Is there an “opposite” to the null coalescing operator? (…in any language?)

Question

null coalescing translates roughly to return x, unless it is null, in which case return y

I often need return null if x is null, otherwise return x

Answer 1

public class ok {
    T s;
    public static implicit operator ok(T s) { return new ok { s = s }; }
    public static implicit operator T(ok _) { return _.s; }

    public static bool operator true(ok _) { return _.s != null; }
    public static bool operator false(ok _) { return _.s == null; }
    public static ok operator &(ok x, ok y) { return y; }
}

I often need this logic for strings:

using ok = ok;

...

string bob = null;
string joe = "joe";

string name = (ok)bob && bob.ToUpper();   // name == null, no error thrown
string boss = (ok)joe && joe.ToUpper();   // boss == "JOE"