PureScript record and mutual recursion problem with Instances

_README

Mutual recursive definitions within records, when using type class constraints, fail to compile.

compile-error-output.txt

Error found:
in module Main
at /home/owi/projects/mutual-recursion-typeclass/src/Main.purs line 14, column 1 - line 14, column 37

  No type class instance was found for
                          
    Control.Monad.Monad m0
                          

while checking that expression { f: \n ->    
                                      (...) n
                               }             
  has type forall m.            
             { f :: Int -> m Int
             }                  
while checking type of property accessor (makeDecr bar).f
while applying a function makeDecr
  of type forall m.                            
            (Monad m) => { f :: Int -> m Int   
                         }                     
                         -> { f :: Int -> m Int
                            }                  
  to argument bar
in binding group foo, bar

where m0 is a rigid type variable
        bound at line 14, column 1 - line 14, column 37

See https://github.com/purescript/purescript/wiki/Error-Code-NoInstanceFound for more information,
or to contribute content related to this error.


Compiling Main
* ERROR: Subcommand terminated with exit code 1

Main.purs

module Main where

import Prelude
import Control.Monad.Eff (Eff)
import Control.Monad.Eff.Console (CONSOLE, log)

type R m = { f ∷ Int → m Int }

makeDecr ∷ ∀ m. Monad m ⇒ R m → R m
makeDecr r = { f: \n → if n > 0 then r.f (n - 1) else pure n }

-- `foo :: ∀ e. R (Eff e)` would compile
foo :: ∀ m. R m
foo = { f: \n → (makeDecr bar).f n }

-- `bar :: ∀ e. R (Eff e)` would compile
bar :: ∀ m. R m
bar = { f: \n → (makeDecr foo).f n }

main :: forall e. Eff ( console :: CONSOLE | e ) Unit
main = show <$> foo.f 10 >>= log