n() { echo $#; }

set --

n "$@"

# should be 1
n "$@"''
n ''"$@"
n ''"$@"''

set -- ''

n "$@"
# should be 1
n "$@"''
n ''"$@"
n ''"$@"''

set -- '' ''

n "$@"
# should be 2
n ''"$@"
# should be 2
n "$@"''
# should be 2
n ''"$@"''

x=x

set --

n ${x+"$@"}

# should be 1
n ${x+"$@"''}
n ${x+''"$@"}
n ${x+''"$@"''}

set -- ''

n ${x+"$@"}
# should be 1
n ${x+"$@"''}
n ${x+''"$@"}
n ${x+''"$@"''}

set -- '' ''

n ${x+"$@"}
# should be 2
n ${x+''"$@"}
# should be 2
n ${x+"$@"''}
# should be 2
n ${x+''"$@"''}


set --

n "$@" "$@"
n "$@""$@"

n ${x+"$@" "$@"}

set -- ''

n ${x+"$@" "$@"}
n "$@" "$@"

set -- '' ''

n ${x+"$@" "$@"}
n "$@" "$@"
n "$@""$@"

# new tests
unset -v x
v=$'\177'

recho ''$'\177'''
recho $'\177'''
recho ''$'\177'

recho ''$v''
recho ''$v
recho $v''