[perl #113050] Put fallback back under "()"

Unfortunately, there is code all over CPAN that assumes fallback is
stored under the "()" stash entry.  And that code also assumes that
the overloadedness flag (the existence of the CV) is in the same spot.
So much for encapsulation.

This commit changes overloading itself to use a different key, "((",
while having it search for "()" first, and then "((" only if "()" is
not found, to preserve compatibility with encapsulation-breaking code.

So the "((" key will only be used by gv.c if there is no fallback
value specified at all.

1 files changed, 12 insertions, 1 deletions

diff --git a/lib/overload.t b/lib/overload.t
index df3a9b825d..72e3b6e621 100644
--- a/lib/overload.t
+++ b/lib/overload.t
@@ -48,7 +48,7 @@ package main;
 
 $| = 1;
 BEGIN { require './test.pl' }
-plan tests => 5081;
+plan tests => 5082;
 
 use Scalar::Util qw(tainted);
 
@@ -2313,6 +2313,17 @@ $a = bless[], mane::;
 is eval { "$a" }, 'twine', ':: in method name' or diag $@;
 is eval { !$a  },   1,      "' in method name" or diag $@;
 
+# [perl #113050] Half of CPAN assumes fallback is under "()"
+{
+  package dodo;
+  use overload '+' => sub {};
+  no strict;
+  *{"dodo::()"} = sub{};
+  ${"dodo::()"} = 1;
+}
+$a = bless [],'dodo';
+is eval {"$a"}, overload::StrVal($a), 'fallback is stored under "()"';
+
 
 { # undefining the overload stash -- KEEP THIS TEST LAST
     package ant;