I updated Solidity to version to 0.6.12. Now the code is broken, how to fix?

Question

How can I fix my code, the chainid is 9999.I tried changing chainId := chainid to chainId := chainid() but it doesn't work. Here is the whole code:

pragma solidity 0.6.12;

import './interfaces/IUniswapV2ERC20.sol';
import 'contracts/libraries/SafeMath.sol';
    
contract AkalinsToken is IUniswapV2ERC20 {
    using SafeMath for uint;

    string public name = 'Akalin';   
    string public constant symbol = 'AKALIN'; 
    uint8 public constant decimals = 18;
    address[] private allHolders;    // save all the holders (there can be also addresses with 0 balance but every address is included only once
    
    
    uint  public totalSupply;
    mapping(address => uint) public balanceOf;
    mapping(address => mapping(address => uint)) public allowance;
    mapping(address => bool) private isHolder; // to check whether the address has been added to allHolders before

    bytes32 public DOMAIN_SEPARATOR;
    // keccak256("Permit(address owner,address spender,uint256 value,uint256 nonce,uint256 deadline)");
    bytes32 public constant PERMIT_TYPEHASH = 0x6e71edae12b1b97f4d1f60370fef10105fa2faae0126114a169c64845d6126c9;
    mapping(address => uint) public nonces;

    event Approval(address indexed owner, address indexed spender, uint value);
    event Transfer(address indexed from, address indexed to, uint value);
    event NameChanged(string newName);

    constructor() public {
        uint chainId;
        assembly{
    chainId := chainid
        }  
        DOMAIN_SEPARATOR = keccak256(
            abi.encode(
                keccak256('EIP712Domain(string name,string version,uint256 chainId,address verifyingContract)'),
                keccak256(bytes(name)),
                keccak256(bytes('1')),
                chainId,
                address(this)
            )
        );
    }

    function _mint(address to, uint value) internal {
        totalSupply = totalSupply.add(value);
        balanceOf[to] = balanceOf[to].add(value);
        emit Transfer(address(0), to, value);
        if(!isHolder[to]){
            allHolders.push(to);
            isHolder[to] = true;
        }
    }

    function _burn(address from, uint value) internal {
        balanceOf[from] = balanceOf[from].sub(value);
        totalSupply = totalSupply.sub(value);
        emit Transfer(from, address(0), value);
    }

    function _approve(address owner, address spender, uint value) private {
        allowance[owner][spender] = value;
        emit Approval(owner, spender, value);
    }

    function _transfer(address from, address to, uint value) private {
        balanceOf[from] = balanceOf[from].sub(value);
        balanceOf[to] = balanceOf[to].add(value);
        emit Transfer(from, to, value);
        if(!isHolder[to]){
            isHolder[to] = true;
            allHolders.push(to);
        }
       


    }

    function approve(address spender, uint value) external returns (bool) {
        _approve(msg.sender, spender, value);
        return true;
    }

    function transfer(address to, uint value) external returns (bool) {
        _transfer(msg.sender, to, value);
        return true;
    }

    function transferFrom(address from, address to, uint value) external returns (bool) {
        if (allowance[from][msg.sender] != uint(-1)) {
            allowance[from][msg.sender] = allowance[from][msg.sender].sub(value);
        }
        _transfer(from, to, value);
        return true;
    }

    function permit(address owner, address spender, uint value, uint deadline, uint8 v, bytes32 r, bytes32 s) external {
        require(deadline >= block.timestamp, 'UniswapV2: EXPIRED');
        bytes32 digest = keccak256(
            abi.encodePacked(
                '\x19\x01',
                DOMAIN_SEPARATOR,
                keccak256(abi.encode(PERMIT_TYPEHASH, owner, spender, value, nonces[owner]++, deadline))
            )
        );
        address recoveredAddress = ecrecover(digest, v, r, s);
        require(recoveredAddress != address(0) && recoveredAddress == owner, 'UniswapV2: INVALID_SIGNATURE');
        _approve(owner, spender, value);
    }



        
    function findLargestHolder() internal view returns (address) {
        address largestHolder = address(0);
        uint largestBalance = 0;
        for (uint i = 0; i < allHolders.length; i++) {
            uint balance = balanceOf[allHolders[i]];
            if (balance > largestBalance) {
                largestBalance = balance;
                largestHolder = allHolders[i];
            }
        }
        return largestHolder;
    }
    
    modifier onlyLargestHolder() {
        require(msg.sender == findLargestHolder(), "Caller is not the largest holder");
        _;
    }
    // The person with the most balance can change the Tokens name
    function changeTokenName(string memory newName) public onlyLargestHolder {
     name = newName; 
     emit NameChanged(newName);
    
}






}

Answer 1

There is no need to use assembly to get chainId, which is a property of the block object. Try to replace your by this constructor:

constructor() public {
        uint256 chainId;
        chainId = block.chainid;

        DOMAIN_SEPARATOR = keccak256(
            abi.encode(
                keccak256(
                    "EIP712Domain(string name,string version,uint256 chainId,address verifyingContract)"
                ),
                keccak256(bytes(name)),
                keccak256(bytes("1")),
                chainId,
                address(this)
            )
        );
    }