Fix error with RequirePermission precondition

src/Discord.Net.Commands/Attributes/Preconditions/RequirePermission.cs

@@ -6,7 +6,7 @@ using System.Threading.Tasks;
 namespace Discord.Commands.Attributes.Preconditions
 {
     [AttributeUsage(AttributeTargets.Class | AttributeTargets.Method, AllowMultiple = true, Inherited = true)]
-    public class RequirePermission : RequireGuildAttribute
+    public class RequirePermission : PreconditionAttribute
     {
         public GuildPermission? GuildPermission { get; set; }
         public ChannelPermission? ChannelPermission { get; set; }
@@ -23,12 +23,10 @@ namespace Discord.Commands.Attributes.Preconditions
             GuildPermission = null;
         }
 
-        public override async Task<PreconditionResult> CheckPermissions(IMessage context, Command executingCommand, object moduleInstance)
+        public override Task<PreconditionResult> CheckPermissions(IMessage context, Command executingCommand, object moduleInstance)
         {
-            var result = await base.CheckPermissions(context, executingCommand, moduleInstance).ConfigureAwait(false);
-
-            if (!result.IsSuccess)
-                return result;
+            if (!(context.Channel is IGuildChannel))
+                return Task.FromResult(PreconditionResult.FromError("Command must be used in a guild channel"));
 
             var author = context.Author as IGuildUser;
 
@@ -36,7 +34,7 @@ namespace Discord.Commands.Attributes.Preconditions
             {
                 var guildPerms = author.GuildPermissions.ToList();
                 if (!guildPerms.Contains(GuildPermission.Value))
-                    return PreconditionResult.FromError($"User is missing guild permission {GuildPermission.Value}");
+                    return Task.FromResult(PreconditionResult.FromError($"User is missing guild permission {GuildPermission.Value}"));
             }
 
             if (ChannelPermission.HasValue)
@@ -45,10 +43,10 @@ namespace Discord.Commands.Attributes.Preconditions
                 var channelPerms = author.GetPermissions(channel).ToList();
 
                 if (!channelPerms.Contains(ChannelPermission.Value))
-                    return PreconditionResult.FromError($"User is missing channel permission {ChannelPermission.Value}");
+                    return Task.FromResult(PreconditionResult.FromError($"User is missing channel permission {ChannelPermission.Value}"));
             }
 
-            return PreconditionResult.FromSuccess();
+            return Task.FromResult(PreconditionResult.FromSuccess());
         }
     }
 }