How can I get cargo to recompile changed files automatically?

I have heard cargo has the ability to automatically recompile changed source files, but I'm having a hard time figuring out how to tell it to do so.

For now, I am manually running cargo build or cargo run every time I want to type check my code. I would prefer to instead simply save the file and see the results in the neighboring terminal window.

In case you still have no idea what I'm talking about, I'm looking for the cargo equivalent of sbt ~compile or sbt ~run.

It seems strangely hard to find, so I'm starting to wonder if it's really supported. It's possible someone had said cargo could detect changed files and recompile them when what he meant to say was that cargo could detect unchanged files and avoid recompiling them, like make.

bacon

Nowadays the recommended tool is bacon. Install:

cargo install --locked bacon

Then run:

bacon

Which will keep running cargo check. See docs for more examples.
Historical answers
cargo watch

In case you are working on a server project (e.g. hyper, iron, etc) that keeps running and you need it to be restarted when files change, you can use cargo watch. Install:

cargo install cargo-watch

And then run:

cargo watch -x run

And to watch changes in only the src folder and clear the console use:

cargo watch -c -w src -x run

See the cargo-watch README for more examples.
watchexec

Alternatively, you can use watchexec. Install it:

cargo install watchexec-cli

And then use it like this:

watchexec -r cargo run

Stack Overflow Q#29461693, score: 171