Updating to the latest mozilla-central on Mac and trying to build, I'm getting:
0:05.96 checking rustc version... 1.47.0
0:05.97 checking cargo version... 1.46.0
0:05.97 ERROR: Cargo package manager 1.46.0 is too old.
0:05.97 To compile Rust language sources please install at least
0:05.97 version 1.47.0 of 'cargo' and make sure it is first in your path.
0:05.98 You can verify this by typing 'cargo --version'.
On further investigation this is due to a homebrew issue, the formula for 1.47.0 is shipping cargo 1.46.0 for some reason:
There is work in progress to release a 1.48.0 version of cargo, though that currently looks blocked on some rust build issues. Maybe there's someone that can help them out?
In any case, since this is going to affect developers, I'm filing it here so it can block mach-busted so that the details can be found more easily.