為什麼它在這個契約中顯示錯誤？

實際上，我在多個文件中編寫了程式碼，但是由於我需要驗證和發布程式碼，所以我嘗試將程式碼扁平化。但現在它顯示了太多錯誤。我把下面的程式碼和錯誤消息放在評論中，你們能幫我解決錯誤嗎？

pragma solidity 0.4.25;

library SafeMath {

/**
* @dev Multiplies two numbers, reverts on overflow.
*/
function mul(uint256 a, uint256 b) internal pure returns (uint256) {
// Gas optimization: this is cheaper than requiring 'a' not being zero, but the
// benefit is lost if 'b' is also tested.
// See: https://github.com/OpenZeppelin/openzeppelin-solidity/pull/522
if (a == 0) {
 return 0;
}

uint256 c = a * b;
require(c / a == b);

return c;
}

/**
* @dev Integer division of two numbers truncating the quotient, reverts on division by zero.
*/
function div(uint256 a, uint256 b) internal pure returns (uint256) {
require(b > 0); // Solidity only automatically asserts when dividing by 0
uint256 c = a / b;
// assert(a == b * c + a % b); // There is no case in which this doesn't hold

return c;
}

/**
* @dev Subtracts two numbers, reverts on overflow (i.e. if subtrahend is greater than minuend).
*/
function sub(uint256 a, uint256 b) internal pure returns (uint256) {
require(b <= a);
uint256 c = a - b;

return c;
}

/**
* @dev Adds two numbers, reverts on overflow.
*/
function add(uint256 a, uint256 b) internal pure returns (uint256) {
uint256 c = a + b;
require(c >= a);

return c;
}

/**
* @dev Divides two numbers and returns the remainder (unsigned integer modulo),
* reverts when dividing by zero.
*/
function mod(uint256 a, uint256 b) internal pure returns (uint256) {
require(b != 0);
return a % b;
}
}


interface IERC20{        
function totalSupply() constant returns (uint256 totalSupply);
/**browser/ballot.sol:65:46: Warning: This declaration shadows an existing declaration.
function totalSupply() constant returns (uint256 totalSupply);
                                        ^-----------------^
browser/ballot.sol:65:5: The shadowed declaration is here:
function totalSupply() constant returns (uint256 totalSupply);
^------------------------------------------------------------^
**/
function balanceOf(address _owner) constant returns (uint256 balance);
function transfer(address _to, uint256 _value) returns (bool success);
function transferFrom(address _from, address _to, uint256 _value) returns (bool success);
function approve(address _spender, uint256 _value) returns (bool success);
function allowance(address _owner, address _spender) constant returns (uint256 remaining);
event Transfer(address indexed _from, address indexed _to, uint256 _value);
event Approval(address indexed _owner, address indexed _spender, uint256 _value);
}

contract FuncToken is IERC20{

using SafeMath for uint256;

uint public constant _totalSupply = 0;

string public constant symbol = "UB";
string public constant name = "UNIFIED BET";
uint8 public constant decimals = 18;

//1 ether = 1 UB
uint256 public constant RATE = 1;

address public owner;

mapping (address => uint256) balances;
mapping (address => mapping(address => uint256)) allowed;

function () payable{
   createToken();
}

constructor (){
   owner = msg.sender;

}

function createToken() payable {
   require(msg.value > 0);

   uint256 tokens = msg.value;
   balances[msg.sender] = balances[msg.sender].add(tokens);

   owner.transfer(msg.value);
}

function totalSupply() constant returns (uint256 totalSupply){
   return _totalSupply;
}

function balanceOf(address _owner) constant returns (uint256 balance){
   return balances[_owner];
}

function transfer(address _to, uint256 _value) returns (bool success){
   require (
       balances[msg.sender] >= _value
       && _value > 0
       );
       balances[msg.sender] = balances[msg.sender].sub(_value);
       balances[_to] = balances[_to].add(_value);
       Transfer(msg.sender, _to, _value);
       /**browser/ballot.sol:126:13: Warning: Invoking events without "emit" prefix is deprecated.
       Transfer(msg.sender, _to, _value);
       ^-------------------------------^ **/
       return true;

}

function transferFrom(address _from, address _to, uint256 _value) returns (bool success){
   require(
       allowed[_from][msg.sender] >= _value
       && balances[_from] >= _value
       && _value > 0
       );

       balances[_from] = balances[_from].sub(_value);
       balances[_to] = balances[_to].add(_value);
       allowed[_from][msg.sender] = allowed[_from][msg.sender].add(_value);
       Transfer(_from, _to, _value);
       return true;
}

function approve(address _spender, uint256 _value) returns (bool success){
   allowed[msg.sender][_spender] = _value;
   Approval(msg.sender, _spender, _value);
   return true;
}

function allowance(address _owner, address _spender) constant returns (uint256 remaining) {
   return allowed[_owner][_spender];
}

}

任何幫助將不勝感激。還有更多帶有相同警告的錯誤，但如果你們可以讓我知道一個，我會修復其他的。所有錯誤都在 /** **/

這些主要是警告，而不是錯誤。

為了幫助您開始，您評論的第一件事與此有關：

interface IERC20{        
   function totalSupply() constant returns (uint256 totalSupply);
   /**browser/ballot.sol:65:46: Warning: This declaration shadows an existing 
   declaration.
   function totalSupply() constant returns (uint256 totalSupply);

還有這個：

function totalSupply() constant returns (uint256 totalSupply){
   return _totalSupply;
}

問題是您的變數名稱與您的函式名稱相同。同樣在您使用的第二個片段_totalSupply中，您傳入的參數是totalSupply，沒有下劃線。

更改為以下內容（帶下劃線），或將變數名稱完全更改為其他名稱，以防止與函式名稱混淆：

function totalSupply() constant returns (uint256 _totalSupply);

---

所有其他警告似乎都是因為您沒有指定函式和變數的可見性。查看文件中的相關部分：Function Visibility Specifiers。

引用自：https://ethereum.stackexchange.com/questions/60555