go-ethereum/contracts/solidity_0.6/fallback.sol

pragma solidity >0.6.1 <0.7.0;
contract Test {
    // This function is called for all messages sent to
    // this contract (there is no other function).
    // Sending Ether to this contract will cause an exception,
    // because the fallback function does not have the `payable`
    // modifier.
    fallback() external { x = 1; }
    uint x;
}
contract TestPayable {
    // This function is called for all messages sent to
    // this contract, except plain Ether transfers
    // (there is no other function except the receive function).
    // Any call with non-empty calldata to this contract will execute
    // the fallback function (even if Ether is sent along with the call).
    fallback() external payable { x = 1; y = msg.value; }
// This function is called for plain Ether transfers, i.e.
    // for every call with empty calldata.
    receive() external payable { x = 2; y = msg.value; }
    uint x;
    uint y;
}