_Merge

type _Merge<Destination, Source> = Simplify<
    SimpleMerge<PickIndexSignature<Destination>, PickIndexSignature<Source>> &
        SimpleMerge<
            OmitIndexSignature<Destination>,
            OmitIndexSignature<Source>
        >
>;

type _Merge<Destination, Source> = Simplify<
    SimpleMerge<PickIndexSignature<Destination>, PickIndexSignature<Source>> &
        SimpleMerge<
            OmitIndexSignature<Destination>,
            OmitIndexSignature<Source>
        >
>;