Remove the distinction between data and newtype families

[ghc-hetmet.git] / compiler / typecheck / TcDeriv.lhs

diff --git a/compiler/typecheck/TcDeriv.lhs b/compiler/typecheck/TcDeriv.lhs
index 98d7fcf..1a9a881 100644 (file)
--- a/compiler/typecheck/TcDeriv.lhs
+++ b/compiler/typecheck/TcDeriv.lhs
@@ -399,7 +399,10 @@ mkEqnHelp orig tvs cls cls_tys tc_app
 
        ; gla_exts <- doptM Opt_GlasgowExts
        ; overlap_flag <- getOverlapFlag
-       ; if isDataTyCon tycon then
+
+          -- Be careful to test rep_tc here: in the case of families, we want
+          -- to check the instance tycon, not the family tycon
+       ; if isDataTyCon rep_tc then
                mkDataTypeEqn orig gla_exts full_tvs cls cls_tys 
                              tycon full_tc_args rep_tc rep_tc_args
          else