Deployed an ERC20 with Hardhat, trying to mint token but getting "TypeError: _mint is not a function"

Question

A bit of messing around with Hardhat and ERC20 deployments. I've deployed a created and tried to mint tokens for an account using this small snippet of code:

const ERC20 = await hre.ethers.getContractFactory("ERC20");
const deployUSDC = await ERC20.deploy("USD Coin", "USDC");
console.log("USDC token address: ", deployUSDC.address);

const mintToken = await deployUSDC._mint(deployer.address, { value: ethers.utils.parseEther("2048") })
console.log(mintToken.hash)

However I'm getting this error when trying to call the _mint function:

TypeError: deployUSDC._mint is not a function

I've also tried calling mint just in case, but I am getting the same error.

Anyone would a solution or an explanation of what I am doing wrong here please? So that I'd be able to mint tokens.

Answer 1

I'm pretty sure _mint is an internal function. It can't be called externally like you're doing, that's why it can't be seen.

In the solidity code you don't have a default mint function, but you can add it like this:

// import OpenZeppelin ERC20 here
// ...

contract MyToken is ERC20 {
    constructor(string memory name, string memory symbol) ERC20(name, symbol) {}

    function mint(address to, uint256 amount) public {
        _mint(to, amount);
    }
}

Now you can use it:

const ERC20 = await hre.ethers.getContractFactory("MyToken");
const deployUSDC = await ERC20.deploy("USD Coin", "USDC");
const mintToken = await deployUSDC.mint(deployer.address, ethers.utils.parseEther("2048"))

I also added the mint amount as a parameter instead of sending ETH.

Answer 2

As @0xSanson said, the _mint function probably doesn't have an external/public visibility and can't be called from outside the contract. Wrap it with a mint function which calls _mint.