Add an INDEX to the Instance trait (#8555)

* Add an index to the Instance trait

* Update frame/support/procedural/src/storage/instance_trait.rs

substrate/frame/support/src/instances.rs

@@ -31,10 +31,6 @@
 //! NOTE: [`frame_support::pallet`] will reexport them inside the module, in order to make them
 //! accessible to [`frame_support::construct_runtime`].
 
-/// Instance0 to be used for instantiable pallet define with `pallet` macro.
-#[derive(Clone, Copy, PartialEq, Eq, crate::RuntimeDebugNoBound)]
-pub struct Instance0;
-
 /// Instance1 to be used for instantiable pallet define with `pallet` macro.
 #[derive(Clone, Copy, PartialEq, Eq, crate::RuntimeDebugNoBound)]
 pub struct Instance1;
@@ -94,3 +90,7 @@ pub struct Instance14;
 /// Instance15 to be used for instantiable pallet define with `pallet` macro.
 #[derive(Clone, Copy, PartialEq, Eq, crate::RuntimeDebugNoBound)]
 pub struct Instance15;
+
+/// Instance16 to be used for instantiable pallet define with `pallet` macro.
+#[derive(Clone, Copy, PartialEq, Eq, crate::RuntimeDebugNoBound)]
+pub struct Instance16;

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

@@ -26,6 +26,8 @@
 pub trait Instance: 'static {
 	/// Unique module prefix. E.g. "InstanceNMyModule" or "MyModule"
 	const PREFIX: &'static str;
+	/// Unique numerical identifier for an instance.
+	const INDEX: u8;
 }
 
 /// An instance of a storage in a pallet.