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`)

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::*;