Undefined class while using __declspec(dllexport) since Visual Studio 17.2

The following code compiles well for Visual Studio < 17.2:

#include <optional>
#include <string>
#include <map>

class __declspec(dllexport) A {
 public:
    using M = std::map<std::string, A>;

 private:
    mutable std::optional<M> map_;
};

But failed for Visual Studio 17.2 and newer with an error:

example.cpp
...utility(330): error C2079: 'std::pair<const std::string,A>::second' uses undefined class 'A'
...optional(159): note: see reference to class template instantiation 'std::pair<const std::string,A>' being compiled
...optional(158): note: while compiling class template member function 'void std::_Optional_construct_base<_Ty>::_Construct_from<const _Base&>(_Self) noexcept(<expr>)'
        with
        [
            _Ty=A::M,
            _Base=std::_Optional_construct_base<A::M>,
            _Self=const std::_Optional_construct_base<A::M> &
        ]
Compiler returned: 2

It works fine in any version if I drop __declspec(dllexport) from the code or change std::optional to boost::optional.

Is this compiler bug, or I’m missing something?