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Make arg_mapper SFINAE-friendly again

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This commit is contained in:
Victor Zverovich 2022-03-27 07:10:15 -07:00
parent e2408f37c8
commit b41890c1e5
1 changed files with 13 additions and 4 deletions
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17
include/fmt/core.h
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@ -1282,6 +1282,15 @@ inline auto format_as(std::byte b) -> unsigned char {
} }
#endif #endif
template <typename T> struct has_format_as {
template <typename U, typename V = decltype(format_as(U())),
FMT_ENABLE_IF(std::is_enum<U>::value&& std::is_integral<V>::value)>
static auto check(U*) -> std::true_type;
static auto check(...) -> std::false_type;
enum { value = decltype(check(static_cast<T*>(nullptr)))::value };
};
// Maps formatting arguments to core types. // Maps formatting arguments to core types.
// arg_mapper reports errors by returning unformattable instead of using // arg_mapper reports errors by returning unformattable instead of using
// static_assert because it's used in the is_formattable trait. // static_assert because it's used in the is_formattable trait.
@ -1436,11 +1445,10 @@ template <typename Context> struct arg_mapper {
return map(static_cast<underlying_t<T>>(val)); return map(static_cast<underlying_t<T>>(val));
} }
template <typename T, typename U = decltype(format_as(T())), template <typename T, FMT_ENABLE_IF(has_format_as<T>::value &&
FMT_ENABLE_IF(std::is_enum<T>::value&& std::is_integral<U>::value)> !has_formatter<T, Context>::value)>
FMT_CONSTEXPR FMT_INLINE auto map(const T& val) FMT_CONSTEXPR FMT_INLINE auto map(const T& val)
-> decltype(std::declval<arg_mapper>().map(U())) { -> decltype(std::declval<arg_mapper>().map(format_as(T()))) {
static_assert(!has_formatter<T, Context>::value, "");
return map(format_as(val)); return map(format_as(val));
} }
@ -1470,6 +1478,7 @@ template <typename Context> struct arg_mapper {
template <typename T, typename U = remove_cvref_t<T>, template <typename T, typename U = remove_cvref_t<T>,
FMT_ENABLE_IF(!is_string<U>::value && !is_char<U>::value && FMT_ENABLE_IF(!is_string<U>::value && !is_char<U>::value &&
!std::is_array<U>::value && !std::is_array<U>::value &&
!has_format_as<U>::value &&
(has_formatter<U, Context>::value || (has_formatter<U, Context>::value ||
has_fallback_formatter<U, char_type>::value))> has_fallback_formatter<U, char_type>::value))>
FMT_CONSTEXPR FMT_INLINE auto map(T&& val) FMT_CONSTEXPR FMT_INLINE auto map(T&& val)