From 6a685571dfc36490ba1d2ef28a6439de89422c55 Mon Sep 17 00:00:00 2001
From: Daniela Engert <dani@ngrt.de>
Date: Sun, 7 Oct 2018 18:54:12 +0200
Subject: [PATCH] Make 'std::*::basic_string_view' a valid argument type for
 'format_str' parameters.

Signed-off-by: Daniela Engert <dani@ngrt.de>
---
 include/fmt/core.h |  6 ++++++
 test/core-test.cc  | 24 ++++++++++++++++++++++++
 2 files changed, 30 insertions(+)

diff --git a/include/fmt/core.h b/include/fmt/core.h
index c6c44e53..2c83f045 100644
--- a/include/fmt/core.h
+++ b/include/fmt/core.h
@@ -493,6 +493,12 @@ template <typename Char>
 struct format_string_traits<std::basic_string<Char>> :
     format_string_traits_base<Char> {};
 
+#ifdef FMT_STRING_VIEW
+template <typename Char>
+struct format_string_traits<FMT_STRING_VIEW<Char>> :
+    format_string_traits_base<Char> {};
+#endif
+
 template <typename S>
 struct format_string_traits<
     S, typename std::enable_if<std::is_base_of<
diff --git a/test/core-test.cc b/test/core-test.cc
index fed78c3b..cb983560 100644
--- a/test/core-test.cc
+++ b/test/core-test.cc
@@ -451,6 +451,30 @@ TEST(CoreTest, IsEnumConvertibleToInt) {
   EXPECT_TRUE((fmt::convert_to_int<enum_with_underlying_type, char>::value));
 }
 
+template <typename T>
+class IsStringTest : public testing::Test {};
+
+typedef ::testing::Types<char, wchar_t, char16_t, char32_t> StringCharTypes;
+TYPED_TEST_CASE(IsStringTest, StringCharTypes);
+
+namespace {
+template <typename Char>
+struct derived_from_string_view : fmt::basic_string_view<Char> {};
+}
+
+TYPED_TEST(IsStringTest, IsString) {
+  EXPECT_TRUE((fmt::internal::is_string<TypeParam *>::value));
+  EXPECT_TRUE((fmt::internal::is_string<const TypeParam *>::value));
+  EXPECT_TRUE((fmt::internal::is_string<TypeParam[2]>::value));
+  EXPECT_TRUE((fmt::internal::is_string<const TypeParam[2]>::value));
+  EXPECT_TRUE((fmt::internal::is_string<std::basic_string<TypeParam>>::value));
+  EXPECT_TRUE((fmt::internal::is_string<fmt::basic_string_view<TypeParam>>::value));
+  EXPECT_TRUE((fmt::internal::is_string<derived_from_string_view<TypeParam>>::value));
+#ifdef FMT_STRING_VIEW
+  EXPECT_TRUE((fmt::internal::is_string<FMT_STRING_VIEW<TypeParam>>::value));
+#endif
+}
+
 TEST(CoreTest, Format) {
   // This should work without including fmt/format.h.
 #ifdef FMT_FORMAT_H_