Simplified PR, renamed Cached to Cacheable.

src/Discord.Net.Core/Utils/Cacheable.cs

@@ -0,0 +1,30 @@
+using System;
+using System.Collections.Generic;
+using System.Threading.Tasks;
+
+namespace Discord
+{
+    public struct Cacheable<TEntity, TId>
+        where TEntity : IEntity<TId>
+        where TId : IEquatable<TId>
+    {
+        public bool HasValue => !EqualityComparer<TEntity>.Default.Equals(Value, default(TEntity));
+        public ulong Id { get; }
+        public TEntity Value { get; }
+        private Func<Task<TEntity>> DownloadFunc { get; }
+
+        internal Cacheable(TEntity value, ulong id, Func<Task<TEntity>> downloadFunc)
+        {
+            Value = value;
+            Id = id;
+            DownloadFunc = downloadFunc;
+        }
+
+        public async Task<TEntity> DownloadAsync()
+        {
+            return await DownloadFunc();
+        }
+
+        public async Task<TEntity> GetOrDownloadAsync() => HasValue ? Value : await DownloadAsync();
+    }
+}