move the property back to IMessage

src/Discord.Net.Core/Entities/Messages/IMessage.cs

@@ -90,6 +90,14 @@ namespace Discord
         IUser Author { get; }
 
         /// <summary>
+        ///     Gets the thread that was started from this message.
+        /// </summary>
+        /// <returns>
+        ///    An <see cref="IThreadChannel"/> object if this message has thread attached; otherwise <see langword="null"/>.
+        /// </returns>
+        IThreadChannel Thread { get; }
+
+        /// <summary>
         ///     Gets all attachments included in this message.
         /// </summary>
         /// <remarks>

src/Discord.Net.Core/Entities/Messages/IUserMessage.cs

@@ -17,14 +17,6 @@ namespace Discord
         IUserMessage ReferencedMessage { get; }
 
         /// <summary>
-        ///     Gets the thread that was started from this message.
-        /// </summary>
-        /// <returns>
-        ///    An <see cref="IThreadChannel"/> object if this message has thread attached; otherwise <see langword="null"/>.
-        /// </returns>
-        IThreadChannel Thread { get; }
-
-        /// <summary>
         ///     Modifies this message.
         /// </summary>
         /// <remarks>

src/Discord.Net.Rest/Entities/Messages/RestMessage.cs

@@ -1,9 +1,13 @@
+using Discord.API;
+
 using Newtonsoft.Json.Linq;
+
 using System;
 using System.Collections.Generic;
 using System.Collections.Immutable;
 using System.Linq;
 using System.Threading.Tasks;
+
 using Model = Discord.API.Message;
 
 namespace Discord.Rest
@@ -45,6 +49,12 @@ namespace Discord.Rest
         /// <inheritdoc />
         public virtual bool MentionedEveryone => false;
 
+        /// <inheritdoc cref="IMessage.Thread"/>
+        public RestThreadChannel Thread { get; private set; }
+
+        /// <inheritdoc />
+        IThreadChannel IMessage.Thread => Thread;
+
         /// <summary>
         ///     Gets a collection of the <see cref="Attachment"/>'s on the message.
         /// </summary>
@@ -255,6 +265,9 @@ namespace Discord.Rest
                     model.RoleSubscriptionData.Value.MonthsSubscribed,
                     model.RoleSubscriptionData.Value.IsRenewal);
             }
+
+            if (model.Thread.IsSpecified)
+                Thread = RestThreadChannel.Create(Discord, new RestGuild(Discord, model.Thread.Value.GuildId.Value), model.Thread.Value);
         }
         /// <inheritdoc />
         public async Task UpdateAsync(RequestOptions options = null)
@@ -296,7 +309,7 @@ namespace Discord.Rest
 
         /// <inheritdoc />
         IReadOnlyCollection<IStickerItem> IMessage.Stickers => Stickers;
-        
+
         #endregion
 
         /// <inheritdoc />

src/Discord.Net.Rest/Entities/Messages/RestUserMessage.cs

@@ -47,12 +47,6 @@ namespace Discord.Rest
         /// <inheritdoc />
         public IUserMessage ReferencedMessage => _referencedMessage;
 
-        /// <inheritdoc cref="IUserMessage.Thread"/>
-        public RestThreadChannel Thread { get; private set; }
-
-        /// <inheritdoc />
-        IThreadChannel IUserMessage.Thread => Thread;
-
         internal RestUserMessage(BaseDiscordClient discord, ulong id, IMessageChannel channel, IUser author, MessageSource source)
             : base(discord, id, channel, author, source)
         {
@@ -136,9 +130,6 @@ namespace Discord.Rest
                 else
                     _stickers = ImmutableArray.Create<StickerItem>();
             }
-
-            if(model.Thread.IsSpecified)
-                Thread = RestThreadChannel.Create(Discord, guild, model.Thread.Value);
         }
 
         /// <inheritdoc />

src/Discord.Net.WebSocket/Entities/Messages/SocketMessage.cs

@@ -81,6 +81,12 @@ namespace Discord.WebSocket
         /// <inheritdoc />
         public MessageRoleSubscriptionData RoleSubscriptionData { get; private set; }
 
+        /// <inheritdoc cref="IMessage.Thread"/>
+        public SocketThreadChannel Thread { get; private set; }
+
+        /// <inheritdoc />
+        IThreadChannel IMessage.Thread => Thread;
+
         /// <summary>
         ///     Returns all attachments included in this message.
         /// </summary>
@@ -283,6 +289,12 @@ namespace Discord.WebSocket
                     model.RoleSubscriptionData.Value.MonthsSubscribed,
                     model.RoleSubscriptionData.Value.IsRenewal);
             }
+
+            if (model.Thread.IsSpecified)
+            {
+                SocketGuild guild = (Channel as SocketGuildChannel)?.Guild;
+                Thread = guild?.AddOrUpdateChannel(state, model.Thread.Value) as SocketThreadChannel;
+            }
         }
 
         /// <inheritdoc />

src/Discord.Net.WebSocket/Entities/Messages/SocketUserMessage.cs

@@ -49,12 +49,6 @@ namespace Discord.WebSocket
         /// <inheritdoc />
         public IUserMessage ReferencedMessage => _referencedMessage;
 
-        /// <inheritdoc cref="IUserMessage.Thread"/>
-        public SocketThreadChannel Thread { get; private set; }
-
-        /// <inheritdoc />
-        IThreadChannel IUserMessage.Thread => Thread;
-
         internal SocketUserMessage(DiscordSocketClient discord, ulong id, ISocketMessageChannel channel, SocketUser author, MessageSource source)
             : base(discord, id, channel, author, source)
         {
@@ -178,11 +172,6 @@ namespace Discord.WebSocket
                 else
                     _stickers = ImmutableArray.Create<SocketSticker>();
             }
-
-            if (model.Thread.IsSpecified)
-            {
-                Thread = guild!.AddOrUpdateChannel(state, model.Thread.Value) as SocketThreadChannel;
-            }
         }
 
         /// <inheritdoc />