removed useless transfers in claimAndStake

contracts/stake/StakedTokenV3.sol

@@ -58,6 +58,11 @@ contract StakedTokenV3 is StakedTokenV2, IStakedTokenV3, RoleManager {
     _;
   }
 
+  modifier onlyStakedTokenIsRewardToken {
+    require((REWARD_TOKEN == STAKED_TOKEN), 'REWARD_TOKEN_IS_NOT_STAKED_TOKEN');
+    _;
+  }
+
   event Staked(address indexed from, address indexed to, uint256 amount, uint256 sharesMinted);
   event Redeem(
     address indexed from,
@@ -156,8 +161,6 @@ contract StakedTokenV3 is StakedTokenV2, IStakedTokenV3, RoleManager {
     _initAdmins(adminsRoles, adminsAddresses);
 
     _maxSlashablePercentage = maxSlashablePercentage;
-
-    IERC20(STAKED_TOKEN).approve(address(this), type(uint256).max);
   }
 
   /**
@@ -166,7 +169,7 @@ contract StakedTokenV3 is StakedTokenV2, IStakedTokenV3, RoleManager {
    * @param amount The amount to be staked
    **/
   function stake(address to, uint256 amount) external override(IStakedToken, StakedTokenV2) {
-    _stake(msg.sender, to, amount);
+    _stake(msg.sender, to, amount, false);
   }
 
   /**
@@ -188,7 +191,7 @@ contract StakedTokenV3 is StakedTokenV2, IStakedTokenV3, RoleManager {
     bytes32 s
   ) external override {
     IERC20WithPermit(address(STAKED_TOKEN)).permit(from, address(this), amount, deadline, v, r, s);
-    _stake(from, to, amount);
+    _stake(from, to, amount, false);
   }
 
   /**
@@ -220,7 +223,7 @@ contract StakedTokenV3 is StakedTokenV2, IStakedTokenV3, RoleManager {
    * @param amount Amount to stake
    **/
   function claimRewards(address to, uint256 amount) external override(StakedTokenV2, IStakedToken) {
-    _claimRewards(msg.sender, to, amount);
+    _claimRewards(msg.sender, to, amount, false);
   }
 
   /**
@@ -234,17 +237,21 @@ contract StakedTokenV3 is StakedTokenV2, IStakedTokenV3, RoleManager {
     address to,
     uint256 amount
   ) external override onlyClaimHelper {
-    _claimRewards(from, to, amount);
+    _claimRewards(from, to, amount, false);
   }
 
   /**
    * @dev Claims an `amount` of `REWARD_TOKEN` amd restakes
    * @param to Address to stake to
    * @param amount Amount to claim
    **/
-  function claimRewardsAndStake(address to, uint256 amount) external override {
-    uint256 rewardsClaimed = _claimRewards(msg.sender, address(this), amount);
-    _stake(address(this), to, rewardsClaimed);
+  function claimRewardsAndStake(address to, uint256 amount)
+    external
+    override
+    onlyStakedTokenIsRewardToken
+  {
+    uint256 rewardsClaimed = _claimRewards(msg.sender, address(this), amount, true);
+    _stake(address(this), to, rewardsClaimed, true);
   }
 
   /**
@@ -257,9 +264,9 @@ contract StakedTokenV3 is StakedTokenV2, IStakedTokenV3, RoleManager {
     address from,
     address to,
     uint256 amount
-  ) external override onlyClaimHelper {
-    uint256 rewardsClaimed = _claimRewards(from, address(this), amount);
-    _stake(address(this), to, rewardsClaimed);
+  ) external override onlyStakedTokenIsRewardToken onlyClaimHelper {
+    uint256 rewardsClaimed = _claimRewards(from, address(this), amount, true);
+    _stake(address(this), to, rewardsClaimed, true);
   }
 
   /**
@@ -273,7 +280,7 @@ contract StakedTokenV3 is StakedTokenV2, IStakedTokenV3, RoleManager {
     uint256 claimAmount,
     uint256 redeemAmount
   ) external override {
-    _claimRewards(msg.sender, to, claimAmount);
+    _claimRewards(msg.sender, to, claimAmount, false);
     _redeem(msg.sender, to, redeemAmount);
   }
 
@@ -290,7 +297,7 @@ contract StakedTokenV3 is StakedTokenV2, IStakedTokenV3, RoleManager {
     uint256 claimAmount,
     uint256 redeemAmount
   ) external override onlyClaimHelper {
-    _claimRewards(from, to, claimAmount);
+    _claimRewards(from, to, claimAmount, false);
     _redeem(from, to, redeemAmount);
   }
 
@@ -372,14 +379,17 @@ contract StakedTokenV3 is StakedTokenV2, IStakedTokenV3, RoleManager {
   function _claimRewards(
     address from,
     address to,
-    uint256 amount
+    uint256 amount,
+    bool claimToReserve
   ) internal returns (uint256) {
     uint256 newTotalRewards = _updateCurrentUnclaimedRewards(from, balanceOf(from), false);
     uint256 amountToClaim = (amount == type(uint256).max) ? newTotalRewards : amount;
 
     stakerRewardsToClaim[from] = newTotalRewards.sub(amountToClaim, 'INVALID_AMOUNT');
 
-    REWARD_TOKEN.safeTransferFrom(REWARDS_VAULT, to, amountToClaim);
+    if (!claimToReserve) {
+      REWARD_TOKEN.safeTransferFrom(REWARDS_VAULT, to, amountToClaim);
+    }
 
     emit RewardsClaimed(from, to, amountToClaim);
     return (amountToClaim);
@@ -388,7 +398,8 @@ contract StakedTokenV3 is StakedTokenV2, IStakedTokenV3, RoleManager {
   function _stake(
     address from,
     address to,
-    uint256 amount
+    uint256 amount,
+    bool stakeFromReserve
   ) internal {
     require(amount != 0, 'INVALID_ZERO_AMOUNT');
 
@@ -407,7 +418,13 @@ contract StakedTokenV3 is StakedTokenV2, IStakedTokenV3, RoleManager {
     uint256 sharesToMint = amount.mul(1e18).div(exchangeRate());
     _mint(to, sharesToMint);
 
-    STAKED_TOKEN.safeTransferFrom(from, address(this), amount);
+    if (stakeFromReserve) {
+      // redondant in current implementation
+      require((REWARD_TOKEN == STAKED_TOKEN), 'SHOULD_BE_SETTLED');
+      REWARD_TOKEN.safeTransferFrom(REWARDS_VAULT, address(this), amount);
+    } else {
+      STAKED_TOKEN.safeTransferFrom(from, address(this), amount);
+    }
 
     emit Staked(from, to, amount, sharesToMint);
   }