return s.dottype1(n.Pos(), n.X.Type(), n.Type(), iface, source, target, targetItab, commaok, nil)
}

// dottype1 implements a x.(T) operation. iface is the argument (x), dst is the type we're asserting to (T)
// and src is the type we're asserting from.
// source is the *runtime._type of src
// target is the *runtime._type of dst.