They are aligning more closely with the Rust 2024 model for unsafety, which requires inner annotations at the point of unsafety in addition to notation of the function (unless it is the safe-unsafe boundary) plus it imposes a requirement for a SAFETY doc notation for describing the specific invariants the caller must enforce to uphold the safety guarantees. Not terribly onerous in my opinion. I maintain a few native library wrappers on nuget, so I will have to do some updates around IntPtr usage, but this doesn’t seem like it will be terribly painful in my case. Thankfully I don’t do much marshalling. Plus you get a nifty badge on nuget for making your library safe.

The blurb toward the end about Rent/return makes me a bit nervous though. They say they’re not going full borrow checker, but rent at least sounds an awful lot like borrow to me. Details were basically non-existent though.

I guess I wonder what the end game is here though. The more they make C# like Rust with a GC, the less incentive people have to use C# except maybe to support legacy work. I am still far more comfortable in C# than Rust, and I believe C# is superior for e.g. web, but over time this advantage could be lessened quite a bit as the Rust ecosystem continues to grow.