GHCi 8.0.1 panic with PatternSynonyms

Loading this code:

{-# LANGUAGE PatternSynonyms #-}

data D1 = MkD1 ()
data D2 = MkD2 D1

pattern P1 x = MkD1 x
pattern P2 x = MkD2 (P1 x)

in GHCi 8.0.1 results in the following panic:

$ ghci Broken.hs         
GHCi, version 8.0.1: http://www.haskell.org/ghc/  :? for help
[1 of 1] Compiling Main             ( Broken.hs, interpreted )
ghc: panic! (the 'impossible' happened)
  (GHC version 8.0.1 for x86_64-unknown-linux):
	kindPrimRep.go rep_a18s

Please report this as a GHC bug:  http://www.haskell.org/ghc/reportabug

> 

The unique name in the error message (rep_a18s) seems to be consistent between executions, but varies after :reloading.

The panic does not occur when the module is simply compiled with ghc; it only occurs when loaded into ghci.

According to ​Gergő Érdi, who is CCed, the error does not occur in GHCi 7.10.3

Trac metadata

Trac field	Value
Version	8.0.1
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	GHCi
Test case
Differential revisions
BlockedBy
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CC	cactus
Operating system
Architecture