// Idea here is to test the following property:
// When a function is called recursively it has locally a monomorphic type.
// Therefore the definition of cons does not work even if it works
// with a proper type annotation.

data Vec a = Nil | Zero (Vec (a,a)) | One a (Vec (a,a))

// cons :: a -> Vec a -> Vec a
cons x Nil        = One x Nil
cons x (Zero ps)  = One x ps
cons x (One y ps) = Zero (cons (x, y) ps)
--
11:21-11:42: Expected <Vec (a, a)> got <Vec a>.
11:32-11:38: Expected <a> got <(b, c)>.
11:39-11:41: Expected <Vec a> got <Vec (a, a)>.