Strange behavior of std::is_nothrow_destructible

The following code triggers static_assert even though I don't think it should:

#include <type_traits>

template< typename T >
struct Tmp
{
  ~Tmp() noexcept( std::is_nothrow_destructible< T >::value ) {}
};

struct Foo;

struct Bar
{
  // Comment this out for the problem to go away
  Tmp< Foo > xx;

  // ..or this
  Bar() {}
};

struct Foo {};

// This triggers
static_assert( std::is_nothrow_destructible< Foo >::value, "That's odd" );

int main()
{
}

When compiled with:

g++-4.9 -std=c++11 nothrow_destructible_bug.cc

The following happens:

nothrow_destructible_bug.cc:20:1: error: static assertion failed: That's odd
 static_assert( std::is_nothrow_destructible< Foo >::value, "That's odd" );
 ^

How come just using Foo to instantiate a template in an unrelated class make it lose its noexcept status? I thought this was a compiler bug, but I tried it with all recent versions of both gcc and clang and they all seem to give the same error.