X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=compiler%2Ftypecheck%2FTcGenDeriv.lhs;h=2c04cf4bc34f0e53ff5299466a5966deb9cf6405;hb=d93785d99261a433075dcbac8c388730a4dec64f;hp=6e5aedc83e058d608a8b236b61c317a8dbff5be4;hpb=e4b5abb6ddfd07a7f95455c94faf2946a1bc078e;p=ghc-hetmet.git

diff --git a/compiler/typecheck/TcGenDeriv.lhs b/compiler/typecheck/TcGenDeriv.lhs
index 6e5aedc..2c04cf4 100644
--- a/compiler/typecheck/TcGenDeriv.lhs
+++ b/compiler/typecheck/TcGenDeriv.lhs
@@ -168,7 +168,7 @@ gen_Eq_binds loc tycon
   where
     (nullary_cons, nonnullary_cons)
        | isNewTyCon tycon = ([], tyConDataCons tycon)
-       | otherwise	      = partition isNullarySrcDataCon (tyConDataCons tycon)
+       | otherwise        = partition isNullarySrcDataCon (tyConDataCons tycon)
 
     no_nullary_cons = null nullary_cons
 
@@ -1457,11 +1457,13 @@ functorLikeTraverse var (FT { ft_triv = caseTrivial,     ft_var = caseVar
             where (_, xc) = go co x
                   (yr,yc) = go co y
         go co ty@(TyConApp con args)
-               | isTupleTyCon con = (caseTuple (tupleTyConBoxity con) xrs,True)
-               | null args        = (caseTrivial,False)	 -- T
-               | or (init xcs)    = (caseWrongArg,True)	 -- T (..var..)    ty
-               | last xcs         = 			 -- T (..no var..) ty
-	       	      		    (caseTyApp (fst (splitAppTy ty)) (last xrs),True)
+               | not (or xcs)     = (caseTrivial, False)   -- Variable does not occur
+               -- At this point we know that xrs, xcs is not empty,
+               -- and at least one xr is True
+               | isTupleTyCon con = (caseTuple (tupleTyConBoxity con) xrs, True)
+               | or (init xcs)    = (caseWrongArg, True)   -- T (..var..)    ty
+               | otherwise        =                        -- T (..no var..) ty
+                                    (caseTyApp (fst (splitAppTy ty)) (last xrs), True)
             where (xrs,xcs) = unzip (map (go co) args)
         go co (ForAllTy v x) | v /= var && xc = (caseForAll v xr,True)
             where (xr,xc) = go co x