考虑以下代码：
#include <any>
struct A {
A();
A(const A&) = default;
explicit A(std::any value);
};
struct B: A {
B() : A() { }
B(const B& b) : A(b) {}
explicit B(std::any value) : A(value) {}
};
编译器在编译时报告以下错误（使用clang ++-5或更高版本）：
In file included from <source>:2:
In file included from /opt/compiler-explorer/gcc-7.3.0/lib/gcc/x86_64-linux-gnu/7.3.0/../../../../include/c++/7.3.0/any:37:
In file included from /opt/compiler-explorer/gcc-7.3.0/lib/gcc/x86_64-linux-gnu/7.3.0/../../../../include/c++/7.3.0/new:40:
In file included from /opt/compiler-explorer/gcc-7.3.0/lib/gcc/x86_64-linux-gnu/7.3.0/../../../../include/c++/7.3.0/exception:143:
In file included from /opt/compiler-explorer/gcc-7.3.0/lib/gcc/x86_64-linux-gnu/7.3.0/../../../../include/c++/7.3.0/bits/nested_exception.h:40:
In file included from /opt/compiler-explorer/gcc-7.3.0/lib/gcc/x86_64-linux-gnu/7.3.0/../../../../include/c++/7.3.0/bits/move.h:54:
/opt/compiler-explorer/gcc-7.3.0/lib/gcc/x86_64-linux-gnu/7.3.0/../../../../include/c++/7.3.0/type_traits:149:31: error: no member named 'value' in 'std::is_copy_constructible<B>'
: public conditional<_B1::value, __and_<_B2, _B3, _Bn...>, _B1>::type
~~~~~^
/opt/compiler-explorer/gcc-7.3.0/lib/gcc/x86_64-linux-gnu/7.3.0/../../../../include/c++/7.3.0/any:192:27: note: in instantiation of template class 'std::__and_<std::is_copy_constructible<B>, std::__not_<std::is_constructible<B, const B &> >, std::__not_<std::__is_in_place_type<B> > >' requested here
enable_if_t<__and_<is_copy_constructible<_Tp>,
^
/opt/compiler-explorer/gcc-7.3.0/lib/gcc/x86_64-linux-gnu/7.3.0/../../../../include/c++/7.3.0/any:196:7: note: while substituting prior template arguments into non-type template parameter [with _ValueType = const B &, _Tp = B, _Mgr = std::any::_Manager_external<B>]
any(_ValueType&& __value)
^~~~~~~~~~~~~~~~~~~~~~~~~
/opt/compiler-explorer/gcc-7.3.0/lib/gcc/x86_64-linux-gnu/7.3.0/../../../../include/c++/7.3.0/type_traits:973:28: note: while substituting deduced template arguments into function template 'any' [with _ValueType = const B &, _Tp = (no value), _Mgr = (no value), $3 = (no value)]
= decltype(::new _Tp(declval<_Arg>()))>
^
/opt/compiler-explorer/gcc-7.3.0/lib/gcc/x86_64-linux-gnu/7.3.0/../../../../include/c++/7.3.0/type_traits:974:24: note: in instantiation of default argument for '__test<B, const B &>' required here
static true_type __test(int);
^~~~~~~~~~~
/opt/compiler-explorer/gcc-7.3.0/lib/gcc/x86_64-linux-gnu/7.3.0/../../../../include/c++/7.3.0/type_traits:984:24: note: while substituting deduced template arguments into function template '__test' [with _Tp = B, _Arg = const B &, $2 = (no value)]
typedef decltype(__test<_Tp, _Arg>(0)) type;
^
/opt/compiler-explorer/gcc-7.3.0/lib/gcc/x86_64-linux-gnu/7.3.0/../../../../include/c++/7.3.0/type_traits:144:14: note: (skipping 9 contexts in backtrace; use -ftemplate-backtrace-limit=0 to see all)
: public conditional<_B1::value, _B2, _B1>::type
^
/opt/compiler-explorer/gcc-7.3.0/lib/gcc/x86_64-linux-gnu/7.3.0/../../../../include/c++/7.3.0/any:170:17: note: in instantiation of template class 'std::__and_<std::is_copy_constructible<B>, std::is_constructible<B, const B &> >' requested here
enable_if<__and_<is_copy_constructible<_Tp>,
^
/opt/compiler-explorer/gcc-7.3.0/lib/gcc/x86_64-linux-gnu/7.3.0/../../../../include/c++/7.3.0/any:175:5: note: in instantiation of template type alias '__any_constructible' requested here
using __any_constructible_t =
^
/opt/compiler-explorer/gcc-7.3.0/lib/gcc/x86_64-linux-gnu/7.3.0/../../../../include/c++/7.3.0/any:181:56: note: in instantiation of template type alias '__any_constructible_t' requested here
__any_constructible_t<_Tp, _ValueType&&> = true,
^
/opt/compiler-explorer/gcc-7.3.0/lib/gcc/x86_64-linux-gnu/7.3.0/../../../../include/c++/7.3.0/any:183:7: note: while substituting prior template arguments into non-type template parameter [with _ValueType = const B &, _Tp = B, _Mgr = std::any::_Manager_external<B>]
any(_ValueType&& __value)
^~~~~~~~~~~~~~~~~~~~~~~~~
<source>:63:23: note: while substituting deduced template arguments into function template 'any' [with _ValueType = const B &, _Tp = (no value), _Mgr = (no value), $3 = (no value), $4 = (no value)]
B(const B& b) : A(b) {
^
1 error generated.
Compiler returned: 1
有趣的是，它可以在gcc-7.1或更高版本中进行编译。
我要发生的是B的复制构造函数调用A的构造函数，而不是A的复制构造函数吗？如果是这样，我如何使B复制构造函数按预期工作？
p.s。这是我用于此https://godbolt.org/z/_22nuW的在线编译器的链接。