Remove As trait bound from Currency::Balance (#2205)

* remove As<64> bond

* Currency trait refactor

* bump spec version

substrate/node/runtime/src/lib.rs

@@ -58,8 +58,8 @@ pub const VERSION: RuntimeVersion = RuntimeVersion {
 	spec_name: create_runtime_str!("node"),
 	impl_name: create_runtime_str!("substrate-node"),
 	authoring_version: 10,
-	spec_version: 72,
-	impl_version: 74,
+	spec_version: 73,
+	impl_version: 73,
 	apis: RUNTIME_API_VERSIONS,
 };
 

substrate/srml/balances/src/lib.rs

@@ -167,7 +167,7 @@ pub use self::imbalances::{PositiveImbalance, NegativeImbalance};
 
 pub trait Subtrait<I: Instance = DefaultInstance>: system::Trait {
 	/// The balance of an account.
-	type Balance: Parameter + Member + SimpleArithmetic + Codec + Default + Copy + As<usize> + As<u64> + MaybeSerializeDebug;
+	type Balance: Parameter + Member + SimpleArithmetic + Codec + Default + Copy + MaybeSerializeDebug;
 
 	/// A function that is invoked when the free-balance has fallen below the existential deposit and
 	/// has been reduced to zero.
@@ -181,7 +181,7 @@ pub trait Subtrait<I: Instance = DefaultInstance>: system::Trait {
 
 pub trait Trait<I: Instance = DefaultInstance>: system::Trait {
 	/// The balance of an account.
-	type Balance: Parameter + Member + SimpleArithmetic + Codec + Default + Copy + As<usize> + As<u64> + MaybeSerializeDebug;
+	type Balance: Parameter + Member + SimpleArithmetic + Codec + Default + Copy + MaybeSerializeDebug;
 
 	/// A function that is invoked when the free-balance has fallen below the existential deposit and
 	/// has been reduced to zero.

substrate/srml/staking/src/lib.rs

@@ -894,8 +894,10 @@ impl<T: Trait> Module<T> {
 				Self::reward_validator(v, reward);
 			}
 			Self::deposit_event(RawEvent::Reward(reward));
-			let total_minted = reward * <BalanceOf<T> as As<usize>>::sa(validators.len());
-			let total_rewarded_stake = Self::slot_stake() * <BalanceOf<T> as As<usize>>::sa(validators.len());
+			let len = validators.len() as u64; // validators length can never overflow u64
+			let len = BalanceOf::<T>::sa(len);
+			let total_minted = reward * len;
+			let total_rewarded_stake = Self::slot_stake() * len;
 			T::OnRewardMinted::on_dilution(total_minted, total_rewarded_stake);
 		}
 

substrate/srml/support/src/traits.rs

@@ -19,7 +19,7 @@
 use crate::rstd::result;
 use crate::codec::{Codec, Encode, Decode};
 use crate::runtime_primitives::traits::{
-	MaybeSerializeDebug, SimpleArithmetic, As
+	MaybeSerializeDebug, SimpleArithmetic
 };
 
 /// The account with the given id was killed.
@@ -195,7 +195,7 @@ pub enum SignedImbalance<B, P: Imbalance<B>>{
 impl<
 	P: Imbalance<B, Opposite=N>,
 	N: Imbalance<B, Opposite=P>,
-	B: SimpleArithmetic + As<usize> + As<u64> + Codec + Copy + MaybeSerializeDebug + Default,
+	B: SimpleArithmetic + Codec + Copy + MaybeSerializeDebug + Default,
 > SignedImbalance<B, P> {
 	pub fn zero() -> Self {
 		SignedImbalance::Positive(P::zero())
@@ -230,7 +230,7 @@ impl<
 /// Abstraction over a fungible assets system.
 pub trait Currency<AccountId> {
 	/// The balance of an account.
-	type Balance: SimpleArithmetic + As<usize> + As<u64> + Codec + Copy + MaybeSerializeDebug + Default;
+	type Balance: SimpleArithmetic + Codec + Copy + MaybeSerializeDebug + Default;
 
 	/// The opaque token type for an imbalance. This is returned by unbalanced operations
 	/// and must be dealt with. It may be dropped but cannot be cloned.