Comment by neonsunset

Swift has just as much concerns for its structs and classes passing across FFI in terms of marshalling/unmarshalling and ensuring the ARC-unaware code performs either manual retain/release calls or adapts them to whatever other mechanism of memory management of the callee.

One of the comments here mentions that Swift has its own stable ABI, which exposes richer type system, so it does stand out in terms of interop (.NET 9 will add support for it natively (library evolution ABI) without having to go through C calls or C "glue" code on iOS and macOS, maybe the first non-Swift/ObjC platform to do so?).

Object pinning in .NET is only a part of equation and at this point far from the biggest concern (it just works, like it did 15 years ago, maybe it's a matter of fuss elsewhere?).