fix: update to_string_view function for fmt 11.1

[chenrui333]

update to_string_view function for fmt 11.1

/tmp/spdlog-20241225-25576-12pt7n/spdlog-1.15.0/include/spdlog/common.h:369:54: error: no template named 'basic_format_string' in namespace 'fmt'; did you mean 'basic_format_arg'?
  369 | inline fmt::basic_string_view<Tasic_sfmt::basic_string_view<T> to_string_view(fmt::basic_format_string<T, Args...> fmt) {
      |                                                 ~~~~~^~~~~~~~~~~~~~~~~~~
      |                                                      basic_format_arg
/opt/homebrew/include/fmt/base.h:2428:35: note: 'basic_format_arg' declared here
 2428 | template <typename Context> class basic_format_arg {
      |                                   ^

relates to Homebrew/homebrew-core#202442

[heitbaum]

Tested - working 👍

[tt4g]

Related #3258, #3202 (PR #3277)

[gabime]

Thanks @chenrui333

[fasiondog]

👍🏻 waiting for new release ...

[jdrouhard]

The new code for fmt >= 11.1.0 in this PR is dead...no reason to have a to_string_view(basic_format_arg<>) since that's never used.

The new fmt::format_string<> in fmt 11.1.0 implicitly converts to spdlog::string_view_t which already has a to_string_view() overload.

[gabime]

@chenrui333 Not sure i understand. It clearly fixed the problem with 11.1.0

[jdrouhard]

@chenrui333 Not sure i understand. It clearly fixed the problem with 11.1.0

It's dead code. You can just make it a #ifndef and remove the to_string_view(fmt::basic_format_arg<>()...) overload. The new overload isn't used.