Replace indexed skill access with skills.First(s is ...)

osu.Game.Rulesets.Catch/Difficulty/CatchDifficultyCalculator.cs

@@ -3,6 +3,7 @@
 
 using System;
 using System.Collections.Generic;
+using System.Linq;
 using osu.Game.Beatmaps;
 using osu.Game.Rulesets.Catch.Beatmaps;
 using osu.Game.Rulesets.Catch.Difficulty.Preprocessing;
@@ -40,7 +41,7 @@ protected override DifficultyAttributes CreateDifficultyAttributes(IBeatmap beat
 
             CatchDifficultyAttributes attributes = new CatchDifficultyAttributes
             {
-                StarRating = Math.Sqrt(skills[0].DifficultyValue()) * difficulty_multiplier,
+                StarRating = Math.Sqrt(skills.First(s => s is Movement).DifficultyValue()) * difficulty_multiplier,
                 Mods = mods,
                 ApproachRate = preempt > 1200.0 ? -(preempt - 1800.0) / 120.0 : -(preempt - 1200.0) / 150.0 + 5.0,
                 MaxCombo = beatmap.GetMaxCombo(),

osu.Game.Rulesets.Mania/Difficulty/ManiaDifficultyCalculator.cs

@@ -48,7 +48,7 @@ protected override DifficultyAttributes CreateDifficultyAttributes(IBeatmap beat
 
             ManiaDifficultyAttributes attributes = new ManiaDifficultyAttributes
             {
-                StarRating = skills[0].DifficultyValue() * difficulty_multiplier,
+                StarRating = skills.First(s => s is Strain).DifficultyValue() * difficulty_multiplier,
                 Mods = mods,
                 // In osu-stable mania, rate-adjustment mods don't affect the hit window.
                 // This is done the way it is to introduce fractional differences in order to match osu-stable for the time being.

osu.Game.Rulesets.Osu/Difficulty/OsuDifficultyCalculator.cs

@@ -36,15 +36,22 @@ protected override DifficultyAttributes CreateDifficultyAttributes(IBeatmap beat
             if (beatmap.HitObjects.Count == 0)
                 return new OsuDifficultyAttributes { Mods = mods };
 
-            double aimRating = Math.Sqrt(skills[0].DifficultyValue()) * difficulty_multiplier;
-            double aimRatingNoSliders = Math.Sqrt(skills[1].DifficultyValue()) * difficulty_multiplier;
-            double speedRating = Math.Sqrt(skills[2].DifficultyValue()) * difficulty_multiplier;
-            double speedNotes = ((Speed)skills[2]).RelevantNoteCount();
+            var aim = (Aim)skills.First(s => s is Aim);
+            var aimWithoutSliders = (AimWithoutSliders)skills.First(s => s is AimWithoutSliders);
+            var speed = (Speed)skills.First(s => s is Speed);
+
+            double aimRating = Math.Sqrt(aim.DifficultyValue()) * difficulty_multiplier;
+            double aimRatingNoSliders = Math.Sqrt(aimWithoutSliders.DifficultyValue()) * difficulty_multiplier;
+            double speedRating = Math.Sqrt(speed.DifficultyValue()) * difficulty_multiplier;
+            double speedNotes = speed.RelevantNoteCount();
 
             double flashlightRating = 0.0;
 
             if (mods.Any(h => h is OsuModFlashlight))
-                flashlightRating = Math.Sqrt(skills[3].DifficultyValue()) * difficulty_multiplier;
+            {
+                var flashlight = (Flashlight)skills.First(s => s is Flashlight);
+                flashlightRating = Math.Sqrt(flashlight.DifficultyValue()) * difficulty_multiplier;
+            }
 
             double sliderFactor = aimRating > 0 ? aimRatingNoSliders / aimRating : 1;
 
@@ -131,8 +138,8 @@ protected override Skill[] CreateSkills(IBeatmap beatmap, Mod[] mods, double clo
         {
             var skills = new List<Skill>
             {
-                new Aim(mods, true),
-                new Aim(mods, false),
+                new Aim(mods),
+                new AimWithoutSliders(mods),
                 new Speed(mods)
             };
 

osu.Game.Rulesets.Osu/Difficulty/Skills/Aim.cs

@@ -13,7 +13,7 @@ namespace osu.Game.Rulesets.Osu.Difficulty.Skills
     /// </summary>
     public class Aim : OsuStrainSkill
     {
-        public Aim(Mod[] mods, bool withSliders)
+        public Aim(Mod[] mods, bool withSliders = true)
             : base(mods)
         {
             this.withSliders = withSliders;

osu.Game.Rulesets.Osu/Difficulty/Skills/AimWithoutSliders.cs

@@ -0,0 +1,18 @@
+// 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 osu.Game.Rulesets.Mods;
+
+namespace osu.Game.Rulesets.Osu.Difficulty.Skills
+{
+    /// <summary>
+    /// Represents the Aim skill that does not include sliders length in it's calculation
+    /// </summary>
+    public class AimWithoutSliders : Aim
+    {
+        public AimWithoutSliders(Mod[] mods)
+            : base(mods, false)
+        {
+        }
+    }
+}