// `??` on an alias-of-optional with a struct-literal default — present + null.
//
// Regression (issue 0180): `?Opt ?? S.{...}` where `Opt :: ?S` must resolve
// the alias child to the same struct TypeId on both branches and lower the
// struct-literal default against that resolved child (issue-0166 threading),
// so the present-payload and the default share the merge TypeId. Both the
// null path (default) and the present path (the payload) are exercised.
#import "modules/std.sx";

S :: struct { a: i64 = 0; b: i64 = 0; }
Opt :: ?S;

main :: () {
    // null lhs -> the struct-literal default.
    o : Opt = null;
    x := o ?? S.{ a = 7, b = 8 };
    print("a={} {}\n", x.a, x.b);

    // present lhs -> the payload, default ignored.
    o2 : Opt = S.{ a = 1, b = 2 };
    y := o2 ?? S.{ a = 7, b = 8 };
    print("b={} {}\n", y.a, y.b);

    // untyped `.{}` default against the alias child (issue-0166 path).
    o3 : Opt = null;
    z := o3 ?? .{};
    print("c={} {}\n", z.a, z.b);
}