ScriptableRenderPipeline/com.unity.shadergraph/Editor/Data/Interfaces/IMayRequireDepthTexture.cs

using UnityEditor.Graphing;

namespace UnityEditor.ShaderGraph
{
    public interface IMayRequireDepthTexture
    {
        bool RequiresDepthTexture(ShaderStageCapability stageCapability = ShaderStageCapability.All);
    }

    public static class MayRequireDepthTextureExtensions
    {
        public static bool RequiresDepthTexture(this ISlot slot)
        {
            var mayRequireDepthTexture = slot as IMayRequireDepthTexture;
            return mayRequireDepthTexture != null && mayRequireDepthTexture.RequiresDepthTexture();
        }
    }
}