デストラクタが宣言されている場合、なぜこのコードはコンパイルされないのですか？

次のC ++ 11コードについて考えてみます。

#include <thread>
#include <vector>

struct A {
    A() {}

    //virtual ~A() = default;
    //~A() = default;
    //~A() {};

    std::thread t;
};

int main()
{
    std::vector<A> v;
    v.emplace_back();
}

前のコードでデストラクタを宣言している行のいずれかがコメント化されていない場合、このコードはコンパイルされません。コンパイラは、コピーコンストラクタstd::threadが削除されたことについて文句を言います。しかしstd::vector::emplace_back、コピーコンストラクターを使用すべきではないので、なぜ失敗するのでしょうか。そして、なぜデストラクタの言及が重要なのですか？

GCC出力（~A() {};コメントなし）：

$ g++ --std=c++11 -o test test.cpp 
In file included from /usr/include/c++/4.8/memory:64:0,
                 from /usr/include/c++/4.8/thread:40,
                 from test.cpp:1:
/usr/include/c++/4.8/bits/stl_construct.h: In instantiation of ‘void std::_Construct(_T1*, _Args&& ...) [with _T1 = A; _Args = {A}]’:
/usr/include/c++/4.8/bits/stl_uninitialized.h:75:53:   required from ‘static _ForwardIterator std::__uninitialized_copy<_TrivialValueTypes>::__uninit_copy(_InputIterator, _InputIterator, _ForwardIterator) [with _InputIterator = std::move_iterator<A*>; _ForwardIterator = A*; bool _TrivialValueTypes = false]’
/usr/include/c++/4.8/bits/stl_uninitialized.h:117:41:   required from ‘_ForwardIterator std::uninitialized_copy(_InputIterator, _InputIterator, _ForwardIterator) [with _InputIterator = std::move_iterator<A*>; _ForwardIterator = A*]’
/usr/include/c++/4.8/bits/stl_uninitialized.h:258:63:   required from ‘_ForwardIterator std::__uninitialized_copy_a(_InputIterator, _InputIterator, _ForwardIterator, std::allocator<_Tp>&) [with _InputIterator = std::move_iterator<A*>; _ForwardIterator = A*; _Tp = A]’
/usr/include/c++/4.8/bits/stl_uninitialized.h:281:69:   required from ‘_ForwardIterator std::__uninitialized_move_if_noexcept_a(_InputIterator, _InputIterator, _ForwardIterator, _Allocator&) [with _InputIterator = A*; _ForwardIterator = A*; _Allocator = std::allocator<A>]’
/usr/include/c++/4.8/bits/vector.tcc:415:43:   required from ‘void std::vector<_Tp, _Alloc>::_M_emplace_back_aux(_Args&& ...) [with _Args = {}; _Tp = A; _Alloc = std::allocator<A>]’
/usr/include/c++/4.8/bits/vector.tcc:101:54:   required from ‘void std::vector<_Tp, _Alloc>::emplace_back(_Args&& ...) [with _Args = {}; _Tp = A; _Alloc = std::allocator<A>]’
test.cpp:17:17:   required from here
/usr/include/c++/4.8/bits/stl_construct.h:75:7: error: use of deleted function ‘A::A(const A&)’
     { ::new(static_cast<void*>(__p)) _T1(std::forward<_Args>(__args)...); }
       ^
test.cpp:4:8: note: ‘A::A(const A&)’ is implicitly deleted because the default definition would be ill-formed:
 struct A {
        ^
test.cpp:4:8: error: use of deleted function ‘std::thread::thread(const std::thread&)’
In file included from test.cpp:1:0:
/usr/include/c++/4.8/thread:126:5: error: declared here
     thread(const thread&) = delete;
     ^

Clang出力（~A() {};コメントなし）：

$ clang++ --std=c++11 -o test test.cpp 
In file included from test.cpp:1:
In file included from /usr/bin/../lib/gcc/x86_64-linux-gnu/4.8/../../../../include/c++/4.8/thread:40:
In file included from /usr/bin/../lib/gcc/x86_64-linux-gnu/4.8/../../../../include/c++/4.8/memory:64:
/usr/bin/../lib/gcc/x86_64-linux-gnu/4.8/../../../../include/c++/4.8/bits/stl_construct.h:75:38: error: 
      call to implicitly-deleted copy constructor of 'A'
    { ::new(static_cast<void*>(__p)) _T1(std::forward<_Args>(__args)...); }
                                     ^   ~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/bin/../lib/gcc/x86_64-linux-gnu/4.8/../../../../include/c++/4.8/bits/stl_uninitialized.h:75:8: note: 
      in instantiation of function template specialization
      'std::_Construct<A, A>' requested here
                std::_Construct(std::__addressof(*__cur), *__first);
                     ^
/usr/bin/../lib/gcc/x86_64-linux-gnu/4.8/../../../../include/c++/4.8/bits/stl_uninitialized.h:117:2: note: 
      in instantiation of function template specialization
      'std::__uninitialized_copy<false>::__uninit_copy<std::move_iterator<A *>,
      A *>' requested here
        __uninit_copy(__first, __last, __result);
        ^
/usr/bin/../lib/gcc/x86_64-linux-gnu/4.8/../../../../include/c++/4.8/bits/stl_uninitialized.h:258:19: note: 
      in instantiation of function template specialization
      'std::uninitialized_copy<std::move_iterator<A *>, A *>' requested here
    { return std::uninitialized_copy(__first, __last, __result); }
                  ^
/usr/bin/../lib/gcc/x86_64-linux-gnu/4.8/../../../../include/c++/4.8/bits/stl_uninitialized.h:279:19: note: 
      in instantiation of function template specialization
      'std::__uninitialized_copy_a<std::move_iterator<A *>, A *, A>' requested
      here
      return std::__uninitialized_copy_a
                  ^
/usr/bin/../lib/gcc/x86_64-linux-gnu/4.8/../../../../include/c++/4.8/bits/vector.tcc:413:15: note: 
      in instantiation of function template specialization
      'std::__uninitialized_move_if_noexcept_a<A *, A *, std::allocator<A> >'
      requested here
              = std::__uninitialized_move_if_noexcept_a
                     ^
/usr/bin/../lib/gcc/x86_64-linux-gnu/4.8/../../../../include/c++/4.8/bits/vector.tcc:101:4: note: 
      in instantiation of function template specialization 'std::vector<A,
      std::allocator<A> >::_M_emplace_back_aux<>' requested here
          _M_emplace_back_aux(std::forward<_Args>(__args)...);
          ^
test.cpp:17:4: note: in instantiation of function template specialization
      'std::vector<A, std::allocator<A> >::emplace_back<>' requested here
        v.emplace_back();
          ^
test.cpp:11:14: note: copy constructor of 'A' is implicitly deleted because
      field 't' has a deleted copy constructor
        std::thread t;
                    ^
/usr/bin/../lib/gcc/x86_64-linux-gnu/4.8/../../../../include/c++/4.8/thread:126:5: note: 
      'thread' has been explicitly marked deleted here
    thread(const thread&) = delete;
    ^
1 error generated.