feat(C++): Support underlying_type for union (#7954)

* feat(C++): support underlying type for union

* chore: add conform checks for underlying type changes

CMakeLists.txt

@@ -540,6 +540,7 @@ if(FLATBUFFERS_BUILD_TESTS)
   compile_schema_for_test(tests/64bit/test_64bit.fbs "${FLATC_OPT_COMP};--bfbs-gen-embed")
   compile_schema_for_test(tests/64bit/evolution/v1.fbs "${FLATC_OPT_COMP}")
   compile_schema_for_test(tests/64bit/evolution/v2.fbs "${FLATC_OPT_COMP}")
+  compile_schema_for_test(tests/union_underlying_type_test.fbs "${FLATC_OPT_COMP}")
 
   if(FLATBUFFERS_CODE_SANITIZE)
     add_fsanitize_to_target(flattests ${FLATBUFFERS_CODE_SANITIZE})

include/flatbuffers/idl.h

@@ -1151,6 +1151,7 @@ class Parser : public ParserState {
   bool SupportsOptionalScalars() const;
   bool SupportsDefaultVectorsAndStrings() const;
   bool Supports64BitOffsets() const;
+  bool SupportsUnionUnderlyingType() const;
   Namespace *UniqueNamespace(Namespace *ns);
 
   FLATBUFFERS_CHECKED_ERROR RecurseError();

src/idl_gen_cpp.cpp

@@ -779,7 +779,12 @@ class CppGenerator : public BaseGenerator {
       if (type.enum_def) return WrapInNameSpace(*type.enum_def);
       if (type.base_type == BASE_TYPE_BOOL) return "bool";
     }
-    return StringOf(type.base_type);
+    // Get real underlying type for union type 
+    auto base_type = type.base_type;
+    if (type.base_type == BASE_TYPE_UTYPE && type.enum_def != nullptr) {
+        base_type = type.enum_def->underlying_type.base_type;
+    }
+    return StringOf(base_type);
   }
 
   // Return a C++ pointer type, specialized to the actual struct/table types,
@@ -1048,7 +1053,7 @@ class CppGenerator : public BaseGenerator {
 
   std::string UnionVectorVerifySignature(const EnumDef &enum_def) {
     const std::string name = Name(enum_def);
-    const std::string &type = opts_.scoped_enums ? name : "uint8_t";
+    const std::string &type = opts_.scoped_enums ? name : GenTypeBasic(enum_def.underlying_type, false); 
     return "bool Verify" + name + "Vector" +
            "(::flatbuffers::Verifier &verifier, " +
            "const ::flatbuffers::Vector<::flatbuffers::Offset<void>> "
@@ -3496,12 +3501,13 @@ class CppGenerator : public BaseGenerator {
           }
           case BASE_TYPE_UTYPE: {
             value = StripUnionType(value);
+            auto underlying_type = GenTypeBasic(vector_type, false);
             const std::string &type = opts_.scoped_enums
                                           ? Name(*field.value.type.enum_def)
-                                          : "uint8_t";
+                                          : underlying_type;
             auto enum_value = "__va->_" + value + "[i].type";
             if (!opts_.scoped_enums)
-              enum_value = "static_cast<uint8_t>(" + enum_value + ")";
+              enum_value = "static_cast<" + underlying_type + ">(" + enum_value + ")";
 
             code += "_fbb.CreateVector<" + type + ">(" + value +
                     ".size(), [](size_t i, _VectorArgs *__va) { return " +

src/idl_parser.cpp

@@ -947,8 +947,12 @@ CheckedError Parser::ParseField(StructDef &struct_def) {
   if (type.base_type == BASE_TYPE_UNION) {
     // For union fields, add a second auto-generated field to hold the type,
     // with a special suffix.
-    ECHECK(AddField(struct_def, name + UnionTypeFieldSuffix(),
-                    type.enum_def->underlying_type, &typefield));
+
+    // To ensure compatibility with many codes that rely on the BASE_TYPE_UTYPE value to identify union type fields.
+    Type union_type(type.enum_def->underlying_type);
+    union_type.base_type = BASE_TYPE_UTYPE;
+    ECHECK(AddField(struct_def, name + UnionTypeFieldSuffix(),union_type, &typefield));
+    
   } else if (IsVector(type) && type.element == BASE_TYPE_UNION) {
     advanced_features_ |= reflection::AdvancedUnionFeatures;
     // Only cpp, js and ts supports the union vector feature so far.
@@ -2482,23 +2486,39 @@ CheckedError Parser::ParseEnum(const bool is_union, EnumDef **dest,
         &GetPooledString(RelativeToRootPath(opts.project_root, filename));
   }
   enum_def->doc_comment = enum_comment;
-  if (!is_union && !opts.proto_mode) {
+  if (!opts.proto_mode) {
     // Give specialized error message, since this type spec used to
     // be optional in the first FlatBuffers release.
+    bool explicit_underlying_type = false;
     if (!Is(':')) {
-      return Error(
-          "must specify the underlying integer type for this"
-          " enum (e.g. \': short\', which was the default).");
+      // Enum is forced to have an explicit underlying type in declaration.
+      if (!is_union) {
+        return Error(
+            "must specify the underlying integer type for this"
+            " enum (e.g. \': short\', which was the default).");
+      }
     } else {
+      // Union underlying type is only supported for cpp
+      if (is_union && !SupportsUnionUnderlyingType()) {
+        return Error(
+            "Underlying type for union is not yet supported in at least one of "
+            "the specified programming languages.");
+      }
       NEXT();
+      explicit_underlying_type = true;
     }
-    // Specify the integer type underlying this enum.
-    ECHECK(ParseType(enum_def->underlying_type));
-    if (!IsInteger(enum_def->underlying_type.base_type) ||
-        IsBool(enum_def->underlying_type.base_type))
-      return Error("underlying enum type must be integral");
-    // Make this type refer back to the enum it was derived from.
-    enum_def->underlying_type.enum_def = enum_def;
+
+    if (explicit_underlying_type) {
+      // Specify the integer type underlying this enum.
+      ECHECK(ParseType(enum_def->underlying_type));
+      if (!IsInteger(enum_def->underlying_type.base_type) || IsBool(enum_def->underlying_type.base_type)) {
+        return Error("underlying " + std::string(is_union ? "union" : "enum") + "type must be integral");
+      }
+        
+      // Make this type refer back to the enum it was derived from.
+      enum_def->underlying_type.enum_def = enum_def;
+    }
+
   }
   ECHECK(ParseMetaData(&enum_def->attributes));
   const auto underlying_type = enum_def->underlying_type.base_type;
@@ -2697,6 +2717,10 @@ bool Parser::Supports64BitOffsets() const {
           ~(IDLOptions::kCpp | IDLOptions::kJson | IDLOptions::kBinary)) == 0;
 }
 
