As of last year, each dotty Error comes with an assigned identifier. It was added as part of the actionable diagnostics #14904.

This allows us to identify errors in other tools, by comparing the codes. Previously we did this with regex. This discussion is a place where we will discuss adding such identifiers to all warnings we emit.

The motivation behind it is almost the same as with error codes:

• we can identify warnings in other tools such as metals, and provide additional operations and utilities based on that information, e.g. language server protocol specifies DiagnosticTag. This tag is used by the LSP client to fade unused code, or cross deprecated one.
• we can provide actionable diagnostics that will remove unused code (this will allow us to easily remove all unused in a specific file without a need of scalafix)

If you have any opinions, comments, tips or anything related to this initiative, feel free to join the discussion.

This feature is going to be implemented by @ghostbuster91