learn: fix redundant ham import on dual matches

When learning and injecting new messages ham, we want to avoid
wasting cycles importing the same message into an inbox twice
(once for the To/Cc match and once for the List-Id match).  Our
existing %seen hash turned out to be ineffective since
PublicInbox::Inbox refs get re-blessed to PublicInbox::InboxWritable.
So we stop letting class name influence the hash key for tracking by
using the reference address instead.  We can get the reference address
by performing an arithmetic operation (+ 0) instead of having to
pay the cost of importing Scalar::Util::refaddr.

1 files changed, 2 insertions, 2 deletions

diff --git a/script/public-inbox-learn b/script/public-inbox-learn
index 54d31cb6..8069d919 100755
--- a/script/public-inbox-learn
+++ b/script/public-inbox-learn
@@ -110,12 +110,12 @@ if ($train eq 'spam' || ($train eq 'rm' && $opt{all})) {
         my %seen;
         while (my ($addr, $ibx) = each %dests) {
                 next unless ref($ibx); # $ibx may be 0
-                next if $seen{"$ibx"}++;
+                next if $seen{0 + $ibx}++;
                 remove_or_add($ibx, $train, $mime, $addr);
         }
         my $dests = PublicInbox::MDA->inboxes_for_list_id($pi_cfg, $mime);
         for my $ibx (@$dests) {
-                next if $seen{"$ibx"}++;
+                next if $seen{0 + $ibx}++;
                 remove_or_add($ibx, $train, $mime, $ibx->{-primary_address});
         }
 }