[GHC] #9181: :browse GHC.TypeLits causes panic

[GHC]

#9181: :browse GHC.TypeLits causes panic
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        Reporter:  nomeata           |            Owner:
            Type:  bug               |           Status:  new
        Priority:  normal            |        Milestone:
       Component:  Compiler          |          Version:  7.8.2
      Resolution:                    |         Keywords:
Operating System:  Unknown/Multiple  |     Architecture:  Unknown/Multiple
 Type of failure:  GHCi crash        |       Difficulty:  Unknown
       Test Case:  T9181             |       Blocked By:
        Blocking:                    |  Related Tickets:
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Comment (by nomeata):

 This is caused by
 {{{
     to_ifsyn_rhs (BuiltInSynFamTyCon {})
       = pprPanic "toIfaceDecl: BuiltInFamTyCon" (ppr tycon)
 }}}
 in `tyConToIfaceDecl`. Of course we don’t want `BuiltInSynFamTyCon` in
 interface files, but we use `tyConToIfaceDecl` (via `pprTyThing`) also for
 pretty-printing. So this function needs to be made “totaler”.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9181#comment:2>
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