lib.rs

				Test,
				GenericData2<T: Config> => Map<(Blake2_128Concat, T::BlockNumber), T::BlockNumber>
			);

			assert_eq!(Module::<Test>::generic_data2(5), None);
			GenericData2::<Test>::insert(5, 5);
			assert_eq!(Module::<Test>::generic_data2(5), Some(5));
		});
	}

	#[test]
	fn map_issue_3318() {
		new_test_ext().execute_with(|| {
			OptionLinkedMap::insert(1, 1);
			assert_eq!(OptionLinkedMap::get(1), Some(1));
			OptionLinkedMap::insert(1, 2);
			assert_eq!(OptionLinkedMap::get(1), Some(2));
		});
	}

	#[test]
	fn map_swap_works() {
		new_test_ext().execute_with(|| {
			OptionLinkedMap::insert(0, 0);
			OptionLinkedMap::insert(1, 1);
			OptionLinkedMap::insert(2, 2);
			OptionLinkedMap::insert(3, 3);

			let collect = || OptionLinkedMap::iter().collect::<Vec<_>>().sorted();
			assert_eq!(collect(), vec![(0, 0), (1, 1), (2, 2), (3, 3)]);

			// Two existing
			OptionLinkedMap::swap(1, 2);
			assert_eq!(collect(), vec![(0, 0), (1, 2), (2, 1), (3, 3)]);

			// Back to normal
			OptionLinkedMap::swap(2, 1);
			assert_eq!(collect(), vec![(0, 0), (1, 1), (2, 2), (3, 3)]);

			// Left existing
			OptionLinkedMap::swap(2, 5);
			assert_eq!(collect(), vec![(0, 0), (1, 1), (3, 3), (5, 2)]);

			// Right existing
			OptionLinkedMap::swap(5, 2);
			assert_eq!(collect(), vec![(0, 0), (1, 1), (2, 2), (3, 3)]);
		});
	}

	#[test]
	fn double_map_swap_works() {
		new_test_ext().execute_with(|| {
			DataDM::insert(0, 1, 1);
			DataDM::insert(1, 0, 2);
			DataDM::insert(1, 1, 3);

			let get_all = || {
				vec![
					DataDM::get(0, 1),
					DataDM::get(1, 0),
					DataDM::get(1, 1),
					DataDM::get(2, 0),
					DataDM::get(2, 1),
				]
			};
			assert_eq!(get_all(), vec![1, 2, 3, 0, 0]);

			// Two existing
			DataDM::swap(0, 1, 1, 0);
			assert_eq!(get_all(), vec![2, 1, 3, 0, 0]);

			// Left existing
			DataDM::swap(1, 0, 2, 0);
			assert_eq!(get_all(), vec![2, 0, 3, 1, 0]);

			// Right existing
			DataDM::swap(2, 1, 1, 1);
			assert_eq!(get_all(), vec![2, 0, 0, 1, 3]);
		});
	}

	#[test]
	fn map_basic_insert_remove_should_work() {
		new_test_ext().execute_with(|| {
			// initialized during genesis
			assert_eq!(Map::get(&15u32), 42u64);

			// get / insert / take
			let key = 17u32;
			assert_eq!(Map::get(&key), 0u64);
			Map::insert(key, 4u64);
			assert_eq!(Map::get(&key), 4u64);
			assert_eq!(Map::take(&key), 4u64);
			assert_eq!(Map::get(&key), 0u64);

			// mutate
			Map::mutate(&key, |val| {
				*val = 15;
			});
			assert_eq!(Map::get(&key), 15u64);

			// remove
			Map::remove(&key);
			assert_eq!(Map::get(&key), 0u64);
		});
	}

	#[test]
	fn map_iteration_should_work() {
		new_test_ext().execute_with(|| {
			assert_eq!(Map::iter().collect::<Vec<_>>().sorted(), vec![(15, 42)]);
			// insert / remove
			let key = 17u32;
			Map::insert(key, 4u64);
			assert_eq!(Map::iter().collect::<Vec<_>>().sorted(), vec![(15, 42), (key, 4)]);
			assert_eq!(Map::take(&15), 42u64);
			assert_eq!(Map::take(&key), 4u64);
			assert_eq!(Map::iter().collect::<Vec<_>>().sorted(), vec![]);

			// Add couple of more elements
			Map::insert(key, 42u64);
			assert_eq!(Map::iter().collect::<Vec<_>>().sorted(), vec![(key, 42)]);
			Map::insert(key + 1, 43u64);
			assert_eq!(Map::iter().collect::<Vec<_>>().sorted(), vec![(key, 42), (key + 1, 43)]);

			// mutate
			let key = key + 2;
			Map::mutate(&key, |val| {
				*val = 15;
			});
			assert_eq!(
				Map::iter().collect::<Vec<_>>().sorted(),
				vec![(key - 2, 42), (key - 1, 43), (key, 15)]
			);
			Map::mutate(&key, |val| {
				*val = 17;
			});
			assert_eq!(
				Map::iter().collect::<Vec<_>>().sorted(),
				vec![(key - 2, 42), (key - 1, 43), (key, 17)]
			);

