Relax restrictions to allow T* extension methods to be defined from C#

[DaZombieKiller]

C# currently supports consuming T* extension methods if they are defined in IL, but attempting to define them in C# will result in a compiler error:

public static unsafe class PointerExtensions
{
    // CS1103: The first parameter of an extension method cannot be of type 'int*'
    public static int* Nop(this int* self) => self;

    // CS1103: The first parameter of an extension method cannot be of type 'T*'
    public static T* Nop<T>(this T* self) where T : unmanaged => self;
}

If you define these in IL, they can be used as expected:

int* pointer = /* ... */;
pointer.Nop();
byte* bytePointer = /* ... */;
bytePointer.Nop();

I propose relaxing the restrictions to allow them to be defined in C#.

[siegfriedpammer]

Note that your example is slightly incorrect. Calling methods on pointers either requires -> instead of . (as in bytePointer->Nop();, or you'd have to dereference the invocation target first, e.g., (*bytePointer).Nop();

What you propose is already possible today using this ref. See https://sharplab.io/#v2:EYLgtghglgdgNAFxFANnAJiA1AHwAIBMAjALABQeAzAASHUDC1A3udW7TQK4wDOEAZgFNaAFmoBZABSwE1AFQAPAJTNW7dQoC0APgByAewAOkpQG416tpMVKAdAeNmL1AL7k3ZclVpEAbLQJqAFEFBEFeKH1eVTJLbzw/UWoHSQQACygeagAnQX5qGWplZg8XIA=

Hope this helps!

[DaZombieKiller]

My example is correct for a pointer extension method (it is the syntax that you can use today if you define a pointer extension method in IL.)
ref this extension methods aren't quite the same thing and do not guarantee that the value is fixed, so they aren't suitable for many of the cases you would need to use pointers for.

[AraHaan]

I agree, unless we could do this to ensure that they are fixed if you make the first parameter fixed ref this to denote that "This can only be used when the pointer is fixed / pinned".

[Atomiz2002]

In the admittedly rare occasions this would be used (I'm here because of one), I also find it quite annoying that it's theoretically possible but practically not.