Emit warning from deprecated torch function signatures (#31514)
Summary:
Fixes https://github.com/pytorch/pytorch/issues/28430
The unpythonic signatures for functions such as `torch.addcdiv` are already seperated in [`deprecated.yaml`] and the signatures marked as deprecated in `PythonArgParser`. However, nothing was done with this information previously. So, this now emits a warning when the deprecated signatures are used.
One minor complication is that if all arguments are passed as keyword args then there is nothing to differentiate the deprecated overload. This can lead to false warnings being emitted. So, I've also modified `PythonArgParser` to prefer non-deprecated signatures.
[`deprecated.yaml`]: https://github.com/pytorch/pytorch/blob/master/tools/autograd/deprecated.yaml
Pull Request resolved: https://github.com/pytorch/pytorch/pull/31514
Differential Revision: D19298735
Pulled By: ezyang
fbshipit-source-id: 03cb78af17658eaab9d577cd2497c6f413f07647
