avoid $a["foo" eq $x ? 0 : 1] warning

RT #123609

The compiling code that looks for OP_MULTIDEREF candidates was
unconditionally numifying the first constant of an array index expression,
before it had confirmed that the expression consisted solely of a const.
So in something like

    $a['foo' eq $x ? 0 : 1]

the 'foo' would be numified and give a spurious warning:

    Argument "foo" isn't numeric

This commit fixes it by skipping the OP_MULTIDEREF optimisation if the
array index const isn't SvIOK(). In theory this means that something like

    $r->["0"]

no longer gets optimised, but I think we can live with that :-)

It also means that the test for the const being SvROK is no longer
necessary.

(Finally, I moved the declaration of the iv var down a few scopes as it
wasn't being used elsewhere in the wider scope.)

1 files changed, 3 insertions, 6 deletions

diff --git a/op.c b/op.c
index 637a60eee3..c1d41722be 100644
--- a/op.c
+++ b/op.c
@@ -12285,7 +12285,6 @@ S_maybe_multideref(pTHX_ OP *start, OP *orig_o, UV orig_action, U8 hints)
             /* look for another (rv2av/hv; get index;
              * aelem/helem/exists/delele) sequence */
 
-            IV iv;
             OP *kid;
             bool is_deref;
             bool ok;
@@ -12397,12 +12396,10 @@ S_maybe_multideref(pTHX_ OP *start, OP *orig_o, UV orig_action, U8 hints)
                     }
                     else {
                         /* it's a constant array index */
+                        IV iv;
                         SV *ix_sv = cSVOPo->op_sv;
-                        if (pass && UNLIKELY(SvROK(ix_sv) && !SvGAMAGIC(ix_sv)
-                                                && ckWARN(WARN_MISC)))
-                        Perl_warner(aTHX_ packWARN(WARN_MISC),
-                                "Use of reference \"%"SVf"\" as array index",
-                                SVfARG(ix_sv));
+                        if (!SvIOK(ix_sv))
+                            break;
                         iv = SvIV(ix_sv);
 
                         if (   action_count == 0