Visual Studio C#7 suggestions

src/Discord.Net.Rest/Entities/Channels/RestGroupChannel.cs

@@ -60,8 +60,7 @@ namespace Discord.Rest
 
         public RestUser GetUser(ulong id)
         {
-            RestGroupUser user;
-            if (_users.TryGetValue(id, out user))
+            if (_users.TryGetValue(id, out RestGroupUser user))
                 return user;
             return null;
         }

src/Discord.Net.Rest/Entities/Guilds/RestGuild.cs

@@ -213,8 +213,7 @@ namespace Discord.Rest
         //Roles
         public RestRole GetRole(ulong id)
         {
-            RestRole value;
-            if (_roles.TryGetValue(id, out value))
+            if (_roles.TryGetValue(id, out RestRole value))
                 return value;
             return null;
         }

src/Discord.Net.Rest/Entities/Invites/RestInvite.cs

@@ -58,8 +58,7 @@ namespace Discord.Rest
             {
                 if (Guild != null)
                     return Guild;
-                var guildChannel = Channel as IGuildChannel;
-                if (guildChannel != null)
+                if (Channel is IGuildChannel guildChannel)
                     return guildChannel.Guild; //If it fails, it'll still return this exception
                 throw new InvalidOperationException("Unable to return this entity's parent unless it was fetched through that object.");
             }

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

@@ -80,8 +80,7 @@ namespace Discord.Rest
                 if (endIndex == -1) break;
                 string content = text.Substring(index, endIndex - index + 1);
 
-                ulong id;
-                if (MentionUtils.TryParseUser(content, out id))
+                if (MentionUtils.TryParseUser(content, out ulong id))
                 {
                     IUser mentionedUser = null;
                     foreach (var mention in userMentions)