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Fix partial specialization problem for filesystem for Visual Studio (#2957)

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* #2954: Provide std::conjunction and std::disjunction substitutes

* #2954: Use conjunction and disjunction substitute to make formatter specializations for ranges and maps more robust (especially for Visual Studio compiler family)

* #2954: As workaround for older MSVC compilers split formatter<std::filesystem::path> partial template specialization into two explicit specialization.

* 2954: Add test case

* Provide simplified implementations of conjunction and disjunction

* Remove workaround explicit specializations if the partial specialization would cause an ambiguity error

* Eliminate extra-test and merge it into existing std-test instead. Add conditionals for filesystem::path testing that does not run into the ambiguity problem.
This commit is contained in:
Daniel Krügler
2022-07-03 20:06:54 +02:00
committed by GitHub
parent 0c06c81da8
commit d2a2320820
4 changed files with 66 additions and 17 deletions
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41
include/fmt/ranges.h
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@@ -246,7 +246,7 @@ template <class Tuple, class F> void for_each(Tuple&& tup, F&& f) {
for_each(indexes, std::forward<Tuple>(tup), std::forward<F>(f));
}
#if FMT_MSC_VERSION
#if FMT_MSC_VERSION && FMT_MSC_VERSION < 1920
// Older MSVC doesn't get the reference type correctly for arrays.
template <typename R> struct range_reference_type_impl {
using type = decltype(*detail::range_begin(std::declval<R&>()));
@@ -396,15 +396,18 @@ template <typename R, typename Char>
struct formatter<
R, Char,
enable_if_t<
fmt::is_range<R, Char>::value
// Workaround a bug in MSVC 2019 and earlier.
#if !FMT_MSC_VERSION
&&
(is_formattable<detail::uncvref_type<detail::maybe_const_range<R>>,
Char>::value ||
detail::has_fallback_formatter<
detail::uncvref_type<detail::maybe_const_range<R>>, Char>::value)
conjunction<fmt::is_range<R, Char>
// Workaround a bug in MSVC 2017 and earlier.
#if !FMT_MSC_VERSION || FMT_MSC_VERSION >= 1920
,
disjunction<
is_formattable<detail::uncvref_type<detail::maybe_const_range<R>>,
Char>,
detail::has_fallback_formatter<
detail::uncvref_type<detail::maybe_const_range<R>>, Char>
>
#endif
>::value
>> {
using range_type = detail::maybe_const_range<R>;
@@ -457,14 +460,20 @@ struct formatter<
template <typename T, typename Char>
struct formatter<
T, Char,
enable_if_t<detail::is_map<T>::value
// Workaround a bug in MSVC 2019 and earlier.
#if !FMT_MSC_VERSION
&& (is_formattable<detail::uncvref_first_type<T>, Char>::value ||
detail::has_fallback_formatter<detail::uncvref_first_type<T>, Char>::value)
&& (is_formattable<detail::uncvref_second_type<T>, Char>::value ||
detail::has_fallback_formatter<detail::uncvref_second_type<T>, Char>::value)
enable_if_t<conjunction<detail::is_map<T>
// Workaround a bug in MSVC 2017 and earlier.
#if !FMT_MSC_VERSION || FMT_MSC_VERSION >= 1920
,
disjunction<
is_formattable<detail::uncvref_first_type<T>, Char>,
detail::has_fallback_formatter<detail::uncvref_first_type<T>, Char>
>,
disjunction<
is_formattable<detail::uncvref_second_type<T>, Char>,
detail::has_fallback_formatter<detail::uncvref_second_type<T>, Char>
>
#endif
>::value
>> {
template <typename ParseContext>
FMT_CONSTEXPR auto parse(ParseContext& ctx) -> decltype(ctx.begin()) {