+bool Parser::SupportsUnionUnderlyingType() const {
+    return (opts.lang_to_generate & ~IDLOptions::kCpp) == 0;
+}
+
 Namespace *Parser::UniqueNamespace(Namespace *ns) {
   for (auto it = namespaces_.begin(); it != namespaces_.end(); ++it) {
     if (ns->components == (*it)->components) {
@@ -4428,6 +4452,10 @@ std::string Parser::ConformTo(const Parser &base) {
           return "values differ for enum: " + enum_val.name;
       }
     }
+    // Check underlying type changes
+    if (enum_def_base->underlying_type.base_type != enum_def.underlying_type.base_type) {
+      return "underlying type differ for " + std::string(enum_def.is_union ? "union: " : "enum: ") + qualified_name;
+    }
   }
   return "";
 }

tests/BUILD.bazel

@@ -65,6 +65,7 @@ cc_test(
         "test_assert.h",
         "test_builder.cpp",
         "test_builder.h",
+        "union_underlying_type_test_generated.h",
         "union_vector/union_vector_generated.h",
         "util_test.cpp",
         "util_test.h",

tests/evolution_test.cpp

@@ -111,6 +111,13 @@ void ConformTest() {
   test_conform(ref2, "enum E:int32 { A } table T2 { df:byte; f:E; }",
                "field renamed to different type: T2.df (renamed from T2.f)");
 
+  // Check enum underlying type changes.
+  test_conform("enum E:int32 {A}", "enum E: byte {A}", "underlying type differ for enum: E");
+  
+  // Check union underlying type changes.
+  const char ref3[] = "table A {} table B {} union C {A, B}";
+  test_conform(ref3, "table A {} table B {} union C:int32 {A, B}", "underlying type differ for union: C");
+
   // Check conformity for Offset64-related changes.
   {
     const char ref[] = "table T { a:[uint8]; b:string; }";

tests/parser_test.cpp

@@ -841,6 +841,15 @@ void ParseUnionTest() {
                         "table B { e:U; } root_type B;"
                         "{ e_type: N_A, e: {} }"),
           true);
+
+  // Test union underlying type
+  const char *source = "table A {} table B {} union U : int {A, B} table C {test_union: U; test_vector_of_union: [U];}";
+  flatbuffers::Parser parser3;
+  parser3.opts.lang_to_generate = flatbuffers::IDLOptions::kCpp;
+  TEST_EQ(parser3.Parse(source), true);
+  
+  parser3.opts.lang_to_generate &= flatbuffers::IDLOptions::kJava;
+  TEST_EQ(parser3.Parse(source), false);
 }
 
 void ValidSameNameDifferentNamespaceTest() {

tests/test.cpp

@@ -39,6 +39,7 @@
 #include "proto_test.h"
 #include "reflection_test.h"
 #include "union_vector/union_vector_generated.h"
+#include "union_underlying_type_test_generated.h"
 #if !defined(_MSC_VER) || _MSC_VER >= 1700
 #  include "arrays_test_generated.h"
 #endif
@@ -1540,6 +1541,41 @@ void DoNotRequireEofTest(const std::string &tests_data_path) {
 }
 #endif
 
+void UnionUnderlyingTypeTest() {
+    using namespace UnionUnderlyingType;
+    TEST_ASSERT(sizeof(ABC) == sizeof(uint32_t));
+    TEST_ASSERT(ABC::ABC_A == 555);
+    TEST_ASSERT(ABC::ABC_B == 666);
+    TEST_ASSERT(ABC::ABC_C == 777);
+
+    DT buffer;
+    AT a;
+    a.a = 42;
+    BT b;
+    b.b = "foo";
+    CT c;
+    c.c = true;
+    buffer.test_union = ABCUnion();
+    buffer.test_union.Set(a);
+    buffer.test_vector_of_union.resize(3);
+    buffer.test_vector_of_union[0].Set(a);
+    buffer.test_vector_of_union[1].Set(b);
+    buffer.test_vector_of_union[2].Set(c);
+
+    flatbuffers::FlatBufferBuilder fbb;
+    auto offset = D::Pack(fbb, &buffer);
+    fbb.Finish(offset);
+
+    auto *root =
+    flatbuffers::GetRoot<D>(fbb.GetBufferPointer());
+    DT unpacked;
+    root->UnPackTo(&unpacked);
+
+    TEST_ASSERT(unpacked.test_union == buffer.test_union);
+    TEST_ASSERT(unpacked.test_vector_of_union == buffer.test_vector_of_union);
+
+}
+
 static void Offset64Tests() {
   Offset64Test();
   Offset64SerializedFirst();
@@ -1663,6 +1699,7 @@ int FlatBufferTests(const std::string &tests_data_path) {
   FixedSizedStructArrayKeyInStructTest();
   EmbeddedSchemaAccess();
   Offset64Tests();
+  UnionUnderlyingTypeTest();
   return 0;
 }
 }  // namespace

tests/union_underlying_type_test.fbs

@@ -0,0 +1,17 @@
+
+namespace UnionUnderlyingType;
+
+table A {
+    a: int;
+}
+table B {
+    b: string;
+}
+table C {
+    c: bool;
+}
+union ABC: int { A = 555, B = 666, C = 777}
+table D {
+    test_union: ABC;
+    test_vector_of_union: [ABC];
+}

