Solidity Compiler – Fixing TypeError: Interfaces Cannot Inherit in ISwapRouter.sol

compilerinterfacessolidity

So I am using some uniswapv3 contracts (which are pragma 0.7+) within another contract (which is pragma 0.5.0) and when compiling I have this error : “`These files import other files that use a different and incompatible version of Solidity:

contracts/Flashloan.sol (^0.5.0) imports contracts/ISwapRouter.sol (>=0.7.5) and contracts/IQuoter.sol (>=0.7.5)“`

so I tried to change the pragma statement from uniswapV3 interfaces I am importing from 0.7.6 to 0.5.0 and I faced this error : contracts/ISwapRouter.sol:11:26: TypeError: Interfaces cannot inherit..

The main question is : How do you handle compiling a contract using solidity v0.5.0 while you use contract that are declared as 0.7+ ?

Best Answer

I wondered how could Uniswap compile its contract if Interfaces can't inherit from other Interfaces ? And I concluded that interfaces imports were added in later solidity versions.

The way I solved this problem was by changing interfaces pragma statement to match the main contract and instead of importing the interfaces and inheriting from it, I directly added them into the code.

This might not be the best way to fix this, but it worked. I am putting it out there as I didn't find an answer to this problem and had to figure it out myself.

If you have a better way to compile contracts which inherit/use contracts with other solidity versions than their own, please feel free to share, I would love to learn.

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Truffle Compiler Error – Solving ‘Could Not Find Compiler Version Matching 0.5.0’ in Truffle

In my case, I run this following command in order to update truffle: npm install -g truffle@5.0.21

[Ethereum] How to import and compile contracts of different versions solidity

First you have to decide which solidity version you want to choose for your project. Its not necessary that you choose the latest version(my opinion). You have to consider the solidity version of external packages that you wish to use in your project.

For example, if you are using Openzeppelin, you can find different versions here: @openzeppelin/contracts.

Here is the updated code compatible with Solidity:0.8.3 with Openzeppelin:

// SPDX-License-Identifier: MIT
pragma solidity >=0.4.23 <0.9.0;

import "https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/contracts/utils/math/SafeMath.sol";
import "https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/contracts/token/ERC20/ERC20.sol";
import "https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/contracts/access/Ownable.sol";

contract StakingToken is ERC20, Ownable{
    using SafeMath for uint256;
    
    constructor()ERC20("MyCoin", "XMC"){}
    
    function addNumber(uint256 number) public pure returns(uint256) {
        return number.add(5);
    }
}

Best Answer

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Truffle Compiler Error – Solving ‘Could Not Find Compiler Version Matching 0.5.0’ in Truffle

[Ethereum] How to import and compile contracts of different versions solidity

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