I'm working on a puzzle where
msg.sender != tx.origin, so the implication is that the
caller needs to be a contract or at least something in between the calling account.
extcodesize(caller) == 0 also needs to be true. So the caller needs to be an address or externally owned account.
How can both of these be true? Can the caller's codesize ever be 0 if not an address/EOA?