Use correct wireformat type for repeated group fields.

PiperOrigin-RevId: 510456181

src/google/protobuf/message_unittest.inc

@@ -465,6 +465,24 @@ TEST(MESSAGE_TEST_NAME, ParseFailsIfGroupFieldMalformed) {
   EXPECT_FALSE(parsed.ParseFromString(data));
 }
 
+TEST(MESSAGE_TEST_NAME, ParseFailsIfRepeatedGroupFieldMalformed) {
+  UNITTEST::TestMutualRecursionA original, parsed;
+  original.mutable_bb()
+      ->mutable_a()
+      ->add_subgroupr()
+      ->mutable_payload()
+      ->set_optional_int64(-1);
+
+  std::string data;
+  ASSERT_TRUE(original.SerializeToString(&data));
+  // Should parse correctly.
+  ASSERT_TRUE(parsed.ParseFromString(data));
+  // Overwriting the last byte of varint (-1) to 0xFF results in malformed wire.
+  data[data.size() - 2] = 0xFF;
+
+  EXPECT_FALSE(parsed.ParseFromString(data));
+}
+
 TEST(MESSAGE_TEST_NAME, UninitializedAndMalformed) {
   UNITTEST::TestRequiredForeign o, p1, p2;
   o.mutable_optional_message()->set_a(-1);

src/google/protobuf/unittest.proto

@@ -552,6 +552,9 @@ message TestMutualRecursionA {
     optional SubMessage sub_message = 3;  // Needed because of bug in javatest
     optional TestAllTypes not_in_this_scc = 4;
   }
+  repeated group SubGroupR = 5 {
+    optional TestAllTypes payload = 6;
+  }
 }
 
 message TestMutualRecursionB {