using statement in C# 8 without a variable

Question

Is there a mechanism for the new c# 8 using statement to work without a local variable?

Given ScopeSomething() returns a IDisposable (or null)...

Previously:

using (ScopeSomething())
{
    // ...
}

However in C# 8 with the using statement, it requires a variable name:

using var _ = ScopeSomething();

The _ here is not treated as a discard.

I would have expected this to have worked:

using ScopeSomething();

Answer 1

There are two kinds of resource_acquisition supported by using as per the specifications: local_variable_declaration and expression.

I believe the local using in C# 8 is a shortcut to local_variable_declaration form not expression form as per the language feature proposal, where you could see:

Restrictions around using declaration:

Must have an initializer for each declarator.

This also provides the ability to use more than one resources in a single using statement as per the language specs states:

When a resource_acquisition takes the form of a local_variable_declaration, it is possible to acquire multiple resources of a given type.

So you could do:

using IDisposable a = Foo1();
using IDisposable a = Foo1(), b = Foo2(), c = Foo3();

It may be possible that the language team could add expression form support in the future versions, but for now, expression is not yet supported.