[zozbot234]

> An immutable GC would only be useful by adding an interior mutability wrapper, which is exactly the kind of friction the paper is trying to avoid.

This would be the most idiomatic approach, yes. They could use a code transformation to automate the 'wrapping' and present an intuitive, frictionless interface to the developer.

[steveklabnik]

Totally, and that’s one of the ideas floated in the issue. I think depending on how it could be done it may not even lost out on ergonomics in most cases, but I haven’t worked through it myself.