Member "sub" not found or not visible after argument-dependent lookup in tuple()

Question

I'm trying to convert a function to solidity 0.8.0 but keep getting a type error any help hold be appreciated

TypeError: Member "sub" not found or not visible after argument-dependent lookup in tuple().

 function createViper(
    uint256 matron,
    uint256 sire,
    address viperOwner
)
    internal
    returns (uint)
{
    require(viperOwner != address(0));
    uint8 newGenes = generateViperGenes(matron, sire);
    Viper memory newViper = Viper({
        genes: newGenes,
        matronId: matron,
        sireId: sire
    });
    uint256 newViperId = vipers.push(newViper).sub(1);
    super._mint(viperOwner, newViperId);
    emit Birth(
        viperOwner,
        newViperId,
        newViper.matronId,
        newViper.sireId,
        newViper.genes
    );
    return newViperId;
}

Answer 1

.sub() in this context is almost certainly a function of the SafeMath library.

In Solidity 0.8+ you don't need to use SafeMath anymore, because the integer underflow/overflow check is performed on a lower level.

So you can safely replace

uint256 newViperId = vipers.push(newViper).sub(1);

with

vipers.push(newViper);
uint256 newViperId = vipers.length - 1;

Answer 2

In cases where you are dealing with potentially larger numbers with less certain values, and you actually should take advantage of the SafeMath checks, you can import it directly:

import './libraries/SafeMath.sol';  // check correct path
...
uint256 newViperId = SafeMath.sub(vipers.length, 1);
...