MsCorLib Array.cs Array.Sort line of code that not compile

Question

in th MsCorLib Array.cs source file there is the following Method, at line 1941:

void Sort<T>(T[] array)

in the body block at line 1948 there is the followin line

var span = new Span<T>(ref MemoryMarshal.GetArrayDataReference(array), array.Length);

if i try to copy paste this line on a my project, with C# 11 and .NET 7, there is a compile error "Argument 1 may not be passed with 'ref' keyword"

How is possible this? Waht i have to do to compile this line?

Answer 1

It uses internal Span<T> constructor which is not publicly available:

#pragma warning disable IDE0060 // https://github.com/dotnet/roslyn-analyzers/issues/6228
// Constructor for internal use only. 
// It is not safe to expose publicly, 
// and is instead exposed via the unsafe MemoryMarshal.CreateSpan.
[MethodImpl(MethodImplOptions.AggressiveInlining)]
internal Span(ref T reference, int length)
{
    Debug.Assert(length >= 0);
 
    _reference = ref reference;
    _length = length;
}
#pragma warning restore IDE0060 // https://github.com/dotnet/roslyn-analyzers/issues/6228

So "outside" compiler has only ctor with 2 parameters available - Span<T>(Void*, Int32) which requires pointer, not a ref parameter, hence the compilation error.

As mentioned in the comment in the source - you can use MemoryMarshal.CreateSpan as a substitute.