BUG?: Period allows construction from Custom freqs

[jbrockmendel]

freq = pd.offsets.CustomBusinessDay(weekmask="Mon Wed Fri")

per = pd.Period("2023-04-06", freq=freq)

>>> freq.is_on_offset(per.to_timestamp())
False

>>> per
Period('2023-04-06', 'C')

The link between DateOffset and Period is a footgun. In this case, the Period machinery sees this CustomBusinessDay and doesn't distinguish between it and BusinessDay (of which CBDay is a subclass).

Probably should raise on CustomBusinessDay.

[jbrockmendel]

@jreback might be able to confirm this is unintentional?

[jreback]

yeah this is not intentional and should raise