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Workaround broken is_default_constructible in MSVC

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This commit is contained in:
Victor Zverovich 2019-01-21 09:54:48 -08:00
parent 5f1ceebc7f
commit 7cdb1e5e40
1 changed files with 16 additions and 17 deletions
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33
include/fmt/core.h
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@ -333,22 +333,19 @@ struct error_handler {
// GCC 4.6.x cannot expand `T...`.
#if FMT_GCC_VERSION && FMT_GCC_VERSION < 407
template <typename... T> struct is_constructible : std::false_type {};
typedef char yes[1];
typedef char no[2];
template <typename T> struct is_default_constructible {
template <typename U> static yes& test(int (*)[sizeof(new U)]);
template <typename T, typename V> struct is_constructible {
template <typename U> static yes& test(int (*)[sizeof(new U(declval<V>()))]);
template <typename U> static no& test(...);
enum { value = sizeof(test<T>(FMT_NULL)) == sizeof(yes) };
};
#else
template <typename... T>
struct is_constructible : std::is_constructible<T...> {};
template <typename T>
struct is_default_constructible : std::is_default_constructible<T> {};
#endif
struct dummy_formatter_arg {}; // Workaround broken is_constructible in MSVC.
} // namespace internal
/**
@ -506,7 +503,7 @@ template <typename Context> class basic_format_args;
// A formatter for objects of type T.
template <typename T, typename Char = char, typename Enable = void>
struct formatter {
formatter() = delete;
explicit formatter(internal::dummy_formatter_arg);
};
template <typename T, typename Char, typename Enable = void>
@ -632,11 +629,12 @@ template <typename Context> class value {
}
value(const void* val) { pointer = val; }
template <typename T,
typename std::enable_if<
is_default_constructible<
typename Context::template formatter_type<T>::type>::value,
int>::type = 0>
template <
typename T,
typename std::enable_if<
!is_constructible<typename Context::template formatter_type<T>::type,
internal::dummy_formatter_arg>::value,
int>::type = 0>
explicit value(const T& val) {
custom.value = &val;
// Get the formatter type through the context to allow different contexts
@ -646,11 +644,12 @@ template <typename Context> class value {
custom.format = &format_custom_arg<T, formatter>;
}
template <typename T,
typename std::enable_if<
!is_default_constructible<
typename Context::template formatter_type<T>::type>::value,
int>::type = 0>
template <
typename T,
typename std::enable_if<
is_constructible<typename Context::template formatter_type<T>::type,
internal::dummy_formatter_arg>::value,
int>::type = 0>
explicit value(const T& val) {
custom.value = &val;
custom.format =