Use the decimal point from locale

test/format-test.cc

@@ -1447,10 +1447,6 @@ TEST(FormatterTest, FormatDouble) {
   EXPECT_EQ(buffer, format("{:A}", -42.0));
 }
 
-TEST(FormatterTest, FormatDoubleLocale) {
-  EXPECT_EQ("1.23", format("{:n}", 1.23));
-}
-
 TEST(FormatterTest, PrecisionRounding) {
   EXPECT_EQ("0", format("{:.0f}", 0.0));
   EXPECT_EQ("0", format("{:.0f}", 0.01));

test/locale-test.cc

@@ -11,9 +11,15 @@
 #ifndef FMT_STATIC_THOUSANDS_SEPARATOR
 template <typename Char> struct numpunct : std::numpunct<Char> {
  protected:
+  Char do_decimal_point() const FMT_OVERRIDE { return '?'; }
   Char do_thousands_sep() const FMT_OVERRIDE { return '~'; }
 };
 
+TEST(LocaleTest, DoubleDecimalPoint) {
+  std::locale loc(std::locale(), new numpunct<char>());
+  EXPECT_EQ("1?23", fmt::format(loc, "{:n}", 1.23));
+}
+
 TEST(LocaleTest, Format) {
   std::locale loc(std::locale(), new numpunct<char>());
   EXPECT_EQ("1,234,567", fmt::format(std::locale(), "{:n}", 1234567));