X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;ds=sidebyside;f=compiler%2Fiface%2FBuildTyCl.lhs;h=9f35453b590cc0e33e561b3e1ec6e8eadc0fe250;hb=e2390e76b2f1f2beecd9a0d308c4890a56ae8bca;hp=333d8084ce4a301144cadb1ddcde85b41ef3c47c;hpb=6777144f7522d8db5935737e12fa451ca3211e6d;p=ghc-hetmet.git

diff --git a/compiler/iface/BuildTyCl.lhs b/compiler/iface/BuildTyCl.lhs
index 333d808..9f35453 100644
--- a/compiler/iface/BuildTyCl.lhs
+++ b/compiler/iface/BuildTyCl.lhs
@@ -148,6 +148,8 @@ mkNewTyConRhs tycon_name tycon con
     rhs_ty = head (dataConInstOrigArgTys con (mkTyVarTys tvs))
 	-- Instantiate the data con with the 
 	-- type variables from the tycon
+	-- NB: a newtype DataCon has no existentials; hence the
+	--     call to dataConInstOrigArgTys has the right type args
 
     etad_tvs :: [TyVar]	-- Matched lazily, so that mkNewTypeCoercion can
     etad_rhs :: Type	-- return a TyCon without pulling on rhs_ty