C++/CLI compiler gives error C3214 when invoking a class with generic constraint by Tom Minka

If you make a C# assembly with the following code:

    public class B
    {
    }
    public class C<T, TB>
        where TB : B
    {
    }
    public class A<T>
    {
        public C<T, TB> makeC<TB>()
            where TB : B
        {
            return new C<T, TB>();
        }
    }

Then make a C++/CLI project that references the previous one and has the following code:

A<bool>^ x = gcnew A<bool>();

The result is:

error C3214: 'TB' : invalid type argument for generic parameter 'TB' of generic 'C', does not meet constraint 'B ^'

This error message should not be there. Interestingly, if the code is written entirely in C# or entirely in C++ (in a single source file), then no error message is generated. Update: If you define classes A,B,C in a C++/CLI assembly instead of C#, then the error message is still generated. So the issue is not about C# but rather referencing any assembly that defines classes A,B,C in the above manner. Here is the analogous C++ code:

public ref class B {};
generic<typename T,typename TB> where TB : B public ref class C {};
generic<typename T>    public ref class A
{
public:
    generic<typename TB> where TB : B
        C<T, TB>^ makeC()
    {
        return gcnew C<T, TB>();
    }
};