crates.io dependencies

The Rust compiler supports building with some dependencies from crates.io. Examples are log and env_logger.

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

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

Note that there is no official policy for vetting new dependencies to the compiler. Decisions are made on a case-by-case basis, during code review.

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.