GHC HEAD internal error when FlexibleContexts isn't enabled

The following code produces a GHC internal error on GHC HEAD:

{-# LANGUAGE GADTs #-}
{-# LANGUAGE ScopedTypeVariables #-}
{-# LANGUAGE TypeInType #-}
module Bug where

import Data.Kind

data A :: Type -> Type where
  MkA :: Show (Maybe a) => A a

data SA :: forall a. A a -> Type where
  SMkA :: SA MkA

$ ~/Software/ghc5/inplace/bin/ghc-stage2 Bug.hs[1 of 1] Compiling Bug              ( Bug.hs, Bug.o )

Bug.hs:9:3: error:
    • Non type-variable argument in the constraint: Show (Maybe a)
      (Use FlexibleContexts to permit this)
    • In the definition of data constructor ‘MkA’
      In the data type declaration for ‘A’
  |
9 |   MkA :: Show (Maybe a) => A a
  |   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Bug.hs:12:14: error:
    • GHC internal error: ‘MkA’ is not in scope during type checking, but it passed the renamer
      tcl_env of environment: [rqU :-> ATcTyCon SA :: forall a. A a -> *,
                               rsV :-> APromotionErr RecDataConPE]
    • In the first argument of ‘SA’, namely ‘MkA’
      In the type ‘SA MkA’
      In the definition of data constructor ‘SMkA’
   |
12 |   SMkA :: SA MkA
   |              ^^^

Enabling FlexibleContexts causes the internal error to go away.

This is a regression from GHC 8.4, which does not give an internal error.

Trac metadata

Trac field	Value
Version	8.4.3
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler (Type checker)
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