Actually how would this make it any simpler?, if we remove PV from the filenames, the correct place to put the variable is in rust-source.inc since all others include it (rust-cross-canadian, rust, rust-llvm), if like I said, rust-source.inc gets included from somewhere else, wouldnt that override PV for the other recipe as well? beating the whole purpose of the change, this, or creating a new .inc file just for this seems too convoluted IMO.
If changing RUST_VERSION is too problematic on every upgrade I think approach #2 its a lot simpler just specifying RUST_VERSION on other recipes since it would be very seldom used and it wont conflict with upgrades
Alejandro