Move some suggestions to warnings, resolve issues

osu.Desktop/Updater/SquirrelUpdateManager.cs

@@ -48,7 +48,7 @@ namespace osu.Desktop.Updater
 
             try
             {
-                if (updateManager == null) updateManager = await UpdateManager.GitHubUpdateManager(@"https://github.com/ppy/osu", @"osulazer", null, null, true);
+                updateManager ??= await UpdateManager.GitHubUpdateManager(@"https://github.com/ppy/osu", @"osulazer", null, null, true);
 
                 var info = await updateManager.CheckForUpdate(!useDeltaPatching);
                 if (info.ReleasesToApply.Count == 0)

osu.Game.Rulesets.Catch/Difficulty/Skills/Movement.cs

@@ -35,8 +35,7 @@ namespace osu.Game.Rulesets.Catch.Difficulty.Skills
         {
             var catchCurrent = (CatchDifficultyHitObject)current;
 
-            if (lastPlayerPosition == null)
+            lastPlayerPosition ??= catchCurrent.LastNormalizedPosition;
-                lastPlayerPosition = catchCurrent.LastNormalizedPosition;
 
             float playerPosition = Math.Clamp(
                 lastPlayerPosition.Value,

osu.Game.Rulesets.Osu/Objects/Drawables/Connections/FollowPointConnection.cs

@@ -135,8 +135,7 @@ namespace osu.Game.Rulesets.Osu.Objects.Drawables.Connections
                 fp.Alpha = 0;
                 fp.Scale = new Vector2(1.5f * osuEnd.Scale);
 
-                if (firstTransformStartTime == null)
+                firstTransformStartTime ??= fadeInTime;
-                    firstTransformStartTime = fadeInTime;
 
                 fp.AnimationStartTime = fadeInTime;
 

osu.Game.Tests/Beatmaps/IO/ImportBeatmapTest.cs

@@ -175,7 +175,7 @@ namespace osu.Game.Tests.Beatmaps.IO
                     var breakTemp = TestResources.GetTestBeatmapForImport();
 
                     MemoryStream brokenOsu = new MemoryStream();
-                    MemoryStream brokenOsz = new MemoryStream(File.ReadAllBytes(breakTemp));
+                    MemoryStream brokenOsz = new MemoryStream(await File.ReadAllBytesAsync(breakTemp));
 
                     File.Delete(breakTemp);
 
@@ -522,7 +522,7 @@ namespace osu.Game.Tests.Beatmaps.IO
 
                     using (var resourceForkFile = File.CreateText(resourceForkFilePath))
                     {
-                        resourceForkFile.WriteLine("adding content so that it's not empty");
+                        await resourceForkFile.WriteLineAsync("adding content so that it's not empty");
                     }
 
                     try

osu.Game.Tests/Scores/IO/ImportScoreTest.cs

@@ -183,11 +183,8 @@ namespace osu.Game.Tests.Scores.IO
         {
             var beatmapManager = osu.Dependencies.Get<BeatmapManager>();
 
-            if (score.Beatmap == null)
+            score.Beatmap ??= beatmapManager.GetAllUsableBeatmapSets().First().Beatmaps.First();
-                score.Beatmap = beatmapManager.GetAllUsableBeatmapSets().First().Beatmaps.First();
+            score.Ruleset ??= new OsuRuleset().RulesetInfo;
-
-            if (score.Ruleset == null)
-                score.Ruleset = new OsuRuleset().RulesetInfo;
 
             var scoreManager = osu.Dependencies.Get<ScoreManager>();
             await scoreManager.Import(score, archive);

osu.Game.Tournament.Tests/LadderTestScene.cs

@@ -24,8 +24,7 @@ namespace osu.Game.Tournament.Tests
         [BackgroundDependencyLoader]
         private void load()
         {
-            if (Ladder.Ruleset.Value == null)
+            Ladder.Ruleset.Value ??= rulesetStore.AvailableRulesets.First();
-                Ladder.Ruleset.Value = rulesetStore.AvailableRulesets.First();
 
             Ruleset.BindTo(Ladder.Ruleset);
         }

osu.Game.Tournament/Screens/Drawings/DrawingsScreen.cs

@@ -47,8 +47,7 @@ namespace osu.Game.Tournament.Screens.Drawings
 
             this.storage = storage;
 
