solidity/test/libsolidity/semanticTests/functionTypes/function_delete_storage.sol

contract C {
    function a() public returns (uint256) {
        return 7;
    }

    function() returns (uint256) internal y;

    function set() public returns (uint256) {
        y = a;
        return y();
    }

    function d() public returns (uint256) {
        delete y;
        return 1;
    }

    function ca() public returns (uint256) {
        return y();
    }
}

// ----
// set() -> 7
// ca() -> 7
// d() -> 1
// ca() -> FAILURE