crates.io Dependencies

The rust compiler supports building with some dependencies from crates.io. For example, log and env_logger come from crates.io.

In general, you should avoid adding dependencies to the compiler for several reasons:

• The dependency may not be high quality or well-maintained, whereas we want the compiler to be high-quality.
• The dependency may not be using a compatible license.
• The dependency may have transitive dependencies that have one of the above problems.

As of July 2021, there is no official policy for vetting new dependencies to the compiler. Generally, new dependencies are not added to the compiler unless there is a good reason to do so.

Permitted dependencies

The tidy tool has a list of crates that are allowed. To add a dependency that is not already in the compiler, you will need to add it to the list.