+ -- Cheap and cheerful; the simplifer moves casts out of the way
+ -- The lambda case is important to spot x = /\a. C (f a)
+ -- which comes up when C is a dictionary constructor and
+ -- f is a default method.
+ -- Example: the instance for Show (ST s a) in GHC.ST
+ is_con_app (Var v) = isDataConWorkId v
+ is_con_app (App f _) = is_con_app f
+ is_con_app (Lam b e) | isTyVar b = is_con_app e
+ is_con_app (Note _ e) = is_con_app e
+ is_con_app other = False