tests/union_underlying_type_test_generated.h

@@ -0,0 +1,880 @@
+// automatically generated by the FlatBuffers compiler, do not modify
+
+
+#ifndef FLATBUFFERS_GENERATED_UNIONUNDERLYINGTYPETEST_UNIONUNDERLYINGTYPE_H_
+#define FLATBUFFERS_GENERATED_UNIONUNDERLYINGTYPETEST_UNIONUNDERLYINGTYPE_H_
+
+#include "flatbuffers/flatbuffers.h"
+
+// Ensure the included flatbuffers.h is the same version as when this file was
+// generated, otherwise it may not be compatible.
+static_assert(FLATBUFFERS_VERSION_MAJOR == 23 &&
+              FLATBUFFERS_VERSION_MINOR == 5 &&
+              FLATBUFFERS_VERSION_REVISION == 9,
+             "Non-compatible flatbuffers version included");
+
+namespace UnionUnderlyingType {
+
+struct A;
+struct ABuilder;
+struct AT;
+
+struct B;
+struct BBuilder;
+struct BT;
+
+struct C;
+struct CBuilder;
+struct CT;
+
+struct D;
+struct DBuilder;
+struct DT;
+
+bool operator==(const AT &lhs, const AT &rhs);
+bool operator!=(const AT &lhs, const AT &rhs);
+bool operator==(const BT &lhs, const BT &rhs);
+bool operator!=(const BT &lhs, const BT &rhs);
+bool operator==(const CT &lhs, const CT &rhs);
+bool operator!=(const CT &lhs, const CT &rhs);
+bool operator==(const DT &lhs, const DT &rhs);
+bool operator!=(const DT &lhs, const DT &rhs);
+
+inline const ::flatbuffers::TypeTable *ATypeTable();
+
+inline const ::flatbuffers::TypeTable *BTypeTable();
+
+inline const ::flatbuffers::TypeTable *CTypeTable();
+
+inline const ::flatbuffers::TypeTable *DTypeTable();
+
+enum ABC : int32_t {
+  ABC_NONE = 0,
+  ABC_A = 555,
+  ABC_B = 666,
+  ABC_C = 777,
+  ABC_MIN = ABC_NONE,
+  ABC_MAX = ABC_C
+};
+
+inline const ABC (&EnumValuesABC())[4] {
+  static const ABC values[] = {
+    ABC_NONE,
+    ABC_A,
+    ABC_B,
+    ABC_C
+  };
+  return values;
+}
+
+inline const char *EnumNameABC(ABC e) {
+  switch (e) {
+    case ABC_NONE: return "NONE";
+    case ABC_A: return "A";
+    case ABC_B: return "B";
+    case ABC_C: return "C";
+    default: return "";
+  }
+}
+
+template<typename T> struct ABCTraits {
+  static const ABC enum_value = ABC_NONE;
+};
+
+template<> struct ABCTraits<UnionUnderlyingType::A> {
+  static const ABC enum_value = ABC_A;
+};
+
+template<> struct ABCTraits<UnionUnderlyingType::B> {
+  static const ABC enum_value = ABC_B;
+};
+
+template<> struct ABCTraits<UnionUnderlyingType::C> {
+  static const ABC enum_value = ABC_C;
+};
+
+template<typename T> struct ABCUnionTraits {
+  static const ABC enum_value = ABC_NONE;
+};
+
+template<> struct ABCUnionTraits<UnionUnderlyingType::AT> {
+  static const ABC enum_value = ABC_A;
+};
+
+template<> struct ABCUnionTraits<UnionUnderlyingType::BT> {
+  static const ABC enum_value = ABC_B;
+};
+
+template<> struct ABCUnionTraits<UnionUnderlyingType::CT> {
+  static const ABC enum_value = ABC_C;
+};
+
+struct ABCUnion {
+  ABC type;
+  void *value;
+
+  ABCUnion() : type(ABC_NONE), value(nullptr) {}
+  ABCUnion(ABCUnion&& u) FLATBUFFERS_NOEXCEPT :
+    type(ABC_NONE), value(nullptr)
+    { std::swap(type, u.type); std::swap(value, u.value); }
+  ABCUnion(const ABCUnion &);
+  ABCUnion &operator=(const ABCUnion &u)
+    { ABCUnion t(u); std::swap(type, t.type); std::swap(value, t.value); return *this; }
+  ABCUnion &operator=(ABCUnion &&u) FLATBUFFERS_NOEXCEPT
+    { std::swap(type, u.type); std::swap(value, u.value); return *this; }
+  ~ABCUnion() { Reset(); }
+
+  void Reset();
+
+  template <typename T>
+  void Set(T&& val) {
+    typedef typename std::remove_reference<T>::type RT;
+    Reset();
+    type = ABCUnionTraits<RT>::enum_value;
+    if (type != ABC_NONE) {
+      value = new RT(std::forward<T>(val));
+    }
+  }
+
+  static void *UnPack(const void *obj, ABC type, const ::flatbuffers::resolver_function_t *resolver);
+  ::flatbuffers::Offset<void> Pack(::flatbuffers::FlatBufferBuilder &_fbb, const ::flatbuffers::rehasher_function_t *_rehasher = nullptr) const;
+
+  UnionUnderlyingType::AT *AsA() {
+    return type == ABC_A ?
+      reinterpret_cast<UnionUnderlyingType::AT *>(value) : nullptr;
+  }
+  const UnionUnderlyingType::AT *AsA() const {
+    return type == ABC_A ?
+      reinterpret_cast<const UnionUnderlyingType::AT *>(value) : nullptr;
+  }
+  UnionUnderlyingType::BT *AsB() {
+    return type == ABC_B ?
+      reinterpret_cast<UnionUnderlyingType::BT *>(value) : nullptr;
+  }
+  const UnionUnderlyingType::BT *AsB() const {
+    return type == ABC_B ?
+      reinterpret_cast<const UnionUnderlyingType::BT *>(value) : nullptr;
+  }
+  UnionUnderlyingType::CT *AsC() {
+    return type == ABC_C ?
+      reinterpret_cast<UnionUnderlyingType::CT *>(value) : nullptr;
+  }
+  const UnionUnderlyingType::CT *AsC() const {
+    return type == ABC_C ?
+      reinterpret_cast<const UnionUnderlyingType::CT *>(value) : nullptr;
+  }
+};
+
+
+inline bool operator==(const ABCUnion &lhs, const ABCUnion &rhs) {
+  if (lhs.type != rhs.type) return false;
+  switch (lhs.type) {
+    case ABC_NONE: {
+      return true;
+    }
+    case ABC_A: {
+      return *(reinterpret_cast<const UnionUnderlyingType::AT *>(lhs.value)) ==
+             *(reinterpret_cast<const UnionUnderlyingType::AT *>(rhs.value));
+    }
+    case ABC_B: {