			// remove first
			Map::remove(&key);
			assert_eq!(
				Map::iter().collect::<Vec<_>>().sorted(),
				vec![(key - 2, 42), (key - 1, 43)]
			);

			// remove last from the list
			Map::remove(&(key - 2));
			assert_eq!(Map::iter().collect::<Vec<_>>().sorted(), vec![(key - 1, 43)]);

			// remove the last element
			Map::remove(&(key - 1));
			assert_eq!(Map::iter().collect::<Vec<_>>().sorted(), vec![]);
		});
	}

	#[test]
	fn double_map_basic_insert_remove_remove_prefix_should_work() {
		new_test_ext().execute_with(|| {
			type DoubleMap = DataDM;
			// initialized during genesis
			assert_eq!(DoubleMap::get(&15u32, &16u32), 42u64);

			// get / insert / take
			let key1 = 17u32;
			let key2 = 18u32;
			assert_eq!(DoubleMap::get(&key1, &key2), 0u64);
			DoubleMap::insert(&key1, &key2, &4u64);
			assert_eq!(DoubleMap::get(&key1, &key2), 4u64);
			assert_eq!(DoubleMap::take(&key1, &key2), 4u64);
			assert_eq!(DoubleMap::get(&key1, &key2), 0u64);

			// mutate
			DoubleMap::mutate(&key1, &key2, |val| {
				*val = 15;
			});
			assert_eq!(DoubleMap::get(&key1, &key2), 15u64);

			// remove
			DoubleMap::remove(&key1, &key2);
			assert_eq!(DoubleMap::get(&key1, &key2), 0u64);

			// remove prefix
			DoubleMap::insert(&key1, &key2, &4u64);
			DoubleMap::insert(&key1, &(key2 + 1), &4u64);
			DoubleMap::insert(&(key1 + 1), &key2, &4u64);
			DoubleMap::insert(&(key1 + 1), &(key2 + 1), &4u64);
			assert!(matches!(
				DoubleMap::remove_prefix(&key1, None),
				sp_io::KillStorageResult::AllRemoved(0), // all in overlay
			));
			assert_eq!(DoubleMap::get(&key1, &key2), 0u64);
			assert_eq!(DoubleMap::get(&key1, &(key2 + 1)), 0u64);
			assert_eq!(DoubleMap::get(&(key1 + 1), &key2), 4u64);
			assert_eq!(DoubleMap::get(&(key1 + 1), &(key2 + 1)), 4u64);
		});
	}

	#[test]
	fn double_map_append_should_work() {
		new_test_ext().execute_with(|| {
			type DoubleMap = AppendableDM<Test>;

			let key1 = 17u32;
			let key2 = 18u32;

			DoubleMap::insert(&key1, &key2, &vec![1]);
			DoubleMap::append(&key1, &key2, 2);
			assert_eq!(DoubleMap::get(&key1, &key2), &[1, 2]);
		});
	}

	#[test]
	fn double_map_mutate_exists_should_work() {
		new_test_ext().execute_with(|| {
			type DoubleMap = DataDM;

			let (key1, key2) = (11, 13);

			// mutated
			DoubleMap::mutate_exists(key1, key2, |v| *v = Some(1));
			assert_eq!(DoubleMap::get(&key1, key2), 1);

			// removed if mutated to `None`
			DoubleMap::mutate_exists(key1, key2, |v| *v = None);
			assert!(!DoubleMap::contains_key(&key1, key2));
		});
	}

	#[test]
	fn double_map_try_mutate_exists_should_work() {
		new_test_ext().execute_with(|| {
			type DoubleMap = DataDM;
			type TestResult = result::Result<(), &'static str>;

			let (key1, key2) = (11, 13);

			// mutated if `Ok`
			assert_ok!(DoubleMap::try_mutate_exists(key1, key2, |v| -> TestResult {
				*v = Some(1);
				Ok(())
			}));
			assert_eq!(DoubleMap::get(&key1, key2), 1);

			// no-op if `Err`
			assert_noop!(
				DoubleMap::try_mutate_exists(key1, key2, |v| -> TestResult {
					*v = Some(2);
					Err("nah")
				}),
				"nah"
			);

