Bug 1628715 made several infallible methods of
NotNull<elem_type*> instead of
elem_type*. Several code locations used to check these for nullptr, and contained dedicated code for that, which was unreachable. In some cases, they might have been meant to use fallible operations instead.
These locations have been marked with
XXX(Bug 1631371). The respective module peers should check if these match their intention.
The remaining comments are planned to be removed by end of October 2020 if they have not been addressed by then, and this bug is going to be closed.