Make Drips balances uint256 (#347)

src/Drips.sol

@@ -78,7 +78,7 @@ contract Drips is Managed, Streams, Splits {
     uint8 public constant DRIVER_ID_OFFSET = 224;
     /// @notice The total amount the protocol can store of each token.
     /// It's the minimum of _MAX_STREAMS_BALANCE and _MAX_SPLITS_BALANCE.
-    uint128 public constant MAX_TOTAL_BALANCE = _MAX_STREAMS_BALANCE;
+    uint256 public constant MAX_TOTAL_BALANCE = _MAX_STREAMS_BALANCE;
     /// @notice On every timestamp `T`, which is a multiple of `cycleSecs`, the receivers
     /// gain access to steams received during `T - cycleSecs` to `T - 1`.
     /// Always higher than 1.
@@ -232,7 +232,7 @@ contract Drips is Managed, Streams, Splits {
         public
         view
         onlyProxy
-        returns (uint128 streamsBalance, uint128 splitsBalance)
+        returns (uint256 streamsBalance, uint256 splitsBalance)
     {
         Balance storage balance = _dripsStorage().balances[erc20];
         return (balance.streams, balance.splits);
@@ -294,7 +294,7 @@ contract Drips is Managed, Streams, Splits {
     /// @param erc20 The used ERC-20 token.
     /// @param amt The amount to increase the streams or splits balance by.
     function _verifyBalanceIncrease(IERC20 erc20, uint128 amt) internal view {
-        (uint256 streamsBalance, uint128 splitsBalance) = balances(erc20);
+        (uint256 streamsBalance, uint256 splitsBalance) = balances(erc20);
         uint256 newTotalBalance = streamsBalance + splitsBalance + amt;
         require(newTotalBalance <= MAX_TOTAL_BALANCE, "Total balance too high");
         require(newTotalBalance <= erc20.balanceOf(address(this)), "Token balance too low");
@@ -316,7 +316,7 @@ contract Drips is Managed, Streams, Splits {
     /// It must be at most the difference between the balance of the token held by the Drips
     /// contract address and the sum of balances managed by the protocol as indicated by `balances`.
     function withdraw(IERC20 erc20, address receiver, uint256 amt) public onlyProxy {
-        (uint128 streamsBalance, uint128 splitsBalance) = balances(erc20);
+        (uint256 streamsBalance, uint256 splitsBalance) = balances(erc20);
         uint256 withdrawable = erc20.balanceOf(address(this)) - streamsBalance - splitsBalance;
         require(amt <= withdrawable, "Withdrawal amount too high");
         emit Withdrawn(erc20, receiver, amt);

src/Giver.sol

@@ -46,7 +46,7 @@ contract GiversRegistry is Managed {
     /// @notice The `Drips` contract used by `addressDriver`.
     Drips internal immutable _drips;
     /// @notice The maximum balance of each token that Drips can hold.
-    uint128 internal immutable _maxTotalBalance;
+    uint256 internal immutable _maxTotalBalance;
 
     /// @param addressDriver_ The driver to use to `give`.
     constructor(AddressDriver addressDriver_) {
@@ -136,7 +136,7 @@ contract GiversRegistry is Managed {
                 address(erc20), "", address(this).balance, "Failed to wrap native tokens"
             );
         }
-        (uint128 streamsBalance, uint128 splitsBalance) = _drips.balances(erc20);
+        (uint256 streamsBalance, uint256 splitsBalance) = _drips.balances(erc20);
         uint256 maxAmt = _maxTotalBalance - streamsBalance - splitsBalance;
         // The balance of the `Giver` clone contract.
         amt = erc20.balanceOf(address(this));

test/Drips.t.sol

@@ -643,7 +643,7 @@ contract DripsTest is Test {
     }
 
     function testMaxBalanceIsNotTooHigh() public {
-        uint128 maxBalance = drips.MAX_TOTAL_BALANCE();
+        uint256 maxBalance = drips.MAX_TOTAL_BALANCE();
         Constants consts = new Constants();
         assertLe(maxBalance, consts.MAX_SPLITS_BALANCE(), "Max balance over max splits balance");
         assertLe(maxBalance, consts.MAX_STREAMS_BALANCE(), "Max balance over max streams balance");