chore: replace require statements with custom errors (#42)

* chore: replace require statements with custom errors

* Update src/contracts/libraries/MerkleTrie.sol

---------

Co-authored-by: Oleksii Matiiasevych <[email protected]>

src/contracts/ERC20Safe.sol

@@ -12,6 +12,11 @@ import "@openzeppelin/contracts/token/ERC20/extensions/ERC20Burnable.sol";
     @notice This contract is intended to be used with ERC20Handler contract.
  */
 contract ERC20Safe {
+
+    error ERC20NonContractCall();
+    error ERC20CallFailed();
+    error ERC20OperationFailed();
+
     /**
         @notice Used to gain custody of deposited token.
         @param tokenAddress Address of ERC20 to transfer.
@@ -88,13 +93,13 @@ contract ERC20Safe {
         assembly {
             tokenSize := extcodesize(token)
         }
-        require(tokenSize > 0, "ERC20: not a contract");
+        if (tokenSize <= 0) revert ERC20NonContractCall();
 
         (bool success, bytes memory returndata) = address(token).call(data);
-        require(success, "ERC20: call failed");
+        if (!success) revert ERC20CallFailed();
 
         if (returndata.length > 0) {
-            require(abi.decode(returndata, (bool)), "ERC20: operation did not succeed");
+            if (!abi.decode(returndata, (bool))) revert ERC20OperationFailed();
         }
     }
 }

src/contracts/Executor.sol

@@ -48,6 +48,7 @@ contract Executor is Context {
     error EmptyProposalsArray();
     error BridgeIsPaused();
     error ZeroAddressProvided();
+    error NoVerifierAddressProvided();
     error AccessNotAllowed(address sender, bytes4 funcSig);
     error TransferHashDoesNotMatchSlotValue(bytes32 transferHash);
     error StateRootDoesNotMatch(IStateRootStorage stateRootStorage, bytes32 stateRoot);
@@ -107,7 +108,7 @@ contract Executor is Context {
         @param verifiersAddresses Array of verifiers addresses which store state roots.
      */
     function adminSetVerifiers(uint8 securityModel, address[] memory verifiersAddresses) external onlyAllowed {
-        require(verifiersAddresses.length > 0, "Should provide at least one verifier address");
+        if (verifiersAddresses.length <= 0) revert NoVerifierAddressProvided();
         _securityModels[securityModel] = verifiersAddresses;
     }
 

src/contracts/Router.sol

@@ -34,6 +34,8 @@ contract Router is Context {
     error AccessNotAllowed(address sender, bytes4 funcSig);
     error BridgeIsPaused();
     error ZeroAddressProvided();
+    error NonceDecrementNotAllowed(uint64 currentNonce);
+    error MsgValueNotZero();
 
     event Deposit(
         uint8 destinationDomainID,
@@ -74,7 +76,8 @@ contract Router is Context {
         @param nonce The nonce value to be set.
      */
     function adminSetDepositNonce(uint8 domainID, uint64 nonce) external onlyAllowed {
-        require(nonce > _depositCounts[domainID], "Does not allow decrements of the nonce");
+        uint64 currentNonce = _depositCounts[domainID];
+        if (nonce <= currentNonce) revert NonceDecrementNotAllowed(currentNonce);
         _depositCounts[domainID] = nonce;
     }
 
@@ -103,7 +106,7 @@ contract Router is Context {
         if (handler == address(0)) revert ResourceIDNotMappedToHandler();
 
         if (address(feeHandler) == address(0)) {
-            require(msg.value == 0, "no FeeHandler, msg.value != 0");
+            if (msg.value != 0) revert MsgValueNotZero();
         } else {
             // Reverts on failure
             feeHandler.collectFee{value: msg.value}(

src/contracts/handlers/ERCHandlerHelpers.sol

@@ -30,6 +30,7 @@ abstract contract ERCHandlerHelpers is IERCHandler {
 
     error ContractAddressNotWhitelisted(address contractAddress);
     error DepositAmountTooSmall(uint256 depositAmount);
+    error SenderNotBridgeRouterOrExecutor();
 
