- | isTupleTyCon con = (caseTuple (tupleTyConBoxity con) xrs,True)
- | null args = (caseTrivial,False) -- T
- | or (init xcs) = (caseWrongArg,True) -- T (..var..) ty
- | last xcs = -- T (..no var..) ty
- (caseTyApp (fst (splitAppTy ty)) (last xrs),True)
+ | not (or xcs) = (caseTrivial, False) -- Variable does not occur
+ -- At this point we know that xrs, xcs is not empty,
+ -- and at least one xr is True
+ | isTupleTyCon con = (caseTuple (tupleTyConBoxity con) xrs, True)
+ | or (init xcs) = (caseWrongArg, True) -- T (..var..) ty
+ | otherwise = -- T (..no var..) ty
+ (caseTyApp (fst (splitAppTy ty)) (last xrs), True)