ERC721A smart contract

Question

I'm writing an ERC721A smart contract and getting a warning in the Remix IDE. There is the code:

function tokenOfOwnerByIndex(address owner, uint256 index) public view override returns (uint256) {
    if (index >= balanceOf(owner)) revert OwnerIndexOutOfBounds();
    uint256 numMintedSoFar = totalSupply();
    uint256 tokenIdsIdx;
    address currOwnershipAddr;

    // Counter overflow is impossible as the loop breaks when uint256 i is equal to another uint256 numMintedSoFar.
    unchecked {
        for (uint256 i; i < numMintedSoFar; i++) {
            TokenOwnership memory ownership = _ownerships[i];
            if (ownership.addr != address(0)) {
                currOwnershipAddr = ownership.addr;
            }
            if (currOwnershipAddr == owner) {
                if (tokenIdsIdx == index) {
                    return i;
                }
                tokenIdsIdx++;
            }
        }
    }

    // Execution should never reach this point.
    assert(false);
}

This code is from the Square Bears collection ( https://etherscan.io/address/0x2b1037def2aa4ed427627903bdef9bdd27ae1ea3#code ). I got it from a YouTube tutorial. I think the code works, but I keep getting a warning.

Warning: Unnamed return variable can remain unassigned. Add an explicit return with value to all non-reverting code paths or name the variable.
--> contracts/ERC721A.sol:103:94:
|
103 | function tokenOfOwnerByIndex(address owner, uint256 index) public view override returns (uint256) {
| ^^^^^^^

I assume that I have to provide a named return value or variable, but the code seems to return an iterated value (i).

Answer 1

Because you've told the compiler that you will return a value from the function, but you didn't.

You should return a mock value even if you don't need to.

   ...

    // Execution should never reach this point.
    assert(false);

    return tokenIdsIdx; // or simply return 0;
}