     // resourceID => token contract address
     mapping(bytes32 => address) public _resourceIDToTokenContractAddress;

src/contracts/handlers/FeeHandlerRouter.sol

@@ -24,14 +24,16 @@ contract FeeHandlerRouter is IFeeHandler, AccessControl {
     event WhitelistChanged(address whitelistAddress, bool isWhitelisted);
 
     error IncorrectFeeSupplied(uint256);
+    error SenderNotRouterContract();
+    error SenderNotAdmin();
 
     modifier onlyRouter() {
         _onlyRouter();
         _;
     }
 
     function _onlyRouter() private view {
-        require(msg.sender == _routerAddress, "sender must be router contract");
+        if (msg.sender != _routerAddress) revert SenderNotRouterContract();
     }
 
     modifier onlyAdmin() {
@@ -40,7 +42,7 @@ contract FeeHandlerRouter is IFeeHandler, AccessControl {
     }
 
     function _onlyAdmin() private view {
-        require(hasRole(DEFAULT_ADMIN_ROLE, _msgSender()), "sender doesn't have admin role");
+        if (!hasRole(DEFAULT_ADMIN_ROLE, _msgSender())) revert SenderNotAdmin();
     }
 
     /**

src/contracts/handlers/PermissionlessGenericHandler.sol

@@ -20,8 +20,14 @@ contract PermissionlessGenericHandler is IHandler {
         _;
     }
 
+    error SenderNotBridgeContract();
+    error SenderNotExecutorContract();
+    error IncorrectDataLength(uint256 dataLength);
+    error RequestedFeeTooLarge(uint256 maxFee);
+    error InvalidExecutioDataDepositor(address executioDataDepositor);
+
     function _onlyBridge() private view {
-        require(msg.sender == _bridgeAddress, "sender must be bridge contract");
+        if (msg.sender != _bridgeAddress) revert SenderNotBridgeContract();
     }
 
     modifier onlyExecutor() {
@@ -30,7 +36,7 @@ contract PermissionlessGenericHandler is IHandler {
     }
 
     function _onlyExecutor() private view {
-        require(msg.sender == _executorAddress, "sender must be executor contract");
+        if (msg.sender != _executorAddress) revert SenderNotExecutorContract();
     }
 
     /**
@@ -113,7 +119,7 @@ contract PermissionlessGenericHandler is IHandler {
             executeFuncSignature(address executionDataDepositor, uint256[] uintArray, address addr)
      */
     function deposit(bytes32 resourceID, address depositor, bytes calldata data) external pure returns (bytes memory) {
-        require(data.length >= 76, "Incorrect data length"); // 32 + 2 + 1 + 1 + 20 + 20
+        if (data.length < 76) revert IncorrectDataLength(data.length); // 32 + 2 + 1 + 1 + 20 + 20
 
         uint256 maxFee;
         uint16 lenExecuteFuncSignature;
@@ -142,8 +148,8 @@ contract PermissionlessGenericHandler is IHandler {
             )
         );
 
-        require(maxFee < MAX_FEE, "requested fee too large");
-        require(depositor == executionDataDepositor, "incorrect depositor in deposit data");
+        if (maxFee > MAX_FEE) revert RequestedFeeTooLarge(maxFee);
+        if (depositor != executionDataDepositor) revert InvalidExecutioDataDepositor(executionDataDepositor);
         return data;
     }
 

src/contracts/handlers/fee/BasicFeeHandler.sol

@@ -22,26 +22,32 @@ contract BasicFeeHandler is IFeeHandler, AccessControl {
 
     event FeeChanged(uint256 newFee);
 
+    error SenderNotBridgeOrRouter();
     error IncorrectFeeSupplied(uint256);
     error ZeroAddressProvided();
+    error SenderNotAdmin();
+    error CannotRenounceOneself();
+    error NewFeeEqualsCurrentFee(uint256 currentFee);
+    error AddressesAndAmountsArraysDifferentLength(
+        uint256 addressesLength,
+        uint256 amountsLength
+    );
+    error EtherFeeTransferFailed();
 
     modifier onlyAdmin() {
-        require(hasRole(DEFAULT_ADMIN_ROLE, msg.sender), "sender doesn't have admin role");
+        if (!hasRole(DEFAULT_ADMIN_ROLE, msg.sender)) revert SenderNotAdmin();
         _;
     }
 
