Reto: utilidades

Comparto mi solución:

// SPDX-License-Identifier: GPL-3.0
pragma solidity >=0.7.0 <0.9.0;

import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
import "@openzeppelin/contracts/token/ERC721/IERC721.sol";
import "@openzeppelin/contracts/utils/introspection/ERC165Checker.sol";

contract IdentificadorToken {

      using ERC165Checker for address;
      
      modifier onlyERC20(address _direccion) {
            require(_direccion.supportsInterface(type(IERC20).interfaceId),"La Direccion no es compatible, no es un token ERC20");
            _;
      }
      modifier onlyERC721 (address _direccion){
            require(_direccion.supportsInterface(type(IERC721).interfaceId),"La Direccion no es compatible, no es un token ERC721");
            _;
      }

      function verificarERC20(address _direccion) onlyERC20(_direccion) public view returns(string memory) {
            return "La Direccion es compatible, es un token ERC20";
      }

      function verificarERC721(address _direccion) onlyERC721(_direccion) public view returns(string memory) {
           return "La Direccion es compatible, es un token ERC721";
      } 
}

Reto, otra solucion:

// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

import "@openzeppelin/contracts/utils/introspection/ERC165Checker.sol";
import "@openzeppelin/contracts/interfaces/IERC20.sol";
import "@openzeppelin/contracts/interfaces/IERC721.sol";

contract introspectionReto3 {

    function whatTypeOfTokenIsIt (address account) public view returns(string memory) {
        if(ERC165Checker.supportsInterface(account, type(IERC20).interfaceId)){
            return "It's ERC-20 Token";
        } else if (ERC165Checker.supportsInterface(account, type(IERC721).interfaceId)){
            return "It's ERC-721 token";
        } else {
            return "It's none";
        }   
    }        
}

Mi solución al desafio:

//SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

import "@openzeppelin/contracts/utils/introspection/ERC165Checker.sol";

contract Verification {
    using ERC165Checker for address;

    bytes4 private InterfaceId_ERC721 = 0x80ac58cd;
    bytes4 private InterfaceId_ERC20 = 0x36372b07;

    function tryERC721(
        address token
    )
        public view returns(bool)
    {
        return token.supportsInterface(InterfaceId_ERC721);
        
    }

    function tryERC20(
        address token
    )
        public view returns(bool)
    {
        return token.supportsInterface(InterfaceId_ERC20);
        
    }
}

Luego de ver la solucion entendi mejor el uso de using en librerias.

// SPDX-License-Identifier: GPL-3.0
pragma solidity >=0.7.0 <0.9.0;

import "@openzeppelin/contracts/token/ERC20/ERC20.sol";
import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
import "@openzeppelin/contracts/token/ERC721/IERC721.sol";
import "@openzeppelin/contracts/utils/introspection/ERC165.sol";
import "@openzeppelin/contracts/utils/introspection/ERC165Checker.sol";

contract IdentificadorToken {
    
    using ERC165Checker for address;
    error InvalidTokenFormat (string message);

    function isERC20 (address _address) public view returns (string memory) {
        if (!_address.supportsInterface(type(IERC20).interfaceId)) {
            revert InvalidTokenFormat("El formato del token no es valido, no hace referencia a un estandar ERC20");
        }
        return "Este contrato si cumple con los requisitos de ERC20";
    }

    function isERC721 (address _address) public view returns (string memory) {
        if (!_address.supportsInterface(type(IERC721).interfaceId)) {
            revert InvalidTokenFormat("El formato del token no es valido, no hace referencia a un estandar ERC721");
        }
        return "Este contrato si cumple con los requisitos de ERC721";
    }
}

Encontré esta parte de interfaces muy apropiado para este caso: https://www.tutorialspoint.com/solidity/solidity_interfaces.htm

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

import "@openzeppelin/contracts/utils/introspection/IERC165.sol";
import "@openzeppelin/contracts/utils/introspection/ERC165Checker.sol";
import "@openzeppelin/contracts/interfaces/IERC1155.sol";
import "@openzeppelin/contracts/interfaces/IERC721.sol";
import "@openzeppelin/contracts/interfaces/IERC20.sol";

interface ITest {
    function isERC1155(address Address) external returns (bool);
    function isERC721(address Address) external returns (bool);
    function isERC20(address Address) external returns (bool);
}

contract Test is ITest, IERC165 {
    using ERC165Checker for address; 

    bytes4 public constant IID_ITEST = type(ITest).interfaceId;
    bytes4 public constant IID_IERC165 = type(IERC165).interfaceId;
    bytes4 public constant IID_IERC20 = type(IERC20).interfaceId;
    bytes4 public constant IID_IERC1155 = type(IERC1155).interfaceId;
    bytes4 public constant IID_IERC721 = type(IERC721).interfaceId;
    
    function isERC1155(address Address) external view returns (bool) {
        return Address.supportsInterface(IID_IERC1155);
    }    
    
    function isERC721(address Address) external view returns (bool) {
        return Address.supportsInterface(IID_IERC721);
    }

    function isERC20(address Address) external view returns (bool) {
        return Address.supportsInterface(IID_IERC20);
    }
    
    function supportsInterface(bytes4 interfaceId) public view virtual returns (bool) {
        return interfaceId == IID_ITEST || interfaceId == IID_IERC165;
    }
}

Tuve algún conflicto con mi contrato ERC20 realizado en clases anteriores que hereda AccessControl.
Por lo que estuve investigando, hay que tener algún reparo cuando un contrato hereda más de 2 interfaces. El orden es importante. Además, REMIX me daba algunos errores y también tuve que hacer el override de AccessControl en la función supportsInterface de la siguiente manera:

    function supportsInterface(bytes4 interfaceId) public view virtual override(ERC165, AccessControl) returns (bool) {
        // ..
    }

Comparto el código del Token ERC20 y el código del ERC165 que desarrollé. Funciona!

Reto:

// SPDX-License-Identifier: GPL-3.0

pragma solidity >=0.7.0 <0.9.0;

import "@openzeppelin/contracts/utils/introspection/ERC165Checker.sol";
import "@openzeppelin/contracts/interfaces/IERC20.sol";
import "@openzeppelin/contracts/interfaces/IERC721.sol";



contract obervador  {

    function isTokenERC20(address account) public view returns (bool) {
        return ERC165Checker.supportsInterface(account, type(IERC20).interfaceId);
    }

    function isTokenERC721(address account) public view returns (bool) {
        return ERC165Checker.supportsInterface(account, type(IERC721).interfaceId);
    }
        
}