std::filesystem::path is not format as a range

[phprus]

Fix: #3322

[vitaut]

std::filesystem::path should be excluded by the recursive range check in

fmt/include/fmt/ranges.h

Line 509 in 73b7cee

static constexpr auto value = std::is_same<range_reference_type<T>, T>::value

See e.g. http://eel.is/c++draft/format#range.fmtkind-2. I wonder why it doesn't work on Windows?

[phprus]

@vitaut

fmt/include/fmt/ranges.h

Lines 560 to 564 in 73b7cee

	template <typename T, typename Char, typename Enable = void>
	struct range_format_kind
	: conditional_t<
	is_range<T, Char>::value, detail::range_format_kind_<T>,
	std::integral_constant<range_format, range_format::disabled>> {};

On windows std::filesystem::path uses wchar_t.
is_range exclude std::filesystem::path on unix because std::filesystem::path is convertible to std::basic_string<char>:

fmt/include/fmt/ranges.h

Lines 382 to 387 in 73b7cee

	template <typename T, typename Char> struct is_range {
	static constexpr const bool value =
	detail::is_range_<T>::value && !detail::is_std_string_like<T>::value &&
	!std::is_convertible<T, std::basic_string<Char>>::value &&
	!std::is_convertible<T, detail::std_string_view<Char>>::value;
	};

On Windows std::filesystem::path does not convertible to std::basic_string<char>.
Demo: https://godbolt.org/z/K1f1jPxjv

Original test for char (UNIX):

fmt/test/ranges-test.cc

Lines 182 to 191 in c644c75

	struct path_like {
	const path_like* begin() const;
	const path_like* end() const;
	operator std::string() const;
	};
	TEST(ranges_test, path_like) {
	EXPECT_FALSE((fmt::is_range<path_like, char>::value));
	}

[phprus]

@vitaut, what do you think about this PR?

[vitaut]

I think it's OK for is_range to return true for path on Windows and the root cause is broken recursion check (it didn't strip cvref). This should be fixed in e0748e6. So I'm closing this PR but thanks anyway, especially for the test case which has been added in the above commit.