[Template-haskell] GADTs

[Simon Peyton-Jones]

| and, i think that adding TH constructs for all new language features
| in 6.6 is really important for all TH developers. otherwise, we will
| be like one-armed invalid. if SPJ don't want to change TH datatypes
| after 6.6 release, it should be done just now

Quite the reverse.  I think it's dangerous to fiddle just now, because
there is only a matter of days before 6.6 is fixed.  But after 6.6 we
can review the data types and change them if there's a consensus.  The
exact design isn't something about which I feel strongly, apart from the
principle in my previous message (avoiding gratuitous sugar)

Simon