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strongdef: add default constructor if the type supports it

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This commit is contained in:
Danny Robson 2018-06-21 13:18:53 +10:00
parent 6dea530f6e
commit 6f3952abcb
1 changed files with 8 additions and 1 deletions
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9
strongdef.hpp
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@ -29,7 +29,11 @@ namespace util {
using value_type = T;
using tag_type = Tag;
constexpr strongdef () = delete;
// TODO: ideally we'd default the constructor, but templated
// constructors can't be defaulted? So we just stub one out.
template <typename = std::enable_if_t<std::is_default_constructible_v<T>>>
constexpr strongdef () { ; }
constexpr strongdef (const T &_data): data (_data) { ; }
// explicitly disable assignment with unequal types or tags. this
@ -59,6 +63,9 @@ namespace util {
operator const T& (void) const& { return data; }
operator T& (void) & { return data; }
auto const& value (void) const { return data; }
auto & value (void) { return data; }
// explicitly disable equality with unequal types or tags. this
// prevents the conversion operator getting invoked and falsely
// allowing equality with different types or tags.