`legacy_imports` future-compatibility warnings

[jseyfried]

This is the summary issue for the legacy_imports future-compatibility warning and other related errors. The goal of this page is describe why this change was made and how you can fix code that is affected by it. It also provides a place to ask questions or register a complaint if you feel the change should not be made.

What is the warning for?

The legacy_imports warning is issued when

• a glob import of an ancestor module (e.g. use super::*) imports a non-pub name,
• the name is also imported by another glob import, making it ambiguous, and
• the name is used, triggering an ambiguity error.

See RFC 1560 for more detailed information.

When will this warning become a hard error?

At the beginning of each 6-week release cycle, the Rust compiler team will review the set of outstanding future compatibility warnings and nominate some of them for Final Comment Period. Toward the end of the cycle, we will review any comments and make a final determination whether to convert the warning into a hard error or remove it entirely.

Current status

• #38271 introduces the legacy_imports lint as warn-by-default
• #42894 makes the legacy_imports lint deny-by-default
• PR ? makes the legacy_imports lint a hard error