			// removed if mutated to`None`
			assert_ok!(DoubleMap::try_mutate_exists(key1, key2, |v| -> TestResult {
				*v = None;
				Ok(())
			}));
			assert!(!DoubleMap::contains_key(&key1, key2));
		});
	}

	fn expected_metadata() -> PalletStorageMetadata {
		PalletStorageMetadata {
			prefix: "Test",
			entries: vec![
				StorageEntryMetadata {
					name: "Data",
					modifier: StorageEntryModifier::Default,
					ty: StorageEntryType::Map {
						hashers: vec![StorageHasher::Twox64Concat],
						key: scale_info::meta_type::<u32>(),
						value: scale_info::meta_type::<u64>(),
					},
					default: vec![0, 0, 0, 0, 0, 0, 0, 0],
					docs: vec![],
				},
				StorageEntryMetadata {
					name: "OptionLinkedMap",
					modifier: StorageEntryModifier::Optional,
					ty: StorageEntryType::Map {
						hashers: vec![StorageHasher::Blake2_128Concat],
						key: scale_info::meta_type::<u32>(),
						value: scale_info::meta_type::<u32>(),
					},
					default: vec![0],
					docs: vec![],
				},
				StorageEntryMetadata {
					name: "GenericData",
					modifier: StorageEntryModifier::Default,
					ty: StorageEntryType::Map {
						hashers: vec![StorageHasher::Identity],
						key: scale_info::meta_type::<u32>(),
						value: scale_info::meta_type::<u32>(),
					},
					default: vec![0, 0, 0, 0],
					docs: vec![],
				},
				StorageEntryMetadata {
					name: "GenericData2",
					modifier: StorageEntryModifier::Optional,
					ty: StorageEntryType::Map {
						hashers: vec![StorageHasher::Blake2_128Concat],
						key: scale_info::meta_type::<u32>(),
						value: scale_info::meta_type::<u32>(),
					},
					default: vec![0],
					docs: vec![],
				},
				StorageEntryMetadata {
					name: "DataDM",
					modifier: StorageEntryModifier::Default,
					ty: StorageEntryType::Map {
						hashers: vec![StorageHasher::Twox64Concat, StorageHasher::Blake2_128Concat],
						key: scale_info::meta_type::<(u32, u32)>(),
						value: scale_info::meta_type::<u64>(),
					},
					default: vec![0, 0, 0, 0, 0, 0, 0, 0],
					docs: vec![],
				},
				StorageEntryMetadata {
					name: "GenericDataDM",
					modifier: StorageEntryModifier::Default,
					ty: StorageEntryType::Map {
						hashers: vec![StorageHasher::Blake2_128Concat, StorageHasher::Identity],
						key: scale_info::meta_type::<(u32, u32)>(),
						value: scale_info::meta_type::<u32>(),
					},
					default: vec![0, 0, 0, 0],
					docs: vec![],
				},
				StorageEntryMetadata {
					name: "GenericData2DM",
					modifier: StorageEntryModifier::Optional,
					ty: StorageEntryType::Map {
						hashers: vec![StorageHasher::Blake2_128Concat, StorageHasher::Twox64Concat],
						key: scale_info::meta_type::<(u32, u32)>(),
						value: scale_info::meta_type::<u32>(),
					},
					default: vec![0],
					docs: vec![],
				},
				StorageEntryMetadata {
					name: "AppendableDM",
					modifier: StorageEntryModifier::Default,
					ty: StorageEntryType::Map {
						hashers: vec![
							StorageHasher::Blake2_128Concat,
							StorageHasher::Blake2_128Concat,
						],
						key: scale_info::meta_type::<(u32, u32)>(),
						value: scale_info::meta_type::<Vec<u32>>(),
					},
					default: vec![0],
					docs: vec![],
				},
			],
		}
	}

	#[test]
	fn store_metadata() {
		let metadata = Module::<Test>::storage_metadata();
		pretty_assertions::assert_eq!(expected_metadata(), metadata);
	}

	parameter_types! {
		storage StorageParameter: u64 = 10;
	}

	#[test]
	fn check_storage_parameter_type_works() {
		TestExternalities::default().execute_with(|| {
			assert_eq!(sp_io::hashing::twox_128(b":StorageParameter:"), StorageParameter::key());

			assert_eq!(10, StorageParameter::get());

			StorageParameter::set(&300);
			assert_eq!(300, StorageParameter::get());
		})
	}

	parameter_types! {
		pub const BlockHashCount: u64 = 250;
		pub static Members: Vec<u64> = vec![];
		pub const Foo: Option<u64> = None;
	}
}

