A first look at Rust in the 6.1 kernel

In that case the Rust support will be disabled silently.
This behaves the same as when using a config file that has compiler-dependent support enabled which is not supported by your compiler (e.g. UBSAN_TRAP, see `git grep "\$(" -- "*Kconf*"' for more).

I guess that's fair enough for an experimental feature that is not yet supported on all architectures?

Note that personally, I never run "make oldconfig", but always use my "linux-oldconfig" script, which prints a diff of all changes between the old and the new config file.