Lua: FieldInfo '==' check isn't really equality

The FieldInfo metamethod for equality (letting you use the '==' operator)
doesn't check for equality, but rather if the left-hand side is within
the right-hand side. It should be equality instead. Also, all of the
FieldInfo operate overloads should push a boolean even if they're false
result.

Bug: 10820
Change-Id: Ibddaab29713f26d22ddb4d5804b9edb15e93fd79
Reviewed-on: https://code.wireshark.org/review/6186
Petri-Dish: Hadriel Kaplan <hadrielk@yahoo.com>
Tested-by: Petri Dish Buildbot <buildbot-no-reply@wireshark.org>
Reviewed-by: Michael Mann <mmann78@netscape.net>

epan/wslua/wslua_field.c

@@ -308,17 +308,15 @@ WSLUA_METAMETHOD FieldInfo__eq(lua_State* L) {
     FieldInfo l = checkFieldInfo(L,1);
     FieldInfo r = checkFieldInfo(L,2);
 
-    if (l->ws_fi->ds_tvb != r->ws_fi->ds_tvb) {
-        WSLUA_ERROR(FieldInfo__eq,"Data source must be the same for both fields");
-        return 0;
-    }
-
-    if (l->ws_fi->start <= r->ws_fi->start && r->ws_fi->start + r->ws_fi->length <= l->ws_fi->start + l->ws_fi->length) {
+    /* it is not an error if their ds_tvb are different... they're just not equal */
+    if (l->ws_fi->ds_tvb == r->ws_fi->ds_tvb &&
+        l->ws_fi->start == r->ws_fi->start &&
+        r->ws_fi->length == l->ws_fi->length) {
         lua_pushboolean(L,1);
-        return 1;
     } else {
-        return 0;
+        lua_pushboolean(L,0);
     }
+    return 1;
 }
 
 WSLUA_METAMETHOD FieldInfo__le(lua_State* L) {
@@ -331,10 +329,10 @@ WSLUA_METAMETHOD FieldInfo__le(lua_State* L) {
 
     if (r->ws_fi->start + r->ws_fi->length <= l->ws_fi->start + l->ws_fi->length) {
         lua_pushboolean(L,1);
-        return 1;
     } else {
-        return 0;
+        lua_pushboolean(L,0);
     }
+    return 1;
 }
 
 WSLUA_METAMETHOD FieldInfo__lt(lua_State* L) {
@@ -349,10 +347,10 @@ WSLUA_METAMETHOD FieldInfo__lt(lua_State* L) {
 
     if (r->ws_fi->start + r->ws_fi->length < l->ws_fi->start) {
         lua_pushboolean(L,1);
-        return 1;
     } else {
-        return 0;
+        lua_pushboolean(L,0);
     }
+    return 1;
 }
 
 /* Gets registered as metamethod automatically by WSLUA_REGISTER_META */