Span and Memory are not included in the standard libraries included with Unity’s .NET Standard 2.0 profile, but can be imported via DLL (just download from Nuget). With the incremental GC, we also have C# 7.3 features, allowing for syntactic sugar using these types; however, it’s not clear if these types are backed by native function calls built into the runtime or managed implementations in C#. An existing benchmark of different run times that both do and don’t have native support on non-game workloads can be seen here: I knew the Span<T> stuff was supposed to be fast, but this is ridiculous! · GitHub.
This has nothing to do with the Native Collections. The intention is for use in reducing GC and simplifying memory management in high performance serialization and networking use cases.
Having engine support for interacting with these types, particularly when interchanging/copying data from native collections, would also be useful.