This change also requires some shuffling to the offsets we generate for
the diagnostic. Previously, we were generating an empty range
immediately *after* the line terminator and immediate before the first
byte of the subsequent line. How this is rendered is somewhat open to
interpretation, but the new version of `annotate-snippets` chooses to
render this at the end of the preceding line instead of the beginning of
the following line.
In this case, we want the diagnostic to point to the beginning of the
following line. So we either need to change `annotate-snippets` to
render such spans at the beginning of the following line, or we need to
change our span to point to the first full character in the following
line. The latter will force `annotate-snippets` to move the caret to the
proper location.
I ended up deciding to change our spans instead of changing how
`annotate-snippets` renders empty spans after a line terminator. While I
didn't investigate it, my guess is that they probably had good reason
for doing so, and it doesn't necessarily strike me as _wrong_.
Furthermore, fixing up our spans seems like a good idea regardless, and
was pretty easy to do.
