make flatbuffers::IsFieldPresent safer (#4988)

Give the vtable offset enum inside each table the name
"FlatBuffersVTableOffset" and base type voffset_t so it can be used as a
dependent type in IsFieldPresent. This makes that function slightly
safer since it prevents calling it with arbitrary, non-table types.
Now, the only way to use IsFieldPresent incorrectly is to create your
own type which does not inherit from flatbuffers::Table but has a
dependent voffset convertible type "FlatBuffersVTableOffset".

1 files changed, 2 insertions, 2 deletions

diff --git a/samples/monster_generated.h b/samples/monster_generated.h
index 4fbbeccc..153eac66 100644
--- a/samples/monster_generated.h
+++ b/samples/monster_generated.h
@@ -235,7 +235,7 @@ struct Monster FLATBUFFERS_FINAL_CLASS : private flatbuffers::Table {
   static const flatbuffers::TypeTable *MiniReflectTypeTable() {
     return MonsterTypeTable();
   }
-  enum {
+  enum FlatBuffersVTableOffset FLATBUFFERS_VTABLE_UNDERLYING_TYPE {
     VT_POS = 4,
     VT_MANA = 6,
     VT_HP = 8,
@@ -443,7 +443,7 @@ struct Weapon FLATBUFFERS_FINAL_CLASS : private flatbuffers::Table {
   static const flatbuffers::TypeTable *MiniReflectTypeTable() {
     return WeaponTypeTable();
   }
-  enum {
+  enum FlatBuffersVTableOffset FLATBUFFERS_VTABLE_UNDERLYING_TYPE {
     VT_NAME = 4,
     VT_DAMAGE = 6
   };