From 61e6d2e38cd967e1c0e7aef8936c3581c56f03a6 Mon Sep 17 00:00:00 2001
From: Victor Zverovich <victor.zverovich@gmail.com>
Date: Wed, 24 Oct 2018 18:42:42 -0700
Subject: [PATCH] Fix core version of vformat_to

---
 include/fmt/core.h   | 15 +++++++--------
 include/fmt/format.h | 15 +++++++++++----
 src/format.cc        |  3 +++
 test/core-test.cc    | 10 ++++++++++
 4 files changed, 31 insertions(+), 12 deletions(-)

diff --git a/include/fmt/core.h b/include/fmt/core.h
index 8180340b..ecd145ee 100644
--- a/include/fmt/core.h
+++ b/include/fmt/core.h
@@ -16,7 +16,7 @@
 #include <type_traits>
 
 // The fmt library version in the form major * 10000 + minor * 100 + patch.
-#define FMT_VERSION 50201
+#define FMT_VERSION 50202
 
 #ifdef __has_feature
 # define FMT_HAS_FEATURE(x) __has_feature(x)
@@ -1350,6 +1350,11 @@ template <typename Char>
 std::basic_string<Char> vformat(
   basic_string_view<Char> format_str,
   basic_format_args<typename buffer_context<Char>::type> args);
+
+template <typename Char>
+typename buffer_context<Char>::type::iterator vformat_to(
+  internal::basic_buffer<Char> &buf, basic_string_view<Char> format_str,
+  basic_format_args<typename buffer_context<Char>::type> args);
 }
 
 /**
@@ -1371,16 +1376,10 @@ inline internal::named_arg<T, wchar_t> arg(wstring_view name, const T &arg) {
   return {name, arg};
 }
 
-// This function template is deleted intentionally to disable nested named
-// arguments as in ``format("{}", arg("a", arg("b", 42)))``.
+// Disable nested named arguments, e.g. ``arg("a", arg("b", 42))``.
 template <typename S, typename T, typename Char>
 void arg(S, internal::named_arg<T, Char>) = delete;
 
-template <typename S>
-typename buffer_context<FMT_CHAR(S)>::type::iterator vformat_to(
-  internal::basic_buffer<FMT_CHAR(S)> &buf, const S &format_str,
-  basic_format_args<buffer_context<FMT_CHAR(S)> > args);
-
 template <typename Container>
 struct is_contiguous: std::false_type {};
 
diff --git a/include/fmt/format.h b/include/fmt/format.h
index bbe4926c..f3302597 100644
--- a/include/fmt/format.h
+++ b/include/fmt/format.h
@@ -3365,15 +3365,22 @@ std::basic_string<Char> to_string(const basic_memory_buffer<Char, SIZE> &buf) {
   return std::basic_string<Char>(buf.data(), buf.size());
 }
 
-template <typename String, typename Char = FMT_CHAR(String)>
-inline typename buffer_context<FMT_CHAR(String)>::type::iterator vformat_to(
-    internal::basic_buffer<Char> &buf, const String &format_str,
+template <typename Char>
+typename buffer_context<Char>::type::iterator internal::vformat_to(
+    internal::basic_buffer<Char> &buf, basic_string_view<Char> format_str,
     basic_format_args<typename buffer_context<Char>::type> args) {
-  typedef back_insert_range<internal::basic_buffer<FMT_CHAR(String)> > range;
+  typedef back_insert_range<internal::basic_buffer<Char> > range;
   return vformat_to<arg_formatter<range>>(
     buf, to_string_view(format_str), args);
 }
 
+template <typename S, typename Char = FMT_CHAR(S)>
+inline typename buffer_context<Char>::type::iterator vformat_to(
+    internal::basic_buffer<Char> &buf, const S &format_str,
+    basic_format_args<typename buffer_context<Char>::type> args) {
+  return vformat_to(buf, to_string_view(format_str), args);
+}
+
 template <
     typename S, typename... Args,
     std::size_t SIZE = inline_buffer_size,
diff --git a/src/format.cc b/src/format.cc
index cd291294..8f7a5991 100644
--- a/src/format.cc
+++ b/src/format.cc
@@ -28,6 +28,9 @@ template FMT_API int internal::char_traits<char>::format_float(
 template FMT_API std::string internal::vformat<char>(
     string_view, basic_format_args<format_context>);
 
+template format_context::iterator internal::vformat_to(
+    internal::buffer &, string_view, basic_format_args<format_context>);
+
 template FMT_API void internal::sprintf_format(
     double, internal::buffer &, core_format_specs);
 template FMT_API void internal::sprintf_format(
diff --git a/test/core-test.cc b/test/core-test.cc
index 77d35428..02fe7267 100644
--- a/test/core-test.cc
+++ b/test/core-test.cc
@@ -532,6 +532,16 @@ TEST(CoreTest, Format) {
   EXPECT_EQ(fmt::format("{}", 42), "42");
 }
 
+TEST(CoreTest, FormatTo) {
+  // This should work without including fmt/format.h.
+#ifdef FMT_FORMAT_H_
+# error fmt/format.h must not be included in the core test
+#endif
+  std::string s;
+  fmt::format_to(std::back_inserter(s), "{}", 42);
+  EXPECT_EQ(s, "42");
+}
+
 TEST(CoreTest, ToStringViewForeignStrings) {
   using namespace my_ns;
   using namespace FakeQt;