From 9fc1db32802df5ac28e1c5510b99269412a85259 Mon Sep 17 00:00:00 2001
From: Andrew Jones <ascjones@gmail.com>
Date: Wed, 8 May 2019 12:20:43 +0100
Subject: [PATCH]  Use saturating_pow for max digest interval  (#2506)

* Use saturating_pow for max digest interval

* Impl version
---
 substrate/core/primitives/src/changes_trie.rs | 11 +----------
 substrate/node/runtime/src/lib.rs             |  2 +-
 2 files changed, 2 insertions(+), 11 deletions(-)

diff --git a/substrate/core/primitives/src/changes_trie.rs b/substrate/core/primitives/src/changes_trie.rs
index 9cf0066d71..2fa11f5641 100644
--- a/substrate/core/primitives/src/changes_trie.rs
+++ b/substrate/core/primitives/src/changes_trie.rs
@@ -53,16 +53,7 @@ impl ChangesTrieConfiguration {
 			return 1;
 		}
 
-		// FIXME: use saturating_pow once stabilized  - https://github.com/rust-lang/rust/issues/48320
-		let mut max_digest_interval = self.digest_interval;
-		for _ in 1..self.digest_levels {
-			max_digest_interval = match max_digest_interval.checked_mul(self.digest_interval) {
-				Some(max_digest_interval) => max_digest_interval,
-				None => return u64::max_value(),
-			}
-		}
-
-		max_digest_interval
+		self.digest_interval.saturating_pow(self.digest_levels)
 	}
 
 	/// Returns Some if digest must be built at given block number.
diff --git a/substrate/node/runtime/src/lib.rs b/substrate/node/runtime/src/lib.rs
index 69a19bf05e..b3daece243 100644
--- a/substrate/node/runtime/src/lib.rs
+++ b/substrate/node/runtime/src/lib.rs
@@ -59,7 +59,7 @@ pub const VERSION: RuntimeVersion = RuntimeVersion {
 	impl_name: create_runtime_str!("substrate-node"),
 	authoring_version: 10,
 	spec_version: 72,
-	impl_version: 73,
+	impl_version: 74,
 	apis: RUNTIME_API_VERSIONS,
 };