[perl #79908] Stop sub inlining from breaking closures

When a closure closes over a variable, it references the variable
itself, as opposed to taking a snapshot of its value.

This was broken by the constant optimisation added for
constant.pm’s sake:

{
    my $x;
    sub () { $x };  # takes a snapshot of the current value of $x
}

constant.pm no longer uses that mechanism, except on older perls, so
we can remove this hack, causing code like this this to start work-
ing again:

BEGIN{
    my $x = 5;
    *foo = sub(){$x};
    $x = 6
}
print foo; # now prints 6, not 5

1 files changed, 0 insertions, 19 deletions

diff --git a/pad.c b/pad.c
index 8407ba60ee..83082a5c90 100644
--- a/pad.c
+++ b/pad.c
@@ -2183,25 +2183,6 @@ S_cv_clone(pTHX_ CV *proto, CV *cv, CV *outside)
 	cv_dump(cv,	 "To");
     );
 
-    if (CvCONST(cv)) {
-	/* Constant sub () { $x } closing over $x - see lib/constant.pm:
-	 * The prototype was marked as a candiate for const-ization,
-	 * so try to grab the current const value, and if successful,
-	 * turn into a const sub:
-	 */
-	SV* const const_sv = op_const_sv(CvSTART(cv), cv);
-	if (const_sv) {
-	    SvREFCNT_dec_NN(cv);
-            /* For this calling case, op_const_sv returns a *copy*, which we
-               donate to newCONSTSUB. Yes, this is ugly, and should be killed.
-               Need to fix how lib/constant.pm works to eliminate this.  */
-	    cv = newCONSTSUB(CvSTASH(proto), NULL, const_sv);
-	}
-	else {
-	    CvCONST_off(cv);
-	}
-    }
-
     return cv;
 }