+      return *(reinterpret_cast<const UnionUnderlyingType::BT *>(lhs.value)) ==
+             *(reinterpret_cast<const UnionUnderlyingType::BT *>(rhs.value));
+    }
+    case ABC_C: {
+      return *(reinterpret_cast<const UnionUnderlyingType::CT *>(lhs.value)) ==
+             *(reinterpret_cast<const UnionUnderlyingType::CT *>(rhs.value));
+    }
+    default: {
+      return false;
+    }
+  }
+}
+
+inline bool operator!=(const ABCUnion &lhs, const ABCUnion &rhs) {
+    return !(lhs == rhs);
+}
+
+bool VerifyABC(::flatbuffers::Verifier &verifier, const void *obj, ABC type);
+bool VerifyABCVector(::flatbuffers::Verifier &verifier, const ::flatbuffers::Vector<::flatbuffers::Offset<void>> *values, const ::flatbuffers::Vector<int32_t> *types);
+
+struct AT : public ::flatbuffers::NativeTable {
+  typedef A TableType;
+  int32_t a = 0;
+};
+
+struct A FLATBUFFERS_FINAL_CLASS : private ::flatbuffers::Table {
+  typedef AT NativeTableType;
+  typedef ABuilder Builder;
+  static const ::flatbuffers::TypeTable *MiniReflectTypeTable() {
+    return ATypeTable();
+  }
+  enum FlatBuffersVTableOffset FLATBUFFERS_VTABLE_UNDERLYING_TYPE {
+    VT_A = 4
+  };
+  int32_t a() const {
+    return GetField<int32_t>(VT_A, 0);
+  }
+  bool mutate_a(int32_t _a = 0) {
+    return SetField<int32_t>(VT_A, _a, 0);
+  }
+  bool Verify(::flatbuffers::Verifier &verifier) const {
+    return VerifyTableStart(verifier) &&
+           VerifyField<int32_t>(verifier, VT_A, 4) &&
+           verifier.EndTable();
+  }
+  AT *UnPack(const ::flatbuffers::resolver_function_t *_resolver = nullptr) const;
+  void UnPackTo(AT *_o, const ::flatbuffers::resolver_function_t *_resolver = nullptr) const;
+  static ::flatbuffers::Offset<A> Pack(::flatbuffers::FlatBufferBuilder &_fbb, const AT* _o, const ::flatbuffers::rehasher_function_t *_rehasher = nullptr);
+};
+
+struct ABuilder {
+  typedef A Table;
+  ::flatbuffers::FlatBufferBuilder &fbb_;
+  ::flatbuffers::uoffset_t start_;
+  void add_a(int32_t a) {
+    fbb_.AddElement<int32_t>(A::VT_A, a, 0);
+  }
+  explicit ABuilder(::flatbuffers::FlatBufferBuilder &_fbb)
+        : fbb_(_fbb) {
+    start_ = fbb_.StartTable();
+  }
+  ::flatbuffers::Offset<A> Finish() {
+    const auto end = fbb_.EndTable(start_);
+    auto o = ::flatbuffers::Offset<A>(end);
+    return o;
+  }
+};
+
+inline ::flatbuffers::Offset<A> CreateA(
+    ::flatbuffers::FlatBufferBuilder &_fbb,
+    int32_t a = 0) {
+  ABuilder builder_(_fbb);
+  builder_.add_a(a);
+  return builder_.Finish();
+}
+
+::flatbuffers::Offset<A> CreateA(::flatbuffers::FlatBufferBuilder &_fbb, const AT *_o, const ::flatbuffers::rehasher_function_t *_rehasher = nullptr);
+
+struct BT : public ::flatbuffers::NativeTable {
+  typedef B TableType;
+  std::string b{};
+};
+
+struct B FLATBUFFERS_FINAL_CLASS : private ::flatbuffers::Table {
+  typedef BT NativeTableType;
+  typedef BBuilder Builder;
+  static const ::flatbuffers::TypeTable *MiniReflectTypeTable() {
+    return BTypeTable();
+  }
+  enum FlatBuffersVTableOffset FLATBUFFERS_VTABLE_UNDERLYING_TYPE {
+    VT_B = 4
+  };
+  const ::flatbuffers::String *b() const {
+    return GetPointer<const ::flatbuffers::String *>(VT_B);
+  }
+  ::flatbuffers::String *mutable_b() {
+    return GetPointer<::flatbuffers::String *>(VT_B);
+  }
+  bool Verify(::flatbuffers::Verifier &verifier) const {
+    return VerifyTableStart(verifier) &&
+           VerifyOffset(verifier, VT_B) &&
+           verifier.VerifyString(b()) &&
+           verifier.EndTable();
+  }
+  BT *UnPack(const ::flatbuffers::resolver_function_t *_resolver = nullptr) const;
+  void UnPackTo(BT *_o, const ::flatbuffers::resolver_function_t *_resolver = nullptr) const;
+  static ::flatbuffers::Offset<B> Pack(::flatbuffers::FlatBufferBuilder &_fbb, const BT* _o, const ::flatbuffers::rehasher_function_t *_rehasher = nullptr);
+};
+
+struct BBuilder {
+  typedef B Table;
+  ::flatbuffers::FlatBufferBuilder &fbb_;
+  ::flatbuffers::uoffset_t start_;
+  void add_b(::flatbuffers::Offset<::flatbuffers::String> b) {
+    fbb_.AddOffset(B::VT_B, b);
+  }
+  explicit BBuilder(::flatbuffers::FlatBufferBuilder &_fbb)
+        : fbb_(_fbb) {
+    start_ = fbb_.StartTable();
+  }
+  ::flatbuffers::Offset<B> Finish() {
+    const auto end = fbb_.EndTable(start_);
+    auto o = ::flatbuffers::Offset<B>(end);
+    return o;
+  }
+};
+
+inline ::flatbuffers::Offset<B> CreateB(
+    ::flatbuffers::FlatBufferBuilder &_fbb,
+    ::flatbuffers::Offset<::flatbuffers::String> b = 0) {
+  BBuilder builder_(_fbb);
+  builder_.add_b(b);
+  return builder_.Finish();
+}
+
+inline ::flatbuffers::Offset<B> CreateBDirect(
+    ::flatbuffers::FlatBufferBuilder &_fbb,
+    const char *b = nullptr) {
+  auto b__ = b ? _fbb.CreateString(b) : 0;
+  return UnionUnderlyingType::CreateB(
+      _fbb,
+      b__);
+}
+
+::flatbuffers::Offset<B> CreateB(::flatbuffers::FlatBufferBuilder &_fbb, const BT *_o, const ::flatbuffers::rehasher_function_t *_rehasher = nullptr);
+
+struct CT : public ::flatbuffers::NativeTable {
+  typedef C TableType;
+  bool c = false;
+};
+
+struct C FLATBUFFERS_FINAL_CLASS : private ::flatbuffers::Table {
+  typedef CT NativeTableType;
+  typedef CBuilder Builder;
