Fix binary op name inference to happen before shape checks (#25563)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/25563
Before, for binary ops, name inference occurred after shape checks. This
defeats the purposes for names because the names are supposed to tell
the user that i.e. their tensors are misaligned or that they are adding
incompatible tensors.
This PR changes TensorIterator so that names are computed before shape checks and
propagated after the binary ops are finished. In order to support this,
this PR makes the following changes:
- adds a `names_` field to TensorIterator, similar to `shape_`. This is
necessary to hold the output names, that are computed in
`compute_names`, until they are used in `propagate_names_to_outputs()`.
Test Plan: Imported from OSS
Differential Revision: D17158869
Pulled By: zou3519
fbshipit-source-id: 0caa90f7a93e4d9bdb2549cd330cc3abd2258868
