Fix bug that branchesArr is not used; remove unused import.
Update scaladoc of a method.
Do toArray once and lazily outside of eval().
Translate CaseKeyWhen to CaseWhen at parsing time.
Cleanups per review comments.
Modify queries in tests to have shorter golden files.
Refactors: remove redundant passes, improve toString, mark transient.
Implement CastNulls, which fixes udf_case and udf_when.