BUG: fix torch.result_type cross-kind promotion (#55)

Author: lucascolley

array_api_compat/torch/_aliases.py

@@ -133,6 +133,8 @@ def result_type(*arrays_and_dtypes: Union[array, Dtype]) -> Dtype:
  # This doesn't result_type(dtype, dtype) for non-array API dtypes
  # because torch.result_type only accepts tensors. This does however, allow
  # cross-kind promotion.
+ x = torch.tensor([], dtype=x) if isinstance(x, torch.dtype) else x
+ y = torch.tensor([], dtype=y) if isinstance(y, torch.dtype) else y
  return torch.result_type(x, y)
 
 def can_cast(from_: Union[Dtype, array], to: Dtype, /) -> bool: