MSVC ++ 2015：仅当使用__declspec（dllexport）时，尝试引用仅移动成员类型的复制构造函数

Question

使用MSVC 19.0.24215.1，可以正确编译以下代码：

#include <memory>
#include <type_traits>
#include <vector>


struct NonCopyable
{
    std::unique_ptr<int> field;
};
static_assert(! std::is_copy_constructible<NonCopyable>::value, "Not copyable");


class NotExported
{

private:
    std::vector<NonCopyable> _member;
};

但是，当我尝试通过DLL导出此类时：

class __declspec(dllexport) Exported
{

private:
    std::vector<NonCopyable> _member;
};

我收到以下错误，显然是在调用NonCopyable的复制构造函数：

example.cpp

/opt/compiler-explorer/windows/19.00.24210/include/xutility(2316): error C2280: 'NonCopyable &NonCopyable::operator =(const NonCopyable &)': attempting to reference a deleted function

<source>(9): note: compiler has generated 'NonCopyable::operator =' here

/opt/compiler-explorer/windows/19.00.24210/include/xutility(2335): note: see reference to function template instantiation '_OutIt std::_Copy_unchecked1<_InIt,_OutIt>(_InIt,_InIt,_OutIt,std::_General_ptr_iterator_tag)' being compiled

        with

        [

            _OutIt=NonCopyable *,

            _InIt=NonCopyable *

        ]

/opt/compiler-explorer/windows/19.00.24210/include/vector(997): note: see reference to function template instantiation '_OutIt *std::_Copy_unchecked<NonCopyable*,NonCopyable*>(_InIt,_InIt,_OutIt)' being compiled

        with

        [

            _OutIt=NonCopyable *,

            _InIt=NonCopyable *

        ]

/opt/compiler-explorer/windows/19.00.24210/include/vector(980): note: while compiling class template member function 'std::vector<NonCopyable,std::allocator<_Ty>> &std::vector<_Ty,std::allocator<_Ty>>::operator =(const std::vector<_Ty,std::allocator<_Ty>> &)'

        with

        [

            _Ty=NonCopyable

        ]

<source>(18): note: see reference to function template instantiation 'std::vector<NonCopyable,std::allocator<_Ty>> &std::vector<_Ty,std::allocator<_Ty>>::operator =(const std::vector<_Ty,std::allocator<_Ty>> &)' being compiled

        with

        [

            _Ty=NonCopyable

        ]

<source>(17): note: see reference to class template instantiation 'std::vector<NonCopyable,std::allocator<_Ty>>' being compiled

        with

        [

            _Ty=NonCopyable

        ]

Compiler returned: 2

我想了解为什么在导出类时调用对NonCopyable的已删除副本构造函数的调用，以及如何解决此问题。

编辑：从类定义中删除__declspec(dllexport)，而是将其放在每个公共/受保护的方法名的前面似乎可以解决此问题。我假设拥有完全导出类的模板成员会强制实例化所有成员函数，这对于std::vector意味着实例化了复制构造函数，然后会导致此错误。