[libc++] Fix typo in comment at __optional_storage_base

[hawkinsw]

Summary

Small typo fix(es) for struct definition of __optional_storage_base for
a reference type.

[philnik]

libcxx/include/optional

395–396

This sentence still doesn't make any sense. I think there is a "not" missing somewhere.

[jloser]

libcxx/include/optional

395–396

I'd be OK with something like this instead - what do you think?

optional<T&> is currently required to be ill-formed. However, it may be allowed in the
future. For this reason, it has already been implemented to ensure we can make the change in an ABI-compatible manner.

[hawkinsw]

libcxx/include/optional

395–396

Yes, of course!! I completely boofed. I was so excited to be able to fit that all within 80 characters that I never thought to reread! I am *so* sorry!

Also, thank you for being as persnickety as I am -- there is definitely a dash needed between ABI and compatible!!

[hawkinsw]

libcxx/include/optional

395–396

And, for the , as well (after the opening clause). You and I are obviously of one mind!

[hawkinsw]

Updating after excellent feedback from @jloser.

[jloser]

libcxx/include/optional

395–396

Just one small thing: do you mind adding the comma after "However", please? Sorry that I'm such a nitpick with this.

After that, LGTM.

[hawkinsw]

Updating to address @jloser comment about comma after however as conjunctive adverb.

[hawkinsw]

libcxx/include/optional

395–396

Thanks for the feedback! I posted a follow up!

[hawkinsw]

@philnik @jloser Sorry, but I don't yet have landing rights. If you could help, that would be great! Thank you!

[Mordante]

Thanks, LGTM! I'll land it on your behalf.

libcxx/include/optional

_LIBCPP_CONSTEXPR_AFTER_CXX17 void __assign_from(_That&& __opt)
         {
             if (this->__engaged_)
                 this->reset();
             else
                 __construct(_VSTD::forward<_That>(__opt).__get());
         }
     }
 };
 
-// optional<T&> is currently required ill-formed, however it may to be in the
-// future. For this reason it has already been implemented to ensure we can
-// make the change in an ABI compatible manner.
+// optional<T&> is currently required to be ill-formed. However it may
+// be allowed in the future. For this reason, it has already been implemented
+// to ensure we can make the change in an ABI-compatible manner.
 template <class _Tp>
 struct __optional_storage_base<_Tp, true>
 {
     using value_type = _Tp;
     using __raw_type = remove_reference_t<_Tp>;
     __raw_type* __value_;
 
     template <class _Up>