I'd lump that analysis somewhere in the d-g, because you have to remember that &mut is also noalias and work out downstream implications of that. It's probably presumptive of me to assume a particular workflow for reconstructing the ownership model to express in Rust, and dividing that into the steps I did isn't the only way to do it.

In any case, it's the difficulty of that reconstruction step that leaves me thinking that automated conversion of whole-application to Rust is a near-impossibility. Conversion of an individual function that works on plain-old-data structures is probably doable, if somewhat challenging.

An off-the-cuff idea I just had is to implement a semi-automated transformation, where the user has to input what a final conversion of a struct type should look like (including all Cell/Rc/whatever wrappers as needed), and the tool can use that to work out the rest of the translation. There's probably a lot of ways that can go horribly wrong, but it seems more feasible than trying to figure out all of the wrappers need to be.