mozilla/rust — pull request #13471 by Ryman (2014-04-12 00:47:29+00:00)
Title: librustc: Improve error message for missing feature attributes.

The current error message is misleading, it asks users to add `#[feature(..)]` which ends up being treated as an outer attribute, which then has no error unless `attribute_usage` lint is enforced. The code will still fail and the user might not understand why.