-            if (TeamList == null)
+            TeamList ??= new StorageBackedTeamList(storage);
-                TeamList = new StorageBackedTeamList(storage);
 
             if (!TeamList.Teams.Any())
             {

osu.Game.Tournament/TournamentGameBase.cs

@@ -150,11 +150,8 @@ namespace osu.Game.Tournament
                     ladder = JsonConvert.DeserializeObject<LadderInfo>(sr.ReadToEnd());
             }
 
-            if (ladder == null)
+            ladder ??= new LadderInfo();
-                ladder = new LadderInfo();
+            ladder.Ruleset.Value ??= RulesetStore.AvailableRulesets.First();
-
-            if (ladder.Ruleset.Value == null)
-                ladder.Ruleset.Value = RulesetStore.AvailableRulesets.First();
 
             Ruleset.BindTo(ladder.Ruleset);
 

osu.Game/Beatmaps/BeatmapManager.cs

@@ -239,8 +239,7 @@ namespace osu.Game.Beatmaps
 
                 if (working == null)
                 {
-                    if (beatmapInfo.Metadata == null)
+                    beatmapInfo.Metadata ??= beatmapInfo.BeatmapSet.Metadata;
-                        beatmapInfo.Metadata = beatmapInfo.BeatmapSet.Metadata;
 
                     workingCache.Add(working = new BeatmapManagerWorkingBeatmap(Files.Store,
                         new LargeTextureStore(host?.CreateTextureLoaderStore(Files.Store)), beatmapInfo, audioManager));

osu.Game/Beatmaps/Formats/LegacyBeatmapDecoder.cs

@@ -425,8 +425,7 @@ namespace osu.Game.Beatmaps.Formats
         private void handleHitObject(string line)
         {
             // If the ruleset wasn't specified, assume the osu!standard ruleset.
-            if (parser == null)
+            parser ??= new Rulesets.Objects.Legacy.Osu.ConvertHitObjectParser(getOffsetTime(), FormatVersion);
-                parser = new Rulesets.Objects.Legacy.Osu.ConvertHitObjectParser(getOffsetTime(), FormatVersion);
 
             var obj = parser.Parse(line);
             if (obj != null)

osu.Game/Online/Chat/ChannelManager.cs

@@ -114,8 +114,7 @@ namespace osu.Game.Online.Chat
         /// <param name="target">An optional target channel. If null, <see cref="CurrentChannel"/> will be used.</param>
         public void PostMessage(string text, bool isAction = false, Channel target = null)
         {
-            if (target == null)
+            target ??= CurrentChannel.Value;
-                target = CurrentChannel.Value;
 
             if (target == null)
                 return;
@@ -198,8 +197,7 @@ namespace osu.Game.Online.Chat
         /// <param name="target">An optional target channel. If null, <see cref="CurrentChannel"/> will be used.</param>
         public void PostCommand(string text, Channel target = null)
         {
-            if (target == null)
+            target ??= CurrentChannel.Value;
-                target = CurrentChannel.Value;
 
             if (target == null)
                 return;
@@ -378,8 +376,7 @@ namespace osu.Game.Online.Chat
                 }
             }
 
-            if (CurrentChannel.Value == null)
+            CurrentChannel.Value ??= channel;
-                CurrentChannel.Value = channel;
 
             return channel;
         }

osu.Game/Online/Chat/StandAloneChatDisplay.cs

@@ -73,8 +73,7 @@ namespace osu.Game.Online.Chat
         [BackgroundDependencyLoader(true)]
         private void load(ChannelManager manager)
         {
-            if (ChannelManager == null)
+            ChannelManager ??= manager;
-                ChannelManager = manager;
         }
 
         protected virtual StandAloneDrawableChannel CreateDrawableChannel(Channel channel) =>

osu.Game/OsuGameBase.cs

@@ -164,7 +164,7 @@ namespace osu.Game
             dependencies.Cache(SkinManager = new SkinManager(Storage, contextFactory, Host, Audio, new NamespacedResourceStore<byte[]>(Resources, "Skins/Legacy")));
             dependencies.CacheAs<ISkinSource>(SkinManager);
 
-            if (API == null) API = new APIAccess(LocalConfig);
+            API ??= new APIAccess(LocalConfig);
 
             dependencies.CacheAs(API);
 