+  static const ::flatbuffers::TypeTable *MiniReflectTypeTable() {
+    return CTypeTable();
+  }
+  enum FlatBuffersVTableOffset FLATBUFFERS_VTABLE_UNDERLYING_TYPE {
+    VT_C = 4
+  };
+  bool c() const {
+    return GetField<uint8_t>(VT_C, 0) != 0;
+  }
+  bool mutate_c(bool _c = 0) {
+    return SetField<uint8_t>(VT_C, static_cast<uint8_t>(_c), 0);
+  }
+  bool Verify(::flatbuffers::Verifier &verifier) const {
+    return VerifyTableStart(verifier) &&
+           VerifyField<uint8_t>(verifier, VT_C, 1) &&
+           verifier.EndTable();
+  }
+  CT *UnPack(const ::flatbuffers::resolver_function_t *_resolver = nullptr) const;
+  void UnPackTo(CT *_o, const ::flatbuffers::resolver_function_t *_resolver = nullptr) const;
+  static ::flatbuffers::Offset<C> Pack(::flatbuffers::FlatBufferBuilder &_fbb, const CT* _o, const ::flatbuffers::rehasher_function_t *_rehasher = nullptr);
+};
+
+struct CBuilder {
+  typedef C Table;
+  ::flatbuffers::FlatBufferBuilder &fbb_;
+  ::flatbuffers::uoffset_t start_;
+  void add_c(bool c) {
+    fbb_.AddElement<uint8_t>(C::VT_C, static_cast<uint8_t>(c), 0);
+  }
+  explicit CBuilder(::flatbuffers::FlatBufferBuilder &_fbb)
+        : fbb_(_fbb) {
+    start_ = fbb_.StartTable();
+  }
+  ::flatbuffers::Offset<C> Finish() {
+    const auto end = fbb_.EndTable(start_);
+    auto o = ::flatbuffers::Offset<C>(end);
+    return o;
+  }
+};
+
+inline ::flatbuffers::Offset<C> CreateC(
+    ::flatbuffers::FlatBufferBuilder &_fbb,
+    bool c = false) {
+  CBuilder builder_(_fbb);
+  builder_.add_c(c);
+  return builder_.Finish();
+}
+
+::flatbuffers::Offset<C> CreateC(::flatbuffers::FlatBufferBuilder &_fbb, const CT *_o, const ::flatbuffers::rehasher_function_t *_rehasher = nullptr);
+
+struct DT : public ::flatbuffers::NativeTable {
+  typedef D TableType;
+  UnionUnderlyingType::ABCUnion test_union{};
+  std::vector<UnionUnderlyingType::ABCUnion> test_vector_of_union{};
+};
+
+struct D FLATBUFFERS_FINAL_CLASS : private ::flatbuffers::Table {
+  typedef DT NativeTableType;
+  typedef DBuilder Builder;
+  static const ::flatbuffers::TypeTable *MiniReflectTypeTable() {
+    return DTypeTable();
+  }
+  enum FlatBuffersVTableOffset FLATBUFFERS_VTABLE_UNDERLYING_TYPE {
+    VT_TEST_UNION_TYPE = 4,
+    VT_TEST_UNION = 6,
+    VT_TEST_VECTOR_OF_UNION_TYPE = 8,
+    VT_TEST_VECTOR_OF_UNION = 10
+  };
+  UnionUnderlyingType::ABC test_union_type() const {
+    return static_cast<UnionUnderlyingType::ABC>(GetField<int32_t>(VT_TEST_UNION_TYPE, 0));
+  }
+  const void *test_union() const {
+    return GetPointer<const void *>(VT_TEST_UNION);
+  }
+  template<typename T> const T *test_union_as() const;
+  const UnionUnderlyingType::A *test_union_as_A() const {
+    return test_union_type() == UnionUnderlyingType::ABC_A ? static_cast<const UnionUnderlyingType::A *>(test_union()) : nullptr;
+  }
+  const UnionUnderlyingType::B *test_union_as_B() const {
+    return test_union_type() == UnionUnderlyingType::ABC_B ? static_cast<const UnionUnderlyingType::B *>(test_union()) : nullptr;
+  }
+  const UnionUnderlyingType::C *test_union_as_C() const {
+    return test_union_type() == UnionUnderlyingType::ABC_C ? static_cast<const UnionUnderlyingType::C *>(test_union()) : nullptr;
+  }
+  void *mutable_test_union() {
+    return GetPointer<void *>(VT_TEST_UNION);
+  }
+  const ::flatbuffers::Vector<int32_t> *test_vector_of_union_type() const {
+    return GetPointer<const ::flatbuffers::Vector<int32_t> *>(VT_TEST_VECTOR_OF_UNION_TYPE);
+  }
+  ::flatbuffers::Vector<int32_t> *mutable_test_vector_of_union_type() {
+    return GetPointer<::flatbuffers::Vector<int32_t> *>(VT_TEST_VECTOR_OF_UNION_TYPE);
+  }
+  const ::flatbuffers::Vector<::flatbuffers::Offset<void>> *test_vector_of_union() const {
+    return GetPointer<const ::flatbuffers::Vector<::flatbuffers::Offset<void>> *>(VT_TEST_VECTOR_OF_UNION);
+  }
+  ::flatbuffers::Vector<::flatbuffers::Offset<void>> *mutable_test_vector_of_union() {
+    return GetPointer<::flatbuffers::Vector<::flatbuffers::Offset<void>> *>(VT_TEST_VECTOR_OF_UNION);
+  }
+  bool Verify(::flatbuffers::Verifier &verifier) const {
+    return VerifyTableStart(verifier) &&
+           VerifyField<int32_t>(verifier, VT_TEST_UNION_TYPE, 1) &&
+           VerifyOffset(verifier, VT_TEST_UNION) &&
+           VerifyABC(verifier, test_union(), test_union_type()) &&
+           VerifyOffset(verifier, VT_TEST_VECTOR_OF_UNION_TYPE) &&
+           verifier.VerifyVector(test_vector_of_union_type()) &&
+           VerifyOffset(verifier, VT_TEST_VECTOR_OF_UNION) &&
+           verifier.VerifyVector(test_vector_of_union()) &&
+           VerifyABCVector(verifier, test_vector_of_union(), test_vector_of_union_type()) &&
+           verifier.EndTable();
+  }
+  DT *UnPack(const ::flatbuffers::resolver_function_t *_resolver = nullptr) const;
+  void UnPackTo(DT *_o, const ::flatbuffers::resolver_function_t *_resolver = nullptr) const;
+  static ::flatbuffers::Offset<D> Pack(::flatbuffers::FlatBufferBuilder &_fbb, const DT* _o, const ::flatbuffers::rehasher_function_t *_rehasher = nullptr);
+};
+
+template<> inline const UnionUnderlyingType::A *D::test_union_as<UnionUnderlyingType::A>() const {
