eoa-contracts/contracts/smart-account/libs/LibAddress.sol

// SPDX-License-Identifier: MIT
pragma solidity 0.8.17;

library LibAddress {
    /**
     * @notice Will return true if provided address is a contract
     * @param account Address to verify if contract or not
     * @dev This contract will return false if called within the constructor of
     *      a contract's deployment, as the code is not yet stored on-chain.
     */
    function isContract(address account) internal view returns (bool) {
        uint256 csize;

        assembly {
            csize := extcodesize(account)
        }
        return csize != 0;
    }
}