Renamer / typechecker hang (UndecidableSuperClasses)

Adapted from hask, this does not look like a normal superclass loop. Loop is avoided by removing instance (Category p, Category q) => Category (Nat p q).

{-# language KindSignatures #-}
{-# language PolyKinds #-}
{-# language DataKinds #-}
{-# language TypeFamilies #-}
{-# language RankNTypes #-}
{-# language NoImplicitPrelude #-}
{-# language FlexibleContexts #-}
{-# language MultiParamTypeClasses #-}
{-# language GADTs #-}
{-# language ConstraintKinds #-}
{-# language FlexibleInstances #-}
{-# language TypeOperators #-}
{-# language ScopedTypeVariables #-}
{-# language DefaultSignatures #-}
{-# language FunctionalDependencies #-}
{-# language UndecidableSuperClasses #-}
{-# language UndecidableInstances #-}
{-# language TypeInType #-}

import GHC.Types (Constraint, Type)

type Cat i = i -> i -> Type

newtype Y p a b = Y { getY :: p b a }

class (Functor p, Dom p ~ Op p, Cod p ~ Nat p (->), Ob (Op p) ~ Ob p) => Category (p :: Cat i) where
  type Op p :: Cat i
  type Op p = Y p

  type Ob p :: i -> Constraint

class (Category (Dom f), Category (Cod f)) => Functor (f :: i -> j) where
  type Dom f :: Cat i
  type Cod f :: Cat j

data Nat :: Cat i -> Cat j -> Cat (i -> j)

instance (Category p, Category q) => Category (Nat p q) 

I get

$ ghci2 -ignore-dot-ghci -v /tmp/Hangs.hs 
GHCi, version 8.3.20171122: http://www.haskell.org/ghc/  :? for help
Glasgow Haskell Compiler, Version 8.3.20171122, stage 2 booted by GHC version 8.2.1
...
Loading package integer-gmp-1.0.1.0 ... linking ... done.
Loading package base-4.11.0.0 ... linking ... done.
*** Parser [source]:
!!! Parser [source]: finished in 0.66 milliseconds, allocated 0.136 megabytes
*** Desugar:
*** Simplify [expr]:
!!! Simplify [expr]: finished in 0.43 milliseconds, allocated 0.233 megabytes
*** CorePrep [expr]:
!!! CorePrep [expr]: finished in 0.23 milliseconds, allocated 0.167 megabytes
*** ByteCodeGen [Ghci1]:
!!! ByteCodeGen [Ghci1]: finished in 0.35 milliseconds, allocated 0.284 megabytes
*** Parser [source]:
!!! Parser [source]: finished in 0.21 milliseconds, allocated 0.197 megabytes
*** Desugar:
*** Simplify [expr]:
!!! Simplify [expr]: finished in 0.52 milliseconds, allocated 0.268 megabytes
*** CorePrep [expr]:
!!! CorePrep [expr]: finished in 0.23 milliseconds, allocated 0.113 megabytes
*** ByteCodeGen [Ghci1]:
!!! ByteCodeGen [Ghci1]: finished in 0.46 milliseconds, allocated 0.334 megabytes
*** Chasing dependencies:
Chasing modules from: 
!!! Chasing dependencies: finished in 0.14 milliseconds, allocated 0.047 megabytes
Stable obj: []
Stable BCO: []
unload: retaining objs []
unload: retaining bcos []
Ready for upsweep []
Upsweep completely successful.
*** Deleting temp files:
Deleting: 
*** Chasing dependencies:
Chasing modules from: */tmp/Hangs.hs
!!! Chasing dependencies: finished in 6.10 milliseconds, allocated 10.504 megabytes
Stable obj: []
Stable BCO: []
unload: retaining objs []
unload: retaining bcos []
Ready for upsweep
  [NONREC
      ModSummary {
         ms_hs_date = 2017-11-28 22:14:57.810561584 UTC
         ms_mod = Main,
         ms_textual_imps = [(Nothing, GHC.Types)]
         ms_srcimps = []
      }]
*** Deleting temp files:
Deleting: 
compile: input file /tmp/Hangs.hs
*** Checking old interface for Main (use -ddump-hi-diffs for more details):
[1 of 1] Compiling Main             ( /tmp/Hangs.hs, interpreted )
*** Parser [Main]:
!!! Parser [Main]: finished in 2.63 milliseconds, allocated 4.821 megabytes
*** Renamer/typechecker [Main]:

Trac metadata

Trac field	Value
Version	8.3
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
Test case
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