[Bug libstdc++/121918] New: [C++26] optional> should be as large as function_ref

[lichray at gmail dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=121918

            Bug ID: 121918
           Summary: [C++26] optional<function_ref<S>> should be as large
                    as function_ref<S>
           Product: gcc
           Version: 16.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libstdc++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: lichray at gmail dot com
  Target Milestone: ---

Although not required by the standard, since function_ref<S> is not a nullable
type, optional<function_ref<S>> is demanded, which happens to be semantically
precise and monadic. But this specialization cannot be added "later" as that
would be an ABI break (for the same reason we can specialize optional<T&> but
not optional<reference_wrapper<T>>).