Class to_stringable

test/compile-test.cc:279–281

TEST(compile_test, empty) { EXPECT_EQ("", fmt::format(FMT_COMPILE(""))); }

struct to_stringable {
  friend fmt::string_view to_string_view(to_stringable) { return {}; }
};

FMT_BEGIN_NAMESPACE
template <> struct formatter<to_stringable> {