Purify Contains, add IsInVec, All and SortedMembers (#8589)

* IsInVec

* Purify `Contains`, introduce SortedMembers

substrate/frame/support/src/lib.rs

@@ -459,13 +459,16 @@ macro_rules! ord_parameter_types {
 	);
 	() => ();
 	(IMPL $name:ident , $type:ty , $value:expr) => {
-		impl $crate::traits::Contains<$type> for $name {
+		impl $crate::traits::SortedMembers<$type> for $name {
 			fn contains(t: &$type) -> bool { &$value == t }
 			fn sorted_members() -> $crate::sp_std::prelude::Vec<$type> { vec![$value] }
 			fn count() -> usize { 1 }
 			#[cfg(feature = "runtime-benchmarks")]
 			fn add(_: &$type) {}
 		}
+		impl $crate::traits::Contains<$type> for $name {
+			fn contains(t: &$type) -> bool { &$value == t }
+		}
 	}
 }
 

substrate/frame/support/src/traits.rs

@@ -29,7 +29,10 @@ pub use tokens::imbalance::{Imbalance, OnUnbalanced, SignedImbalance};
 pub use tokens::{ExistenceRequirement, WithdrawReasons, BalanceStatus};
 
 mod members;
-pub use members::{Contains, ContainsLengthBound, InitializeMembers, ChangeMembers};
+pub use members::{
+	Contains, ContainsLengthBound, SortedMembers, InitializeMembers, ChangeMembers, All, IsInVec,
+	AsContains,
+};
 
 mod validation;
 pub use validation::{

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

@@ -17,16 +17,28 @@
 
 //! Traits for dealing with the idea of membership.
 
-use sp_std::prelude::*;
+use sp_std::{prelude::*, marker::PhantomData};
 
 /// A trait for querying whether a type can be said to "contain" a value.
-pub trait Contains<T: Ord> {
+pub trait Contains<T> {
 	/// Return `true` if this "contains" the given value `t`.
-	fn contains(t: &T) -> bool { Self::sorted_members().binary_search(t).is_ok() }
+	fn contains(t: &T) -> bool;
+}
 
+/// A `Contains` implementation which always returns `true`.
+pub struct All<T>(PhantomData<T>);
+impl<T: Ord> Contains<T> for All<T> {
+	fn contains(_: &T) -> bool { true }
+}
+
+/// A trait for a set which can enumerate its members in order.
+pub trait SortedMembers<T: Ord> {
 	/// Get a vector of all members in the set, ordered.
 	fn sorted_members() -> Vec<T>;
 
+	/// Return `true` if this "contains" the given value `t`.
+	fn contains(t: &T) -> bool { Self::sorted_members().binary_search(t).is_ok() }
+
 	/// Get the number of items in the set.
 	fn count() -> usize { Self::sorted_members().len() }
 
@@ -38,6 +50,21 @@ pub trait Contains<T: Ord> {
 	fn add(_t: &T) { unimplemented!() }
 }
 
+/// Adapter struct for turning an `OrderedMembership` impl into a `Contains` impl.
+pub struct AsContains<OM>(PhantomData<(OM,)>);
+impl<T: Ord + Eq, OM: SortedMembers<T>> Contains<T> for AsContains<OM> {
+	fn contains(t: &T) -> bool { OM::contains(t) }
+}
+
+/// Trivial utility for implementing `Contains`/`OrderedMembership` with a `Vec`.
+pub struct IsInVec<T>(PhantomData<T>);
+impl<X: Eq, T: super::Get<Vec<X>>> Contains<X> for IsInVec<T> {
+	fn contains(t: &X) -> bool { T::get().contains(t) }
+}
+impl<X: Ord + PartialOrd, T: super::Get<Vec<X>>> SortedMembers<X> for IsInVec<T> {
+	fn sorted_members() -> Vec<X> { let mut r = T::get(); r.sort(); r }
+}
+
 /// A trait for querying bound for the length of an implementation of `Contains`
 pub trait ContainsLengthBound {
 	/// Minimum number of elements contained