470f036b

By: Tom Sydney Kerckhove <syd@cs-syd.eu>

ical-recurrence: test that ByWeekNo 53 does not occur in a 52 week year

byWeekNoExpand bounds negative week numbers by the number of weeks in
the year but passes positive ones through unchecked, and
fromWeekDateWithStart never returns Nothing: it just keeps adding weeks
to the first day of the year.  Nothing then checks that the day it
produced still falls in the year being expanded.

Week 53 of 2019 therefore resolves to the 30th of December 2019, which
is a day in ISO year 2020, and a week number that does not exist in a
year should be ignored for that year like the 30th of February is.

2019 and 2021 have 52 weeks, 2020 has 53.

Timeline