Nesting Just and Identity results in java.lang.ClassCastException.

[luminusian]

In cats,

(m/>>= (identity/identity (maybe/just 0))
       (fn [x]
         (m/return (m/<$> identity x))))
CompilerException java.lang.ClassCastException: cats.monad.maybe.Just cannot be cast to cats.monad.identity.Identity

In Haskell,

*Main> Identity (Just 0) >>= (\x -> return (id <$> x))
Identity (Just 0)

[luminusian]

Reordering cond in infer in cats.context seems to resolve the issue.

(defn infer
  "Given an optional value infer its context. If context is already set, it
  is returned as is without any inference operation."
  {:no-doc true}
  ([]
   (when (nil? *context*)
     (throw-illegal-argument "No context is set."))
   *context*)
  ([v]
   (cond
     (satisfies? p/Contextual v)
     (p/-get-context v)
     (not (nil? *context*))
     *context*
     :else
     (throw-illegal-argument
      (str "No context is set and it can not be automatically "
           "resolved from provided value")))))

Now,

(m/>>= (identity/identity (maybe/just 0))
       (fn [x]
         (m/return (m/<$> identity x))))
=> #<Identity #<Just 0>>