`LibraryImport` do not copy `this`

[MrScautHD]

Description

Hello, i tried to make extensions methods for my project and as i tried doing this it gave me a compile error.

There is no this in the generated code:

It told me:

0>LibraryImports.g.cs(1075,72): Error CS0755 : Both partial method declarations must be extension methods, or neither can be an extension method.

Reproduction Steps

Here is a small example:

public static partial class Camera3DExtensions {

    /// <summary>
    /// Update camera position for selected mode.
    /// </summary>
    /// <param name="camera">The camera to update.</param>
    /// <param name="mode">The camera mode.</param>
    [LibraryImport(Raylib.Name, EntryPoint = "UpdateCamera")]
    [UnmanagedCallConv(CallConvs = [typeof(CallConvCdecl)])]
    public static partial void Update(this ref Camera3D camera, CameraMode mode);
}

Expected behavior

No compile error.

Actual behavior

Regression?

No response

Known Workarounds

No response

Configuration

No response

Other information

No response

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[AaronRobinsonMSFT]

@MrScautHD Thanks for asking about this. Does a workaround of creating a private static method for the LibraryImport and then calling that in the extension method work? I realize the expectation here is to propogate the this, but can you confirm if that workaround unblocks you please.

@jkoritzinsky and @jtschuster I assume all we need to do here is propogate the this keyword. I can't think of any real issue with providing this support but I avoid extension methods. Any concerns?

[MrScautHD]

@MrScautHD Thanks for asking about this. Does a workaround of creating a private static method for the LibraryImport and then calling that in the extension method work? I realize the expectation here is to propogate the this, but can you confirm if that workaround unblocks you please.

@jkoritzinsky and @jtschuster I assume all we need to do here is propogate the this keyword. I can't think of any real issue with providing this support but I avoid extension methods. Any concerns?

Yes, I can confirm that the problem is resolved by implementing a new method that calls the LibraryImport function.

[jtschuster]

I assume all we need to do here is propogate the this keyword. I can't think of any real issue with providing this support but I avoid extension methods. Any concerns?

I can't think of any concerns off the top of my head. It looks like Roslyn has no issues making DllImports extension methods, so I imagine LibraryImport should support it too.

[AaronRobinsonMSFT]

It looks like Roslyn has no issues making DllImports extension methods, so I imagine LibraryImport should support it too.

@jtschuster Okay. I'll mark this for .NET 9. Interested in taking it on? If not, I assume one of us can handle this before we ship, seem like a simple change.

[jtschuster]

Yeah, I can take this one