Move fn to sdk

programs/stake/src/stake_state.rs

@@ -13,7 +13,7 @@ use solana_sdk::{
     account::Account,
     account_utils::{State, StateMut},
     clock::{Clock, Epoch, UnixTimestamp},
-    instruction::InstructionError,
+    instruction::{checked_add, InstructionError},
     keyed_account::KeyedAccount,
     pubkey::Pubkey,
     rent::{Rent, ACCOUNT_STORAGE_OVERHEAD},
@@ -52,13 +52,6 @@ impl Default for StakeState {
     }
 }
 
-fn checked_add(a: u64, b: u64) -> Result<u64, InstructionError> {
-    match a.checked_add(b) {
-        Some(sum) => Ok(sum),
-        None => Err(InstructionError::InsufficientFunds),
-    }
-}
-
 impl StakeState {
     pub fn get_rent_exempt_reserve(rent: &Rent) -> u64 {
         rent.minimum_balance(std::mem::size_of::<StakeState>())