ASSERT( isId new_bndr )
WARN( new_arity < old_arity || new_arity < dmd_arity,
(ptext (sLit "Arity decrease:") <+> ppr final_id <+> ppr old_arity
- <+> ppr new_arity <+> ppr dmd_arity) $$ ppr new_rhs )
+ <+> ppr new_arity <+> ppr dmd_arity) )
-- Note [Arity decrease]
final_id `seq` -- This seq forces the Id, and hence its IdInfo,