the TransferHelper will not work with USDT

[hats-bug-reporter]

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Submission hash (on-chain): 0x813181e42fd163f8e690aaf146d9cddfc36d53fcbcb68173accb75c6b00fce87
Severity: medium

Description:
The safeTransferFrom() function used to transfer erc20 tokens

function safeTransferFrom(
        address token,
        address from,
        address to,
        uint256 value
    ) internal {
        (bool success, bytes memory data) =
                            token.call(abi.encodeWithSelector(IERC20.transferFrom.selector, from, to, value));
        require(success && (data.length == 0 || abi.decode(data, (bool))), 'STF');
    }

but the issue is this will not work with USDT because as we know USDT not implemented fully erc20 standard and it doesnt return bool.

therefor if protocol wanted to support USDT tokens in future, users will not be able to use it because all swaps will revert due to this issue.

POC
please run this POC

// SPDX-License-Identifier: UNLICENSED
pragma solidity ^0.8.13;

import {Test, console} from "forge-std/Test.sol";

interface IERC20{
    function transferFrom(address from, address to, uint256 value) external returns (bool);
    function balanceOf(address account) external view returns (uint256);
}

contract TransferTest is Test {
    IERC20 public usdt;

    function setUp() public {
      usdt = IERC20(0xdAC17F958D2ee523a2206206994597C13D831ec7);
    }

    function safeTransferFrom(
        address token,
        address from,
        address to,
        uint256 value
    ) internal {
        (bool success, bytes memory data) =
                            token.call(abi.encodeWithSelector(IERC20.transferFrom.selector, from, to, value));
        require(success && (data.length == 0 || abi.decode(data, (bool))), 'STF');
    }

    function test_poc() public{
        deal(address(usdt), address(this), 100e6);
        deal(address(usdt), address(msg.sender), 0);
        console.log(usdt.balanceOf(address(this)));
        safeTransferFrom(address(usdt), address(this), msg.sender, 100e6);
        console.log(usdt.balanceOf(address(this)));
        console.log(usdt.balanceOf(address(msg.sender)));
    }


}

Recommendation
to prevent this issue consider using OZ safeTransferFrom() and safeTransfer()

[omega-audits]

There's no issue with the Oasis USDT contract