When there were too many arguments given for the frame select command, the error message wasn't particularly helpful and then lldb would try to select frame -1, which resulted in an additional confusing error message.
This happened when the user expects f s 1 to be a short form of frame select 1, but the f itself is an alias for frame select, so the s is extraneous.
The new output should make it easier for the user to understand what went wrong:
(lldb) f s 1
error: too many arguments; expect frame-index, saw 's'.
Command Options Usage:
frame select [-r <offset>] [<frame-index>] -r <offset> ( --relative <offset> ) A relative frame index offset from the current frame index.