Champion "Implicitly scoped using statement" (16.3, Core 3)

[gafter]

• [x] Proposal added (https://github.com/dotnet/csharplang/blob/master/proposals/using.md)
• [x] Discussed in LDM
• [ ] Decision in LDM
• [ ] Finalized (done, rejected, inactive)
• [ ] Spec'ed

This is for some form of using statement, where the statements executed while the resource is held are the following statements in the same block that contains the using statement; the resource is freed at the end of the block.

See https://github.com/dotnet/csharplang/issues/114 and https://github.com/dotnet/csharplang/issues/114#issuecomment-349773994

LDM history:

• https://github.com/dotnet/csharplang/blob/master/meetings/2018/LDM-2018-07-09.md

[Joe4evr]

using X = Y is already valid syntax in C# that means something else entirely (it introduces a namespace or a type alias).

But it's not legal to use inside of a method scope. In fact, the compiler doesn't even consider it being a namespace/type alias when used in a method scope, so there's no ambiguity here.

[DaZombieKiller]

using X = Y is already valid syntax in C# that means something else entirely (it introduces a namespace or a type alias).

But it's not legal to use inside of a method scope. In fact, the compiler doesn't even consider it being a namespace/type alias when used in a method scope, so there's no ambiguity here.

I'm curious as to how that would interact with the scripting form of C#, where this doesn't necessarily apply.

[wanton7]

This is great feature, but is there anything similar planned for namespaces?

Most if not all .cs files will have this wrapping namespace in them.

namespace MyNameSpace
{
    public class MyClass
    {
    }
}

It seems very redundant because most of the files will have single namespace just wrapping everything. It would be great to able to do this this instead

namespace MyNameSpace;

public class MyClass
{
}

[Joe4evr]

@wanton7 #137.

[JesperTreetop]

The documentation seems to imply that this (multi-declaration implicitly typed variables) is possible:

using var f2 = new FileStream("..."), f3 = new FileStream("...");

But it doesn't look to be possible with SharpLab. Is it supposed to be possible, and wouldn't it then clash with disallowing multi-declaration var generally?

I'd file this as a bug on the documentation but the proposal says the same thing.

[YairHalberstadt]

@JesperTreetop You can never use var with multiple declarations. You always have to specify the type explicitly.

[munael]

Should #114 just mention this issue instead of both being put on the project board?