Add a MonadRec instance to UnifyT

spago.dhall

@@ -19,6 +19,7 @@ to generate this file without the comments in this block.
   , "newtype"
   , "ordered-collections"
   , "prelude"
+  , "tailrec"
   , "transformers"
   , "tuples"
   ]

src/Control/Monad/Unify/Trans.purs

@@ -4,6 +4,7 @@ import Prelude (($), (<<<), const, flip, unit)
 
 import Control.Plus (class Plus)
 import Control.Monad (class Monad)
+import Control.Monad.Rec.Class (class MonadRec)
 import Control.Monad.State.Trans (StateT, runStateT)
 import Control.Monad.State.Class (gets, modify)
 import Control.Monad.Unify.Class (class MonadUnify, class Unifiable, class UnificationVariable, Stream, pop, squash, variable, variables, reify, unify)
@@ -41,6 +42,7 @@ derive newtype instance (Monad m, Alt m) => Alt (UnifyT k f m)
 derive newtype instance (Monad m, Plus m) => Plus (UnifyT k f m)
 instance (Monad m, Alternative m) => Alternative (UnifyT k f m)
 instance (MonadPlus m) => MonadPlus (UnifyT k f m)
+derive newtype instance MonadRec m => MonadRec (UnifyT k f m)
 
 instance (Unifiable k f, MonadPlus m) => MonadUnify k f (UnifyT k f m) where
     fresh = MkUnifyT $ do