'ret T's aka byref pointers aka managed references in their current form is a relatively recent addition. I can't seem to find which exact version but if my mem

'ret T's aka byref pointers aka managed references in their current form is a relatively recent addition. I can't seem to find which exact version but if my memory is correct - around .NET 5 or so, before that e.g. Spans had to use a specially annotated field with [ByRefLike] attribute. There wasn't really such a forefront support in both the language and the runtime to enable the user scenarios and even, if limited, ref escape analysis that are possible today. .NET 9 goes further and allows types that hold byrefs to be generic arguments, so you can now handroll your own "true" span-based LINQ-like code as well.