删除的构造函数和模板

Question

Consider the following:

template<typename T>
class A
{
public:
    A(int a)
    {}

    A() = delete;
};

class B
{
public:
    B()
    {
        A<int> a;
    }
};

Of course this code does not compile because class B's constructor is attempting to default-construct a class A object and I've explicitly deleted that constructor. All well and good.

However, if I make B a class template

template<typename T>
class A
{
public:
    A(int a)
    {}

    A() = delete;
};

template<typename T>
class B
{
public:
    B()
    {
        A<int> a;
    }
};

then the code does compile and it seems I can now default-construct an instance of class A.

Why is this? What am I missing?

Thanks.

Answer 1

D'oh! It appears that the compiler doesn't see the error until it attempts to instantiate a class from the template.

Actually trying to create an object of type B<> generates the expected error.

Sorry if I wasted your time.