    function permit(address issuer, address spender, uint256 value, uint256 deadline, uint8 v, bytes32 r, bytes32 s) external {
        if (block.timestamp > deadline) revert PermitExpired();

        if (uint256(s) > 0x7FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF5D576E7357A4501DDFE92F46681B20A0) revert InvalidS();

        if (v != 27 && v != 28) revert InvalidV();

        bytes32 digest = keccak256(
            abi.encodePacked(
                EIP191_PREFIX_FOR_EIP712_STRUCTURED_DATA,
                DOMAIN_SEPARATOR(),
                keccak256(abi.encode(PERMIT_SIGNATURE_HASH, issuer, spender, value, nonces[issuer]++, deadline))
            )
        );

        address recoveredAddress = ecrecover(digest, v, r, s);

        if (recoveredAddress != issuer) revert InvalidSignature();

        // _approve will revert if issuer is address(0x0)
        _approve(issuer, spender, value);
    }
    function permit(address issuer, address spender, uint256 value, uint256 deadline, uint8 v, bytes32 r, bytes32 s) external {
        if (block.timestamp > deadline) revert PermitExpired();

        if (uint256(s) > 0x7FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF5D576E7357A4501DDFE92F46681B20A0) revert InvalidS();

-        if (v != 27 && v != 28) revert InvalidV();

        bytes32 digest = keccak256(
            abi.encodePacked(
                EIP191_PREFIX_FOR_EIP712_STRUCTURED_DATA,
                DOMAIN_SEPARATOR(),
                keccak256(abi.encode(PERMIT_SIGNATURE_HASH, issuer, spender, value, nonces[issuer]++, deadline))
            )
        );

        address recoveredAddress = ecrecover(digest, v, r, s);

        if (recoveredAddress != issuer) revert InvalidSignature();

        // _approve will revert if issuer is address(0x0)
        _approve(issuer, spender, value);
    }
