Multi-Stage build with --mount=type=cache and COPY from mount-cache location in next stage?

I'm trying to optimize my multi-stage build by using RUN --mount=type=cache,id=xx,target=/zz. I need to re-use the cached location in my next build-stage that will finalize the build. It came in my mind, that I could use something like COPY --mount=type=cache,id=xx /zz but obviously as far as I consulted the buildkit-reference --mount=type=cache statements are only supported for RUN, but not for COPY.

Are there any plans to realize that? As far as I see (in theorie) the only workaround would be something like this:

FROM ... AS stage-1
RUN \
  --mount=type=cache,id=xx,target=/usr/lib/foo \
  do-some-build

FROM final-distro AS stage-2
RUN \
  --mount=type=cache,id=xx,target=/build/usr/lib/foo \
  cp -rf /build/usr/lib/foo /usr/lib/foo

Or is there any smarter solution?

Start with the BuildKit reference for RUN --mount=type=cache and the existing multi-stage behavior described in the issue. Define the intended semantics for exposing a cache mount to a later stage, then assess the two-stage example; the work is done when the behavior is specified and supported consistently.