Incorrect signatures for span indexers

[svick]

The signatures for indexers of Span<T> and ReadOnlySpan<T> don't show correctly in API reference.

For Span<T>, it shows as:

public T this[int index] { get; }

When it should be:

public ref T this[int index] { get; }

For ReadOnlySpan<T>, it shows as:

public T& this[int index] { get; }

When it should be:

public ref readonly T this[int index] { get; }

This seems to be caused by incorrect behavior of mdoc, so I have created and issue about this there: mono/api-doc-tools#249. But I thought it might make sense to also track fixing the output here (if and when mdoc is fixed), which is why I created this issue.

[pkulikov]

The same remark is valid for the Span<T>.Enumerator.Current property that should be:

public ref T Current { get; }

[mairaw]

Thanks for filing this tracking issue @svick and the corresponding issue for mdoc. The other interesting thing is that Property value is empty, when it usually shows the property type. @TianqiZhang can you take a look?

[BillWagner]

In a related issue, it seems that types declared as ref struct (like Span<T> are shown as struct. That's an important distinction.

[BillWagner]

Moved to MicrosoftDocs/feedback#468