Remove the thread-local cache; it seems to cause massive memory leaks.

ICSharpCode.NRefactory.CSharp/Resolver/Conversions.cs

@@ -21,6 +21,7 @@ using System.Collections.Concurrent;
 using System.Collections.Generic;
 using System.Diagnostics;
 using System.Linq;
+using System.Threading;
 using ICSharpCode.NRefactory.Semantics;
 using ICSharpCode.NRefactory.TypeSystem;
 using ICSharpCode.NRefactory.Utils;
@@ -55,13 +56,7 @@ namespace ICSharpCode.NRefactory.CSharp.Resolver
 		/// </summary>
 		public static Conversions Get(ICompilation compilation)
 		{
-			CacheManager cache = compilation.CacheManager;
-			Conversions conversions = (Conversions)cache.GetThreadLocal(typeof(Conversions));
-			if (conversions == null) {
-				conversions = new Conversions(compilation);
-				cache.SetThreadLocal(typeof(Conversions), conversions);
-			}
-			return conversions;
+			return new Conversions(compilation);
 		}
 		
 		#region TypePair (for caching)

ICSharpCode.NRefactory/Utils/CacheManager.cs

@@ -25,14 +25,14 @@ namespace ICSharpCode.NRefactory.Utils
 {
 	/// <summary>
 	/// Allows caching values for a specific compilation.
-	/// A CacheManager consists of two dictionaries: one for shared instances (shared among all threads working with that resolve context),
-	/// and one for thread-local instances.
+	/// A CacheManager consists of a for shared instances (shared among all threads working with that resolve context).
 	/// </summary>
 	/// <remarks>This class is thread-safe</remarks>
 	public sealed class CacheManager
 	{
 		readonly ConcurrentDictionary<object, object> sharedDict = new ConcurrentDictionary<object, object>(ReferenceComparer.Instance);
-		readonly ThreadLocal<Dictionary<object, object>> localDict = new ThreadLocal<Dictionary<object, object>>(() => new Dictionary<object, object>(ReferenceComparer.Instance));
+		// There used to be a thread-local dictionary here, but I removed it as it was causing memory
+		// leaks in some use cases.
 		
 		public object GetShared(object key)
 		{
@@ -55,17 +55,5 @@ namespace ICSharpCode.NRefactory.Utils
 		{
 			sharedDict[key] = val;
 		}
-		
-		public object GetThreadLocal(object key)
-		{
-			object val;
-			localDict.Value.TryGetValue(key, out val);
-			return val;
-		}
-		
-		public void SetThreadLocal(object key, object val)
-		{
-			localDict.Value[key] = val;
-		}
 	}
 }