Default elements when resizing arrays by assigning to length

[hajduakos]

When we resize an array by assigning to length, the new elements are not set to their default value (except in the constructor). We should give at least give a warning (bug) as long as it is not implemented (enhancement).

pragma solidity >=0.5.0;

contract Issue097 {
    int[] arr;

    constructor() public {
        arr.length += 1;
        assert(arr[arr.length-1] == 0);
    }

    function() external payable {
        arr.length += 1;
        assert(arr[arr.length-1] == 0);
    }
}

$ solc-verify.py issues/Issue097.sol 
Issue097::[constructor]: OK
Issue097::[fallback]: ERROR
 - issues/Issue097.sol:13:9: Assertion might not hold.
Errors were found by the verifier.

[hajduakos]

Warning as of 37ef21f

[dddejan]

Length is planned as read-only in 0.6, so marking this as won't fix.

ethereum#3515

[hajduakos]

We should not forget to remove the check and the warning message introduced in 37ef21f as it will basically become a dead code.

[dddejan]

Yes, we keep open to remind.