Fix Trac #2138: print the 'stupid theta' of a data type

diff --git a/compiler/main/PprTyThing.hs b/compiler/main/PprTyThing.hs
index 2a7abb4..c379d97 100644 (file)
--- a/compiler/main/PprTyThing.hs
+++ b/compiler/main/PprTyThing.hs
@@ -28,7 +28,7 @@ module PprTyThing (
 import qualified GHC
 
 import GHC     ( TyThing(..) )
-import TyCon   ( tyConFamInst_maybe )
+import TyCon   ( tyConFamInst_maybe, isAlgTyCon, tyConStupidTheta )
 import Type    ( TyThing(..), tidyTopType, pprTypeApp )
 import TcType  ( tcMultiSplitSigmaTy, mkPhiTy )
 import SrcLoc  ( SrcSpan )
@@ -86,7 +86,7 @@ pprTyConHdr pefas tyCon
   | Just (fam_tc, tys) <- tyConFamInst_maybe tyCon
   = ptext keyword <+> ptext SLIT("instance") <+> pprTypeApp tyCon (ppr_bndr tyCon) tys
   | otherwise
-  = ptext keyword <+> opt_family <+> ppr_bndr tyCon <+> hsep (map ppr vars)
+  = ptext keyword <+> opt_family <+> opt_stupid <+> ppr_bndr tyCon <+> hsep (map ppr vars)
   where
     vars | GHC.isPrimTyCon tyCon || 
           GHC.isFunTyCon tyCon = take (GHC.tyConArity tyCon) GHC.alphaTyVars
@@ -100,6 +100,10 @@ pprTyConHdr pefas tyCon
       | GHC.isOpenTyCon tyCon = ptext SLIT("family")
       | otherwise             = empty
 
+    opt_stupid         -- The "stupid theta" part of the declaration
+       | isAlgTyCon tyCon = GHC.pprThetaArrow (tyConStupidTheta tyCon)
+       | otherwise        = empty      -- Returns 'empty' if null theta
+
 pprDataConSig pefas dataCon =
   ppr_bndr dataCon <+> dcolon <+> pprTypeForUser pefas (GHC.dataConType dataCon)