Fix class construction

Wed Aug  2 13:34:58 EDT 2006  Manuel M T Chakravarty <chak@cse.unsw.edu.au>
  * Fix class construction

compiler/hsSyn/Convert.lhs

@@ -125,11 +125,11 @@ cvtTop (NewtypeD ctxt tc tvs constr derivs)
 	; returnL $ TyClD (mkTyData NewType stuff Nothing [con'] derivs') }
 
 cvtTop (ClassD ctxt cl tvs fds decs)
-  = do	{ stuff <- cvt_tycl_hdr ctxt cl tvs
+  = do	{ (cxt', tc', tvs', _) <- cvt_tycl_hdr ctxt cl tvs
 	; fds'  <- mapM cvt_fundep fds
 	; (binds', sigs') <- cvtBindsAndSigs decs
-	; returnL $ TyClD $ mkClassDecl stuff fds' sigs' binds' []  
-							     -- ^^no ATs in TH
+	; returnL $ TyClD $ mkClassDecl (cxt', tc', tvs') fds' sigs' binds' []
+							     -- no ATs in TH^^
 	}
 
 cvtTop (InstanceD tys ty decs)