- Implement DNF method signatures with parameter contravariance and return covariance
- Add new test cases for DNF inheritance variance scenarios
- Extend stub generation to handle DNF union and intersection types
- Create DNF type declaration code generation in gen_stub.php
- Add support for DNF properties and dynamic property writes
- Implement closure support with DNF parameters and return types
- Add error handling for invalid DNF type operations
- Update inheritance checks to validate DNF parameter and return type compatibility
- Introduce test cases for DNF inheritance errors
- Refactor type comparison logic to support DNF clause subtyping relations
