How to push elements in an array within a function?

Question

Can anyone help me figure out the issue with this function in the code?

function getVerifiedProposals(uint index) public returns (string[] memory, string[][] memory, address, uint[] memory) {
        string[][] storage tempDocuments;
        address tempAddresses;
        uint[] memory tempAmount;
        
        if (allBidderProposals[index].status == ProposalStatus.verified) { 
            tempDocuments.push(allBidderProposals[index].constraintDocuments);
            tempAddresses = allBidderProposals[index].bidderAddress;
            tempAmount = allBidderProposals[index].quotationAmount;
        }
        return (constraints, tempDocuments, tempAddresses, tempAmount);
    } 

The error message shows :

Error: This variable is of storage pointer type and can be accessed without prior assignment, which would lead to undefined behaviour.

Answer 1

Here is the link to a GitHub issue that has the correct explanation. https://github.com/ethereum/solidity/issues/12549

Reasoning - If you are defining a local variable inside a function even if it's a storage type, it should point to a state variable. So, tempDocuments needs to point to a state variable.

I hope this resolves your issue.

The other answer on this post doesn't have the correct explanation so please ignore

Answer 2

I don't think you can declare an array inside a function and set the storage type as "storage". Every variable or array defined inside a function should always be of "memory" type.

string[][] memory tempDocuments;

This should resolve the issue.

Although I am not sure if this is a right approach. Solidity considers string as an array, so tempDocuments is actually a 3D array. Do check.