[PATCH] D131062: [docs] Add "C++20 Modules"

[Chuanqi Xu via Phabricator via cfe-commits]

ChuanqiXu added inline comments.


================
Comment at: clang/docs/CPlusPlus20Modules.rst:676-678
+So the final answer for why we don't reuse the interface of Clang modules for header units is that
+we've see some differences between header units and Clang modules and we think the differences may
+be too large to be acceptable in the future.
----------------
iains wrote:
> h-vetinari wrote:
> > ChuanqiXu wrote:
> > > h-vetinari wrote:
> > > > 
> > > Since it says `in the future`, if it is better to use `may be` or `will be` than `are` ?
> > > Since it says `in the future`, if it is better to use `may be` or `will be` than `are` ?
> > 
> > The "we think" already contains built-in subjectiveness, so the "may be" is redundant in terms of uncertainty. It's not a big deal, but in general: either "they may be" or "we think they are".
> > 
> > It would also be possible to say something like:
> > 
> > > So the final answer for why we don't reuse the interface of Clang modules for header units is that
> > > there are some differences between header units and Clang modules and that ignoring those
> > > differences now would likely become a problem in the future.
> > 
> Is it not simpler than this?
> 
> Since clang header modules have different semantics from c++20 header units, if we were to force c++20 semantics on clang header modules, that would break existing code (and therefore to support existing code, we would expect clang header modules to be retained indefinitely).
> 
I think we need to express the concern about future changes. We **may** be able to handle the differences properly **now**.


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