberFor<T>) {

substrate/frame/bounties/src/migrations/v4.rs

@@ -15,6 +15,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+use core::str;
 use frame_support::{
 	storage::{generator::StorageValue, StoragePrefixedMap},
 	traits::{
@@ -25,7 +26,6 @@ use frame_support::{
 };
 use sp_core::hexdisplay::HexDisplay;
 use sp_io::{hashing::twox_128, storage};
-use sp_std::str;
 
 use crate as pallet_bounties;
 

substrate/frame/collective/src/benchmarking.rs

@@ -20,8 +20,8 @@
 use super::*;
 use crate::Pallet as Collective;
 
+use core::mem::size_of;
 use sp_runtime::traits::Bounded;
-use sp_std::mem::size_of;
 
 use frame_benchmarking::v1::{account, benchmarks_instance_pallet, whitelisted_caller};
 use frame_system::{

substrate/frame/contracts/src/gas.rs

@@ -16,14 +16,14 @@
 // limitations under the License.
 
 use crate::{exec::ExecError, Config, Error};
+use core::marker::PhantomData;
 use frame_support::{
 	dispatch::{DispatchErrorWithPostInfo, DispatchResultWithPostInfo, PostDispatchInfo},
 	weights::Weight,
 	DefaultNoBound,
 };
 use sp_core::Get;
 use sp_runtime::{traits::Zero, DispatchError};
-use sp_std::marker::PhantomData;
 
 #[cfg(test)]
 use std::{any::Any, fmt::Debug};

substrate/frame/contracts/src/migration/v10.rs

@@ -25,7 +25,10 @@ use crate::{
 	CodeHash, Config, Pallet, TrieId, Weight, LOG_TARGET,
 };
 use codec::{Decode, Encode};
-use core::cmp::{max, min};
+use core::{
+	cmp::{max, min},
+	ops::Deref,
+};
 use frame_support::{
 	pallet_prelude::*,
 	storage_alias,
@@ -42,7 +45,7 @@ use sp_runtime::{
 	traits::{Hash, TrailingZeroInput, Zero},
 	Perbill, Saturating,
 };
-use sp_std::{ops::Deref, prelude::*};
+use sp_std::prelude::*;
 
 mod old {
 	use super::*;

substrate/frame/contracts/src/schedule.rs

@@ -21,11 +21,11 @@
 use crate::{weights::WeightInfo, Config};
 
 use codec::{Decode, Encode};
+use core::marker::PhantomData;
 use frame_support::{weights::Weight, DefaultNoBound};
 use scale_info::TypeInfo;
 #[cfg(feature = "std")]
 use serde::{Deserialize, Serialize};
-use sp_std::marker::PhantomData;
 
 /// Definition of the cost schedule and other parameterizations for the wasm vm.
 ///

substrate/frame/core-fellowship/src/tests/unit.rs

@@ -19,6 +19,7 @@
 
 use std::collections::BTreeMap;
 
+use core::cell::RefCell;
 use frame_support::{
 	assert_noop, assert_ok, derive_impl, ord_parameter_types,
 	pallet_prelude::Weight,
@@ -27,7 +28,6 @@ use frame_support::{
 };
 use frame_system::EnsureSignedBy;
 use sp_runtime::{traits::TryMorphInto, BuildStorage, DispatchError, DispatchResult};
-use sp_std::cell::RefCell;
 
 use crate as pallet_core_fellowship;
 use crate::*;

substrate/frame/democracy/src/conviction.rs

@@ -19,12 +19,12 @@
 
 use crate::types::Delegations;
 use codec::{Decode, Encode, MaxEncodedLen};
+use core::result::Result;
 use scale_info::TypeInfo;
 use sp_runtime::{
 	traits::{Bounded, CheckedDiv, CheckedMul, Zero},
 	RuntimeDebug,
 };
-use sp_std::{prelude::*, result::Result};
 
 /// A value denoting the strength of conviction of a vote.
 #[derive(

substrate/frame/democracy/src/migrations/v1.rs

@@ -54,7 +54,7 @@ pub mod v1 {
 	use super::*;
 
