From 71c63792dd7462cc6d1654bf3a3c82eb073cde03 Mon Sep 17 00:00:00 2001
From: Victor Zverovich <victor.zverovich@gmail.com>
Date: Thu, 29 Jan 2026 21:54:47 -0800
Subject: [PATCH] Move _BitInt to format.h

---
 include/fmt/base.h   | 31 -------------------------------
 include/fmt/format.h | 40 ++++++++++++++++++++++++++++++++++++++--
 2 files changed, 38 insertions(+), 33 deletions(-)

diff --git a/include/fmt/base.h b/include/fmt/base.h
index d6d32e97..83e36d6c 100644
--- a/include/fmt/base.h
+++ b/include/fmt/base.h
@@ -409,23 +409,6 @@ inline auto map(int128_opt) -> monostate { return {}; }
 inline auto map(uint128_opt) -> monostate { return {}; }
 #endif
 
-#ifdef FMT_USE_BITINT
-// Use the provided definition.
-#elif FMT_CLANG_VERSION >= 1500 && !defined(__CUDACC__)
-#  define FMT_USE_BITINT 1
-#else
-#  define FMT_USE_BITINT 0
-#endif
-
-#if FMT_USE_BITINT
-FMT_PRAGMA_CLANG(diagnostic ignored "-Wbit-int-extension")
-template <int N> using bitint = _BitInt(N);
-template <int N> using ubitint = unsigned _BitInt(N);
-#else
-template <int N> struct bitint {};
-template <int N> struct ubitint {};
-#endif  // FMT_USE_BITINT
-
 // Casts a nonnegative integer to unsigned.
 template <typename Int>
 FMT_CONSTEXPR auto to_unsigned(Int value) -> make_unsigned_t<Int> {
@@ -1177,11 +1160,6 @@ template <typename Char> struct type_mapper {
   static auto map(uint128_opt) -> uint128_opt;
   static auto map(bool) -> bool;
 
-  template <int N>
-  static auto map(bitint<N>) -> conditional_t<N <= 64, long long, void>;
-  template <int N>
-  static auto map(ubitint<N>) -> conditional_t<N <= 64, ullong, void>;
-
   template <typename T, FMT_ENABLE_IF(is_code_unit<T>::value)>
   static auto map(T) -> conditional_t<
       std::is_same<T, char>::value || std::is_same<T, Char>::value, Char, void>;
@@ -2130,15 +2108,6 @@ template <typename Context> class value {
   FMT_INLINE value(uint128_opt x FMT_BUILTIN) : uint128_value(x) {}
   constexpr FMT_INLINE value(bool x FMT_BUILTIN) : bool_value(x) {}
 
-  template <int N>
-  constexpr FMT_INLINE value(bitint<N> x FMT_BUILTIN) : long_long_value(x) {
-    static_assert(N <= 64, "unsupported _BitInt");
-  }
-  template <int N>
-  constexpr FMT_INLINE value(ubitint<N> x FMT_BUILTIN) : ulong_long_value(x) {
-    static_assert(N <= 64, "unsupported _BitInt");
-  }
-
   template <typename T, FMT_ENABLE_IF(is_code_unit<T>::value)>
   constexpr FMT_INLINE value(T x FMT_BUILTIN) : char_value(x) {
     static_assert(
diff --git a/include/fmt/format.h b/include/fmt/format.h
index 1fd4a59e..57944612 100644
--- a/include/fmt/format.h
+++ b/include/fmt/format.h
@@ -198,6 +198,23 @@ struct is_contiguous<std::basic_string<Char, Traits, Allocator>>
 
 namespace detail {
 
+#ifdef FMT_USE_BITINT
+// Use the provided definition.
+#elif FMT_CLANG_VERSION >= 1500 && !defined(__CUDACC__)
+#  define FMT_USE_BITINT 1
+#else
+#  define FMT_USE_BITINT 0
+#endif
+
+#if FMT_USE_BITINT
+FMT_PRAGMA_CLANG(diagnostic ignored "-Wbit-int-extension")
+template <int N> using bitint = _BitInt(N);
+template <int N> using ubitint = unsigned _BitInt(N);
+#else
+template <int N> struct bitint {};
+template <int N> struct ubitint {};
+#endif  // FMT_USE_BITINT
+
 // __builtin_clz is broken in clang with Microsoft codegen:
 // https://github.com/fmtlib/fmt/issues/519.
 #if !FMT_MSC_VERSION
@@ -4039,9 +4056,28 @@ class formatter<std::basic_string<Char, Traits, Allocator>, Char>
     : public formatter<basic_string_view<Char>, Char> {};
 
 template <int N, typename Char>
-struct formatter<detail::bitint<N>, Char> : formatter<long long, Char> {};
+struct formatter<detail::bitint<N>, Char> : formatter<long long, Char> {
+  static_assert(N <= 64, "unsupported _BitInt");
+  static auto format_as(detail::bitint<N> x) -> long long {
+    return static_cast<long long>(x);
+  }
+  template <typename Context>
+  auto format(detail::bitint<N> x, Context& ctx) const -> decltype(ctx.out()) {
+    return formatter<long long, Char>::format(format_as(x), ctx);
+  }
+};
+
 template <int N, typename Char>
-struct formatter<detail::ubitint<N>, Char> : formatter<ullong, Char> {};
+struct formatter<detail::ubitint<N>, Char> : formatter<ullong, Char> {
+  static_assert(N <= 64, "unsupported _BitInt");
+  static auto format_as(detail::ubitint<N> x) -> ullong {
+    return static_cast<ullong>(x);
+  }
+  template <typename Context>
+  auto format(detail::ubitint<N> x, Context& ctx) const -> decltype(ctx.out()) {
+    return formatter<ullong, Char>::format(format_as(x), ctx);
+  }
+};
 
 template <typename Char>
 struct formatter<detail::float128, Char>