-- | Given a type of the form
--     term -> term -> ... -> term,
--   returns the number of "term" occurrences in negative position.
termArity' :: A -> Int
termArity' (A bindings _) = length bindings
termArity' :: A -> Int
termArity' (A bindings _) = length bindings
termArity' (A bindings _) = length bindings