 	/// Migration for translating bare `Hash`es into `Bounded<Call>`s.
-	pub struct Migration<T>(sp_std::marker::PhantomData<T>);
+	pub struct Migration<T>(core::marker::PhantomData<T>);
 
 	impl<T: Config + frame_system::Config<Hash = H256>> OnRuntimeUpgrade for Migration<T> {
 		#[cfg(feature = "try-runtime")]

substrate/frame/democracy/src/vote_threshold.rs

@@ -19,11 +19,11 @@
 
 use crate::Tally;
 use codec::{Decode, Encode, MaxEncodedLen};
+use core::ops::{Add, Div, Mul, Rem};
 use scale_info::TypeInfo;
 #[cfg(feature = "std")]
 use serde::{Deserialize, Serialize};
 use sp_runtime::traits::{IntegerSquareRoot, Zero};
-use sp_std::ops::{Add, Div, Mul, Rem};
 
 /// A means of determining if a vote is past pass threshold.
 #[derive(

substrate/frame/election-provider-multi-phase/src/benchmarking.rs

@@ -496,7 +496,7 @@ frame_benchmarking::benchmarks! {
 				let (_, stake, _) = voters[*idx];
 				stake
 			}).unwrap_or_default();
-			sp_std::cmp::Reverse(stake)
+			core::cmp::Reverse(stake)
 		});
 
 		let mut index_assignments = assignments

substrate/frame/election-provider-support/src/tests.rs

@@ -29,7 +29,7 @@ mod solution_type {
 	// these need to come from the same dev-dependency `frame-election-provider-support`, not from
 	// the crate.
 	use crate::{generate_solution_type, Assignment, Error as NposError, NposSolution};
-	use sp_std::fmt::Debug;
+	use core::fmt::Debug;
 
 	#[allow(dead_code)]
 	mod __private {

substrate/frame/examples/basic/src/lib.rs

@@ -54,6 +54,7 @@
 #![cfg_attr(not(feature = "std"), no_std)]
 
 use codec::{Decode, Encode};
+use core::marker::PhantomData;
 use frame_support::{
 	dispatch::{ClassifyDispatch, DispatchClass, DispatchResult, Pays, PaysFee, WeighData},
 	traits::IsSubType,
@@ -68,7 +69,7 @@ use sp_runtime::{
 		InvalidTransaction, TransactionValidity, TransactionValidityError, ValidTransaction,
 	},
 };
-use sp_std::{marker::PhantomData, prelude::*};
+use sp_std::vec::Vec;
 
 // Re-export pallet items so that they can be accessed from the crate namespace.
 pub use pallet::*;
@@ -485,8 +486,8 @@ impl<T: Config> Pallet<T> {
 #[scale_info(skip_type_params(T))]
 pub struct WatchDummy<T: Config + Send + Sync>(PhantomData<T>);
 
-impl<T: Config + Send + Sync> sp_std::fmt::Debug for WatchDummy<T> {
-	fn fmt(&self, f: &mut sp_std::fmt::Formatter) -> sp_std::fmt::Result {
+impl<T: Config + Send + Sync> core::fmt::Debug for WatchDummy<T> {
+	fn fmt(&self, f: &mut core::fmt::Formatter) -> core::fmt::Result {
 		write!(f, "WatchDummy")
 	}
 }
@@ -501,7 +502,7 @@ where
 	type AdditionalSigned = ();
 	type Pre = ();
 
-	fn additional_signed(&self) -> sp_std::result::Result<(), TransactionValidityError> {
+	fn additional_signed(&self) -> core::result::Result<(), TransactionValidityError> {
 		Ok(())
 	}
 

substrate/frame/grandpa/src/migrations.rs

@@ -35,7 +35,7 @@ mod v5;
 /// This migration should be added with a runtime upgrade that introduces the
 /// `MaxSetIdSessionEntries` constant to the pallet (although it could also be
 /// done later on).
-pub struct CleanupSetIdSessionMap<T>(sp_std::marker::PhantomData<T>);
+pub struct CleanupSetIdSessionMap<T>(core::marker::PhantomData<T>);
 impl<T: Config> OnRuntimeUpgrade for CleanupSetIdSessionMap<T> {
 	fn on_runtime_upgrade() -> Weight {
 		// NOTE: since this migration will loop over all stale entries in the

substrate/frame/im-online/src/migration.rs

@@ -56,7 +56,7 @@ pub mod v1 {
 	use super::*;
 
 	/// Simple migration that replaces `ReceivedHeartbeats` values with `true`.
-	pub struct Migration<T>(sp_std::marker::PhantomData<T>);
+	pub struct Migration<T>(core::marker::PhantomData<T>);
 
 	impl<T: Config> OnRuntimeUpgrade for Migration<T> {
 		#[cfg(feature = "try-runtime")]