Commit ae6378d0 authored by Ian Lynagh's avatar Ian Lynagh
Browse files

Treat () as an enumeration tycon

This fixes deriving Ord (), which previously failed with
  ghc-stage1: panic! (the 'impossible' happened)
    (GHC version 6.13.20091123 for x86_64-unknown-linux):
          TcGenDeriv:mk_FunBind
parent 0dcea0d9
......@@ -864,6 +864,7 @@ isGadtSyntaxTyCon _ = False
-- | Is this an algebraic 'TyCon' which is just an enumeration of values?
isEnumerationTyCon :: TyCon -> Bool
isEnumerationTyCon (AlgTyCon {algTcRhs = DataTyCon { is_enum = res }}) = res
isEnumerationTyCon (TupleTyCon {tyConArity = arity}) = arity == 0
isEnumerationTyCon _ = False
-- | Is this a 'TyCon', synonym or otherwise, that may have further instances appear?
......@@ -1093,8 +1094,9 @@ tyConFamilySize other = pprPanic "tyConFamilySize:" (ppr other)
-- | Extract an 'AlgTyConRhs' with information about data constructors from an algebraic or tuple
-- 'TyCon'. Panics for any other sort of 'TyCon'
algTyConRhs :: TyCon -> AlgTyConRhs
algTyConRhs (AlgTyCon {algTcRhs = rhs}) = rhs
algTyConRhs (TupleTyCon {dataCon = con}) = DataTyCon { data_cons = [con], is_enum = False }
algTyConRhs (AlgTyCon {algTcRhs = rhs}) = rhs
algTyConRhs (TupleTyCon {dataCon = con, tyConArity = arity})
= DataTyCon { data_cons = [con], is_enum = arity == 0 }
algTyConRhs other = pprPanic "algTyConRhs" (ppr other)
\end{code}
......
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