Type instantiate(Env<AttrContext> env,
                     Type site,
                     Symbol m,
                     List<Type> argtypes,
                     List<Type> typeargtypes,
                     boolean allowBoxing,
                     boolean useVarargs,
                     Warner warn) {
        try {
            return rawInstantiate(env, site, m, argtypes, typeargtypes,
                                  allowBoxing, useVarargs, warn);
        } catch (Infer.NoInstanceException ex) {
            return null;
        }
    }