[perl #129916] Allow sub-in-stash outside of main

The sub-in-stash optimization introduced in 2eaf799e only applied to
subs in the main stash, not in other stashes, due to a problem with
the logic in newATTRSUB.

This comment:

	   Also, we may be called from load_module at run time, so
	   PL_curstash (which sets CvSTASH) may not point to the stash the
	   sub is stored in.

explains why we need the PL_curstash != CopSTASH(PL_curcop) check.
(Perl_load_module will fail without it.) But that logic does not work
properly at compile time (when PL_curcop == &PL_compiling).

The value of CopSTASH(&PL_compiling) is never actually used.  It is
always set to the main stash.  So if we check that PL_curstash !=
CopSTASH(PL_curcop) and forego the optimization in that case, we will
never optimize subs outside of the main stash.

What we really need is to check IN_PERL_RUNTIME && PL_curstash !=
opSTASH(PL_curcop).  I.e., forego the optimization at run time if the
stashes differ.  That is what this commit implements.

One observable side effect of this change is that deleting a stash
element no longer anonymizes the CV if the CV had no GV that it was
depending on to provide its name.  Since the main thing in such situa-
tions is that we do not get a crash, I think this change (arguably an
improvement) is acceptable.)

-----------

A bit of explanation of various other changes:

gv.c:require_tie_mod needed a bit of help, since it could not handle
sub refs in stashes.

To keep localisation of stash elements working the same way,
local($Stash::{foo}) now upgrades a coderef to a full GV before the
localisation.  (Changes in two pp*.c files and in scope.c:save_gp.)

t/op/stash.t contains a test that makes sure that perl does not crash
when a GV with a CV pointing to it gets deleted.  This commit tweaks
the test so that it continues to test that.  (There has to be a GV for
the test to test what it is meant to test.)

Similarly with t/uni/caller.t and t/uni/stash.t.

op.c:rv2cv_op_cv with the _MAYBE_NAME_GV flag was returning the cal-
ling GV in those cases where a GV-less sub is called via a GV.  E.g.,
*main = \&Foo::foo; main().  This meant that errors like ‘Not enough
arguments’ were giving the wrong sub name.

newATTRSUB was not calling mro_method_changed_in when storing a
sub as an RV.

gv_init needs to arrange for the new GV to have the file and line num-
ber corresponding to the sub in it.  These are taken from CvSTART,
which may be off by a few lines, but is the closest we have to the
place the sub was declared.

1 files changed, 1 insertions, 1 deletions

diff --git a/pp_hot.c b/pp_hot.c
index 40b850780c..f356d09353 100644
--- a/pp_hot.c
+++ b/pp_hot.c
@@ -2561,7 +2561,7 @@ PP(pp_helem)
 	    RETURN;
 	}
 	if (localizing) {
-	    if (HvNAME_get(hv) && isGV(*svp))
+	    if (HvNAME_get(hv) && isGV_or_RVCV(*svp))
 		save_gp(MUTABLE_GV(*svp), !(PL_op->op_flags & OPf_SPECIAL));
 	    else if (preeminent)
 		save_helem_flags(hv, keysv, svp,