Add support for tuples in OnNewAccount hook (#2765)

* Add support for tuples in `OnNewAccount` hook

* Bump impl version

* Use `for_each_tuple` with `OnNewAccount` hook

* Update `OnFreeBalanceZero` to also use `for_each_tuple`

* Fix spelling/typo

* Bump spec again

* Update srml/support/src/traits.rs

Co-Authored-By: Bastian Köcher <bkchr@users.noreply.github.com>

* Update srml/system/src/lib.rs

Co-Authored-By: Bastian Köcher <bkchr@users.noreply.github.com>

substrate/node/runtime/src/lib.rs

@@ -59,7 +59,7 @@ pub const VERSION: RuntimeVersion = RuntimeVersion {
 	impl_name: create_runtime_str!("substrate-node"),
 	authoring_version: 10,
 	spec_version: 90,
-	impl_version: 90,
+	impl_version: 91,
 	apis: RUNTIME_API_VERSIONS,
 };
 

substrate/srml/support/src/traits.rs

@@ -24,6 +24,8 @@ use crate::runtime_primitives::traits::{
 	MaybeSerializeDebug, SimpleArithmetic
 };
 
+use super::for_each_tuple;
+
 /// New trait for querying a single fixed value from a type.
 pub trait Get<T> {
 	/// Return a constant value.
@@ -36,20 +38,24 @@ pub trait OnFreeBalanceZero<AccountId> {
 	fn on_free_balance_zero(who: &AccountId);
 }
 
-impl<AccountId> OnFreeBalanceZero<AccountId> for () {
-	fn on_free_balance_zero(_who: &AccountId) {}
-}
-impl<
-	AccountId,
-	X: OnFreeBalanceZero<AccountId>,
-	Y: OnFreeBalanceZero<AccountId>,
-> OnFreeBalanceZero<AccountId> for (X, Y) {
-	fn on_free_balance_zero(who: &AccountId) {
-		X::on_free_balance_zero(who);
-		Y::on_free_balance_zero(who);
+macro_rules! impl_on_free_balance_zero {
+	() => (
+		impl<AccountId> OnFreeBalanceZero<AccountId> for () {
+			fn on_free_balance_zero(_: &AccountId) {}
+		}
+	);
+
+	( $($t:ident)* ) => {
+		impl<AccountId, $($t: OnFreeBalanceZero<AccountId>),*> OnFreeBalanceZero<AccountId> for ($($t,)*) {
+			fn on_free_balance_zero(who: &AccountId) {
+				$($t::on_free_balance_zero(who);)*
+			}
+		}
 	}
 }
 
+for_each_tuple!(impl_on_free_balance_zero);
+
 /// Trait for a hook to get called when some balance has been minted, causing dilution.
 pub trait OnDilution<Balance> {
 	/// Some `portion` of the total balance just "grew" by `minted`. `portion` is the pre-growth

substrate/srml/system/src/lib.rs

@@ -85,7 +85,7 @@ use primitives::traits::Zero;
 use substrate_primitives::storage::well_known_keys;
 use srml_support::{
 	storage, decl_module, decl_event, decl_storage, StorageDoubleMap, StorageValue,
-	StorageMap, Parameter,
+	StorageMap, Parameter, for_each_tuple,
 };
 use safe_mix::TripletMix;
 use parity_codec::{Encode, Decode};
@@ -102,10 +102,24 @@ pub trait OnNewAccount<AccountId> {
 	fn on_new_account(who: &AccountId);
 }
 
-impl<AccountId> OnNewAccount<AccountId> for () {
-	fn on_new_account(_who: &AccountId) {}
+macro_rules! impl_on_new_account {
+	() => (
+		impl<AccountId> OnNewAccount<AccountId> for () {
+			fn on_new_account(_: &AccountId) {}
+		}
+	);
+
+	( $($t:ident)* ) => {
+		impl<AccountId, $($t: OnNewAccount<AccountId>),*> OnNewAccount<AccountId> for ($($t,)*) {
+			fn on_new_account(who: &AccountId) {
+				$($t::on_new_account(who);)*
+			}
+		}
+	}
 }
 
+for_each_tuple!(impl_on_new_account);
+
 /// Determiner to say whether a given account is unused.
 pub trait IsDeadAccount<AccountId> {
 	/// Is the given account dead?