Enum constraint for enum dropdown.

osu.Game/Graphics/UserInterface/OsuEnumDropdown.cs

@@ -6,12 +6,10 @@ using System;
 namespace osu.Game.Graphics.UserInterface
 {
     public class OsuEnumDropdown<T> : OsuDropdown<T>
+        where T : struct, Enum
     {
         public OsuEnumDropdown()
         {
-            if (!typeof(T).IsEnum)
-                throw new InvalidOperationException("OsuEnumDropdown only supports enums as the generic type argument");
-
             Items = (T[])Enum.GetValues(typeof(T));
         }
     }

osu.Game/Overlays/SearchableList/DisplayStyleControl.cs

@@ -1,6 +1,7 @@
 // Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
+using System;
 using osu.Framework.Bindables;
 using osuTK;
 using osu.Framework.Graphics;
@@ -11,6 +12,7 @@ using osu.Game.Graphics.Containers;
 namespace osu.Game.Overlays.SearchableList
 {
     public class DisplayStyleControl<T> : Container
+        where T : struct, Enum
     {
         public readonly SlimEnumDropdown<T> Dropdown;
         public readonly Bindable<PanelDisplayStyle> DisplayStyle = new Bindable<PanelDisplayStyle>();

osu.Game/Overlays/SearchableList/SearchableListFilterControl.cs

@@ -13,7 +13,9 @@ using osu.Framework.Graphics.Shapes;
 
 namespace osu.Game.Overlays.SearchableList
 {
-    public abstract class SearchableListFilterControl<T, U> : Container
+    public abstract class SearchableListFilterControl<TTab, TCategory> : Container
+        where TTab : struct, Enum
+        where TCategory : struct, Enum
     {
         private const float padding = 10;
 
@@ -21,12 +23,12 @@ namespace osu.Game.Overlays.SearchableList
         private readonly Box tabStrip;
 
         public readonly SearchTextBox Search;
-        public readonly PageTabControl<T> Tabs;
+        public readonly PageTabControl<TTab> Tabs;
-        public readonly DisplayStyleControl<U> DisplayStyleControl;
+        public readonly DisplayStyleControl<TCategory> DisplayStyleControl;
 
         protected abstract Color4 BackgroundColour { get; }
-        protected abstract T DefaultTab { get; }
+        protected abstract TTab DefaultTab { get; }
-        protected abstract U DefaultCategory { get; }
+        protected abstract TCategory DefaultCategory { get; }
         protected virtual Drawable CreateSupplementaryControls() => null;
 
         /// <summary>
@@ -36,9 +38,6 @@ namespace osu.Game.Overlays.SearchableList
 
         protected SearchableListFilterControl()
         {
-            if (!typeof(T).IsEnum)
-                throw new InvalidOperationException("SearchableListFilterControl's sort tabs only support enums as the generic type argument");
-
             RelativeSizeAxes = Axes.X;
 
             var controls = CreateSupplementaryControls();
@@ -90,7 +89,7 @@ namespace osu.Game.Overlays.SearchableList
                                     RelativeSizeAxes = Axes.X,
                                     AutoSizeAxes = Axes.Y,
                                     Padding = new MarginPadding { Right = 225 },
-                                    Child = Tabs = new PageTabControl<T>
+                                    Child = Tabs = new PageTabControl<TTab>
                                     {
                                         RelativeSizeAxes = Axes.X,
                                     },
@@ -105,7 +104,7 @@ namespace osu.Game.Overlays.SearchableList
                         },
                     },
                 },
-                DisplayStyleControl = new DisplayStyleControl<U>
+                DisplayStyleControl = new DisplayStyleControl<TCategory>
                 {
                     Anchor = Anchor.TopRight,
                     Origin = Anchor.TopRight,

osu.Game/Overlays/SearchableList/SearchableListHeader.cs

@@ -14,6 +14,7 @@ using osu.Framework.Graphics.Sprites;
 namespace osu.Game.Overlays.SearchableList
 {
     public abstract class SearchableListHeader<T> : Container
+        where T : struct, Enum
     {
         public readonly HeaderTabControl<T> Tabs;
 
@@ -24,9 +25,6 @@ namespace osu.Game.Overlays.SearchableList
 
         protected SearchableListHeader()
         {
-            if (!typeof(T).IsEnum)
-                throw new InvalidOperationException("BrowseHeader only supports enums as the generic type argument");
-
             RelativeSizeAxes = Axes.X;
             Height = 90;
 

osu.Game/Overlays/SearchableList/SearchableListOverlay.cs

@@ -1,6 +1,7 @@
 // Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
+using System;
 using osuTK.Graphics;
 using osu.Framework.Graphics;
 using osu.Framework.Graphics.Containers;
@@ -16,19 +17,22 @@ namespace osu.Game.Overlays.SearchableList
         public const float WIDTH_PADDING = 80;
     }
 
-    public abstract class SearchableListOverlay<T, U, S> : SearchableListOverlay
+    public abstract class SearchableListOverlay<THeader, TTab, TCategory> : SearchableListOverlay
+        where THeader : struct, Enum
+        where TTab : struct, Enum
+        where TCategory : struct, Enum
     {
         private readonly Container scrollContainer;
 
-        protected readonly SearchableListHeader<T> Header;
+        protected readonly SearchableListHeader<THeader> Header;
-        protected readonly SearchableListFilterControl<U, S> Filter;
+        protected readonly SearchableListFilterControl<TTab, TCategory> Filter;
         protected readonly FillFlowContainer ScrollFlow;
 
         protected abstract Color4 BackgroundColour { get; }
         protected abstract Color4 TrianglesColourLight { get; }
         protected abstract Color4 TrianglesColourDark { get; }
-        protected abstract SearchableListHeader<T> CreateHeader();
+        protected abstract SearchableListHeader<THeader> CreateHeader();
-        protected abstract SearchableListFilterControl<U, S> CreateFilterControl();
+        protected abstract SearchableListFilterControl<TTab, TCategory> CreateFilterControl();
 
         protected SearchableListOverlay()
         {

osu.Game/Overlays/SearchableList/SlimEnumDropdown.cs

@@ -1,6 +1,7 @@
 // Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
+using System;
 using osuTK.Graphics;
 using osu.Framework.Extensions.Color4Extensions;
 using osu.Framework.Graphics;
@@ -11,6 +12,7 @@ using osuTK;
 namespace osu.Game.Overlays.SearchableList
 {
     public class SlimEnumDropdown<T> : OsuEnumDropdown<T>
+        where T : struct, Enum
     {
         protected override DropdownHeader CreateHeader() => new SlimDropdownHeader();
 

osu.Game/Overlays/Settings/SettingsEnumDropdown.cs

@@ -1,12 +1,14 @@
 // Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
+using System;
 using osu.Framework.Graphics;
 using osu.Game.Graphics.UserInterface;
 
 namespace osu.Game.Overlays.Settings
 {
     public class SettingsEnumDropdown<T> : SettingsDropdown<T>
+        where T : struct, Enum
     {
         protected override OsuDropdown<T> CreateDropdown() => new DropdownControl();