julia

27eee413 - Revert "Let tmerge form a Union more often (#27843)" (#39406)

Revert "Let tmerge form a Union more often (#27843)" (#39406) This reverts commit 6c1824d99769fa79f69eb866ce76df674fd37878. Fixes #39349. The extra inference precision is nice, but seems to carry too much risk of blowup.