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optional is "is_copy_constructible" when T is not. #54
Description
Hi.
I encountered issues while trying to use std::vector<boost::optional<std::tuple<NonCopyable, std::function<...>>>. THis failed to compile on msvc.
Looks like it boiled down to this repro: https://godbolt.org/g/cFNcUN
#include <boost/optional.hpp>
#include <type_traits>
#include <optional>
struct NonCopyAble
{
NonCopyAble() = default;
NonCopyAble(const NonCopyAble&) = delete;
NonCopyAble& operator=(const NonCopyAble&) = delete;
NonCopyAble(NonCopyAble&&) = default;
NonCopyAble& operator=(NonCopyAble&&) = default;
};
static_assert(!std::is_copy_constructible<NonCopyAble>::value, "NonCopyAble is_copy_constructible when shouldn't be");
static_assert(!std::is_copy_constructible<std::optional<NonCopyAble>>::value, "std::optional<NonCopyAble> is_copy_constructible when shouldn't be");
static_assert(!std::is_copy_constructible<boost::optional<NonCopyAble>>::value, "boost::optional<NonCopyAble> is_copy_constructible when shouldn't be"); // This assert fails
Activity
akrzemi1 commentedon May 11, 2018
Thanks for the report. I will investigate. I acknowledge the divergence between
std::optionalandboost::optional. But in general the expectation on transitive detectable copiability is not valid:joergbrech commentedon Mar 14, 2024
I encountered the same issue with
std::is_copy_assignable, see here: https://stackoverflow.com/q/78157267/12173376