Add MaxEncodeLen to implement_per_thing! (#10715)

* fix doc

Signed-off-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>

* Add MaxEncodedLen to implement_per_thing!

Signed-off-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>

* Test that Percent et.al. can be used in Storage.

Signed-off-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>

* Add comment

Signed-off-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>

* Revert "Test that Percent et.al. can be used in Storage."

This reverts commit 52558af.

* Test MaxEncodedLen in implement_per_thing!

Signed-off-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>

* Revert "Add comment"

This reverts commit 27a96f6.

frame/support/test/tests/pallet.rs

@@ -432,7 +432,7 @@ pub mod pallet {
 }
 
 // Test that a pallet with non generic event and generic genesis_config is correctly handled
-// and that a pallet without the attribute generate_storage_info is correctly handled.
+// and that a pallet with the attribute without_storage_info is correctly handled.
 #[frame_support::pallet]
 pub mod pallet2 {
 	use super::{SomeAssociation1, SomeType1};

primitives/arithmetic/src/per_things.rs

@@ -425,7 +425,7 @@ macro_rules! implement_per_thing {
 		///
 		#[doc = $title]
 		#[cfg_attr(feature = "std", derive(Serialize, Deserialize))]
-		#[derive(Encode, Copy, Clone, PartialEq, Eq, PartialOrd, Ord, RuntimeDebug, scale_info::TypeInfo)]
+		#[derive(Encode, Copy, Clone, PartialEq, Eq, codec::MaxEncodedLen, PartialOrd, Ord, RuntimeDebug, scale_info::TypeInfo)]
 		pub struct $name($type);
 
 		/// Implementation makes any compact encoding of `PerThing::Inner` valid,
@@ -905,6 +905,15 @@ macro_rules! implement_per_thing {
 				}
 			}
 
+			#[test]
+			fn has_max_encoded_len() {
+				struct AsMaxEncodedLen<T: codec::MaxEncodedLen> {
+					_data: T,
+				}
+
+				let _ = AsMaxEncodedLen { _data: $name(1) };
+			}
+
 			#[test]
 			fn fail_on_invalid_encoded_value() {
 				let value = <$upper_type>::from($max) * 2;