For the recently rewritten RFC PR #1147 Target Version, a few denominators could use some bikeshedding:

Cargo has a package attribute whose name is currently defined as ‘rust’. Alternatives include:

std (but this may confuse people who use --nostd)

rust_lang

target

rustc needs a command line option, currently named ‘–target-version=1.2.0’. This could be:

–std

–source

–version

I’m sure there are other options I haven’t yet considered. So what do you think?