Cascading False Positives in Scala Compiler-based Highlighting

Problem

When using the Scala plugin in IntelliJ IDEA with the compiler-based error highlighting, users experience cascading false positives in unrelated files whenever there are real compilation errors in the project.

Cause

This issue arises due to a known limitation in the Scala 3 compiler-based highlighting.

Resolution

To mitigate the issue, switch the error highlighting mode to the built-in error highlighting in IntelliJ IDEA. This avoids cascading errors by using IntelliJ's type analysis engine instead of the Scala compiler. Follow these steps:

1. Navigate to Settings | Languages & Frameworks | Scala | Editor | Error Highlighting.
2. Change the mode from Compiler to Built-in.
3. Click OK to apply the changes.

For most regular development, the built-in mode should suffice. However, note that it may miss some edge cases handled by the compiler-based mode, especially related to advanced type-level features or macros.

Keep track of the permanent fix to this issue through the YouTrack link: SCL-20414. Starring the issue will provide notifications on updates. You can revert to compiler-based mode after the fix is implemented.