Simon Peyton-Jones wrote:
Fortunately, I don't think a lot of people use the feature in anger. Please yell if you *are* using impredicative polymorphism for something serious. But if you are, we need to think of a workaround. The current situation seems unsustainable.
I think darcs is using it. At least, I had to enable ImpredicativePolymorphism to successfully build darcs with GHC 6.11 (a snapshot from about February), although the flag is not required with GHC 6.10. I haven't had a chance to try with the RC yet, but will do this weekend. I'll have to check the full details of why it's needed, but from memory I think it can be worked around at the cost of more verbosity by using some newtypes in appropriate places. Cheers, Ganesh =============================================================================== Please access the attached hyperlink for an important electronic communications disclaimer: http://www.credit-suisse.com/legal/en/disclaimer_email_ib.html ===============================================================================