`Infallible` is a more appropriate type in comparsion to `()` for
comments that do not require a `CodeLocation`.
That is because if the type for `location` is `Option<()>`, this means
that `Some(())` can be constructed, however, we never intend to
construct that variant. On the other hand, `Infallible` can never be
constructed, and so, only `None` can be used.
This requires updates to some functions to use the generic `T` and
also handle the different kinds of `Comment`s -- `Infallible` and
`CodeLocation`.
X-Co-Authored-By: Fintan Halpenny <fintan.halpenny@gmail.com>
Lorenz Leutgeb
Sebastian Martinez
cloudhead