Discussion: Span of ref struct?

[HanabishiRecca]

Why we can't declare Span of ref struct?

ref struct A {...}
...
Span<A> arr = stackalloc A[10]; //error

Span itself is already a ref struct. So, if manually created ref struct of ref structs is ok, why we can't use Span of ref struct?
Of course ref struct can't be used as a generic type, but this is just a formal restriction. This means Span just needs some workaround.
E.g. such thing is possible in the unsafe context

var arr = stackalloc A[10];

We need something similar in the safe context.

[Joe4evr]

This would have to require something like #1148.

[quinmars]

Of course ref struct can't be used as a generic type, but this is just a formal restriction. This means Span just needs some workaround.

It's more than that. How should the compiler know that you cannot pass your Span<A> to the following test function?

public class C
{
    object remember;
    public bool Test<T>(Span<T> s)
    {
        remember = s.ToArray();
        return true;
    }
}

[HanabishiRecca]

@quinmars, exactly as I said.
In perfect case we need a native language feature for the stack array. (Also because Span is available only in the NET Core.)
Such as

A[] arr = stackalloc A[10];
var arr = stackalloc A[10]; //this will be interpreted as A[] - valid in the safe context

P.S. A[] is not the default array here, this is just an example, syntax may differ.

[yaakov-h]

(Also because Span is available only in the NET Core.)

@HanabishiRecca Span is available on .NET Framework 4.5 and higher with a NuGet package, as well as Mono, Xamarin, UWP, and PCLs.