[perl #71286] fallback/nomethod failures

This fixes two bugs related to overload and fallback on binary ops.

First, if *either* of the args has a 'nomethod', this will now be used;
previously the RH nomethod was ignored if the LH arg had fallback value
of undef or 1.

Second, if neither arg has a 'nomethod', then the fallback to the built-in
op will now only occur if *both* args have fallback => 1; previously it
would do so if the *RHS* had fallback => 1. Clearly the old behaviour was
wrong, but there were two ways to fix this: (a) *both* args have fallback
=> 1; (b) *either* arg has fallback=> 1. It could be argued either way,
but the the choice of 'both' was that classes that hadn't set 'fallback =>
1' were implicitly implying that their objects aren't suitable for
fallback, regardless of the presence of conversion methods.

1 files changed, 19 insertions, 6 deletions

diff --git a/gv.c b/gv.c
index 9cfc70d00c..5d7837c01c 100644
--- a/gv.c
+++ b/gv.c
@@ -2076,6 +2076,7 @@ Perl_amagic_call(pTHX_ SV *left, SV *right, int method, int flags)
   int postpr = 0, force_cpy = 0;
   int assign = AMGf_assign & flags;
   const int assignshift = assign ? 1 : 0;
+  int use_default_op = 0;
 #ifdef DEBUGGING
   int fl=0;
 #endif
@@ -2239,9 +2240,8 @@ Perl_amagic_call(pTHX_ SV *left, SV *right, int method, int flags)
 	       && (cv = cvp[off=method])) { /* Method for right
 					     * argument found */
       lr=1;
-    } else if (((ocvp && oamtp->fallback > AMGfallNEVER
-		 && (cvp=ocvp) && (lr = -1))
-		|| (cvp && amtp->fallback > AMGfallNEVER && (lr=1)))
+    } else if (((cvp && amtp->fallback > AMGfallNEVER)
+                || (ocvp && oamtp->fallback > AMGfallNEVER))
 	       && !(flags & AMGf_unary)) {
 				/* We look for substitution for
 				 * comparison operations and
@@ -2269,7 +2269,17 @@ Perl_amagic_call(pTHX_ SV *left, SV *right, int method, int flags)
              off = scmp_amg;
              break;
 	 }
-      if ((off != -1) && (cv = cvp[off]))
+      if (off != -1) {
+          if (ocvp && (oamtp->fallback > AMGfallNEVER)) {
+              cv = ocvp[off];
+              lr = -1;
+          }
+          if (!cv && (cvp && amtp->fallback > AMGfallNEVER)) {
+              cv = cvp[off];
+              lr = 1;
+          }
+      }
+      if (cv)
           postpr = 1;
       else
           goto not_found;
@@ -2289,7 +2299,10 @@ Perl_amagic_call(pTHX_ SV *left, SV *right, int method, int flags)
 	notfound = 1; lr = -1;
       } else if (cvp && (cv=cvp[nomethod_amg])) {
 	notfound = 1; lr = 1;
-      } else if ((amtp && amtp->fallback >= AMGfallYES) && !DEBUG_o_TEST) {
+      } else if ((use_default_op =
+                  (!ocvp || oamtp->fallback >= AMGfallYES)
+                  && (!cvp || amtp->fallback >= AMGfallYES))
+                 && !DEBUG_o_TEST) {
 	/* Skip generating the "no method found" message.  */
 	return NULL;
       } else {
@@ -2313,7 +2326,7 @@ Perl_amagic_call(pTHX_ SV *left, SV *right, int method, int flags)
 		      SvAMAGIC(right)?
 		        HvNAME_get(SvSTASH(SvRV(right))):
 		        ""));
-	if (amtp && amtp->fallback >= AMGfallYES) {
+        if (use_default_op) {
 	  DEBUG_o( Perl_deb(aTHX_ "%s", SvPVX_const(msg)) );
 	} else {
 	  Perl_croak(aTHX_ "%"SVf, SVfARG(msg));