[boost] Re: utility::string_view and core::detail::string_view

On 4 Nov 2025 22:19, Peter Dimov via Boost wrote:

Mungo Gill wrote:

...

In case anyone is curious how to implement support for <format> in boost::string_view by delegating to the formatter for std::string_view: https://godbolt.org/z/YsWKrEz3P

There's no way to portably forward-declare things in std (even if we discount the fact that this is explicitly called out as undefined behavior.)

https://godbolt.org/z/9f5xMEPd1

Although this is true, we also have utilities for doing this in all widespread implementations, and some Boost libraries already forward-declare std components: https://godbolt.org/z/GrEY377qb I wish this utility was made more public.