-tcHsInstHead hs_ty
- = do { kinded_ty <- kcHsSigType hs_ty
- ; poly_ty <- tcHsKindedType kinded_ty
- ; return (tcSplitSigmaTy poly_ty) }
+tcHsInstHead (L loc ty)
+ = setSrcSpan loc $ -- No need for an "In the type..." context
+ tc_inst_head ty -- because that comes from the caller
+ where
+ -- tc_inst_head expects HsPredTy, which isn't usually even allowed
+ tc_inst_head (HsPredTy pred)
+ = do { pred' <- kcHsPred pred
+ ; pred'' <- dsHsPred pred'
+ ; return ([], [], mkPredTy pred'') }
+
+ tc_inst_head (HsForAllTy _ tvs ctxt (L _ (HsPredTy pred)))
+ = kcHsTyVars tvs $ \ tvs' ->
+ do { ctxt' <- kcHsContext ctxt
+ ; pred' <- kcHsPred pred
+ ; tcTyVarBndrs tvs' $ \ tvs'' ->
+ do { ctxt'' <- mapM dsHsLPred (unLoc ctxt')
+ ; pred'' <- dsHsPred pred'
+ ; return (tvs'', ctxt'', mkPredTy pred'') } }
+
+ tc_inst_head _ = failWithTc (ptext (sLit "Malformed instance type"))