cluster-info: Get rid of some integer math while we're here

core/src/cluster_info.rs

@@ -907,9 +907,9 @@ impl ClusterInfo {
 
     pub fn contact_info_trace(&self) -> String {
         let now = timestamp();
-        let mut shred_spy_nodes = 0;
-        let mut total_spy_nodes = 0;
-        let mut different_shred_nodes = 0;
+        let mut shred_spy_nodes = 0usize;
+        let mut total_spy_nodes = 0usize;
+        let mut different_shred_nodes = 0usize;
         let my_pubkey = self.id();
         let my_shred_version = self.my_shred_version();
         let nodes: Vec<_> = self
@@ -918,16 +918,16 @@ impl ClusterInfo {
             .filter_map(|(node, last_updated)| {
                 let is_spy_node = Self::is_spy_node(&node);
                 if is_spy_node {
-                    total_spy_nodes += 1;
+                    total_spy_nodes = total_spy_nodes.saturating_add(1);
                 }
 
                 let node_version = self.get_node_version(&node.id);
                 if my_shred_version != 0 && (node.shred_version != 0 && node.shred_version != my_shred_version) {
-                    different_shred_nodes += 1;
+                    different_shred_nodes = different_shred_nodes.saturating_add(1);
                     None
                 } else {
                     if is_spy_node {
-                        shred_spy_nodes += 1;
+                        shred_spy_nodes = shred_spy_nodes.saturating_add(1);
                     }
                     fn addr_to_string(default_ip: &IpAddr, addr: &SocketAddr) -> String {
                         if ContactInfo::is_valid_address(addr) {
@@ -977,7 +977,7 @@ impl ClusterInfo {
              {}\
              Nodes: {}{}{}",
             nodes.join(""),
-            nodes.len() - shred_spy_nodes,
+            nodes.len().saturating_sub(shred_spy_nodes),
             if total_spy_nodes > 0 {
                 format!("\nSpies: {}", total_spy_nodes)
             } else {