internal static void DeregisterHandle()

in binding/SkiaSharp/HandleDictionary.cs [176:227]
42 lines of code
13 McCabe index (conditional complexity)

		internal static void DeregisterHandle (IntPtr handle, SKObject instance)
		{
			if (handle == IntPtr.Zero)
				return;

			if (instance is ISKSkipObjectRegistration)
				return;

			instancesLock.EnterWriteLock ();
			try {
				var existed = instances.TryGetValue (handle, out var weak);
				if (existed && (!weak.IsAlive || weak.Target == instance)) {
					instances.Remove (handle);
#if DEBUG
					stackTraces.Remove (handle);
#endif
				} else {
#if THROW_OBJECT_EXCEPTIONS
					InvalidOperationException ex = null;
					if (!existed) {
						// the object may have been replaced

						if (!instance.IsDisposed) {
							// recoverable error
							// there was no object there, but we are still alive
							ex = new InvalidOperationException (
								$"A managed object did not exist for the specified native object. " +
								$"H: {handle.ToString ("x")} Type: {instance.GetType ()}");
						}
					} else if (weak.Target is SKObject o && o != instance) {
						// there was an object in the dictionary, but it was NOT this object

						if (!instance.IsDisposed) {
							// recoverable error
							// there was a new living object there, but we are still alive
							ex = new InvalidOperationException (
								$"Trying to remove a different object with the same native handle. " +
								$"H: {handle.ToString ("x")} Type: ({o.GetType ()}, {instance.GetType ()})");
						}
					}
					if (ex != null) {
						if (instance.fromFinalizer)
							exceptions.Add (ex);
						else
							throw ex;
					}
#endif
				}
			} finally {
				instancesLock.ExitWriteLock ();
			}
		}