-    modifier onlyBridgeOrRouter() {
-        _onlyBridgeOrRouter();
+    modifier onlyRouterOrFeeRouter() {
+        _onlyRouterOrFeeRouter();
         _;
     }
 
-    function _onlyBridgeOrRouter() private view {
-        require(
-            msg.sender == _bridgeAddress ||
-            msg.sender == _feeHandlerRouterAddress ||
-            msg.sender == _routerAddress,
-            "sender must be bridge or fee router contract"
-        );
+    function _onlyRouterOrFeeRouter() private view {
+        if (msg.sender != _feeHandlerRouterAddress &&
+            msg.sender != _routerAddress
+        ) revert SenderNotBridgeOrRouter();
     }
 
     /**
@@ -67,7 +73,7 @@ contract BasicFeeHandler is IFeeHandler, AccessControl {
      */
     function renounceAdmin(address newAdmin) external {
         address sender = _msgSender();
-        require(sender != newAdmin, "Cannot renounce oneself");
+        if (sender == newAdmin) revert CannotRenounceOneself();
         grantRole(DEFAULT_ADMIN_ROLE, newAdmin);
         renounceRole(DEFAULT_ADMIN_ROLE, sender);
     }
@@ -90,7 +96,7 @@ contract BasicFeeHandler is IFeeHandler, AccessControl {
         uint8 securityModel,
         bytes calldata depositData,
         bytes calldata feeData
-    ) external virtual payable onlyBridgeOrRouter {
+    ) external virtual payable onlyRouterOrFeeRouter {
         uint256 currentFee = _domainResourceIDSecurityModelToFee[destinationDomainID][resourceID][securityModel];
         if (msg.value != currentFee) revert IncorrectFeeSupplied(msg.value);
         emit FeeCollected(sender, fromDomainID, destinationDomainID, resourceID, currentFee, address(0));
@@ -135,7 +141,7 @@ contract BasicFeeHandler is IFeeHandler, AccessControl {
             uint256 newFee
         ) external onlyAdmin {
         uint256 currentFee = _domainResourceIDSecurityModelToFee[destinationDomainID][resourceID][securityModel];
-        require(currentFee != newFee, "Current fee is equal to new fee");
+        if (currentFee == newFee) revert NewFeeEqualsCurrentFee(currentFee);
         _domainResourceIDSecurityModelToFee[destinationDomainID][resourceID][securityModel] = newFee;
         emit FeeChanged(newFee);
     }
@@ -148,10 +154,13 @@ contract BasicFeeHandler is IFeeHandler, AccessControl {
         @param amounts Array of amounts to transfer to {addrs}.
      */
     function transferFee(address payable[] calldata addrs, uint256[] calldata amounts) external onlyAdmin {
-        require(addrs.length == amounts.length, "addrs[], amounts[]: diff length");
+        if (addrs.length != amounts.length) revert AddressesAndAmountsArraysDifferentLength(
+            addrs.length,
+            amounts.length
+        );
         for (uint256 i = 0; i < addrs.length; i++) {
             (bool success, ) = addrs[i].call{value: amounts[i]}("");
-            require(success, "Fee ether transfer failed");
+            if (!success) revert EtherFeeTransferFailed();
             emit FeeDistributed(address(0), addrs[i], amounts[i]);
         }
     }

src/contracts/handlers/fee/PercentageERC20FeeHandlerEVM.sol

@@ -29,6 +29,10 @@ contract PercentageERC20FeeHandlerEVM is BasicFeeHandler, ERC20Safe {
 
     event FeeBoundsChanged(uint256 newLowerBound, uint256 newUpperBound);
 
