Simplify/improve beatmap conversion precheck

osu.Game.Rulesets.Catch/Beatmaps/CatchBeatmapConverter.cs

@@ -4,7 +4,7 @@
 using osu.Game.Beatmaps;
 using osu.Game.Rulesets.Catch.Objects;
 using System.Collections.Generic;
-using System;
+using System.Linq;
 using osu.Game.Rulesets.Catch.UI;
 using osu.Game.Rulesets.Objects.Types;
 using osu.Game.Rulesets.Objects;
@@ -19,7 +19,7 @@ namespace osu.Game.Rulesets.Catch.Beatmaps
         {
         }
 
-        protected override IEnumerable<Type> ValidConversionTypes { get; } = new[] { typeof(IHasXPosition) };
+        public override bool CanConvert() => Beatmap.HitObjects.All(h => h is IHasXPosition);
 
         protected override IEnumerable<CatchHitObject> ConvertHitObject(HitObject obj, IBeatmap beatmap)
         {

osu.Game.Rulesets.Mania/Beatmaps/ManiaBeatmapConverter.cs

@@ -24,8 +24,6 @@ namespace osu.Game.Rulesets.Mania.Beatmaps
         /// </summary>
         private const int max_notes_for_density = 7;
 
-        protected override IEnumerable<Type> ValidConversionTypes { get; } = new[] { typeof(IHasXPosition) };
-
         public int TargetColumns;
         public bool Dual;
         public readonly bool IsForCurrentRuleset;
@@ -69,6 +67,8 @@ namespace osu.Game.Rulesets.Mania.Beatmaps
             }
         }
 
+        public override bool CanConvert() => Beatmap.HitObjects.All(h => h is IHasXPosition || h is ManiaHitObject);
+
         protected override Beatmap<ManiaHitObject> ConvertBeatmap(IBeatmap original)
         {
             BeatmapDifficulty difficulty = original.BeatmapInfo.BaseDifficulty;

osu.Game.Rulesets.Osu/Beatmaps/OsuBeatmapConverter.cs

@@ -7,7 +7,7 @@ using osu.Game.Rulesets.Objects;
 using osu.Game.Rulesets.Osu.Objects;
 using System.Collections.Generic;
 using osu.Game.Rulesets.Objects.Types;
-using System;
+using System.Linq;
 using osu.Game.Rulesets.Osu.UI;
 using osu.Framework.Extensions.IEnumerableExtensions;
 
@@ -20,7 +20,7 @@ namespace osu.Game.Rulesets.Osu.Beatmaps
         {
         }
 
-        protected override IEnumerable<Type> ValidConversionTypes { get; } = new[] { typeof(IHasPosition) };
+        public override bool CanConvert() => Beatmap.HitObjects.All(h => h is IHasPosition);
 
         protected override IEnumerable<OsuHitObject> ConvertHitObject(HitObject original, IBeatmap beatmap)
         {

osu.Game.Rulesets.Taiko/Beatmaps/TaikoBeatmapConverter.cs

@@ -39,14 +39,14 @@ namespace osu.Game.Rulesets.Taiko.Beatmaps
 
         private readonly bool isForCurrentRuleset;
 
-        protected override IEnumerable<Type> ValidConversionTypes { get; } = new[] { typeof(HitObject) };
-
         public TaikoBeatmapConverter(IBeatmap beatmap)
             : base(beatmap)
         {
             isForCurrentRuleset = beatmap.BeatmapInfo.Ruleset.Equals(new TaikoRuleset().RulesetInfo);
         }
 
+        public override bool CanConvert() => true;
+
         protected override Beatmap<TaikoHitObject> ConvertBeatmap(IBeatmap original)
         {
             // Rewrite the beatmap info to add the slider velocity multiplier

osu.Game.Tests/Visual/Gameplay/TestSceneDrawableScrollingRuleset.cs

@@ -273,7 +273,7 @@ namespace osu.Game.Tests.Visual.Gameplay
             {
             }
 
-            protected override IEnumerable<Type> ValidConversionTypes => new[] { typeof(HitObject) };
+            public override bool CanConvert() => true;
 
             protected override IEnumerable<TestHitObject> ConvertHitObject(HitObject original, IBeatmap beatmap)
             {

osu.Game/Beatmaps/BeatmapConverter.cs

@@ -33,7 +33,7 @@ namespace osu.Game.Beatmaps
         /// <summary>
         /// Whether <see cref="Beatmap"/> can be converted by this <see cref="BeatmapConverter{T}"/>.
         /// </summary>
-        public bool CanConvert => !Beatmap.HitObjects.Any() || ValidConversionTypes.All(t => Beatmap.HitObjects.Any(t.IsInstanceOfType));
+        public abstract bool CanConvert();
 
         /// <summary>
         /// Converts <see cref="Beatmap"/>.
@@ -92,11 +92,6 @@ namespace osu.Game.Beatmaps
             return result;
         }
 
-        /// <summary>
-        /// The types of HitObjects that can be converted to be used for this Beatmap.
-        /// </summary>
-        protected abstract IEnumerable<Type> ValidConversionTypes { get; }
-
         /// <summary>
         /// Creates the <see cref="Beatmap{T}"/> that will be returned by this <see cref="BeatmapProcessor"/>.
         /// </summary>

osu.Game/Beatmaps/DummyWorkingBeatmap.cs

@@ -76,7 +76,7 @@ namespace osu.Game.Beatmaps
 
                     public IBeatmap Beatmap { get; set; }
 
-                    public bool CanConvert => true;
+                    public bool CanConvert() => true;
 
                     public IBeatmap Convert()
                     {

osu.Game/Beatmaps/IBeatmapConverter.cs

@@ -25,7 +25,7 @@ namespace osu.Game.Beatmaps
         /// <summary>
         /// Whether <see cref="Beatmap"/> can be converted by this <see cref="IBeatmapConverter"/>.
         /// </summary>
-        bool CanConvert { get; }
+        bool CanConvert();
 
         /// <summary>
         /// Converts <see cref="Beatmap"/>.

osu.Game/Beatmaps/WorkingBeatmap.cs

@@ -108,7 +108,7 @@ namespace osu.Game.Beatmaps
             IBeatmapConverter converter = CreateBeatmapConverter(Beatmap, rulesetInstance);
 
             // Check if the beatmap can be converted
-            if (!converter.CanConvert)
+            if (!converter.CanConvert())
                 throw new BeatmapInvalidForRulesetException($"{nameof(Beatmaps.Beatmap)} can not be converted for the ruleset (ruleset: {ruleset.InstantiationInfo}, converter: {converter}).");
 
             // Apply conversion mods