Add one-line using without variable

[B1Z0N]

What I mean is instead of doing using var _ = GIL.Acquire(); it would make sense to enable using GIL.Acquire();. This same feature is already enabled in block using:

using (GIL.Acquire())
{
    // do stuff
}

Akin to defer in Golang and others, but this one will support only IDisposable and not just any statement.
I think this will make the code simpler.

[CyrusNajmabadi]

The challenge here is that is using expr; is already legal syntax, and this would be ambiguous in a top level program.

[alexrp]

If there isn't a solution to the ambiguity, it seems like it might be reasonable to just say "tough luck, you can't do that, unless you move it into a block of some kind". Even as a user of top-level programs myself, I'd wager almost nobody would hit this restriction, and those few that do would have an easy alternative. Seems like a small price to pay. 🤔

[RenderMichael]

I think he best syntax for this would be

using _ = GIL.Acquire();

No conflicts with existing syntax (this doesn’t compile today including on top-level statements), and I think a discard is a very good indicator to the reader that a value is generated, and ignored.

[HaloFour]

It is still legal syntax, as _ is still a valid identifier for aliases. It would only fail to compile during semantic analysis when the expression doesn't yield a disposable value.

using _ = System.Console;

[RenderMichael]

I guess all we can hope for is for the breaking changes discussion to go through and for discards-as-identifiers to be obsoleted

[jnm2]

See existing discussions on this:

• Using statement parity with block #2593 (another duplicate: Allow `using` declarations without `var` ) #6860)

• Championed proposal: Can't use C# 8.0 using declaration with a discard #2235

• await using use case for this, because ConfigureAwait does not return a usable object to assign to a variable:
  Using ConfigureAwait in "await using" declaration #2661

[B1Z0N]

Thanks. Very helpful!