This was a regression introduced by 7deeabc7c7526786df6894429ce89a9c4b614086
to address CVE-2019-14234.
Thanks Tim Kleinschmidt for the report and Mariusz for the tests.
SQLite doesn't repoint table aliases in partial index conditions on table
rename which breaks the documented table alteration procedure.
Thanks Pēteris Caune for the report.