BUG: Index.fillna silently ignoring 'downcast' kwarg by jbrockmendel · Pull Request #44873 · pandas-dev/pandas (original) (raw)

• closes BUG: Index.fillna ignores 'downcast' #44048
• tests added / passed
• Ensure all linting tests pass, see here for how to run them
• whatsnew entry

Decided to raise rather than silently give incorrect result. Haven't decided about deprecation, since there's an argument to be made for trying to make the downcast kwarg/behavior match Series.fillna (which is itself a can of worms).

Found along the way that CategoricalIndex.fillna can be removed; can make this a separate PR upon request.