[project @ 2001-07-24 16:42:11 by simonpj]
A major demand-analyser fix, which made it say something was
absent when it wasn't at all. Here's the comment from the
Case equation of dmdAnal.
-- Figure out whether the case binder is used, and use
-- that to set the keepity of the demand. This is utterly essential.
-- Consider f x = case x of y { (a,b) -> k y a }
-- If we just take scrut_demand = U(L,A), then we won't pass x to the
-- worker, so the worker will rebuild
-- x = (a, absent-error)
-- and that'll crash.