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src/Workspaces/Core/Portable/FindSymbols/FindReferences/DependentTypeFinder.cs

@@ -17,7 +17,6 @@
 namespace Microsoft.CodeAnalysis.FindSymbols
 {
     using SymbolAndProjectIdSet = HashSet<SymbolAndProjectId<INamedTypeSymbol>>;
-
     using RelatedTypeCache = ConditionalWeakTable<Solution, ConcurrentDictionary<(SymbolKey, IImmutableSet<Project>), AsyncLazy<ImmutableArray<(SymbolKey, ProjectId)>>>>;
 
     /// <summary>
@@ -47,6 +46,9 @@ internal static class DependentTypeFinder
         // Kept as a cache so that clients who make many calls into us won't end up computing
         // the same data over and over again.  Will be let go the moment the solution they're
         // based off of is no longer alive.
+        //
+        // Importantly, the caches only store SymbolKeys and Ids.  As such, they will not hold
+        // any Symbols or Compilations alive.
 
         private static readonly RelatedTypeCache s_typeToImmediatelyDerivedClassesMap = new RelatedTypeCache();
         private static readonly RelatedTypeCache s_typeToTransitivelyDerivedClassesMap = new RelatedTypeCache();