-Wall -Werror

[Ross Paterson]

On Tue, Aug 12, 2008 at 12:54:04AM -0700, Ashley Yakeley wrote:
> What I meant was, the module in which the instance is defined, and
> the module in which the type is defined are both hidden, and only
> re-exported by another module. Thus it is not possible to import the
> type without importing the instance.

Not quite:
* Data.Time.Calendar exports Day without its Read instance.
* Data.Time.Clock exports UTCTime without Read or Show instances.
* Data.Time.LocalTime exports TimeOfDay, LocalTime, TimeZone, UTCTime
  and ZonedTime without Read instances.