# This isn't perfect behavior, but it establishes a baseline and will provide
# a way to detect behavior changes

echo a1
a[0]= a[1]=; recho "${a[@]:-y}"
unset a

echo a2
a[1]=; recho "${a[@]:-y}"
a[1]=; recho "${a[*]:-z}"
unset a

echo a3
a[0]= a[1]=x; recho "${a[@]:-y}"
unset a

echo a4
a[0]= a[1]=x; recho ${a[@]:+y}
unset a

echo p1
set '' ''
recho "${@:-y}"

shift $#

echo p2
set '' x
recho "${@:-y}"

shift $#

echo p3
set '' x
recho ${@:+y}

# problems with * and null expansions dating back to bash's earliest days
A=(''); set -- ''

echo "<${A[*]:-X}>" "<${*:-X}>" "<${A:-X}>" "<${A[0]:-X}>" 

IFS=
A=('' ''); set -- '' ''
B=''

echo "<${A[*]:-X}>" "<${*:-X}>" "<${B:-X}>" "<${B[*]:-X}>"