diff --git a/cpp/src/arrow/array/array_dict.cc b/cpp/src/arrow/array/array_dict.cc
index 55e086af30bc2..86f7ac465964b 100644
--- a/cpp/src/arrow/array/array_dict.cc
+++ b/cpp/src/arrow/array/array_dict.cc
@@ -270,7 +270,7 @@ struct CompactTransposeMapVisitor {
                           AllocateBuffer(dict_length * sizeof(int32_t), pool));
     auto* output_map_raw = output_map->mutable_data_as<int32_t>();
     int32_t current_index = 0;
-    for (CType i = 0; i < dict_len; i++) {
+    for (CType i = 0; i < dict_len; ++i) {
       if (dict_used[i]) {
         dict_indices_builder.UnsafeAppend(i);
         output_map_raw[i] = current_index;
@@ -309,7 +309,7 @@ Result<std::unique_ptr<Buffer>> CompactTransposeMap(
   CompactTransposeMapVisitor visitor{data, pool, nullptr, nullptr};
   RETURN_NOT_OK(VisitTypeInline(*dict_type.index_type(), &visitor));
 
-  out_compact_dictionary = visitor.out_compact_dictionary;
+  out_compact_dictionary = std::move(visitor.out_compact_dictionary);
   return std::move(visitor.output_map);
 }
 }  // namespace
@@ -520,8 +520,8 @@ struct RecursiveUnifier {
 
 Result<std::unique_ptr<DictionaryUnifier>> DictionaryUnifier::Make(
     std::shared_ptr<DataType> value_type, MemoryPool* pool) {
-  MakeUnifier maker(pool, value_type);
-  RETURN_NOT_OK(VisitTypeInline(*value_type, &maker));
+  MakeUnifier maker(pool, std::move(value_type));
+  RETURN_NOT_OK(VisitTypeInline(*maker.value_type, &maker));
   return std::move(maker.result);
 }
 
diff --git a/cpp/src/arrow/array/array_dict.h b/cpp/src/arrow/array/array_dict.h
index bf376b51f8c94..24cdd3b59525c 100644
--- a/cpp/src/arrow/array/array_dict.h
+++ b/cpp/src/arrow/array/array_dict.h
@@ -90,7 +90,10 @@ class ARROW_EXPORT DictionaryArray : public Array {
   /// \param[in] type the new type object
   /// \param[in] dictionary the new dictionary
   /// \param[in] transpose_map transposition array of this array's indices
-  ///   into the target array's indices
+  ///   into the target array's indices. The value of transpose_map should
+  ///   be in the range [0, dictionary->length()). And the dictionary indices
+  ///   at transpose_map[i] should not be out of bounds.
+  ///
   /// \param[in] pool a pool to allocate the array data from
   Result<std::shared_ptr<Array>> Transpose(
       const std::shared_ptr<DataType>& type, const std::shared_ptr<Array>& dictionary,