Expand on the future ref rules a bit

[jaredpar]

No description provided.

[jaredpar]

@agocke, @AaronRobinsonMSFT PTAL

[jaredpar]

@AaronRobinsonMSFT here you go.

[AaronRobinsonMSFT]

I would like to confirm the following example:

struct OS
{
    public IS inner;
}

struct IS
{ }

TypedReference M4(TypedReference os)
{
    // os contains a 'ref OS'
    // Return a 'ref IS' via the TypedReference
}

[jaredpar]

Are you trying to get the following to compile?

TypedReference M4(TypedReference os)
{
  ref IS local = __refvalue(os, IS);
  return __makeref(local);
}

That will compile. It's logically equivalent to the following:

TR M(TR tr)
{
    ref int local = ref tr.field;
    return new TR { field = ref local };
}

ref struct TR
{
    public ref int field;
}

[En3Tho]

@jaredpar I wonder if there is some document describing your view of the C# lifetime system with goals, imaginary syntax and so on? I'm really curious how you envision such a big feature/change. (Even if it might never come).

[jaredpar]

I'm really curious how you envision such a big feature/change. (Even if it might never come).

Which change are you referring to here: a world where we have explicit lifetimes?

[En3Tho]

@jaredpar Yes, explicit lifetime annotations in C#. How they would work with IDisposable, would they work with reference types, pointers?

What would be design goals: is it to enhance ref usage only or to enable developers with something like automatic disposal on scope exit?

I think it's fun to experiment with such features and I'm curious what do you have in mind.

[En3Tho]

@jaredpar Yes, explicit lifetime annotations in C#. How they would work with IDisposable, would they work with reference types, pointers?

What would be design goals: is it to enhance ref usage only or to enable developers with something like automatic disposal on scope exit?

I think it's fun to olay with such features and I'm curious what do you have in mind.

[jaredpar]

Yes, explicit lifetime annotations in C#. How they would work with IDisposable, would they work with reference types, pointers?

I've never sat down and wrote a doc about this because I wanted to focus on how far we could take the existing system. Once we know the limitations of how far you can take scoped plus a few expert level attributes it helps define what is left and what level of investment you would use to solve those problems.

Once I get pas this though, I will likely sit down and write a doc for where we'd go beyond scoped.which wolud include explicit lifetime rules.