From 64a779094f58728cb4d5f63fde64590435678193 Mon Sep 17 00:00:00 2001
From: "David P. Sicilia" <dpsicilia@gmail.com>
Date: Wed, 13 Nov 2019 09:11:19 -0500
Subject: [PATCH] Move has_formatter into the public fmt namespace.

This will allow users to do SFINAE-friendly checks for
the formattability of a type.

Fixes #1369
---
 include/fmt/core.h  | 4 ++--
 test/core-test.cc   | 8 ++++----
 test/format-test.cc | 4 ++--
 3 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/include/fmt/core.h b/include/fmt/core.h
index 02a389fa..68b022a5 100644
--- a/include/fmt/core.h
+++ b/include/fmt/core.h
@@ -541,14 +541,14 @@ struct FMT_DEPRECATED convert_to_int
     : bool_constant<!std::is_arithmetic<T>::value &&
                     std::is_convertible<T, int>::value> {};
 
-namespace internal {
-
 // Specifies if T has an enabled formatter specialization. A type can be
 // formattable even if it doesn't have a formatter e.g. via a conversion.
 template <typename T, typename Context>
 using has_formatter =
     std::is_constructible<typename Context::template formatter_type<T>>;
 
+namespace internal {
+
 /** A contiguous memory buffer with an optional growing ability. */
 template <typename T> class buffer {
  private:
diff --git a/test/core-test.cc b/test/core-test.cc
index acfd2cd0..9aef6aa9 100644
--- a/test/core-test.cc
+++ b/test/core-test.cc
@@ -453,11 +453,11 @@ template <> struct formatter<enabled_formatter> {
 FMT_END_NAMESPACE
 
 TEST(CoreTest, HasFormatter) {
-  using fmt::internal::has_formatter;
+  using fmt::has_formatter;
   using context = fmt::format_context;
-  EXPECT_TRUE((has_formatter<enabled_formatter, context>::value));
-  EXPECT_FALSE((has_formatter<disabled_formatter, context>::value));
-  EXPECT_FALSE((has_formatter<disabled_formatter_convertible, context>::value));
+  static_assert(has_formatter<enabled_formatter, context>::value);
+  static_assert(!has_formatter<disabled_formatter, context>::value);
+  static_assert(!has_formatter<disabled_formatter_convertible, context>::value);
 }
 
 struct convertible_to_int {
diff --git a/test/format-test.cc b/test/format-test.cc
index 61b893c4..165a1425 100644
--- a/test/format-test.cc
+++ b/test/format-test.cc
@@ -1974,8 +1974,8 @@ enum TestEnum { A };
 TEST(FormatTest, Enum) { EXPECT_EQ("0", fmt::format("{}", A)); }
 
 TEST(FormatTest, FormatterNotSpecialized) {
-  EXPECT_FALSE((fmt::internal::has_formatter<fmt::formatter<TestEnum>,
-                                             fmt::format_context>::value));
+  static_assert(!fmt::has_formatter<fmt::formatter<TestEnum>,
+                                    fmt::format_context>::value);
 }
 
 #if FMT_HAS_FEATURE(cxx_strong_enums)