Should setApprovalForAll throw when operator == msg.sender?

[mg6maciej]

No description provided.

[MoMannn]

Actually I would answer this the same way I did #122 .

[mg6maciej]

I'm not sure here. Looking at different implementations shows different additions to what's written in eip-721. You have require(_operator != address(0));, OZ has require(_operator != msg.sender); in setApprovalForAll; both have require(_approved != tokenOwner); in approve.

I think require(_to != address(0)); in transferFrom is the single best check to avoid problems with bugs in frontend and that's why it's even written in eip-721. Possibly other checks not specified there might be almost as important, like approving or transfering to this, i.e. ERC721 contract.
It's probably important to look at it using gas cost / potential user confusion formula. These kind of checks use under 10 gas, which is nothing compared to each 5000 (or sometimes 20000) storage update.