@@ -311,11 +311,10 @@ namespace osu.Game
         {
             base.SetHost(host);
 
-            if (Storage == null) // may be non-null for certain tests
+            // may be non-null for certain tests
-                Storage = new OsuStorage(host);
+            Storage ??= new OsuStorage(host);
 
-            if (LocalConfig == null)
+            LocalConfig ??= new OsuConfigManager(Storage);
-                LocalConfig = new OsuConfigManager(Storage);
         }
 
         private readonly List<ICanAcceptFiles> fileImporters = new List<ICanAcceptFiles>();

osu.Game/Overlays/Chat/Tabs/ChannelTabControl.cs

@@ -68,8 +68,7 @@ namespace osu.Game.Overlays.Chat.Tabs
             if (!Items.Contains(channel))
                 AddItem(channel);
 
-            if (Current.Value == null)
+            Current.Value ??= channel;
-                Current.Value = channel;
         }
 
         /// <summary>

osu.Game/Rulesets/Objects/HitObject.cs

@@ -133,8 +133,7 @@ namespace osu.Game.Rulesets.Objects
         {
             Kiai = controlPointInfo.EffectPointAt(StartTime + control_point_leniency).KiaiMode;
 
-            if (HitWindows == null)
+            HitWindows ??= CreateHitWindows();
-                HitWindows = CreateHitWindows();
             HitWindows?.SetDifficulty(difficulty.OverallDifficulty);
         }
 

osu.Game/Rulesets/UI/FrameStabilityContainer.cs

@@ -181,8 +181,7 @@ namespace osu.Game.Rulesets.UI
         private void setClock()
         {
             // in case a parent gameplay clock isn't available, just use the parent clock.
-            if (parentGameplayClock == null)
+            parentGameplayClock ??= Clock;
-                parentGameplayClock = Clock;
 
             Clock = GameplayClock;
             ProcessCustomClock = false;

osu.Game/Scoring/ScoreInfo.cs

@@ -115,9 +115,7 @@ namespace osu.Game.Scoring
             get => User?.Username;
             set
             {
-                if (User == null)
+                User ??= new User();
-                    User = new User();
-
                 User.Username = value;
             }
         }
@@ -129,9 +127,7 @@ namespace osu.Game.Scoring
             get => User?.Id ?? 1;
             set
             {
-                if (User == null)
+                User ??= new User();
-                    User = new User();
-
                 User.Id = value ?? 1;
             }
         }

osu.Game/Screens/Edit/Timing/Section.cs

@@ -57,7 +57,7 @@ namespace osu.Game.Screens.Edit.Timing
                     {
                         checkbox = new OsuCheckbox
                         {
-                            LabelText = typeof(T).Name.Replace(typeof(ControlPoint).Name, string.Empty)
+                            LabelText = typeof(T).Name.Replace(nameof(Beatmaps.ControlPoints.ControlPoint), string.Empty)
                         }
                     }
                 },

osu.Game/Screens/Multi/Lounge/Components/FilterControl.cs

@@ -34,8 +34,7 @@ namespace osu.Game.Screens.Multi.Lounge.Components
         [BackgroundDependencyLoader]
         private void load()
         {
-            if (filter == null)
+            filter ??= new Bindable<FilterCriteria>();
-                filter = new Bindable<FilterCriteria>();
         }
 
         protected override void LoadComplete()

osu.Game/Screens/Select/BeatmapCarousel.cs

@@ -607,10 +607,7 @@ namespace osu.Game.Screens.Select
 
             // todo: remove the need for this.
             foreach (var b in beatmapSet.Beatmaps)
-            {
+                b.Metadata ??= beatmapSet.Metadata;
-                if (b.Metadata == null)
-                    b.Metadata = beatmapSet.Metadata;
-            }
 
             var set = new CarouselBeatmapSet(beatmapSet)
             {

osu.Game/Users/Drawables/DrawableAvatar.cs

@@ -43,7 +43,7 @@ namespace osu.Game.Users.Drawables
 
             Texture texture = null;
             if (user != null && user.Id > 1) texture = textures.Get($@"https://a.ppy.sh/{user.Id}");
-            if (texture == null) texture = textures.Get(@"Online/avatar-guest");
+            texture ??= textures.Get(@"Online/avatar-guest");
 
