On 10/11/2025 13:24, Arnaud Le Blanc wrote:
As I'm seeing it, a File object that was explicitly closed would throw
an exception like "FileIsClosedError". It would indicate a lifetime
bug that needs to be fixed, not something that should be handled by
the program. This is reasonable, as closing is a clear intent that the
resource should not be used anymore. This is not an exception that
needs to be handled/checked. Under these intentions, leaving the
resource open (for the reason it's still referenced) and allowing
writes to it would be much worse.
C# / .net has an ObjectDisposedException for this purpose. The
documentation does indeed advise against catching it:
In most cases, this exception results from developer error. Instead of
handling the error in a |try|/|catch| block, you should correct the
error, typically by reinstantiating the object.
https://learn.microsoft.com/en-us/dotnet/api/system.objectdisposedexception
Note that using() does not prevent this. For example, in the
following, the using() block will implicitly call ms.Dispose(), but the
variable is still in scope.
MemoryStream ms= new MemoryStream(16);
using (ms)
{
ms.ReadByte();
}
ms.ReadByte(); // throws ObjectDisposedException
Similarly, additional references to the object can be made with
lifetimes which exceed the using() block:
MemoryStream ms_outer;
using (MemoryStream ms_inner = new MemoryStream(16))
{
ms_inner.ReadByte();
ms_outer = ms_inner;
}
ms_outer.ReadByte(); // throws ObjectDisposedException
In Hack, I believe both of these would be rejected by the compiler,
because any object implementing IDisposable is subject to strict usage
restrictions.
--
Rowan Tommins
[IMSoP]