/// Prelude to be used alongside pallet macro, for ease of use.
pub mod pallet_prelude {
	#[cfg(feature = "std")]
	pub use crate::traits::GenesisBuild;
	pub use crate::{
		dispatch::{DispatchError, DispatchResult, DispatchResultWithPostInfo, Parameter},
		ensure,
		inherent::{InherentData, InherentIdentifier, ProvideInherent},
		storage,
		storage::{
			bounded_vec::BoundedVec,
			types::{
				CountedStorageMap, Key as NMapKey, OptionQuery, StorageDoubleMap, StorageMap,
				StorageNMap, StorageValue, ValueQuery,
			},
		},
		traits::{
			ConstU32, EnsureOrigin, Get, GetDefault, GetStorageVersion, Hooks, IsType,
			PalletInfoAccess, StorageInfoTrait, StorageVersion,
		},
		weights::{DispatchClass, Pays, Weight},
		Blake2_128, Blake2_128Concat, Blake2_256, CloneNoBound, DebugNoBound, EqNoBound, Identity,
		PartialEqNoBound, RuntimeDebug, RuntimeDebugNoBound, Twox128, Twox256, Twox64Concat,
	};
	pub use codec::{Decode, Encode, MaxEncodedLen};
	pub use scale_info::TypeInfo;
	pub use sp_runtime::{
		traits::{MaybeSerializeDeserialize, Member, ValidateUnsigned},
		transaction_validity::{
			InvalidTransaction, TransactionLongevity, TransactionPriority, TransactionSource,
			TransactionTag, TransactionValidity, TransactionValidityError, UnknownTransaction,
			ValidTransaction,
		},
		MAX_MODULE_ERROR_ENCODED_SIZE,
	};
	pub use sp_std::marker::PhantomData;
}

