Commit 54ef1c3c authored by's avatar
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Fix Trac #2433 (deriving Typeable)

parent 6344b150
......@@ -467,13 +467,17 @@ mkEqnHelp orig tvs cls cls_tys tc_app mtheta
-- we want to check the instance tycon, not the family tycon
-- For standalone deriving (mtheta /= Nothing),
-- check that all the data constructors are in scope
-- check that all the data constructors are in scope.
-- No need for this when deriving Typeable, becuase we don't need
-- the constructors for that.
-- By this time we know that the thing is algebraic
-- because we've called checkInstHead in derivingStandalone
; rdr_env <- getGlobalRdrEnv
; let hidden_data_cons = isAbstractTyCon rep_tc || any not_in_scope (tyConDataCons rep_tc)
not_in_scope dc = null (lookupGRE_Name rdr_env (dataConName dc))
; checkTc (isNothing mtheta || not hidden_data_cons)
; checkTc (isNothing mtheta ||
not hidden_data_cons ||
className cls `elem` typeableClassNames)
(derivingHiddenErr tycon)
; mayDeriveDataTypeable <- doptM Opt_DeriveDataTypeable
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