Address OZ's feedback on USDT comet support

contracts/Comet.sol

@@ -2,7 +2,7 @@
 pragma solidity 0.8.15;
 
 import "./CometMainInterface.sol";
-import "./IERC20NonStandard.sol";
+import "./ERC20.sol";
 import "./IPriceFeed.sol";
 
 /**
@@ -139,7 +139,7 @@ contract Comet is CometMainInterface {
      **/
     constructor(Configuration memory config) {
         // Sanity checks
-        uint8 decimals_ = IERC20NonStandard(config.baseToken).decimals();
+        uint8 decimals_ = ERC20(config.baseToken).decimals();
         if (decimals_ > MAX_BASE_DECIMALS) revert BadDecimals();
         if (config.storeFrontPriceFactor > FACTOR_SCALE) revert BadDiscount();
         if (config.assetConfigs.length > MAX_ASSETS) revert TooManyAssets();
@@ -241,7 +241,7 @@ contract Comet is CometMainInterface {
 
         // Sanity check price feed and asset decimals
         if (IPriceFeed(priceFeed).decimals() != PRICE_FEED_DECIMALS) revert BadDecimals();
-        if (IERC20NonStandard(asset).decimals() != decimals_) revert BadDecimals();
+        if (ERC20(asset).decimals() != decimals_) revert BadDecimals();
 
         // Ensure collateral factors are within range
         if (assetConfig.borrowCollateralFactor >= assetConfig.liquidateCollateralFactor) revert BorrowCFTooLarge();
@@ -482,15 +482,15 @@ contract Comet is CometMainInterface {
      * @param asset The collateral asset
      */
     function getCollateralReserves(address asset) override public view returns (uint) {
-        return IERC20NonStandard(asset).balanceOf(address(this)) - totalsCollateral[asset].totalSupplyAsset;
+        return ERC20(asset).balanceOf(address(this)) - totalsCollateral[asset].totalSupplyAsset;
     }
 
     /**
      * @notice Gets the total amount of protocol reserves of the base asset
      */
     function getReserves() override public view returns (int) {
         (uint64 baseSupplyIndex_, uint64 baseBorrowIndex_) = accruedInterestIndices(getNowInternal() - lastAccrualTime);
-        uint balance = IERC20NonStandard(baseToken).balanceOf(address(this));
+        uint balance = ERC20(baseToken).balanceOf(address(this));
         uint totalSupply_ = presentValueSupply(baseSupplyIndex_, totalSupplyBase);
         uint totalBorrow_ = presentValueBorrow(baseBorrowIndex_, totalBorrowBase);
         return signed256(balance) - signed256(totalSupply_) + signed256(totalBorrow_);
@@ -764,20 +764,20 @@ contract Comet is CometMainInterface {
      * @dev Note: Safely handles non-standard ERC-20 tokens that do not return a value. See here: https://medium.com/coinmonks/missing-return-value-bug-at-least-130-tokens-affected-d67bf08521ca
      */
     function doTransferIn(address asset, address from, uint amount) internal returns (uint) {
-        uint256 preTransferBalance = IERC20NonStandard(asset).balanceOf(address(this));
-        (bool success, bytes memory returndata) = asset.call(abi.encodeWithSelector(IERC20NonStandard.transferFrom.selector, from, address(this), amount));
+        uint256 preTransferBalance = ERC20(asset).balanceOf(address(this));
+        (bool success, bytes memory returndata) = asset.call(abi.encodeWithSelector(ERC20.transferFrom.selector, from, address(this), amount));
         if (!success || !(returndata.length == 0 || abi.decode(returndata, (bool)))) {
             revert TransferInFailed();
         }
-        return IERC20NonStandard(asset).balanceOf(address(this)) - preTransferBalance;
+        return ERC20(asset).balanceOf(address(this)) - preTransferBalance;
     }
 
     /**
      * @dev Safe ERC20 transfer out
      * @dev Note: Safely handles non-standard ERC-20 tokens that do not return a value. See here: https://medium.com/coinmonks/missing-return-value-bug-at-least-130-tokens-affected-d67bf08521ca
      */
     function doTransferOut(address asset, address to, uint amount) internal {
-        (bool success, bytes memory returndata) = asset.call(abi.encodeWithSelector(IERC20NonStandard.transfer.selector, to, amount));
+        (bool success, bytes memory returndata) = asset.call(abi.encodeWithSelector(ERC20.transfer.selector, to, amount));
         if (!success || !(returndata.length == 0 || abi.decode(returndata, (bool)))) {
             revert TransferOutFailed();
         }
@@ -1262,14 +1262,15 @@ contract Comet is CometMainInterface {
      * @dev Only callable by governor
      * @dev Note: Setting the `asset` as Comet's address will allow the manager
      * to withdraw from Comet's Comet balance
+     * @dev Note: For USDT, if there is non-zero prior allowance, it must be reset to 0 first before setting a new value in proposal
      * @param asset The asset that the manager will gain approval of
      * @param manager The account which will be allowed or disallowed
      * @param amount The amount of an asset to approve
      */
     function approveThis(address manager, address asset, uint amount) override external {
         if (msg.sender != governor) revert Unauthorized();
 
-        IERC20NonStandard(asset).approve(manager, amount);
+        ERC20(asset).approve(manager, amount);
     }
 
     /**

contracts/IERC20NonStandard.sol

@@ -7,9 +7,37 @@ pragma solidity 0.8.15;
  *  See https://medium.com/coinmonks/missing-return-value-bug-at-least-130-tokens-affected-d67bf08521ca
  */
 interface IERC20NonStandard {
+    function name() external view returns (string memory);
+    function symbol() external view returns (string memory);
     function decimals() external view returns (uint8);
+
+    /**
+     * @notice Approve `spender` to transfer up to `amount` from `src`
+     * @dev This will overwrite the approval amount for `spender`
+     *  and is subject to issues noted [here](https://eips.ethereum.org/EIPS/eip-20#approve)
+     * @param spender The address of the account which may transfer tokens
+     * @param amount The number of tokens that are approved (-1 means infinite)
+     */
     function approve(address spender, uint256 amount) external;
+
+    /**
+     * @notice Transfer `amount` tokens from `msg.sender` to `dst`
+     * @param dst The address of the destination account
+     * @param amount The number of tokens to transfer
+     */
     function transfer(address to, uint256 value) external;
+
+    /**
+     * @notice Transfer `amount` tokens from `src` to `dst`
+     * @param src The address of the source account
+     * @param dst The address of the destination account
+     * @param amount The number of tokens to transfer
+     */
     function transferFrom(address from, address to, uint256 value) external;
+
+    /**
+     * @notice Gets the balance of the specified address
+     * @param owner The address from which the balance will be retrieved
+     */
     function balanceOf(address account) external view returns (uint256);
-}
+}