+  return test_union_as_A();
+}
+
+template<> inline const UnionUnderlyingType::B *D::test_union_as<UnionUnderlyingType::B>() const {
+  return test_union_as_B();
+}
+
+template<> inline const UnionUnderlyingType::C *D::test_union_as<UnionUnderlyingType::C>() const {
+  return test_union_as_C();
+}
+
+struct DBuilder {
+  typedef D Table;
+  ::flatbuffers::FlatBufferBuilder &fbb_;
+  ::flatbuffers::uoffset_t start_;
+  void add_test_union_type(UnionUnderlyingType::ABC test_union_type) {
+    fbb_.AddElement<int32_t>(D::VT_TEST_UNION_TYPE, static_cast<int32_t>(test_union_type), 0);
+  }
+  void add_test_union(::flatbuffers::Offset<void> test_union) {
+    fbb_.AddOffset(D::VT_TEST_UNION, test_union);
+  }
+  void add_test_vector_of_union_type(::flatbuffers::Offset<::flatbuffers::Vector<int32_t>> test_vector_of_union_type) {
+    fbb_.AddOffset(D::VT_TEST_VECTOR_OF_UNION_TYPE, test_vector_of_union_type);
+  }
+  void add_test_vector_of_union(::flatbuffers::Offset<::flatbuffers::Vector<::flatbuffers::Offset<void>>> test_vector_of_union) {
+    fbb_.AddOffset(D::VT_TEST_VECTOR_OF_UNION, test_vector_of_union);
+  }
+  explicit DBuilder(::flatbuffers::FlatBufferBuilder &_fbb)
+        : fbb_(_fbb) {
+    start_ = fbb_.StartTable();
+  }
+  ::flatbuffers::Offset<D> Finish() {
+    const auto end = fbb_.EndTable(start_);
+    auto o = ::flatbuffers::Offset<D>(end);
+    return o;
+  }
+};
+
+inline ::flatbuffers::Offset<D> CreateD(
+    ::flatbuffers::FlatBufferBuilder &_fbb,
+    UnionUnderlyingType::ABC test_union_type = UnionUnderlyingType::ABC_NONE,
+    ::flatbuffers::Offset<void> test_union = 0,
+    ::flatbuffers::Offset<::flatbuffers::Vector<int32_t>> test_vector_of_union_type = 0,
+    ::flatbuffers::Offset<::flatbuffers::Vector<::flatbuffers::Offset<void>>> test_vector_of_union = 0) {
+  DBuilder builder_(_fbb);
+  builder_.add_test_vector_of_union(test_vector_of_union);
+  builder_.add_test_vector_of_union_type(test_vector_of_union_type);
+  builder_.add_test_union(test_union);
+  builder_.add_test_union_type(test_union_type);
+  return builder_.Finish();
+}
+
+inline ::flatbuffers::Offset<D> CreateDDirect(
+    ::flatbuffers::FlatBufferBuilder &_fbb,
+    UnionUnderlyingType::ABC test_union_type = UnionUnderlyingType::ABC_NONE,
+    ::flatbuffers::Offset<void> test_union = 0,
+    const std::vector<int32_t> *test_vector_of_union_type = nullptr,
+    const std::vector<::flatbuffers::Offset<void>> *test_vector_of_union = nullptr) {
+  auto test_vector_of_union_type__ = test_vector_of_union_type ? _fbb.CreateVector<int32_t>(*test_vector_of_union_type) : 0;
+  auto test_vector_of_union__ = test_vector_of_union ? _fbb.CreateVector<::flatbuffers::Offset<void>>(*test_vector_of_union) : 0;
+  return UnionUnderlyingType::CreateD(
+      _fbb,
+      test_union_type,
+      test_union,
+      test_vector_of_union_type__,
+      test_vector_of_union__);
+}
+
+::flatbuffers::Offset<D> CreateD(::flatbuffers::FlatBufferBuilder &_fbb, const DT *_o, const ::flatbuffers::rehasher_function_t *_rehasher = nullptr);
+
+
+inline bool operator==(const AT &lhs, const AT &rhs) {
+  return
+      (lhs.a == rhs.a);
+}
+
+inline bool operator!=(const AT &lhs, const AT &rhs) {
+    return !(lhs == rhs);
+}
+
+
+inline AT *A::UnPack(const ::flatbuffers::resolver_function_t *_resolver) const {
+  auto _o = std::unique_ptr<AT>(new AT());
+  UnPackTo(_o.get(), _resolver);
+  return _o.release();
+}
+
+inline void A::UnPackTo(AT *_o, const ::flatbuffers::resolver_function_t *_resolver) const {
+  (void)_o;
+  (void)_resolver;
+  { auto _e = a(); _o->a = _e; }
+}
+
+inline ::flatbuffers::Offset<A> A::Pack(::flatbuffers::FlatBufferBuilder &_fbb, const AT* _o, const ::flatbuffers::rehasher_function_t *_rehasher) {
+  return CreateA(_fbb, _o, _rehasher);
+}
+
+inline ::flatbuffers::Offset<A> CreateA(::flatbuffers::FlatBufferBuilder &_fbb, const AT *_o, const ::flatbuffers::rehasher_function_t *_rehasher) {
+  (void)_rehasher;
+  (void)_o;
+  struct _VectorArgs { ::flatbuffers::FlatBufferBuilder *__fbb; const AT* __o; const ::flatbuffers::rehasher_function_t *__rehasher; } _va = { &_fbb, _o, _rehasher}; (void)_va;
+  auto _a = _o->a;
+  return UnionUnderlyingType::CreateA(
+      _fbb,
+      _a);
+}
+
+
+inline bool operator==(const BT &lhs, const BT &rhs) {
+  return
+      (lhs.b == rhs.b);
+}
+
+inline bool operator!=(const BT &lhs, const BT &rhs) {
+    return !(lhs == rhs);
+}
+
+
+inline BT *B::UnPack(const ::flatbuffers::resolver_function_t *_resolver) const {
+  auto _o = std::unique_ptr<BT>(new BT());
+  UnPackTo(_o.get(), _resolver);
+  return _o.release();
+}
+
+inline void B::UnPackTo(BT *_o, const ::flatbuffers::resolver_function_t *_resolver) const {
+  (void)_o;
+  (void)_resolver;
+  { auto _e = b(); if (_e) _o->b = _e->str(); }
+}
+
+inline ::flatbuffers::Offset<B> B::Pack(::flatbuffers::FlatBufferBuilder &_fbb, const BT* _o, const ::flatbuffers::rehasher_function_t *_rehasher) {
+  return CreateB(_fbb, _o, _rehasher);
+}
+
+inline ::flatbuffers::Offset<B> CreateB(::flatbuffers::FlatBufferBuilder &_fbb, const BT *_o, const ::flatbuffers::rehasher_function_t *_rehasher) {
+  (void)_rehasher;
+  (void)_o;
