Helper macro for Morph impls (#11570)

* Helper macro for Morph impls

* No need to deprecate for now

* Improved macro

* Doc tests

* Grumbles

substrate/frame/support/src/traits.rs

@@ -97,7 +97,7 @@ mod dispatch;
 pub use dispatch::EnsureOneOf;
 pub use dispatch::{
 	AsEnsureOriginWithArg, DispatchableWithStorageLayer, EitherOf, EitherOfDiverse, EnsureOrigin,
-	EnsureOriginWithArg, MapSuccess, NeverEnsureOrigin, OriginTrait, ReduceBy, TryMapSuccess,
+	EnsureOriginWithArg, MapSuccess, NeverEnsureOrigin, OriginTrait, TryMapSuccess,
 	UnfilteredDispatchable,
 };
 

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

@@ -18,15 +18,12 @@
 //! Traits for dealing with dispatching calls and the origin from which they are dispatched.
 
 use crate::dispatch::{DispatchResultWithPostInfo, Parameter, RawOrigin};
-use sp_arithmetic::traits::{CheckedSub, Zero};
 use sp_runtime::{
 	traits::{BadOrigin, Member, Morph, TryMorph},
 	Either,
 };
 use sp_std::marker::PhantomData;
 
-use super::TypedGet;
-
 /// Some sort of check on the origin is performed by this object.
 pub trait EnsureOrigin<OuterOrigin> {
 	/// A return type.
@@ -226,27 +223,6 @@ impl<
 	}
 }
 
-/// Mutator which reduces a scalar by a particular amount.
-pub struct ReduceBy<N>(PhantomData<N>);
-impl<N: TypedGet> TryMorph<N::Type> for ReduceBy<N>
-where
-	N::Type: CheckedSub,
-{
-	type Outcome = N::Type;
-	fn try_morph(r: N::Type) -> Result<N::Type, ()> {
-		r.checked_sub(&N::get()).ok_or(())
-	}
-}
-impl<N: TypedGet> Morph<N::Type> for ReduceBy<N>
-where
-	N::Type: CheckedSub + Zero,
-{
-	type Outcome = N::Type;
-	fn morph(r: N::Type) -> N::Type {
-		r.checked_sub(&N::get()).unwrap_or(Zero::zero())
-	}
-}
-
 /// Type that can be dispatched with an origin but without checking the origin filter.
 ///
 /// Implemented for pallet dispatchable type by `decl_module` and for runtime dispatchable by

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

@@ -21,6 +21,11 @@ use crate::dispatch::Parameter;
 use codec::{CompactLen, Decode, DecodeAll, Encode, EncodeLike, Input, MaxEncodedLen};
 use scale_info::{build::Fields, meta_type, Path, Type, TypeInfo, TypeParameter};
 use sp_arithmetic::traits::{CheckedAdd, CheckedMul, CheckedSub, Saturating};
+#[doc(hidden)]
+pub use sp_runtime::traits::{
+	ConstBool, ConstI128, ConstI16, ConstI32, ConstI64, ConstI8, ConstU128, ConstU16, ConstU32,
+	ConstU64, ConstU8, Get, GetDefault, TypedGet,
+};
 use sp_runtime::{traits::Block as BlockT, DispatchError};
 use sp_std::{cmp::Ordering, prelude::*};
 
@@ -387,73 +392,6 @@ where
 	}
 }
 
-/// A trait for querying a single value from a type defined in the trait.
-///
-/// It is not required that the value is constant.
-pub trait TypedGet {
-	/// The type which is returned.
-	type Type;
-	/// Return the current value.
-	fn get() -> Self::Type;
-}
-
-/// A trait for querying a single value from a type.
-///
-/// It is not required that the value is constant.
-pub trait Get<T> {
-	/// Return the current value.
-	fn get() -> T;
-}
-
-impl<T: Default> Get<T> for () {
-	fn get() -> T {
-		T::default()
-	}
-}
-
-/// Implement Get by returning Default for any type that implements Default.
-pub struct GetDefault;
-impl<T: Default> Get<T> for GetDefault {
-	fn get() -> T {
-		T::default()
-	}
-}
-
-macro_rules! impl_const_get {
-	($name:ident, $t:ty) => {
-		#[derive($crate::RuntimeDebug)]
-		pub struct $name<const T: $t>;
-		impl<const T: $t> Get<$t> for $name<T> {
-			fn get() -> $t {
-				T
-			}
-		}
-		impl<const T: $t> Get<Option<$t>> for $name<T> {
-			fn get() -> Option<$t> {
-				Some(T)
-			}
-		}
-		impl<const T: $t> TypedGet for $name<T> {
-			type Type = $t;
-			fn get() -> $t {
-				T
-			}
-		}
-	};
-}
-
-impl_const_get!(ConstBool, bool);
-impl_const_get!(ConstU8, u8);
-impl_const_get!(ConstU16, u16);
-impl_const_get!(ConstU32, u32);
-impl_const_get!(ConstU64, u64);
-impl_const_get!(ConstU128, u128);
-impl_const_get!(ConstI8, i8);
-impl_const_get!(ConstI16, i16);
-impl_const_get!(ConstI32, i32);
-impl_const_get!(ConstI64, i64);
-impl_const_get!(ConstI128, i128);
-
 /// A type for which some values make sense to be able to drop without further consideration.
 pub trait TryDrop: Sized {
 	/// Drop an instance cleanly. Only works if its value represents "no-operation".