reference type get retagged. On every assignment, if the assigned value is of
reference type, it gets retagged. Moreover, we do this even when the reference
value is inside the field of a `struct` or `enum`, to make sure we really cover
reference type get retagged. On every assignment, if the assigned value is of
reference type, it gets retagged. Moreover, we do this even when the reference
value is inside the field of a `struct` or `enum`, to make sure we really cover