// `?Protocol = null` — optional protocol boxes use sentinel-shape
// (ctx == null is the "none" state), so they cost no extra storage
// beyond the protocol's standard 2-pointer layout. Method calls on
// a non-null optional protocol auto-unwrap and dispatch through the
// vtable / inline fn-ptrs as usual.

#import "modules/std.sx";

GPU :: protocol {
  ping :: () -> s64;
}

Impl :: struct {}
impl GPU for Impl {
  ping :: (self: *Impl) -> s64 { 42 }
}

main :: () -> s32 {
  g : ?GPU = null;
  if g != null {
    print("BAD: g not null at start\n");
  } else {
    print("g initially null\n");
  }

  g = xx @Impl.{};
  if g != null {
    n := g.ping();
    print("after assign: g.ping() = {}\n", n);
  } else {
    print("BAD: g still null after assign\n");
  }
  0
}