BitVector shifts don't accept negative counts

[eschnett]

Arithmetic shifts accept negative shift counts, and then shift in the opposite direction. BitVector does not yet do this.

The standard implementation would be to change the count argument in the current implementation from Int to UInt, and have an additional selector function that accepts Int and chooses the shift direction.

[sg1101]

Hi @eschnett . I would like to try and solve this issue. I am new to open source and had not contributed yet. I can really use some guidience from you about how to proceed. Thank You :)

[StefanKarpinski]

Unless I'm mistaken, this was fixed by #19760.

[tkelman]

they could still use docs though

[StefanKarpinski]

Agreed, but that is a different issue.