/// `pallet` attribute macro allows to define a pallet to be used in `construct_runtime!`.
///
/// It is define by a module item:
/// ```ignore
/// #[pallet]
/// pub mod pallet {
/// ...
/// }
/// ```
///
/// Inside the module the macro will parse item with the attribute: `#[pallet::*]`, some
/// attributes are mandatory, some other optional.
///
/// The attribute are explained with the syntax of non instantiable pallets, to see how pallet
/// with instance work see below example.
///
/// Note various type can be automatically imported using pallet_prelude in frame_support and
/// frame_system:
/// ```ignore
/// #[pallet]
/// pub mod pallet {
/// 		use frame_support::pallet_prelude::*;
/// 		use frame_system::pallet_prelude::*;
/// 		...
/// }
/// ```
///
/// # Config trait: `#[pallet::config]` mandatory
///
/// The trait defining generics of the pallet.
///
/// Item must be defined as
/// ```ignore
/// #[pallet::config]
/// pub trait Config: frame_system::Config + $optionally_some_other_supertraits
/// $optional_where_clause
/// {
/// ...
/// }
/// ```
/// I.e. a regular trait definition named `Config`, with supertrait `frame_system::Config`,
/// optionally other supertrait and where clause.
///
/// The associated type `Event` is reserved, if defined it must bounds `From<Event>` and
/// `IsType<<Self as frame_system::Config>::Event>`, see `#[pallet::event]` for more
/// information.
///
/// To put `Get` associated type into metadatas, use the attribute `#[pallet::constant]`, e.g.:
/// ```ignore
/// #[pallet::config]
/// pub trait Config: frame_system::Config {
/// 		#[pallet::constant]
/// 		type Foo: Get<u32>;
/// }
/// ```
///
/// To bypass the `frame_system::Config` supertrait check, use the attribute
/// `#[pallet::disable_frame_system_supertrait_check]`, e.g.:
/// ```ignore
/// #[pallet::config]
/// #[pallet::disable_frame_system_supertrait_check]
/// pub trait Config: pallet_timestamp::Config {}
/// ```
///
/// ### Macro expansion:
///
/// The macro expand pallet constant metadata with the information given by
/// `#[pallet::constant]`.
///
/// # Pallet struct placeholder: `#[pallet::pallet]` mandatory
///
/// The placeholder struct, on which is implemented pallet informations.
///
/// Item must be defined as followed:
/// ```ignore
/// #[pallet::pallet]
/// pub struct Pallet<T>(_);
/// ```
/// I.e. a regular struct definition named `Pallet`, with generic T and no where clause.
///
/// To generate a `Store` trait associating all storages, use the attribute
/// `#[pallet::generate_store($vis trait Store)]`, e.g.:
/// ```ignore
/// #[pallet::pallet]
/// #[pallet::generate_store(pub(super) trait Store)]
/// pub struct Pallet<T>(_);
/// ```
/// More precisely the store trait contains an associated type for each storage. It is
/// implemented for `Pallet` allowing to access the storage from pallet struct.
///
/// Thus when defining a storage named `Foo`, it can later be accessed from `Pallet` using
/// `<Pallet as Store>::Foo`.
///
/// To generate the full storage info (used for PoV calculation) use the attribute
/// `#[pallet::generate_storage_info]`, e.g.:
/// ```ignore
/// #[pallet::pallet]
/// #[pallet::generate_storage_info]
/// pub struct Pallet<T>(_);
/// ```
///
/// This require all storage to implement the trait [`traits::StorageInfoTrait`], thus all keys
/// and value types must bound [`pallet_prelude::MaxEncodedLen`].
/// Some individual storage can opt-out from this constraint by using `#[pallet::unbounded]`,
/// see `#[pallet::storage]` documentation.
///
/// As the macro implements [`traits::GetStorageVersion`], the current storage version needs to
/// be communicated to the macro. This can be done by using the `storage_version` attribute:
///
/// ```ignore
/// const STORAGE_VERSION: StorageVersion = StorageVersion::new(5);
///
/// #[pallet::pallet]
/// #[pallet::storage_version(STORAGE_VERSION)]
/// pub struct Pallet<T>(_);
/// ```
///
/// If not present, the current storage version is set to the default value.
///
/// ### Macro expansion:
///
/// The macro add this attribute to the struct definition:
/// ```ignore
/// #[derive(
/// 	frame_support::CloneNoBound,
/// 	frame_support::EqNoBound,
/// 	frame_support::PartialEqNoBound,
/// 	frame_support::RuntimeDebugNoBound,
/// )]
/// ```
/// and replace the type `_` by `PhantomData<T>`.
///
/// It implements on pallet:
/// * [`traits::GetStorageVersion`]
/// * [`traits::OnGenesis`]: contains some logic to write pallet version into storage.
/// * `PalletErrorTypeInfo`: provides the type information for the pallet error, if defined.
///
/// It declares `type Module` type alias for `Pallet`, used by [`construct_runtime`].
///
/// It implements [`traits::PalletInfoAccess`] on `Pallet` to ease access to pallet
/// informations given by [`frame_support::traits::PalletInfo`].
/// (The implementation uses the associated type `frame_system::Config::PalletInfo`).
///
/// It implements [`traits::StorageInfoTrait`] on `Pallet` which give information about all
/// storages.
///
/// If the attribute generate_store is set then the macro creates the trait `Store` and
/// implements it on `Pallet`.
///
/// If the attribute set_storage_max_encoded_len is set then the macro call
/// [`traits::StorageInfoTrait`] for each storage in the implementation of
/// [`traits::StorageInfoTrait`] for the pallet.
/// Otherwise it implements [`traits::StorageInfoTrait`] for the pallet using the