+    error MsgValueNotZero();
+    error InvalidBoundsRatio(uint128 newLowerBound, uint128 newUpperBound);
+    error NewBoundsEqualCurrentBounds(uint128 currentLowerBound, uint128 currentUpperBound);
+
     /**
         @param bridgeAddress Contract address of previously deployed Bridge.
         @param feeHandlerRouterAddress Contract address of previously deployed FeeHandlerRouter.
@@ -121,8 +125,8 @@ contract PercentageERC20FeeHandlerEVM is BasicFeeHandler, ERC20Safe {
         uint8 securityModel,
         bytes calldata depositData,
         bytes calldata feeData
-    ) external payable override onlyBridgeOrRouter {
-        require(msg.value == 0, "collectFee: msg.value != 0");
+    ) external payable override onlyRouterOrFeeRouter {
+        if (msg.value != 0) revert MsgValueNotZero();
 
         (uint256 fee, address tokenAddress) = _calculateFee(
             sender,
@@ -146,15 +150,14 @@ contract PercentageERC20FeeHandlerEVM is BasicFeeHandler, ERC20Safe {
         @param newUpperBound Value {_newUpperBound} will be updated to.
      */
     function changeFeeBounds(bytes32 resourceID, uint128 newLowerBound, uint128 newUpperBound) external onlyAdmin {
-        require(
-            newUpperBound == 0 || (newUpperBound > newLowerBound),
-            "Upper bound must be larger than lower bound or 0"
-        );
+        if (newUpperBound != 0 && (newUpperBound <= newLowerBound)) {
+            revert InvalidBoundsRatio(newLowerBound, newUpperBound);
+        }
+
         Bounds memory existingBounds = _resourceIDToFeeBounds[resourceID];
-        require(
-            existingBounds.lowerBound != newLowerBound || existingBounds.upperBound != newUpperBound,
-            "Current bounds are equal to new bounds"
-        );
+        if (existingBounds.lowerBound == newLowerBound && existingBounds.upperBound == newUpperBound) {
+            revert NewBoundsEqualCurrentBounds(existingBounds.lowerBound, existingBounds.upperBound);
+        }
 
         Bounds memory newBounds = Bounds(newLowerBound, newUpperBound);
         _resourceIDToFeeBounds[resourceID] = newBounds;
@@ -175,7 +178,10 @@ contract PercentageERC20FeeHandlerEVM is BasicFeeHandler, ERC20Safe {
         address[] calldata addrs,
         uint256[] calldata amounts
     ) external onlyAdmin {
-        require(addrs.length == amounts.length, "addrs[], amounts[]: diff length");
+        if (addrs.length != amounts.length) revert AddressesAndAmountsArraysDifferentLength(
+            addrs.length,
+            amounts.length
+        );
         address tokenHandler = IBridge(_bridgeAddress)._resourceIDToHandlerAddress(resourceID);
         address tokenAddress = IERCHandler(tokenHandler)._resourceIDToTokenContractAddress(resourceID);
         for (uint256 i = 0; i < addrs.length; i++) {

src/contracts/libraries/Bytes.sol

@@ -7,6 +7,10 @@ pragma solidity ^0.8.11;
  * @notice Bytes is a library for manipulating byte arrays.
  */
 library Bytes {
+
+    error SliceOwerflow();
+    error SliceOutOfBounds();
+
     /**
      * @notice Slices a byte array with a given starting index and length. Returns a new byte array
      *         as opposed to a pointer to the original array. Will throw if trying to slice more
@@ -24,9 +28,9 @@ library Bytes {
         uint256 _length
     ) internal pure returns (bytes memory) {
         unchecked {
-            require(_length + 31 >= _length, "slice_overflow");
-            require(_start + _length >= _start, "slice_overflow");
-            require(_bytes.length >= _start + _length, "slice_outOfBounds");
+            if (_length + 31 < _length) revert SliceOwerflow();
+            if (_start + _length < _start) revert SliceOwerflow();
+            if (_bytes.length < _start + _length) revert SliceOutOfBounds();
         }
 
         bytes memory tempBytes;