What are sources/slots?

[vibe-tyeh]

Hi, apologies for creating an issue for what should be a discussion/Q&A topic:

In the L2Voter architecture, what is the purpose of the address[] private _sources and bytes32[] private _slots arrays in the L1Governor.sol? My hunch is that it's how voting weights are stored (and then passed to the L2Voter), but I'm not positive. Could you provide some clarification?

[tarrencev]

Hi, sources and slots store the location for balance lookups. So _source should be a contract that stores some balance, usually a token balance, and _slot should point to the storage slot where that value can be read from.