The following is a genuine type error, but the first message appears
to be rather 'parasitic', not to mention not making any actual sense.
It's caused by having a spurious type context around a type with no
type vriables (as per the second error message, which is immaculate...)
Case.hs:378:
The constraint `PO b' does not mention any of
the universally quantified type variables {}
of the type `Metric HolidayR NumInf
-> HolidayR -> SetOf HolidayR -> SetOf HolidayR'
In the type signature for `s_max2'
Case.hs:378:
The constraint `PO b'
mentions type variables that do not appear in the type
`Metric HolidayR NumInf
-> HolidayR -> SetOf HolidayR -> SetOf HolidayR'
In the type signature for `s_max2'
Cheers,
Alex.
