Commit cf7e2fa4 authored by Simon Peyton Jones's avatar Simon Peyton Jones
Browse files

Accept derived Read on an empty data type (Trac #7931)

parent 20d8e8c3
......@@ -902,7 +902,8 @@ gen_Read_binds get_fixity loc tycon
read_prec = mkHsVarBind loc readPrec_RDR
(nlHsApp (nlHsVar parens_RDR) read_cons)
read_cons = foldr1 mk_alt (read_nullary_cons ++ read_non_nullary_cons)
read_cons | null data_cons = error_Expr "Derived Read on empty data type" -- Trac #7931
| otherwise = foldr1 mk_alt (read_nullary_cons ++ read_non_nullary_cons)
read_non_nullary_cons = map read_non_nullary_con non_nullary_cons
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