a!! should be no-op if we know the variable is not null

[i582]

import "@stdlib/deploy";

contract Test with Deployable {
    get fun getValue(val: Int?): Int {
        if (val != null) {
            return val!!;
        }
        return 10
    }
}

Then we will save about 62 gas for each !!.

[anton-trunov]

We will remove the non-null runtime checks here: #1282 (with a config option). See also this related issue: #259.