net9.0 
namespace System.Buffers
{
    [Experimental("SYSLIB5001", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
    public readonly struct NIndex : IEquatable<NIndex>
    {
        public Index ToIndexUnchecked();
    }
}
Design Reviews
.NET 8.09.010.0
Information specific to net9.0
Assemblies

System.Numerics.Tensors , Version=9.0.0.3, PublicKeyToken=cc7b13ffcd2ddd51

System.Numerics.Tensors , Version=10.0.0.0, PublicKeyToken=cc7b13ffcd2ddd51

Referencing

Your project needs a package reference to System.Numerics.Tensors.

Package System.Numerics.Tensors (9.0.3) net9.0
Platform Restrictions

This API is supported on all platforms.

  • Built-in API
  • Package-provided API