Use 'Clear' to empty a CWT when on .net core

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

@@ -61,10 +61,12 @@ private void ClearCompilationsWithAnalyzersCache()
             // we basically eagarly clear the cache on some known changes
             // to let CompilationWithAnalyzer go.
 
-            // we create new conditional weak table every time, it turns out 
-            // only way to clear ConditionalWeakTable is re-creating it.
-            // also, conditional weak table has a leak - https://github.com/dotnet/coreclr/issues/665
+            // we create new conditional weak table every time netstandard as that's the only way it has to clear it.
+#if NETSTANDARD
             _projectCompilationsWithAnalyzers = new ConditionalWeakTable<Project, CompilationWithAnalyzers?>();
+#else
+            _projectCompilationsWithAnalyzers.Clear();
+#endif
         }
 
         [Conditional("DEBUG")]

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

@@ -33,7 +33,12 @@ internal partial class DiagnosticIncrementalAnalyzer : IIncrementalAnalyzer
         private readonly StateManager _stateManager;
         private readonly InProcOrRemoteHostAnalyzerRunner _diagnosticAnalyzerRunner;
         private readonly IDocumentTrackingService _documentTrackingService;
+
+#if NETSTANDARD
         private ConditionalWeakTable<Project, CompilationWithAnalyzers?> _projectCompilationsWithAnalyzers = new();
+#else
+        private readonly ConditionalWeakTable<Project, CompilationWithAnalyzers?> _projectCompilationsWithAnalyzers = new();
+#endif
 
         internal DiagnosticAnalyzerService AnalyzerService { get; }
         internal Workspace Workspace { get; }