BUG: preserve object dtype for Index set ops#31401

Merged

jreback merged 7 commits intopandas-dev:masterfrom

jbrockmendel:ref-index-wrap_setop_result

Feb 2, 2020

Commits on Jan 27, 2020

BUG: consistently retain object dtype for set ops
jbrockmendel
committed

Commits on Jan 28, 2020