After installing, i cant expand - could not compile <filename>

[conormdowney]

Im brand new to Rust and i saw this tool mentioned in an article i was reading and it looks like it will be very handy for debugging.
After I installed it, when i run cargo expand I get:

error: the option 'Z' is only accepted on the nightly compiler error: could not compile 'traits'

I see the actual command is "cargo rustc --profile=check -- -Zunpretty=expanded", so it seems like it has a problem with the Z option there but I dont know what. Can anyone let me know what the issue is and how to fi it?