/// [`traits::PartialStorageInfoTrait`] implementation of storages.
///
/// # Hooks: `#[pallet::hooks]` optional
///
/// Implementation of `Hooks` on `Pallet` allowing to define some specific pallet logic.
///
/// Item must be defined as
/// ```ignore
/// #[pallet::hooks]
/// impl<T: Config> Hooks<BlockNumberFor<T>> for Pallet<T> $optional_where_clause {
/// }
/// ```
/// I.e. a regular trait implementation with generic bound: `T: Config`, for the trait
/// `Hooks<BlockNumberFor<T>>` (they are defined in preludes), for the type `Pallet<T>`
/// and with an optional where clause.
///
/// If no `#[pallet::hooks]` exists, then a default implementation corresponding to the
/// following code is automatically generated:
/// ```ignore
/// #[pallet::hooks]
/// impl<T: Config> Hooks<BlockNumberFor<T>> for Pallet<T> {}
/// ```
///
/// ### Macro expansion:
///
/// The macro implements the traits `OnInitialize`, `OnIdle`, `OnFinalize`, `OnRuntimeUpgrade`,
/// `OffchainWorker`, `IntegrityTest` using `Hooks` implementation.
///
/// NOTE: OnRuntimeUpgrade is implemented with `Hooks::on_runtime_upgrade` and some additional
/// logic. E.g. logic to write pallet version into storage.
///
/// NOTE: The macro also adds some tracing logic when implementing the above traits. The
/// following  hooks emit traces: `on_initialize`, `on_finalize` and `on_runtime_upgrade`.
///
/// # Call: `#[pallet::call]` optional
///
/// Implementation of pallet dispatchables.
///
/// Item must be defined as:
/// ```ignore
/// #[pallet::call]
/// impl<T: Config> Pallet<T> {
/// 	/// $some_doc
/// 	#[pallet::weight($ExpressionResultingInWeight)]
/// 	pub fn $fn_name(
/// 		origin: OriginFor<T>,
/// 		$some_arg: $some_type,
/// 		// or with compact attribute: #[pallet::compact] $some_arg: $some_type,
/// 		...
/// 	) -> DispatchResultWithPostInfo { // or `-> DispatchResult`
/// 		...
/// 	}
/// 	...
/// }
/// ```
/// I.e. a regular type implementation, with generic `T: Config`, on type `Pallet<T>`, with
/// optional where clause.
///
/// Each dispatchable needs to define a weight with `#[pallet::weight($expr)]` attribute,
/// the first argument must be `origin: OriginFor<T>`, compact encoding for argument can be
/// used using `#[pallet::compact]`, function must return `DispatchResultWithPostInfo` or
/// `DispatchResult`.
///
/// All arguments must implement `Debug`, `PartialEq`, `Eq`, `Decode`, `Encode`, `Clone`. For
/// ease of use, bound the trait `Member` available in frame_support::pallet_prelude.
///
/// If no `#[pallet::call]` exists, then a default implementation corresponding to the
/// following code is automatically generated:
/// ```ignore
/// #[pallet::call]
/// impl<T: Config> Pallet<T> {}
/// ```
///
/// **WARNING**: modifying dispatchables, changing their order, removing some must be done with
/// care. Indeed this will change the outer runtime call type (which is an enum with one
/// variant per pallet), this outer runtime call can be stored on-chain (e.g. in
/// pallet-scheduler). Thus migration might be needed.
///
/// ### Macro expansion
///
/// The macro create an enum `Call` with one variant per dispatchable. This enum implements:
/// `Clone`, `Eq`, `PartialEq`, `Debug` (with stripped implementation in `not("std")`),
/// `Encode`, `Decode`, `GetDispatchInfo`, `GetCallName`, `UnfilteredDispatchable`.
///
/// The macro implement on `Pallet`, the `Callable` trait and a function `call_functions` which
/// returns the dispatchable metadatas.
///
/// # Extra constants: `#[pallet::extra_constants]` optional
///
/// Allow to define some extra constants to put into constant metadata.
///
/// Item must be defined as:
/// ```ignore
/// #[pallet::extra_constants]
/// impl<T: Config> Pallet<T> where $optional_where_clause {
/// 	/// $some_doc
/// 	$vis fn $fn_name() -> $some_return_type {
/// 		...
/// 	}
/// 	...
/// }
/// ```
/// I.e. a regular rust implement block with some optional where clause and functions with 0
/// args, 0 generics, and some return type.
///
/// ### Macro expansion
///
/// The macro add some extra constant to pallet constant metadata.
///
/// # Error: `#[pallet::error]` optional
///
/// Allow to define an error type to be return from dispatchable on error.
/// This error type informations are put into metadata.
///
/// Item must be defined as:
/// ```ignore
/// #[pallet::error]
/// pub enum Error<T> {
/// 	/// $some_optional_doc
/// 	$SomeFieldLessVariant,
/// 	/// $some_more_optional_doc
/// 	$SomeVariantWithOneField(FieldType),
/// 	...
/// }
/// ```
/// I.e. a regular rust enum named `Error`, with generic `T` and fieldless or multiple-field
/// variants.
///
/// Any field type in the enum variants must implement [`scale_info::TypeInfo`] in order to be
/// properly used in the metadata, and its encoded size should be as small as possible,
/// preferably 1 byte in size in order to reduce storage size. The error enum itself has an
/// absolute maximum encoded size specified by [`MAX_MODULE_ERROR_ENCODED_SIZE`].
///
/// Field types in enum variants must also implement [`PalletError`](traits::PalletError),
/// otherwise the pallet will fail to compile. Rust primitive types have already implemented
/// the [`PalletError`](traits::PalletError) trait along with some commonly used stdlib types
/// such as `Option` and `PhantomData`, and hence in most use cases, a manual implementation is
/// not necessary and is discouraged.
///
/// The generic `T` mustn't bound anything and where clause is not allowed. But bounds and
