Repository : ssh://darcs.haskell.org//srv/darcs/ghc On branch : master
http://hackage.haskell.org/trac/ghc/changeset/661c1c112eb40efd75ac61643c3e1231f60d58d4 >--------------------------------------------------------------- commit 661c1c112eb40efd75ac61643c3e1231f60d58d4 Author: Simon Peyton Jones <simo...@microsoft.com> Date: Mon Nov 26 12:18:15 2012 +0000 Improve error message when a variable is used both as kind and type variable Fixes Trac #7404 >--------------------------------------------------------------- compiler/rename/RnTypes.lhs | 15 +++++++++++++++ 1 files changed, 15 insertions(+), 0 deletions(-) diff --git a/compiler/rename/RnTypes.lhs b/compiler/rename/RnTypes.lhs index 7867c5c..b515f3a 100644 --- a/compiler/rename/RnTypes.lhs +++ b/compiler/rename/RnTypes.lhs @@ -370,9 +370,17 @@ bindHsTyVars doc mb_assoc kv_bndrs tv_bndrs thing_inside , kv <- kvs ] all_kvs = filterOut (`elemLocalRdrEnv` rdr_env) $ nub (kv_bndrs ++ kvs_from_tv_bndrs) + overlap_kvs = [ kv | kv <- all_kvs, any ((==) kv . hsLTyVarName) tvs ] + -- These variables appear both as kind and type variables + -- in the same declaration; eg type family T (x :: *) (y :: x) + -- We disallow this: too confusing! + ; poly_kind <- xoptM Opt_PolyKinds ; unless (poly_kind || null all_kvs) (addErr (badKindBndrs doc all_kvs)) + ; unless (null overlap_kvs) + (addErr (overlappingKindVars doc overlap_kvs)) + ; loc <- getSrcSpanM ; kv_names <- mapM (newLocalBndrRn . L loc) all_kvs ; bindLocalNamesFV kv_names $ @@ -428,6 +436,13 @@ rnHsBndrSig doc (HsWB { hswb_cts = ty@(L loc _) }) thing_inside ; (res, fvs2) <- thing_inside (HsWB { hswb_cts = ty', hswb_kvs = kv_names, hswb_tvs = tv_names }) ; return (res, fvs1 `plusFV` fvs2) } } +overlappingKindVars :: HsDocContext -> [RdrName] -> SDoc +overlappingKindVars doc kvs + = vcat [ ptext (sLit "Kind variable") <> plural kvs <+> + ptext (sLit "also used as type variable") <> plural kvs + <> colon <+> pprQuotedList kvs + , docOfHsDocContext doc ] + badKindBndrs :: HsDocContext -> [RdrName] -> SDoc badKindBndrs doc kvs = vcat [ hang (ptext (sLit "Unexpected kind variable") <> plural kvs _______________________________________________ Cvs-ghc mailing list Cvs-ghc@haskell.org http://www.haskell.org/mailman/listinfo/cvs-ghc
