ak.argsort returns floats

[jrueb]

import awkward as ak
arr = ak.Array([[]])
print(ak.argsort(arr))

Will print <Array [[]] type='1 * var * float64'>, which has the value type float64 instead of int64. It works normally (returning int64) if arr is not empty. If you try to use this result to sort arr, you will get ValueError: only arrays of integers or booleans may be used as a slice.

Related to this I noticed that the following does not raise an error, even though argsort still returns floats here

arr = ak.Array([])
arr[ak.argsort(arr)]

I'm not sure if this is to be expected.

Tested on the latest git main (1.2.0rc2).

[jpivarski]

Thanks; that was just an oversight in the definition of EmptyArray::argsort_next.

The second example probably should be raising an error because the type is wrong—it certainly does when the array is not empty. It's complicated by the fact that EmptyArray declares itself to be an array of integers when used in a slice, but an array of floats when used in other contexts (except ak.argsort, after PR #764 goes through), though I think your example has an empty NumpyArray, rather than an EmptyArray. As for that case, I think it would be better for it to be picky about the type, even if the array is empty, but it's pretty low priority.