Add generic [AutocompleteAttribute] (#2611)

* add generic AutocompleteAttribute

* fancy syntax

* it didn't work -_-

---------

Co-authored-by: Misha133 <mihagribkov133@gmail.com>

src/Discord.Net.Interactions/Attributes/AutocompleteAttribute.cs

@@ -1,36 +1,46 @@
 using System;
 
-namespace Discord.Interactions
+namespace Discord.Interactions;
+
+/// <summary>
+///     Set the <see cref="ApplicationCommandOptionProperties.IsAutocomplete"/> to <see langword="true"/>.
+/// </summary>
+[AttributeUsage(AttributeTargets.Parameter, AllowMultiple = false, Inherited = true)]
+public class AutocompleteAttribute : Attribute
 {
     /// <summary>
-    ///     Set the <see cref="ApplicationCommandOptionProperties.IsAutocomplete"/> to <see langword="true"/>.
+    ///     Type of the <see cref="AutocompleteHandler"/>.
     /// </summary>
-    [AttributeUsage(AttributeTargets.Parameter, AllowMultiple = false, Inherited = true)]
+    public Type AutocompleteHandlerType { get; }
-    public class AutocompleteAttribute : Attribute
+
+    /// <summary>
+    ///     Set the <see cref="ApplicationCommandOptionProperties.IsAutocomplete"/> to <see langword="true"/> and define a <see cref="AutocompleteHandler"/> to handle
+    ///     Autocomplete interactions targeting the parameter this <see cref="Attribute"/> is applied to.
+    /// </summary>
+    /// <remarks>
+    ///     <see cref="InteractionServiceConfig.EnableAutocompleteHandlers"/> must be set to <see langword="true"/> to use this constructor.
+    /// </remarks>
+    public AutocompleteAttribute(Type autocompleteHandlerType)
     {
-        /// <summary>
+        if (!typeof(IAutocompleteHandler).IsAssignableFrom(autocompleteHandlerType))
-        ///     Type of the <see cref="AutocompleteHandler"/>.
+            throw new InvalidOperationException($"{autocompleteHandlerType.FullName} isn't a valid {nameof(IAutocompleteHandler)} type");
-        /// </summary>
-        public Type AutocompleteHandlerType { get; }
 
-        /// <summary>
+        AutocompleteHandlerType = autocompleteHandlerType;
-        ///     Set the <see cref="ApplicationCommandOptionProperties.IsAutocomplete"/> to <see langword="true"/> and define a <see cref="AutocompleteHandler"/> to handle
-        ///     Autocomplete interactions targeting the parameter this <see cref="Attribute"/> is applied to.
-        /// </summary>
-        /// <remarks>
-        ///     <see cref="InteractionServiceConfig.EnableAutocompleteHandlers"/> must be set to <see langword="true"/> to use this constructor.
-        /// </remarks>
-        public AutocompleteAttribute(Type autocompleteHandlerType)
-        {
-            if (!typeof(IAutocompleteHandler).IsAssignableFrom(autocompleteHandlerType))
-                throw new InvalidOperationException($"{autocompleteHandlerType.FullName} isn't a valid {nameof(IAutocompleteHandler)} type");
-
-            AutocompleteHandlerType = autocompleteHandlerType;
-        }
-
-        /// <summary>
-        ///     Set the <see cref="ApplicationCommandOptionProperties.IsAutocomplete"/> to <see langword="true"/> without specifying a <see cref="AutocompleteHandler"/>.
-        /// </summary>
-        public AutocompleteAttribute() { }
     }
+
+    /// <summary>
+    ///     Set the <see cref="ApplicationCommandOptionProperties.IsAutocomplete"/> to <see langword="true"/> without specifying a <see cref="AutocompleteHandler"/>.
+    /// </summary>
+    public AutocompleteAttribute() { }
+}
+
+/// <summary>
+///     Set the <see cref="ApplicationCommandOptionProperties.IsAutocomplete"/> to <see langword="true"/>.
+/// </summary>
+/// <typeparam name="T">Type of the <see cref="AutocompleteHandler"/> that will be used to handle Autocomplete interactions targeting the parameter.</typeparam>
+[AttributeUsage(AttributeTargets.Parameter, AllowMultiple = false, Inherited = true)]
+public class AutocompleteAttribute<T> : AutocompleteAttribute
+    where T : class, IAutocompleteHandler
+{
+    public AutocompleteAttribute() : base(typeof(T)) { }
 }

src/Discord.Net.Interactions/Discord.Net.Interactions.csproj

@@ -3,12 +3,14 @@
   <Import Project="../../StyleAnalyzer.targets" />
   <PropertyGroup>
     <TargetFrameworks Condition=" '$(OS)' == 'Windows_NT' ">net6.0;net5.0;net461;netstandard2.0;netstandard2.1</TargetFrameworks>
+    <LangVersion>preview</LangVersion>
     <TargetFrameworks Condition=" '$(OS)' != 'Windows_NT' ">net6.0;net5.0;netstandard2.0;netstandard2.1</TargetFrameworks>
     <RootNamespace>Discord.Interactions</RootNamespace>
     <AssemblyName>Discord.Net.Interactions</AssemblyName>
     <Description>A Discord.Net extension adding support for Application Commands.</Description>
     <WarningLevel>5</WarningLevel>
     <TreatWarningsAsErrors>True</TreatWarningsAsErrors>
+    <EnablePreviewFeatures>true</EnablePreviewFeatures>
   </PropertyGroup>
   
   <ItemGroup>