+  struct _VectorArgs { ::flatbuffers::FlatBufferBuilder *__fbb; const BT* __o; const ::flatbuffers::rehasher_function_t *__rehasher; } _va = { &_fbb, _o, _rehasher}; (void)_va;
+  auto _b = _o->b.empty() ? 0 : _fbb.CreateString(_o->b);
+  return UnionUnderlyingType::CreateB(
+      _fbb,
+      _b);
+}
+
+
+inline bool operator==(const CT &lhs, const CT &rhs) {
+  return
+      (lhs.c == rhs.c);
+}
+
+inline bool operator!=(const CT &lhs, const CT &rhs) {
+    return !(lhs == rhs);
+}
+
+
+inline CT *C::UnPack(const ::flatbuffers::resolver_function_t *_resolver) const {
+  auto _o = std::unique_ptr<CT>(new CT());
+  UnPackTo(_o.get(), _resolver);
+  return _o.release();
+}
+
+inline void C::UnPackTo(CT *_o, const ::flatbuffers::resolver_function_t *_resolver) const {
+  (void)_o;
+  (void)_resolver;
+  { auto _e = c(); _o->c = _e; }
+}
+
+inline ::flatbuffers::Offset<C> C::Pack(::flatbuffers::FlatBufferBuilder &_fbb, const CT* _o, const ::flatbuffers::rehasher_function_t *_rehasher) {
+  return CreateC(_fbb, _o, _rehasher);
+}
+
+inline ::flatbuffers::Offset<C> CreateC(::flatbuffers::FlatBufferBuilder &_fbb, const CT *_o, const ::flatbuffers::rehasher_function_t *_rehasher) {
+  (void)_rehasher;
+  (void)_o;
+  struct _VectorArgs { ::flatbuffers::FlatBufferBuilder *__fbb; const CT* __o; const ::flatbuffers::rehasher_function_t *__rehasher; } _va = { &_fbb, _o, _rehasher}; (void)_va;
+  auto _c = _o->c;
+  return UnionUnderlyingType::CreateC(
+      _fbb,
+      _c);
+}
+
+
+inline bool operator==(const DT &lhs, const DT &rhs) {
+  return
+      (lhs.test_union == rhs.test_union) &&
+      (lhs.test_vector_of_union == rhs.test_vector_of_union);
+}
+
+inline bool operator!=(const DT &lhs, const DT &rhs) {
+    return !(lhs == rhs);
+}
+
+
+inline DT *D::UnPack(const ::flatbuffers::resolver_function_t *_resolver) const {
+  auto _o = std::unique_ptr<DT>(new DT());
+  UnPackTo(_o.get(), _resolver);
+  return _o.release();
+}
+
+inline void D::UnPackTo(DT *_o, const ::flatbuffers::resolver_function_t *_resolver) const {
+  (void)_o;
+  (void)_resolver;
+  { auto _e = test_union_type(); _o->test_union.type = _e; }
+  { auto _e = test_union(); if (_e) _o->test_union.value = UnionUnderlyingType::ABCUnion::UnPack(_e, test_union_type(), _resolver); }
+  { auto _e = test_vector_of_union_type(); if (_e) { _o->test_vector_of_union.resize(_e->size()); for (::flatbuffers::uoffset_t _i = 0; _i < _e->size(); _i++) { _o->test_vector_of_union[_i].type = static_cast<UnionUnderlyingType::ABC>(_e->Get(_i)); } } else { _o->test_vector_of_union.resize(0); } }
+  { auto _e = test_vector_of_union(); if (_e) { _o->test_vector_of_union.resize(_e->size()); for (::flatbuffers::uoffset_t _i = 0; _i < _e->size(); _i++) { _o->test_vector_of_union[_i].value = UnionUnderlyingType::ABCUnion::UnPack(_e->Get(_i), test_vector_of_union_type()->GetEnum<ABC>(_i), _resolver); } } else { _o->test_vector_of_union.resize(0); } }
+}
+
+inline ::flatbuffers::Offset<D> D::Pack(::flatbuffers::FlatBufferBuilder &_fbb, const DT* _o, const ::flatbuffers::rehasher_function_t *_rehasher) {
+  return CreateD(_fbb, _o, _rehasher);
+}
+
+inline ::flatbuffers::Offset<D> CreateD(::flatbuffers::FlatBufferBuilder &_fbb, const DT *_o, const ::flatbuffers::rehasher_function_t *_rehasher) {
+  (void)_rehasher;
+  (void)_o;
+  struct _VectorArgs { ::flatbuffers::FlatBufferBuilder *__fbb; const DT* __o; const ::flatbuffers::rehasher_function_t *__rehasher; } _va = { &_fbb, _o, _rehasher}; (void)_va;
+  auto _test_union_type = _o->test_union.type;
+  auto _test_union = _o->test_union.Pack(_fbb);
+  auto _test_vector_of_union_type = _o->test_vector_of_union.size() ? _fbb.CreateVector<int32_t>(_o->test_vector_of_union.size(), [](size_t i, _VectorArgs *__va) { return static_cast<int32_t>(__va->__o->test_vector_of_union[i].type); }, &_va) : 0;
+  auto _test_vector_of_union = _o->test_vector_of_union.size() ? _fbb.CreateVector<::flatbuffers::Offset<void>>(_o->test_vector_of_union.size(), [](size_t i, _VectorArgs *__va) { return __va->__o->test_vector_of_union[i].Pack(*__va->__fbb, __va->__rehasher); }, &_va) : 0;
+  return UnionUnderlyingType::CreateD(
+      _fbb,
+      _test_union_type,
+      _test_union,
+      _test_vector_of_union_type,
+      _test_vector_of_union);
+}
+
+inline bool VerifyABC(::flatbuffers::Verifier &verifier, const void *obj, ABC type) {
+  switch (type) {
+    case ABC_NONE: {
+      return true;
+    }
+    case ABC_A: {
+      auto ptr = reinterpret_cast<const UnionUnderlyingType::A *>(obj);
+      return verifier.VerifyTable(ptr);
+    }
+    case ABC_B: {
+      auto ptr = reinterpret_cast<const UnionUnderlyingType::B *>(obj);
+      return verifier.VerifyTable(ptr);
+    }
+    case ABC_C: {
+      auto ptr = reinterpret_cast<const UnionUnderlyingType::C *>(obj);
+      return verifier.VerifyTable(ptr);
+    }
+    default: return true;
+  }
+}
+
+inline bool VerifyABCVector(::flatbuffers::Verifier &verifier, const ::flatbuffers::Vector<::flatbuffers::Offset<void>> *values, const ::flatbuffers::Vector<int32_t> *types) {
+  if (!values || !types) return !values && !types;
+  if (values->size() != types->size()) return false;
+  for (::flatbuffers::uoffset_t i = 0; i < values->size(); ++i) {
