msg_iter: pass $idx as a scalar, not array

This doesn't make any difference for most multipart
messages (or any single part messages).  However,
this starts having space savings when parts start
nesting.

It also slightly simplifies callers.

2 files changed, 4 insertions, 3 deletions

diff --git a/t/mime.t b/t/mime.t
index 0d478ace..b9a4d66b 100644
--- a/t/mime.t
+++ b/t/mime.t
@@ -98,9 +98,10 @@ $msg = PublicInbox::MIME->new($raw);
 my $nr = 0;
 msg_iter($msg, sub {
         my ($part, $level, @ex) = @{$_[0]};
-        if ($ex[0] == 1) {
+        is($level, 1, 'at expected level');
+        if (join('fail if $#ex > 0', @ex) eq '1') {
                 is($part->body_str, "your tree directly? \r\n", 'body OK');
-        } elsif ($ex[0] == 2) {
+        } elsif (join('fail if $#ex > 0', @ex) eq '2') {
                 is($part->body, "-----BEGIN PGP SIGNATURE-----\n\n" .
                                 "=7wIb\n" .
                                 "-----END PGP SIGNATURE-----\n",
diff --git a/t/msg_iter.t b/t/msg_iter.t
index 5c57e043..e8115e25 100644
--- a/t/msg_iter.t
+++ b/t/msg_iter.t
@@ -28,7 +28,7 @@ use_ok('PublicInbox::MsgIter');
                 $s =~ s/\s+//s;
                 push @parts, [ $s, $level, @ex ];
         });
-        is_deeply(\@parts, [ [qw(a 2 1 1)], [qw(b 2 1 2)], [qw(sig 1 2)] ],
+        is_deeply(\@parts, [ [qw(a 2 1.1)], [qw(b 2 1.2)], [qw(sig 1 2)] ],
                 'nested part shows up properly');
 }