             ClickableArea clickableArea;
             Add(clickableArea = new ClickableArea

osu.sln.DotSettings

@@ -60,6 +60,7 @@
 	<s:String x:Key="/Default/CodeInspection/Highlighting/InspectionSeverities/=ConvertClosureToMethodGroup/@EntryIndexedValue">WARNING</s:String>
 	<s:String x:Key="/Default/CodeInspection/Highlighting/InspectionSeverities/=ConvertIfDoToWhile/@EntryIndexedValue">WARNING</s:String>
 	<s:String x:Key="/Default/CodeInspection/Highlighting/InspectionSeverities/=ConvertIfStatementToConditionalTernaryExpression/@EntryIndexedValue">WARNING</s:String>
+	<s:String x:Key="/Default/CodeInspection/Highlighting/InspectionSeverities/=ConvertIfStatementToNullCoalescingAssignment/@EntryIndexedValue">WARNING</s:String>
 	<s:String x:Key="/Default/CodeInspection/Highlighting/InspectionSeverities/=ConvertIfStatementToNullCoalescingExpression/@EntryIndexedValue">WARNING</s:String>
 	<s:String x:Key="/Default/CodeInspection/Highlighting/InspectionSeverities/=ConvertIfToOrExpression/@EntryIndexedValue">WARNING</s:String>
 	<s:String x:Key="/Default/CodeInspection/Highlighting/InspectionSeverities/=ConvertNullableToShortForm/@EntryIndexedValue">WARNING</s:String>
@@ -105,6 +106,8 @@
 	<s:String x:Key="/Default/CodeInspection/Highlighting/InspectionSeverities/=MergeCastWithTypeCheck/@EntryIndexedValue">HINT</s:String>
 	<s:String x:Key="/Default/CodeInspection/Highlighting/InspectionSeverities/=MergeConditionalExpression/@EntryIndexedValue">WARNING</s:String>
 	<s:String x:Key="/Default/CodeInspection/Highlighting/InspectionSeverities/=MergeSequentialChecks/@EntryIndexedValue">WARNING</s:String>
+	<s:String x:Key="/Default/CodeInspection/Highlighting/InspectionSeverities/=MethodHasAsyncOverload/@EntryIndexedValue">WARNING</s:String>
+	<s:String x:Key="/Default/CodeInspection/Highlighting/InspectionSeverities/=MethodHasAsyncOverloadWithCancellation/@EntryIndexedValue">WARNING</s:String>
 	<s:String x:Key="/Default/CodeInspection/Highlighting/InspectionSeverities/=MethodSupportsCancellation/@EntryIndexedValue">WARNING</s:String>
 	<s:String x:Key="/Default/CodeInspection/Highlighting/InspectionSeverities/=MissingBlankLines/@EntryIndexedValue">WARNING</s:String>
 	<s:String x:Key="/Default/CodeInspection/Highlighting/InspectionSeverities/=MissingIndent/@EntryIndexedValue">WARNING</s:String>
@@ -222,6 +225,7 @@
 	<s:String x:Key="/Default/CodeInspection/Highlighting/InspectionSeverities/=UseFormatSpecifierInInterpolation/@EntryIndexedValue">WARNING</s:String>
 	<s:String x:Key="/Default/CodeInspection/Highlighting/InspectionSeverities/=UseIndexFromEndExpression/@EntryIndexedValue">WARNING</s:String>
 	<s:String x:Key="/Default/CodeInspection/Highlighting/InspectionSeverities/=UseNameofExpression/@EntryIndexedValue">WARNING</s:String>
+	<s:String x:Key="/Default/CodeInspection/Highlighting/InspectionSeverities/=UseNameOfInsteadOfTypeOf/@EntryIndexedValue">WARNING</s:String>
 	<s:String x:Key="/Default/CodeInspection/Highlighting/InspectionSeverities/=UseNegatedPatternMatching/@EntryIndexedValue"></s:String>
 	<s:Boolean x:Key="/Default/CodeInspection/Highlighting/InspectionSeverities/=UseNegatedPatternMatching/@EntryIndexRemoved">True</s:Boolean>
 	<s:String x:Key="/Default/CodeInspection/Highlighting/InspectionSeverities/=UseNullPropagation/@EntryIndexedValue">WARNING</s:String>