Ensure correct variant count in Runtime[Hold/Freeze]Reason

substrate/bin/node/runtime/src/lib.rs

@@ -512,6 +512,8 @@ parameter_types! {
 }
 
 impl pallet_balances::Config for Runtime {
+	type RuntimeHoldReason = RuntimeHoldReason;
+	type RuntimeFreezeReason = RuntimeFreezeReason;
 	type MaxLocks = MaxLocks;
 	type MaxReserves = MaxReserves;
 	type ReserveIdentifier = [u8; 8];
@@ -523,7 +525,6 @@ impl pallet_balances::Config for Runtime {
 	type WeightInfo = pallet_balances::weights::SubstrateWeight<Runtime>;
 	type FreezeIdentifier = RuntimeFreezeReason;
 	type MaxFreezes = ConstU32<1>;
-	type RuntimeHoldReason = RuntimeHoldReason;
 	type MaxHolds = ConstU32<2>;
 }
 

substrate/frame/balances/src/lib.rs

@@ -207,7 +207,7 @@ pub mod pallet {
 	use super::*;
 	use frame_support::{
 		pallet_prelude::*,
-		traits::{fungible::Credit, tokens::Precision},
+		traits::{fungible::Credit, tokens::Precision, VariantCount},
 	};
 	use frame_system::pallet_prelude::*;
 
@@ -229,6 +229,8 @@ pub mod pallet {
 			type RuntimeEvent = ();
 			#[inject_runtime_type]
 			type RuntimeHoldReason = ();
+			#[inject_runtime_type]
+			type RuntimeFreezeReason = ();
 
 			type Balance = u64;
 			type ExistentialDeposit = ConstU64<1>;
@@ -256,7 +258,11 @@ pub mod pallet {
 
 		/// The overarching hold reason.
 		#[pallet::no_default_bounds]
-		type RuntimeHoldReason: Parameter + Member + MaxEncodedLen + Copy;
+		type RuntimeHoldReason: Parameter + Member + MaxEncodedLen + Copy + VariantCount;
+
+		/// The overarching freeze reason.
+		#[pallet::no_default_bounds]
+		type RuntimeFreezeReason: VariantCount;
 
 		/// Weight information for extrinsics in this pallet.
 		type WeightInfo: WeightInfo;
@@ -544,6 +550,16 @@ pub mod pallet {
 				!<T as Config<I>>::ExistentialDeposit::get().is_zero(),
 				"The existential deposit must be greater than zero!"
 			);
+
+			assert!(
+				T::MaxHolds::get() >= <T::RuntimeHoldReason as VariantCount>::variant_count(),
+				"MaxHolds should be greater than or equal to the number of hold reasons"
+			);
+
+			assert!(
+				T::MaxFreezes::get() >= <T::RuntimeFreezeReason as VariantCount>::variant_count(),
+				"MaxFreezes should be greater than or equal to the number of freeze reasons"
+			);
 		}
 	}
 

substrate/frame/support/procedural/src/construct_runtime/expand/freeze_reason.rs

@@ -46,6 +46,7 @@ pub fn expand_outer_freeze_reason(pallet_decls: &[Pallet], scrate: &TokenStream)
 			));
 		}
 	}
+	let freeze_reason_variants_count = freeze_reason_variants.len() as u32;
 
 	quote! {
 		/// A reason for placing a freeze on funds.
@@ -59,6 +60,12 @@ pub fn expand_outer_freeze_reason(pallet_decls: &[Pallet], scrate: &TokenStream)
 			#( #freeze_reason_variants )*
 		}
 
+		impl #scrate::traits::VariantCount for RuntimeFreezeReason {
+			fn variant_count() -> u32 {
+				#freeze_reason_variants_count
+			}
+		}
+
 		#( #conversion_fns )*
 	}
 }

substrate/frame/support/procedural/src/construct_runtime/expand/hold_reason.rs

@@ -46,6 +46,7 @@ pub fn expand_outer_hold_reason(pallet_decls: &[Pallet], scrate: &TokenStream) -
 			));
 		}
 	}
+	let hold_reason_variants_count = hold_reason_variants.len() as u32;
 
 	quote! {
 		/// A reason for placing a hold on funds.
@@ -59,6 +60,12 @@ pub fn expand_outer_hold_reason(pallet_decls: &[Pallet], scrate: &TokenStream) -
 			#( #hold_reason_variants )*
 		}
 
+		impl #scrate::traits::VariantCount for RuntimeHoldReason {
+			fn variant_count() -> u32 {
+				#hold_reason_variants_count
+			}
+		}
+
 		#( #conversion_fns )*
 	}
 }

substrate/frame/support/src/traits.rs

@@ -60,7 +60,7 @@ pub use misc::{
 	DefensiveTruncateFrom, EnsureInherentsAreFirst, EqualPrivilegeOnly, EstimateCallFee,
 	ExecuteBlock, ExtrinsicCall, Get, GetBacking, GetDefault, HandleLifetime, IsSubType, IsType,
 	Len, OffchainWorker, OnKilledAccount, OnNewAccount, PrivilegeCmp, SameOrOther, Time,
-	TryCollect, TryDrop, TypedGet, UnixTime, WrapperKeepOpaque, WrapperOpaque,
+	TryCollect, TryDrop, TypedGet, UnixTime, VariantCount, WrapperKeepOpaque, WrapperOpaque,
 };
 #[allow(deprecated)]
 pub use misc::{PreimageProvider, PreimageRecipient};

substrate/frame/support/src/traits/misc.rs

@@ -36,6 +36,14 @@ pub const DEFENSIVE_OP_PUBLIC_ERROR: &str = "a defensive failure has been trigge
 #[doc(hidden)]
 pub const DEFENSIVE_OP_INTERNAL_ERROR: &str = "Defensive failure has been triggered!";
 
+/// Trait to get the number of variants in any enum.
+///
+/// NOTE: can be removed once https://doc.rust-lang.org/std/mem/fn.variant_count.html is stable.
+pub trait VariantCount {
+	/// Get the number of variants.
+	fn variant_count() -> u32;
+}
+
 /// Generic function to mark an execution path as ONLY defensive.
 ///
 /// Similar to mark a match arm or `if/else` branch as `unreachable!`.