Remove dead code from diagnostics subsystem

src/LanguageServer/Protocol/Features/Diagnostics/EngineV2/DiagnosticIncrementalAnalyzer.ProjectAnalyzerReferenceChangedEventArgs.cs

@@ -5,28 +5,23 @@
 using System;
 using System.Collections.Immutable;
 
-namespace Microsoft.CodeAnalysis.Diagnostics.EngineV2
+namespace Microsoft.CodeAnalysis.Diagnostics.EngineV2;
+
+internal partial class DiagnosticIncrementalAnalyzer
 {
-    internal partial class DiagnosticIncrementalAnalyzer
+    /// <summary>
+    /// EventArgs for <see cref="StateManager.ProjectAnalyzerReferenceChanged"/>
+    /// 
+    /// this event args contains information such as <see cref="Project"/> the <see cref="AnalyzerReference"/> has changed
+    /// and what <see cref="StateSet"/> has changed.
+    /// </summary>
+    private sealed class ProjectAnalyzerReferenceChangedEventArgs : EventArgs
     {
-        /// <summary>
-        /// EventArgs for <see cref="StateManager.ProjectAnalyzerReferenceChanged"/>
-        /// 
-        /// this event args contains information such as <see cref="Project"/> the <see cref="AnalyzerReference"/> has changed
-        /// and what <see cref="StateSet"/> has changed.
-        /// </summary>
-        private class ProjectAnalyzerReferenceChangedEventArgs : EventArgs
-        {
-            public readonly Project Project;
-            public readonly ImmutableArray<StateSet> Added;
-            public readonly ImmutableArray<StateSet> Removed;
+        public readonly ImmutableArray<StateSet> Removed;
 
-            public ProjectAnalyzerReferenceChangedEventArgs(Project project, ImmutableArray<StateSet> added, ImmutableArray<StateSet> removed)
-            {
-                Project = project;
-                Added = added;
-                Removed = removed;
-            }
+        public ProjectAnalyzerReferenceChangedEventArgs(ImmutableArray<StateSet> removed)
+        {
+            Removed = removed;
         }
     }
 }

src/LanguageServer/Protocol/Features/Diagnostics/EngineV2/DiagnosticIncrementalAnalyzer.StateManager.ProjectStates.cs

@@ -107,8 +107,7 @@ private async Task<ProjectAnalyzerStateSets> UpdateProjectStateSetsAsync(Project
                     if (projectStateSets == null)
                     {
                         projectStateSets = CreateProjectStateSets(project);
-
-                        analyzerReferenceChangedEventArgs = GetProjectAnalyzerReferenceChangedEventArgs(project, projectStateSets.Value.MapPerReferences, projectStateSets.Value.StateSetMap);
+                        analyzerReferenceChangedEventArgs = GetProjectAnalyzerReferenceChangedEventArgs(project);
 
                         // update cache. 
                         _projectAnalyzerStateMap = _projectAnalyzerStateMap.SetItem(project.Id, projectStateSets.Value);
@@ -121,37 +120,22 @@ private async Task<ProjectAnalyzerStateSets> UpdateProjectStateSetsAsync(Project
                 return projectStateSets.Value;
             }
 
-            private ProjectAnalyzerReferenceChangedEventArgs? GetProjectAnalyzerReferenceChangedEventArgs(
-                Project project,
-                ImmutableDictionary<object, ImmutableArray<DiagnosticAnalyzer>> newMapPerReference,
-                ImmutableDictionary<DiagnosticAnalyzer, StateSet> newMap)
+            private ProjectAnalyzerReferenceChangedEventArgs? GetProjectAnalyzerReferenceChangedEventArgs(Project project)
             {
                 // No need to use _projectAnalyzerStateMapGuard during reads of _projectAnalyzerStateMap
                 if (!_projectAnalyzerStateMap.TryGetValue(project.Id, out var entry))
                 {
-                    // no previous references and we still don't have any references
-                    if (newMap.Count == 0)
-                    {
-                        return null;
-                    }
-
                     // new reference added
-                    return new ProjectAnalyzerReferenceChangedEventArgs(project, newMap.Values.ToImmutableArrayOrEmpty(), []);
+                    return null;
                 }
 
-                Debug.Assert(!entry.AnalyzerReferences.Equals(project.AnalyzerReferences));
-
                 // there has been change. find out what has changed
-                var addedStates = DiffStateSets(project.AnalyzerReferences.Except(entry.AnalyzerReferences), newMapPerReference, newMap);
                 var removedStates = DiffStateSets(entry.AnalyzerReferences.Except(project.AnalyzerReferences), entry.MapPerReferences, entry.StateSetMap);
 
-                // nothing has changed
-                if (addedStates.Length == 0 && removedStates.Length == 0)
-                {
+                if (removedStates.Length == 0)
                     return null;
-                }
 
-                return new ProjectAnalyzerReferenceChangedEventArgs(project, addedStates, removedStates);
+                return new ProjectAnalyzerReferenceChangedEventArgs(removedStates);
             }
 
             private static ImmutableArray<StateSet> DiffStateSets(