failures=0

check() {
	if ! eval "[ $* ]"; then
		echo "Failed: $*"
		: $((failures += 1))
	fi
}

check '"$(cat <<EOF
hi
EOF
)" = hi'

check '"$(cat <<EOF
${$+hi}
EOF
)" = hi'

unset yy
check '"$(cat <<EOF
${yy-hi}
EOF
)" = hi'

check '"$(cat <<EOF
${$+hi
there}
EOF
)" = "hi
there"'

check '"$(cat <<EOF
$((1+1))
EOF
)" = 2'

check '"$(cat <<EOF
$(echo hi)
EOF
)" = hi'

check '"$(cat <<EOF
`echo hi`
EOF
)" = hi'

check '"$(cat <<\EOF
${$+hi}
EOF
)" = "\${\$+hi}"'

check '"$(cat <<\EOF
$(
EOF
)" = \$\('

check '"$(cat <<\EOF
`
EOF
)" = \`'

check '"$(cat <<EOF
"
EOF
)" = \"'

check '"$(cat <<\EOF
"
EOF
)" = \"'

check '"$(cat <<esac
'"'"'
esac
)" = "'"'"'"'

check '"$(cat <<\)
'"'"'
)
)" = "'"'"'"'

exit $((failures != 0))