Co / Contravariant Interface Typeparameters - Pointer type

[bernd5]

Currently it is possible to define an interface like:

unsafe interface IX<in T>
{
    void Do(T* data);
}

Is this really allowed?
I ask because we explicitly dissallow ref/in/out on non invariant parameter types...

[svick]

It doesn't seem to be allowed by the runtime:

System.TypeLoadException: Could not load type 'IX`1' from assembly '...' because a covariant or contravariant type parameter was used illegally in the signature for an argument in method 'Do'.

The C# specification doesn't seem to be of much help here, since the variance rules are underspecified (see dotnet/csharpstandard#195).