Hello,

After lots of discussions and trying to find solutions on how to make
Importable Headers work, I have come to the unfortunate conclusion
that they are not implementable in a way that would be acceptable in
all environments where C++ is used.

Moreover, I believe the goals that were set for the specification of
Importable Headers can be achieved in a much simpler way, without
introducing the special semantics that those provide.

In other words, we can make the standard allow the optimizations
achieved by Explicit Clang Header Modules as well as the early
adoption reports from MSVC, while at the same time maintaining the
semantics of source inclusion as the "canonical" behavior for when a
given environment cannot make use of those optimizations.

This revision of the paper does not include wording changes yet, as I
want to build consensus on this prior to going through the effort of
figuring out what wording needs changing.

See the paper at: https://wg21.link/P2898R0

daniel