+    if (!VerifyABC(
+        verifier,  values->Get(i), types->GetEnum<ABC>(i))) {
+      return false;
+    }
+  }
+  return true;
+}
+
+inline void *ABCUnion::UnPack(const void *obj, ABC type, const ::flatbuffers::resolver_function_t *resolver) {
+  (void)resolver;
+  switch (type) {
+    case ABC_A: {
+      auto ptr = reinterpret_cast<const UnionUnderlyingType::A *>(obj);
+      return ptr->UnPack(resolver);
+    }
+    case ABC_B: {
+      auto ptr = reinterpret_cast<const UnionUnderlyingType::B *>(obj);
+      return ptr->UnPack(resolver);
+    }
+    case ABC_C: {
+      auto ptr = reinterpret_cast<const UnionUnderlyingType::C *>(obj);
+      return ptr->UnPack(resolver);
+    }
+    default: return nullptr;
+  }
+}
+
+inline ::flatbuffers::Offset<void> ABCUnion::Pack(::flatbuffers::FlatBufferBuilder &_fbb, const ::flatbuffers::rehasher_function_t *_rehasher) const {
+  (void)_rehasher;
+  switch (type) {
+    case ABC_A: {
+      auto ptr = reinterpret_cast<const UnionUnderlyingType::AT *>(value);
+      return CreateA(_fbb, ptr, _rehasher).Union();
+    }
+    case ABC_B: {
+      auto ptr = reinterpret_cast<const UnionUnderlyingType::BT *>(value);
+      return CreateB(_fbb, ptr, _rehasher).Union();
+    }
+    case ABC_C: {
+      auto ptr = reinterpret_cast<const UnionUnderlyingType::CT *>(value);
+      return CreateC(_fbb, ptr, _rehasher).Union();
+    }
+    default: return 0;
+  }
+}
+
+inline ABCUnion::ABCUnion(const ABCUnion &u) : type(u.type), value(nullptr) {
+  switch (type) {
+    case ABC_A: {
+      value = new UnionUnderlyingType::AT(*reinterpret_cast<UnionUnderlyingType::AT *>(u.value));
+      break;
+    }
+    case ABC_B: {
+      value = new UnionUnderlyingType::BT(*reinterpret_cast<UnionUnderlyingType::BT *>(u.value));
+      break;
+    }
+    case ABC_C: {
+      value = new UnionUnderlyingType::CT(*reinterpret_cast<UnionUnderlyingType::CT *>(u.value));
+      break;
+    }
+    default:
+      break;
+  }
+}
+
+inline void ABCUnion::Reset() {
+  switch (type) {
+    case ABC_A: {
+      auto ptr = reinterpret_cast<UnionUnderlyingType::AT *>(value);
+      delete ptr;
+      break;
+    }
+    case ABC_B: {
+      auto ptr = reinterpret_cast<UnionUnderlyingType::BT *>(value);
+      delete ptr;
+      break;
+    }
+    case ABC_C: {
+      auto ptr = reinterpret_cast<UnionUnderlyingType::CT *>(value);
+      delete ptr;
+      break;
+    }
+    default: break;
+  }
+  value = nullptr;
+  type = ABC_NONE;
+}
+
+inline const ::flatbuffers::TypeTable *ABCTypeTable() {
+  static const ::flatbuffers::TypeCode type_codes[] = {
+    { ::flatbuffers::ET_SEQUENCE, 0, -1 },
+    { ::flatbuffers::ET_SEQUENCE, 0, 0 },
+    { ::flatbuffers::ET_SEQUENCE, 0, 1 },
+    { ::flatbuffers::ET_SEQUENCE, 0, 2 }
+  };
+  static const ::flatbuffers::TypeFunction type_refs[] = {
+    UnionUnderlyingType::ATypeTable,
+    UnionUnderlyingType::BTypeTable,
+    UnionUnderlyingType::CTypeTable
+  };
+  static const int64_t values[] = { 0, 555, 666, 777 };
+  static const char * const names[] = {
+    "NONE",
+    "A",
+    "B",
+    "C"
+  };
+  static const ::flatbuffers::TypeTable tt = {
+    ::flatbuffers::ST_UNION, 4, type_codes, type_refs, nullptr, values, names
+  };
+  return &tt;
+}
+
+inline const ::flatbuffers::TypeTable *ATypeTable() {
+  static const ::flatbuffers::TypeCode type_codes[] = {
+    { ::flatbuffers::ET_INT, 0, -1 }
+  };
+  static const char * const names[] = {
+    "a"
+  };
+  static const ::flatbuffers::TypeTable tt = {
+    ::flatbuffers::ST_TABLE, 1, type_codes, nullptr, nullptr, nullptr, names
+  };
+  return &tt;
+}
+
+inline const ::flatbuffers::TypeTable *BTypeTable() {
+  static const ::flatbuffers::TypeCode type_codes[] = {
+    { ::flatbuffers::ET_STRING, 0, -1 }
+  };
+  static const char * const names[] = {
+    "b"
+  };
+  static const ::flatbuffers::TypeTable tt = {
+    ::flatbuffers::ST_TABLE, 1, type_codes, nullptr, nullptr, nullptr, names
+  };
+  return &tt;
+}
+
+inline const ::flatbuffers::TypeTable *CTypeTable() {
+  static const ::flatbuffers::TypeCode type_codes[] = {
+    { ::flatbuffers::ET_BOOL, 0, -1 }
+  };
+  static const char * const names[] = {
+    "c"
+  };
+  static const ::flatbuffers::TypeTable tt = {
+    ::flatbuffers::ST_TABLE, 1, type_codes, nullptr, nullptr, nullptr, names
+  };
+  return &tt;
+}
+
+inline const ::flatbuffers::TypeTable *DTypeTable() {
+  static const ::flatbuffers::TypeCode type_codes[] = {
+    { ::flatbuffers::ET_UTYPE, 0, 0 },
+    { ::flatbuffers::ET_SEQUENCE, 0, 0 },
+    { ::flatbuffers::ET_UTYPE, 1, 0 },
+    { ::flatbuffers::ET_SEQUENCE, 1, 0 }
+  };
+  static const ::flatbuffers::TypeFunction type_refs[] = {
+    UnionUnderlyingType::ABCTypeTable
+  };
+  static const char * const names[] = {
+    "test_union_type",
+    "test_union",
+    "test_vector_of_union_type",
+    "test_vector_of_union"
+  };
+  static const ::flatbuffers::TypeTable tt = {
+    ::flatbuffers::ST_TABLE, 4, type_codes, type_refs, nullptr, nullptr, names
+  };
+  return &tt;
+}
+
+}  // namespace UnionUnderlyingType
+
+#endif  // FLATBUFFERS_GENERATED_UNIONUNDERLYINGTYPETEST_UNIONUNDERLYINGTYPE_H_