make your NFTs compatible with more smart contracts that expect erc20s with this 1 weird trick

EIP4521.sol

// SPDX-License-Identifier: AGPL-3.0-only

pragma solidity >=0.8.4;

import 'https://github.com/Rari-Capital/solmate/blob/main/src/tokens/ERC721.sol';

error NotOwner();
error InvalidRecipient();

contract EIP4521 is ERC721("WEIRD", "WEIRD") {
    constructor() {
        _mint(msg.sender, 1);
    }
    function tokenURI(uint256) public override pure returns (string memory) {
        return "PLACEHOLDER";
    }

    /// -----------------------------------------------------------------------
    /// ERC-20-like Logic (EIP-4521)
    /// -----------------------------------------------------------------------
    
    function transfer(address to, uint256 tokenId) public virtual returns (bool) {
        if (msg.sender != ownerOf[tokenId]) revert NotOwner();
        if (to == address(0)) revert InvalidRecipient();
        
        // underflow of the sender's balance is impossible because we check for
        // ownership above and the recipient's balance can't realistically overflow
        unchecked {
            balanceOf[msg.sender]--; 
            balanceOf[to]++;
        }
        
        delete getApproved[tokenId];
        
        ownerOf[tokenId] = to;
        
        emit Transfer(msg.sender, to, tokenId); 
        
        return true;
    }
}