void Add(CallingConventionSig sig)
        {
            if (sig is null)
            {
                return;
            }

            if (sig is FieldSig fs)
            {
                Add(fs);
                return;
            }

            if (sig is MethodBaseSig mbs)
            {
                Add(mbs);
                return;
            }

            if (sig is LocalSig ls)
            {
                Add(ls);
                return;
            }

            if (sig is GenericInstMethodSig gims)
            {
                Add(gims);
                return;
            }
        }
        void Add(CallingConventionSig sig)
        {
            if (sig is MethodBaseSig msig)
            {
                Add(msig);
                return;
            }

            if (sig is FieldSig fsig)
            {
                Add(fsig);
                return;
            }

            if (sig is LocalSig lsig)
            {
                Add(lsig);
                return;
            }

            if (sig is GenericInstMethodSig gsig)
            {
                Add(gsig);
                return;
            }

            Debug.Assert(sig is null);
        }