[GHC] #8028: Panic on degenerate closed type family

[GHC]

#8028: Panic on degenerate closed type family
----------------------------------------------+-----------------------------
Reporter:  monoidal                           |          Owner:                         
    Type:  bug                                |         Status:  new                    
Priority:  normal                             |      Component:  Compiler (Type checker)
 Version:  7.7                                |       Keywords:                         
      Os:  Unknown/Multiple                   |   Architecture:  Unknown/Multiple       
 Failure:  Incorrect warning at compile-time  |      Blockedby:                         
Blocking:                                     |        Related:                         
----------------------------------------------+-----------------------------
 Creating a degenerate closed type family via TH gives a panic in
 `toBranchList`.

 {{{
 module T where

 import Language.Haskell.TH

 x = do n <- newName "F"
        return [ClosedTypeFamilyD n [] Nothing []]
 }}}

 {{{
 module A where

 import T

 $(x)
 }}}

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/8028>
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