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fix: downcasting facility for non-default-constructible types

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This commit is contained in:
Johel Ernesto Guerrero Peña
2021-02-17 01:25:47 -04:00
committed by Mateusz Pusz
parent 02ea4825e8
commit 052d818385
2 changed files with 4 additions and 3 deletions
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1
docs/CHANGELOG.md
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@@ -21,6 +21,7 @@
- fix: quantity's operators fixed to behave like the underlying types do - fix: quantity's operators fixed to behave like the underlying types do
- fix: `quantity_cast()` fixed to work correctly with representation types not convertible from `std::intmax_t` - fix: `quantity_cast()` fixed to work correctly with representation types not convertible from `std::intmax_t`
- fix: ambiguous case for empty type list resolved - fix: ambiguous case for empty type list resolved
- fix: downcasting facility for non-default-constructible types
- (!) build: `BUILD_DOCS` CMake option renamed to `UNITS_BUILD_DOCS` - (!) build: `BUILD_DOCS` CMake option renamed to `UNITS_BUILD_DOCS`
- build: doxygen updated to 1.8.20 - build: doxygen updated to 1.8.20
- build: catch2 updated to 2.13.4 - build: catch2 updated to 2.13.4

6
src/include/units/bits/external/downcasting.h vendored
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@@ -56,7 +56,7 @@ concept has_downcast_poison_pill = requires(T t) { downcast_poison_pill(t); };
template<typename Target, Downcastable T> template<typename Target, Downcastable T>
struct downcast_child : T { struct downcast_child : T {
friend auto downcast_guide(typename T::downcast_base) friend auto downcast_guide(typename T::downcast_base)
{ return Target(); } { return std::type_identity<Target>(); }
}; };
template<Downcastable T> template<Downcastable T>
@@ -89,13 +89,13 @@ constexpr auto downcast_impl()
if constexpr(has_downcast_guide<T> && !has_downcast_poison_pill<T>) if constexpr(has_downcast_guide<T> && !has_downcast_poison_pill<T>)
return decltype(downcast_guide(std::declval<downcast_base<T>>()))(); return decltype(downcast_guide(std::declval<downcast_base<T>>()))();
else else
return T(); return std::type_identity<T>();
} }
} // namespace detail } // namespace detail
template<Downcastable T> template<Downcastable T>
using downcast = decltype(detail::downcast_impl<T>()); using downcast = TYPENAME decltype(detail::downcast_impl<T>())::type;
template<Downcastable T> template<Downcastable T>
using downcast_base_t = TYPENAME T::downcast_base_type; using downcast_base_t = TYPENAME T::downcast_base_type;