-XTypeInType uses up all memory when used in data family instance

Compiling this code with GHC 8.1 causes all my memory to be used very quickly:

{-# LANGUAGE TypeFamilies #-}
{-# LANGUAGE TypeInType #-}
module TypeInTypeEatsAllMemory where

import Data.Kind

type Const a b = a

data family UhOh (f :: k1) (a :: k2) (b :: k3)
data instance UhOh (f :: * -> * -> *) (a :: forall a) (b :: Const * a) = UhOh

On the other hand, this code compiles without issue:

{-# LANGUAGE TypeInType #-}
module TypeInTypeEatsAllMemory where

import Data.Kind

type Const a b = a

data UhOh (f :: * -> * -> *) (a :: forall a) (b :: Const * a) = UhOh

Trac metadata

Trac field	Value
Version	8.1
Type	Bug
TypeOfFailure	OtherFailure
Priority	high
Resolution	Unresolved
Component	Compiler (Type checker)
Test case
Differential revisions
BlockedBy
Related
Blocking
CC	goldfire
Operating system
Architecture