shell: remove ${#+} tests, it is not a valid construct

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

shell/ash_test/ash-vars/param_expand_alt.right

@@ -1,6 +1,6 @@
 SHELL: line 1: syntax error: bad substitution
 SHELL: line 1: syntax error: bad substitution
-_0_ __
+__
 _z_ _z_
 _ _ _ _ _
 _aaaa _ _ _word _word

shell/ash_test/ash-vars/param_expand_alt.tests

@@ -6,8 +6,13 @@
 # now some funky ones.
 # ${V+word} "if V unset, then substitute nothing, else substitute word"
 # ${V:+word} "if V unset or '', then substitute nothing, else substitute word"
-# bash doesn't accept ${#+}. ash prints 0 (not $#): "len of $+"
-echo _${#+}_ _${#:+}_
+#
+# ${#:+} is a :+ op on $#, but ${#+} (and any other ${#c}) is "length of $c",
+# not + op on $#.
+# bash and dash do not accept ${#+}. it's possible for some shell to skip
+# the check that c is valid and interpret ${#+} as "len of $+". Not testing it.
+# echo _${#+}_
+echo _${#:+}_
 # Forms with non-empty word work as expected in both ash and bash.
 echo _${#+z}_ _${#:+z}_
 

shell/hush_test/hush-vars/param_expand_alt.right

@@ -1,6 +1,6 @@
 hush: syntax error: unterminated ${name}
 hush: syntax error: unterminated ${name}
-__ __
+__
 _z_ _z_
 _ _ _ _ _
 _aaaa _ _ _word _word

shell/hush_test/hush-vars/param_expand_alt.tests

@@ -6,8 +6,13 @@
 # now some funky ones.
 # ${V+word} "if V unset, then substitute nothing, else substitute word"
 # ${V:+word} "if V unset or '', then substitute nothing, else substitute word"
-# bash doesn't accept ${#+}. ash prints 0 (not $#): "len of $+"
-echo _${#+}_ _${#:+}_
+#
+# ${#:+} is a :+ op on $#, but ${#+} (and any other ${#c}) is "length of $c",
+# not + op on $#.
+# bash and dash do not accept ${#+}. it's possible for some shell to skip
+# the check that c is valid and interpret ${#+} as "len of $+". Not testing it.
+# echo _${#+}_
+echo _${#:+}_
 # Forms with non-empty word work as expected in both ash and bash.
 echo _${#+z}_ _${#:+z}_