ParserError: Expected '{' but got reserved keyword 'override'

Question

Can someone explain to me about this error? I just tried override feature in Solidity v0.6, but I got error Expected '{' but got reserved keyword 'override' function totalSupply() public override view returns (uint256) when compile contract.

pragma solidity >=0.4.21 <0.7.0;

import "./IERC20.sol";

    contract ERC20 is IERC20 {

    mapping (address => uint256) private _balances;

    mapping (address => mapping (address => uint256)) private _allowances;

    uint256 private _totalSupply;

    /**
    * @dev See `IERC20.totalSupply`.
    */
    function totalSupply()  public override  view returns (uint256) {
        return _totalSupply;
    } 
} 

Interface contract

pragma solidity >=0.4.21 <0.7.0;

interface IERC20 {
        /**
         * @dev Returns the amount of tokens in existence.
         */
        function totalSupply() external view returns (uint256);
}

Answer 1

I think you missed few '}' at the end of your contract and interface. the following works perfectly :

pragma solidity >=0.4.21 <0.7.0;

interface IERC20 {
    /**
     * @dev Returns the amount of tokens in existence.
     */
    function totalSupply() external view returns (uint256);
}

contract ERC20 is IERC20 {

mapping (address => uint256) private _balances;

mapping (address => mapping (address => uint256)) private _allowances;

uint256 private _totalSupply;

/**
* @dev See `IERC20.totalSupply`.
*/
function totalSupply()  public override  view returns (uint256) {
    return _totalSupply;
}  
}

Answer 2

I had the same problem and I solved it setting the Solidity compiler version to 0.6.8 (the latest at the current moment).

This can be done on Remix in the Compiler section, or in Truffle editing the file truffle-config.js.