okay, we gotta dispose stuff in this order

Author: SuuperW

src/BizHawk.Client.Common/FileStreamWithTemp.cs

@@ -7,7 +7,7 @@ namespace BizHawk.Client.Common
 {
 	internal class FileStreamWithTemp : IDisposable
 	{
-		public readonly FileStream Stream;
+		public FileStream Stream;
 		public string FinalPath;
 		public string TempPath;
 
@@ -95,7 +95,9 @@ public FileWriteResult EndWrite()
 
 		public void Dispose()
 		{
-			Stream.Dispose();
+			Stream?.Flush(flushToDisk: true);
+			Stream?.Dispose();
+			Stream = null;
 
 			// The caller should call EndWrite and handle potential failure.
 			Debug.Assert(_finished, $"{nameof(FileWriteResult)} should not be disposed before calling {nameof(EndWrite)}");

src/BizHawk.Client.Common/FrameworkZipWriter.cs

@@ -49,6 +49,12 @@ public static FileWriteResult<FrameworkZipWriter> Create(string path, int compre
 		public FileWriteResult EndWrite()
 		{
 			if (_fs == null) throw new ObjectDisposedException("Cannot use disposed ZipWriter.");
+
+			// We actually have to do this here since it has to be done before the file stream is closed.
+			// (and it gets closed in EndWrite)
+			_archive!.Dispose();
+			_archive = null;
+
 			return _fs.EndWrite();
 		}
 
@@ -76,13 +82,13 @@ public void Dispose()
 			if (_disposed) return;
 			_disposed = true;
 
-			_archive!.Dispose();
+			// _archive MUST be disposed before _fs. Or it throws.
+			_archive?.Dispose();
 			_archive = null;
 			_zstd!.Dispose();
 			_zstd = null;
 
-			_fs!.Stream.Flush(flushToDisk: true);
-			_fs.Dispose();
+			_fs!.Dispose();
 			_fs = null;
 		}
 	}