Skip to content

Fix formatter specialization for adapted enum #85

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
saki7 merged 1 commit into from
Sep 12, 2026
Merged

Fix formatter specialization for adapted enum #85

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
40 changes: 23 additions & 17 deletions include/iris/enum/enum.hpp
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -12,7 +12,6 @@
#include <array>
#include <concepts>
#include <type_traits>
#include <numbers>

#ifndef NDEBUG
#include <bit>
Expand All @@ -29,6 +28,8 @@ struct enum_traits_not_defined {};

} // detail

// May only be specialized for program-defined enumeration types;
// otherwise, the program invokes UB when the type is formatted.
template<class EnumT>
struct enum_traits : detail::enum_traits_not_defined
{};
Expand Down Expand Up @@ -231,39 +232,44 @@ struct each_bit_fn
}
};

template<class T, class CharT>
constexpr bool to_string_formattable = requires(T const& val) {
{ to_string(val) } -> std::formattable<CharT>;
};

template<class T>
using to_string_t = std::remove_cvref_t<decltype(to_string(std::declval<T const&>()))>;

} // detail

inline constexpr detail::each_bit_fn each_bit{};

} // iris

template<iris::Enum EnumT, class CharT>
requires requires(EnumT const& val) {
{ to_string(val) } -> std::formattable<CharT>;
}
struct std::formatter<EnumT, CharT> : std::formatter<std::underlying_type_t<EnumT>, CharT>
requires iris::detail::to_string_formattable<EnumT, CharT>
struct std::formatter<EnumT, CharT> : std::formatter<iris::detail::to_string_t<EnumT>, CharT>
{
using base_formatter = std::formatter<std::underlying_type_t<EnumT>, CharT>;
using base_formatter = std::formatter<iris::detail::to_string_t<EnumT>, CharT>;

template<class Context>
constexpr auto parse(Context& ctx)
auto format(EnumT const& val, Context& ctx) const
{
if (ctx.begin() == ctx.end()) return ctx.end();
has_format_spec_ = true;
return base_formatter::parse(ctx);
return base_formatter::format(to_string(val), ctx);
}
};

template<iris::Enum EnumT, class CharT>
requires (!iris::detail::to_string_formattable<EnumT, CharT>)
struct std::formatter<EnumT, CharT> : std::formatter<std::underlying_type_t<EnumT>, CharT>
{
using base_formatter = std::formatter<std::underlying_type_t<EnumT>, CharT>;

template<class Context>
auto format(EnumT const& val, Context& ctx) const
{
if (has_format_spec_) {
return base_formatter::format(std::to_underlying(val), ctx);
}
return format_to(ctx.out(), "{}", to_string(val));
return base_formatter::format(std::to_underlying(val), ctx);
}

private:
bool has_format_spec_ = false;
};

#endif
Loading