1 files changed, 47 insertions, 0 deletions
diff --git a/testsuite/tests/dcoercion/DCo_HsType.hs b/testsuite/tests/dcoercion/DCo_HsType.hs
new file mode 100644
index 0000000000..067b5a8091
--- /dev/null
+++ b/testsuite/tests/dcoercion/DCo_HsType.hs
@@ -0,0 +1,47 @@
+
+{-# LANGUAGE DataKinds #-}
+{-# LANGUAGE ScopedTypeVariables #-}
+{-# LANGUAGE TypeFamilies #-}
+
+module DCo_HsType ( hsWcScopedTvs ) where
+
+import Prelude (undefined)
+
+data GhcPass (c :: Pass)
+data Pass = Renamed | Typechecked
+type GhcRn   = GhcPass 'Renamed
+
+data HsTyVarBndr pass
+type LHsTyVarBndr pass = XRec pass (HsTyVarBndr pass)
+
+type LHsSigType   pass = XRec pass (HsSigType pass)
+type LHsSigWcType pass = HsWildCardBndrs pass (LHsSigType pass)
+
+type HsOuterSigTyVarBndrs = HsOuterTyVarBndrs
+data HsSigType pass
+  = HsSig { sig_bndrs :: HsOuterSigTyVarBndrs pass }
+
+data HsWildCardBndrs pass thing
+  = HsWC { hswc_body :: thing }
+
+data HsOuterTyVarBndrs pass
+
+type family NoGhcTc p
+type instance NoGhcTc (GhcPass pass) = GhcPass (NoGhcTcPass pass)
+
+type family NoGhcTcPass (p :: Pass) :: Pass where
+  NoGhcTcPass 'Typechecked = 'Renamed
+  NoGhcTcPass other        = other
+
+type family   XRec p           a
+type instance XRec (GhcPass p) a = a
+
+hsOuterExplicitBndrs :: HsOuterTyVarBndrs (GhcPass p)
+                     -> LHsTyVarBndr (NoGhcTc (GhcPass p))
+hsOuterExplicitBndrs = undefined
+
+hsWcScopedTvs :: LHsSigWcType GhcRn -> LHsTyVarBndr GhcRn
+hsWcScopedTvs sig_wc_ty
+  | HsWC { hswc_body = sig_ty } <- sig_wc_ty
+  , HsSig { sig_bndrs = outer_bndrs } <- sig_ty
+  = hsOuterExplicitBndrs outer_bndrs