Annex D (normative) Compatibility features [depr]

D.22 Deprecated formatting [depr.format]

D.22.1 Header <format> synopsis [depr.format.syn]

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The header <format>format.syn has the following additions:
namespace std { template<class Visitor, class Context> decltype(auto) visit_format_arg(Visitor&& vis, basic_format_arg<Context> arg); }