[Metal] Unable to CreateFramebuffer with more than 3 textures in Metal Backend

[partyalarm]

Create a frame buffer with 3 or more textures bind at the Metal backend.

var depthStencil = factory.CreateTexture(TextureDescription.Texture2D(w, h, 1, 1, PixelFormat.R16_UNorm, TextureUsage.DepthStencil ));
var colorRT  = factory.CreateTexture(TextureDescription.Texture2D(w, h, 1, 1, PixelFormat.R8_G8_B8_A8_UNorm, TextureUsage.RenderTarget | TextureUsage.Sampled));
var normalRT = factory.CreateTexture(TextureDescription.Texture2D(w, h, 1, 1, PixelFormat.R8_G8_B8_A8_UNorm, TextureUsage.RenderTarget | TextureUsage.Sampled));
var depthRT = factory.CreateTexture(TextureDescription.Texture2D(w, h, 1, 1, PixelFormat.R8_G8_B8_A8_UNorm, TextureUsage.RenderTarget | TextureUsage.Sampled));
var mrtFramebuffer = factory.CreateFramebuffer(new FramebufferDescription(depthStencil, colorRT, normalRT, depthRT));

Creating a PipelineDescription using this framebuffer and calling CreateGraphicsPipeline() will throw System.IndexOutOfRangeException.

var mrtPipeline = factory.CreateGraphicsPipeline(pipelineDesc);

For one or two textures, this exception does not seem to occur.
Also, the OpenGL backend does not seem to raise any exceptions.
I have not tried Vulkan Backend because I could not figure out how to run it on a Mac.

[mellinoe]

Could you provide a bit more information, especially regarding the other properties of the GraphicsPipelineDescription? I suspect there might be a mismatch in the number of attachments that you have in BlendStateDescription.AttachmentStates as that does not seem to be directly validated anywhere (and would very likely behave differently across backends if the size wasn't correct).