/// where clause shouldn't be needed for any usecase.
///
/// ### Macro expansion
///
/// The macro implements `Debug` trait and functions `as_u8` using variant position, and
/// `as_str` using variant doc.
///
/// The macro implements `From<Error<T>>` for `&'static str`.
/// The macro implements `From<Error<T>>` for `DispatchError`.
///
/// # Event: `#[pallet::event]` optional
///
/// Allow to define pallet events, pallet events are stored in the block when they deposited
/// (and removed in next block).
///
/// Item is defined as:
/// ```ignore
/// #[pallet::event]
/// #[pallet::generate_deposit($visibility fn deposit_event)] // Optional
/// pub enum Event<$some_generic> $optional_where_clause {
/// 	/// Some doc
/// 	$SomeName($SomeType, $YetanotherType, ...),
/// 	...
/// }
/// ```
/// I.e. an enum (with named or unnamed fields variant), named Event, with generic: none or `T`
/// or `T: Config`, and optional where clause.
///
/// Each field must implement `Clone`, `Eq`, `PartialEq`, `Encode`, `Decode`, and `Debug` (on
/// std only).
/// For ease of use, bound the trait `Member` available in frame_support::pallet_prelude.
///
/// The attribute `#[pallet::generate_deposit($visibility fn deposit_event)]` generate a helper
/// function on `Pallet` to deposit event.
///
/// NOTE: For instantiable pallet, event must be generic over T and I.
///
/// ### Macro expansion:
///
/// Macro will add on enum `Event` the attributes:
/// * `#[derive(frame_support::CloneNoBound)]`,
/// * `#[derive(frame_support::EqNoBound)]`,
/// * `#[derive(frame_support::PartialEqNoBound)]`,
/// * `#[derive(codec::Encode)]`,
/// * `#[derive(codec::Decode)]`,
/// * `#[derive(frame_support::RuntimeDebugNoBound)]`
///
/// Macro implements `From<Event<..>>` for ().
///
/// Macro implements metadata function on `Event` returning the `EventMetadata`.
///
/// If `#[pallet::generate_deposit]` then macro implement `fn deposit_event` on `Pallet`.
///
/// # Storage: `#[pallet::storage]` optional
///
/// Allow to define some abstract storage inside runtime storage and also set its metadata.
/// This attribute can be used multiple times.
///
/// Item is defined as:
/// ```ignore
/// #[pallet::storage]
/// #[pallet::getter(fn $getter_name)] // optional
/// $vis type $StorageName<$some_generic> $optional_where_clause
/// 	= $StorageType<$generic_name = $some_generics, $other_name = $some_other, ...>;
/// ```
/// or with unnamed generic
/// ```ignore
/// #[pallet::storage]
/// #[pallet::getter(fn $getter_name)] // optional
/// $vis type $StorageName<$some_generic> $optional_where_clause
/// 	= $StorageType<_, $some_generics, ...>;
/// ```
/// I.e. it must be a type alias, with generics: `T` or `T: Config`, aliased type must be one
/// of `StorageValue`, `StorageMap` or `StorageDoubleMap` (defined in frame_support).
/// The generic arguments of the storage type can be given in two manner: named and unnamed.
/// For named generic argument: the name for each argument is the one as define on the storage
/// struct:
/// * [`pallet_prelude::StorageValue`] expect `Value` and optionally `QueryKind` and `OnEmpty`,
/// * [`pallet_prelude::StorageMap`] expect `Hasher`, `Key`, `Value` and optionally `QueryKind`
///   and `OnEmpty`,
/// * [`pallet_prelude::CountedStorageMap`] expect `Hasher`, `Key`, `Value` and optionally
///   `QueryKind` and `OnEmpty`,
/// * [`pallet_prelude::StorageDoubleMap`] expect `Hasher1`, `Key1`, `Hasher2`, `Key2`, `Value`
///   and optionally `QueryKind` and `OnEmpty`.
///
/// For unnamed generic argument: Their first generic must be `_` as it is replaced by the
/// macro and other generic must declared as a normal declaration of type generic in rust.
///
/// The Prefix generic written by the macro is generated using
/// `PalletInfo::name::<Pallet<..>>()` and the name of the storage type.
/// E.g. if runtime names the pallet "MyExample" then the storage `type Foo<T> = ...` use the
/// prefix: `Twox128(b"MyExample") ++ Twox128(b"Foo")`.
///
/// For the `CountedStorageMap` variant, the Prefix also implements
/// `CountedStorageMapInstance`. It associate a `CounterPrefix`, which is implemented same as
/// above, but the storage prefix is prepend with `"CounterFor"`.
/// E.g. if runtime names the pallet "MyExample" then the storage
/// `type Foo<T> = CountedStorageaMap<...>` will store its counter at the prefix:
/// `Twox128(b"MyExample") ++ Twox128(b"CounterForFoo")`.
///
/// E.g:
/// ```ignore
/// #[pallet::storage]
/// pub(super) type MyStorage<T> = StorageMap<Hasher = Blake2_128Concat, Key = u32, Value = u32>;
/// ```
/// In this case the final prefix used by the map is
/// `Twox128(b"MyExample") ++ Twox128(b"OtherName")`.
///
/// The optional attribute `#[pallet::getter(fn $my_getter_fn_name)]` allows to define a
/// getter function on `Pallet`.
///
/// The optional attribute `#[pallet::storage_prefix = "SomeName"]` allow to define the storage
/// prefix to use, see how `Prefix` generic is implemented above.
///
/// E.g:
/// ```ignore
/// #[pallet::storage]
/// #[pallet::storage_prefix = "foo"]
/// #[pallet::getter(fn my_storage)]
/// pub(super) type MyStorage<T> = StorageMap<Hasher = Blake2_128Concat, Key = u32, Value = u32>;
/// ```
/// or
/// ```ignore
/// #[pallet::storage]
/// #[pallet::getter(fn my_storage)]
/// pub(super) type MyStorage<T> = StorageMap<_, Blake2_128Concat, u32, u32>;
/// ```
///
/// The optional attribute `#[pallet::unbounded]` allows to declare the storage as unbounded.
