Array expansions in scalar assignments

[Dan Douglas]

Hi, it looks like these expansions still aren't quite being delimited
by IFS consistently. Probably strangest of these is a4 where `$*`
doesn't agree with `${a[*]}`, and a3 vs. a4 where quoting modifies the
result. I would think bash should look like the ksh output with all
@'s space-separated and all *'s comma-separated.

This was essentially the same bug, though I didn't test typeset vs
plain assignments or quoting variations back then:
https://lists.gnu.org/archive/html/bug-bash/2013-01/msg00167.html

+smorgbox bash-build # cat ~ormaaj/doc/projects/bash/testcases/peflattening2
shopt -s extglob
{ for sh in /bin/bash?(-*) ~ormaaj/doc/programs/bash-build/bash ksh
mksh; do "$sh" /dev/fd/3; done; } 3<<\EOF
function f {
   typeset -a a
   a=("$@")
   typeset IFS=,
   typeset a1="${a[@]} ${a[*]} $@ $*"
   typeset a2=${a[@]}\ ${a[*]}\ $@\ $* a3 a4
   a3="${a[@]} ${a[*]} $@ $*"
   a4=${a[@]}\ ${a[*]}\ $@\ $*
   unset -v IFS
   printf '%s\n' "${BASH_VERSION:-${KSH_VERSION}}:" "a1=$a1" "a2=$a2"
"a3=$a3" "a4=$a4"
}

echo
f a b c
# vim: ft=sh et
EOF

+smorgbox bash-build # bash ~ormaaj/doc/projects/bash/testcases/peflattening2

4.3.42(1)-release:
a1=a,b,c a,b,c a,b,c a,b,c
a2=a,b,c a,b,c a,b,c a,b,c
a3=a b c a,b,c a b c a,b,c
a4=a b c a,b,c a b c a b c

4.4.0(1)-rc2:
a1=a,b,c a,b,c a,b,c a,b,c
a2=a,b,c a,b,c a,b,c a,b,c
a3=a b c a,b,c a b c a,b,c
a4=a b c a,b,c a b c a b c

Version ABIJM 93v- 2014-12-24:
a1=a b c a,b,c a b c a,b,c
a2=a b c a,b,c a b c a,b,c
a3=a b c a,b,c a b c a,b,c
a4=a b c a,b,c a b c a,b,c

@(#)MIRBSD KSH R52 2016/04/09:
a1=a b c a,b,c a b c a,b,c
a2=a b c a,b,c a b c a,b,c
a3=a b c a,b,c a b c a,b,c
a4=a b c a,b,c a b c a,b,c