Return number of keys removed when calling storage_kill on child trie (#8166)

* Initial piping of returning amount of keys killed

* One more test for `None` limit

* forgot to update

* fix return value

* use version 3

* Update to return `KillOutcome`

* Update name to KillChildStorageResult

substrate/frame/contracts/src/storage.rs

@@ -32,7 +32,7 @@ use sp_core::crypto::UncheckedFrom;
 use frame_support::{
 	dispatch::DispatchResult,
 	debug,
-	storage::child::{self, KillOutcome},
+	storage::child::{self, KillChildStorageResult},
 	traits::Get,
 	weights::Weight,
 };
@@ -269,13 +269,13 @@ where
 				let removed = queue.swap_remove(0);
 				match outcome {
 					// This should not happen as our budget was large enough to remove all keys.
-					KillOutcome::SomeRemaining => {
+					KillChildStorageResult::SomeRemaining(_) => {
 						debug::error!(
 							"After deletion keys are remaining in this child trie: {:?}",
 							removed.trie_id,
 						);
 					},
-					KillOutcome::AllRemoved => (),
+					KillChildStorageResult::AllRemoved(_) => (),
 				}
 			}
 			remaining_key_budget = remaining_key_budget

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

@@ -24,14 +24,7 @@
 use crate::sp_std::prelude::*;
 use codec::{Codec, Encode, Decode};
 pub use sp_core::storage::{ChildInfo, ChildType};
-
-/// The outcome of calling [`kill_storage`].
-pub enum KillOutcome {
-	/// No key remains in the child trie.
-	AllRemoved,
-	/// At least one key still resides in the child trie due to the supplied limit.
-	SomeRemaining,
-}
+pub use crate::sp_io::KillChildStorageResult;
 
 /// Return the value of the item in storage under `key`, or `None` if there is no explicit entry.
 pub fn get<T: Decode + Sized>(
@@ -177,16 +170,12 @@ pub fn exists(
 pub fn kill_storage(
 	child_info: &ChildInfo,
 	limit: Option<u32>,
-) -> KillOutcome {
-	let all_removed = match child_info.child_type() {
+) -> KillChildStorageResult {
+	match child_info.child_type() {
 		ChildType::ParentKeyId => sp_io::default_child_storage::storage_kill(
 			child_info.storage_key(),
 			limit
 		),
-	};
-	match all_removed {
-		true => KillOutcome::AllRemoved,
-		false => KillOutcome::SomeRemaining,
 	}
 }