Remove SafeMatch usage and rely on Solidity 0.8 built in safe math functionality

packages/contracts/contracts/L1/messaging/L1StandardBridge.sol

@@ -10,7 +10,6 @@ import { IERC20 } from "@openzeppelin/contracts/token/ERC20/IERC20.sol";
 /* Library Imports */
 import { CrossDomainEnabled } from "../../libraries/bridge/CrossDomainEnabled.sol";
 import { Lib_PredeployAddresses } from "../../libraries/constants/Lib_PredeployAddresses.sol";
-import { SafeMath } from "@openzeppelin/contracts/utils/math/SafeMath.sol";
 import { Address } from "@openzeppelin/contracts/utils/Address.sol";
 import { SafeERC20 } from "@openzeppelin/contracts/token/ERC20/utils/SafeERC20.sol";
 
@@ -23,7 +22,6 @@ import { SafeERC20 } from "@openzeppelin/contracts/token/ERC20/utils/SafeERC20.s
  * Runtime target: EVM
  */
 contract L1StandardBridge is IL1StandardBridge, CrossDomainEnabled {
-    using SafeMath for uint;
     using SafeERC20 for IERC20;
 
     /********************************
@@ -263,7 +261,7 @@ contract L1StandardBridge is IL1StandardBridge, CrossDomainEnabled {
             message
         );
 
-        deposits[_l1Token][_l2Token] = deposits[_l1Token][_l2Token].add(_amount);
+        deposits[_l1Token][_l2Token] = deposits[_l1Token][_l2Token] + _amount;
 
         emit ERC20DepositInitiated(_l1Token, _l2Token, _from, _to, _amount, _data);
     }
@@ -306,7 +304,7 @@ contract L1StandardBridge is IL1StandardBridge, CrossDomainEnabled {
         override
         onlyFromCrossDomainAccount(l2TokenBridge)
     {
-        deposits[_l1Token][_l2Token] = deposits[_l1Token][_l2Token].sub(_amount);
+        deposits[_l1Token][_l2Token] = deposits[_l1Token][_l2Token] - _amount;
 
         // When a withdrawal is finalized on L1, the L1 Bridge transfers the funds to the withdrawer
         IERC20(_l1Token).safeTransfer(_to, _amount);

packages/contracts/contracts/L1/rollup/StateCommitmentChain.sol

@@ -12,9 +12,6 @@ import { ICanonicalTransactionChain } from "./ICanonicalTransactionChain.sol";
 import { IBondManager } from "../verification/IBondManager.sol";
 import { IChainStorageContainer } from "./IChainStorageContainer.sol";
 
-/* External Imports */
-import "@openzeppelin/contracts/utils/math/SafeMath.sol";
-
 /**
  * @title StateCommitmentChain
  * @dev The State Commitment Chain (SCC) contract contains a list of proposed state roots which
@@ -243,7 +240,7 @@ contract StateCommitmentChain is IStateCommitmentChain, Lib_AddressResolver {
             timestamp != 0,
             "Batch header timestamp cannot be zero"
         );
-        return SafeMath.add(timestamp, FRAUD_PROOF_WINDOW) > block.timestamp;
+        return (timestamp + FRAUD_PROOF_WINDOW) > block.timestamp;
     }
 
 

packages/contracts/contracts/test-helpers/TestERC20.sol

@@ -3,8 +3,6 @@ pragma solidity ^0.8.4;
 
 // a test ERC20 token with an open mint function
 contract TestERC20 {
-    using SafeMath for uint;
-
     string public constant name = "Test";
     string public constant symbol = "TST";
     uint8 public constant decimals = 18;
@@ -18,8 +16,8 @@ contract TestERC20 {
     constructor() {}
 
     function mint(address to, uint256 value) public {
-        totalSupply = totalSupply.add(value);
-        balanceOf[to] = balanceOf[to].add(value);
+        totalSupply = totalSupply + value;
+        balanceOf[to] = balanceOf[to] + value;
         emit Transfer(address(0), to, value);
     }
 
@@ -29,8 +27,8 @@ contract TestERC20 {
     }
 
     function _transfer(address from, address to, uint256 value) private {
-        balanceOf[from] = balanceOf[from].sub(value);
-        balanceOf[to] = balanceOf[to].add(value);
+        balanceOf[from] = balanceOf[from] - value;
+        balanceOf[to] = balanceOf[to] + value;
         emit Transfer(from, to, value);
     }
 
@@ -46,23 +44,9 @@ contract TestERC20 {
 
     function transferFrom(address from, address to, uint256 value) external returns (bool) {
         if (allowance[from][msg.sender] != type(uint).max) {
-            allowance[from][msg.sender] = allowance[from][msg.sender].sub(value);
+            allowance[from][msg.sender] = allowance[from][msg.sender] - value;
         }
         _transfer(from, to, value);
         return true;
     }
 }
-
-library SafeMath {
-    function add(uint256 x, uint256 y) internal pure returns (uint256 z) {
-        require((z = x + y) >= x, "ds-math-add-overflow");
-    }
-
-    function sub(uint256 x, uint256 y) internal pure returns (uint256 z) {
-        require((z = x - y) <= x, "ds-math-sub-underflow");
-    }
-
-    function mul(uint256 x, uint256 y) internal pure returns (uint256 z) {
-        require(y == 0 || (z = x * y) / y == x, "ds-math-mul-overflow");
-    }
-}