/// When implementating the storage info (when `#[pallet::generate_storage_info]` is specified
/// on the pallet struct placeholder), the size of the storage will be declared as unbounded.
/// This can be useful for storage which can never go into PoV (Proof of Validity).
///
/// The optional attributes `#[cfg(..)]` allow conditional compilation for the storage.
///
/// E.g:
/// ```ignore
/// #[cfg(feature = "my-feature")]
/// #[pallet::storage]
/// pub(super) type MyStorage<T> = StorageValue<Value = u32>;
/// ```
///
/// All the `cfg` attributes are automatically copied to the items generated for the storage,
/// i.e. the getter, storage prefix, and the metadata element etc.
///
/// NOTE: If the `QueryKind` generic parameter is still generic at this stage or is using some
/// type alias then the generation of the getter might fail. In this case the getter can be
/// implemented manually.
///
/// NOTE: The generic `Hasher` must implement the [`StorageHasher`] trait (or the type is not
/// usable at all). We use [`StorageHasher::METADATA`] for the metadata of the hasher of the
/// storage item. Thus generic hasher is supported.
///
/// ### Macro expansion
///
/// For each storage item the macro generates a struct named
/// `_GeneratedPrefixForStorage$NameOfStorage`, and implements
/// [`StorageInstance`](traits::StorageInstance) on it using the pallet and storage name. It
/// then uses it as the first generic of the aliased type.
/// For `CountedStorageMap`, `CountedStorageMapInstance` is implemented, and another similar
/// struct is generated.
///
/// For named generic, the macro will reorder the generics, and remove the names.
///
/// The macro implements the function `storage_metadata` on `Pallet` implementing the metadata
/// for all storage items based on their kind:
/// * for a storage value, the type of the value is copied into the metadata
/// * for a storage map, the type of the values and the key's type is copied into the metadata
/// * for a storage double map, the type of the values, and the types of key1 and key2 are
///   copied into the metadata.
///
/// # Type value: `#[pallet::type_value]` optional
///
/// Helper to define a struct implementing `Get` trait. To ease use of storage types.
/// This attribute can be used multiple time.
///
/// Item is defined as
/// ```ignore
/// #[pallet::type_value]
/// fn $MyDefaultName<$some_generic>() -> $default_type $optional_where_clause { $expr }
/// ```
/// I.e.: a function definition with generics none or `T: Config` and a returned type.
///
/// E.g.:
/// ```ignore
/// #[pallet::type_value]
/// fn MyDefault<T: Config>() -> T::Balance { 3.into() }
/// ```
///
/// NOTE: This attribute is meant to be used alongside `#[pallet::storage]` to defined some
/// specific default value in storage.
///
/// ### Macro expansion
///
/// Macro renames the function to some internal name, generate a struct with the original name
/// of the function and its generic, and implement `Get<$ReturnType>` by calling the user
/// defined function.
///
/// # Genesis config: `#[pallet::genesis_config]` optional
///
/// Allow to define the genesis configuration of the pallet.
///
/// Item is defined as either an enum or a struct.
/// It needs to be public and implement trait GenesisBuild with `#[pallet::genesis_build]`.
/// The type generics is constrained to be either none, or `T` or `T: Config`.
///
/// E.g:
/// ```ignore
/// #[pallet::genesis_config]
/// pub struct GenesisConfig<T: Config> {
/// 	_myfield: BalanceOf<T>,
/// }
/// ```
///
/// ### Macro expansion
///
/// Macro will add the following attribute on it:
/// * `#[cfg(feature = "std")]`
/// * `#[derive(Serialize, Deserialize)]`
/// * `#[serde(rename_all = "camelCase")]`
/// * `#[serde(deny_unknown_fields)]`
/// * `#[serde(bound(serialize = ""))]`
/// * `#[serde(bound(deserialize = ""))]`
///
/// # Genesis build: `#[pallet::genesis_build]` optional
///
/// Allow to define how genesis_configuration is built.
///
/// Item is defined as
/// ```ignore
/// #[pallet::genesis_build]
/// impl<T: Config> GenesisBuild<T> for GenesisConfig<$maybe_generics> {
/// 	fn build(&self) { $expr }
/// }
/// ```
/// I.e. a rust trait implementation with generic `T: Config`, of trait `GenesisBuild<T>` on
/// type `GenesisConfig` with generics none or `T`.
///
/// E.g.:
/// ```ignore
/// #[pallet::genesis_build]
/// impl<T: Config> GenesisBuild<T> for GenesisConfig {
/// 	fn build(&self) {}
/// }
/// ```
///
/// ### Macro expansion
///
/// Macro will add the following attribute on it:
/// * `#[cfg(feature = "std")]`
///
/// Macro will implement `sp_runtime::BuildModuleGenesisStorage` using `()` as second generic
/// for non-instantiable pallets.
///
/// # Inherent: `#[pallet::inherent]` optional
///
/// Allow the pallet to provide some inherent:
///
/// Item is defined as:
/// ```ignore
/// #[pallet::inherent]
/// impl<T: Config> ProvideInherent for Pallet<T> {
/// 	// ... regular trait implementation
/// }
/// ```
/// I.e. a trait implementation with bound `T: Config`, of trait `ProvideInherent` for type
/// `Pallet<T>`, and some optional where clause.
///
/// ### Macro expansion
///
/// Macro make currently no use of this information, but it might use this information in the
/// future to give information directly to construct_runtime.
///
/// # Validate unsigned: `#[pallet::validate_unsigned]` optional
///
/// Allow the pallet to validate some unsigned transaction: