Actually model scalar type promotion in shape analysis (#18811)
Summary:
This was causing some numerical issues in the fuser
Pull Request resolved: https://github.com/pytorch/pytorch/pull/18811
Differential Revision: D14767390
Pulled By: jamesr66a
fbshipit-source-id: f1123d1aab5501abad850d2edc996f8aa8dafe04
