Assert ValueTask completion in SslStream.Read/Write

src/System.Net.Security/src/System/Net/Security/SslStream.cs

@@ -754,7 +754,9 @@ public override int Read(byte[] buffer, int offset, int count)
             ThrowIfExceptionalOrNotAuthenticated();
             ValidateParameters(buffer, offset, count);
             SslReadSync reader = new SslReadSync(this);
-            return ReadAsyncInternal(reader, new Memory<byte>(buffer, offset, count)).GetAwaiter().GetResult();
+            ValueTask<int> vt = ReadAsyncInternal(reader, new Memory<byte>(buffer, offset, count));
+            Debug.Assert(vt.IsCompleted, "Sync operation must have completed synchronously");
+            return vt.GetAwaiter().GetResult();
         }
 
         public void Write(byte[] buffer) => Write(buffer, 0, buffer.Length);
@@ -765,7 +767,9 @@ public override void Write(byte[] buffer, int offset, int count)
             ValidateParameters(buffer, offset, count);
 
             SslWriteSync writeAdapter = new SslWriteSync(this);
-            WriteAsyncInternal(writeAdapter, new ReadOnlyMemory<byte>(buffer, offset, count)).AsTask().GetAwaiter().GetResult();
+            ValueTask vt = WriteAsyncInternal(writeAdapter, new ReadOnlyMemory<byte>(buffer, offset, count));
+            Debug.Assert(vt.IsCompleted, "Sync operation must have completed synchronously");
+            vt.GetAwaiter().GetResult();
         }
 
         public override IAsyncResult BeginRead(byte[] buffer, int offset, int count, AsyncCallback asyncCallback, object asyncState)