Make `BeatmapVerifier` an interface

osu.Game.Rulesets.Osu/Edit/OsuBeatmapVerifier.cs

@@ -10,21 +10,13 @@
 
 namespace osu.Game.Rulesets.Osu.Edit
 {
-    public class OsuBeatmapVerifier : BeatmapVerifier
+    public class OsuBeatmapVerifier : IBeatmapVerifier
     {
         private readonly List<ICheck> checks = new List<ICheck>
         {
             new CheckOffscreenObjects()
         };
 
-        public override IEnumerable<Issue> Run(IBeatmap beatmap)
-        {
-            // Also run mode-invariant checks.
-            foreach (var issue in base.Run(beatmap))
-                yield return issue;
-
-            foreach (var issue in checks.SelectMany(check => check.Run(beatmap)))
-                yield return issue;
-        }
+        public IEnumerable<Issue> Run(IBeatmap beatmap) => checks.SelectMany(check => check.Run(beatmap));
     }
 }

osu.Game.Rulesets.Osu/OsuRuleset.cs

@@ -206,7 +206,7 @@ public override IEnumerable<Mod> GetModsFor(ModType type)
 
         public override HitObjectComposer CreateHitObjectComposer() => new OsuHitObjectComposer(this);
 
-        public override BeatmapVerifier CreateBeatmapVerifier() => new OsuBeatmapVerifier();
+        public override IBeatmapVerifier CreateBeatmapVerifier() => new OsuBeatmapVerifier();
 
         public override string Description => "osu!";
 

osu.Game/Rulesets/Edit/BeatmapVerifier.cs

@@ -2,27 +2,13 @@
 // See the LICENCE file in the repository root for full licence text.
 
 using System.Collections.Generic;
-using System.Linq;
 using osu.Game.Beatmaps;
-using osu.Game.Rulesets.Edit.Checks;
 using osu.Game.Rulesets.Edit.Checks.Components;
 
 namespace osu.Game.Rulesets.Edit
 {
-    public abstract class BeatmapVerifier
+    public interface IBeatmapVerifier
     {
-        /// <summary>
-        /// Checks which are performed regardless of ruleset.
-        /// These handle things like beatmap metadata, timing, and other ruleset agnostic elements.
-        /// </summary>
-        private readonly IReadOnlyList<ICheck> generalChecks = new List<ICheck>
-        {
-            new CheckBackground()
-        };
-
-        public virtual IEnumerable<Issue> Run(IBeatmap beatmap)
-        {
-            return generalChecks.SelectMany(check => check.Run(beatmap));
-        }
+        public IEnumerable<Issue> Run(IBeatmap beatmap);
     }
 }

osu.Game/Rulesets/Ruleset.cs

@@ -202,7 +202,7 @@ public PerformanceCalculator CreatePerformanceCalculator(WorkingBeatmap beatmap,
 
         public virtual HitObjectComposer CreateHitObjectComposer() => null;
 
-        public virtual BeatmapVerifier CreateBeatmapVerifier() => null;
+        public virtual IBeatmapVerifier CreateBeatmapVerifier() => null;
 
         public virtual Drawable CreateIcon() => new SpriteIcon { Icon = FontAwesome.Solid.QuestionCircle };
 

osu.Game/Screens/Edit/Verify/VerifyScreen.cs

@@ -21,7 +21,7 @@ namespace osu.Game.Screens.Edit.Verify
     public class VerifyScreen : EditorScreen
     {
         private Ruleset ruleset;
-        private static BeatmapVerifier beatmapVerifier;
+        private static IBeatmapVerifier beatmapVerifier;
 
         [Cached]
         private Bindable<Issue> selectedIssue = new Bindable<Issue>();