Backport #19019 to 20.12: Fix return type of groupUniqArray

src/AggregateFunctions/AggregateFunctionGroupArray.h

@@ -112,7 +112,6 @@ class GroupArrayNumericImpl final
 {
     using Data = GroupArrayNumericData<T, Trait::sampler != Sampler::NONE>;
     static constexpr bool limit_num_elems = Trait::has_limit;
-    DataTypePtr & data_type;
     UInt64 max_elems;
     UInt64 seed;
 
@@ -121,7 +120,6 @@ public:
         const DataTypePtr & data_type_, UInt64 max_elems_ = std::numeric_limits<UInt64>::max(), UInt64 seed_ = 123456)
         : IAggregateFunctionDataHelper<GroupArrayNumericData<T, Trait::sampler != Sampler::NONE>, GroupArrayNumericImpl<T, Trait>>(
             {data_type_}, {})
-        , data_type(this->argument_types[0])
         , max_elems(max_elems_)
         , seed(seed_)
     {
@@ -129,7 +127,7 @@ public:
 
     String getName() const override { return getNameByTrait<Trait>(); }
 
-    DataTypePtr getReturnType() const override { return std::make_shared<DataTypeArray>(data_type); }
+    DataTypePtr getReturnType() const override { return std::make_shared<DataTypeArray>(this->argument_types[0]); }
 
     void insert(Data & a, const T & v, Arena * arena) const
     {

src/AggregateFunctions/AggregateFunctionGroupUniqArray.h

@@ -56,7 +56,7 @@ public:
 
     DataTypePtr getReturnType() const override
     {
-        return std::make_shared<DataTypeArray>(std::make_shared<DataTypeNumber<T>>());
+        return std::make_shared<DataTypeArray>(this->argument_types[0]);
     }
 
     void add(AggregateDataPtr place, const IColumn ** columns, size_t row_num, Arena *) const override

tests/queries/0_stateless/01651_group_uniq_array_enum.reference

+['Hello','World','Упячка']
+['Hello','World','World','Упячка','Упячка','Упячка']
+['world','hello']	Array(Enum8(\'world\' = 0, \'hello\' = 1))	['world','hello']	Array(Enum8(\'world\' = 0, \'hello\' = 1))

tests/queries/0_stateless/01651_group_uniq_array_enum.sql

+SELECT arraySort(groupUniqArray(x)) FROM (SELECT CAST(arrayJoin([1, 2, 3, 2, 3, 3]) AS Enum('Hello' = 1, 'World' = 2, 'Упячка' = 3)) AS x);
+SELECT arraySort(groupArray(x)) FROM (SELECT CAST(arrayJoin([1, 2, 3, 2, 3, 3]) AS Enum('Hello' = 1, 'World' = 2, 'Упячка' = 3)) AS x);
+
+SELECT
+    arraySort(groupUniqArray(val)) AS uniq,
+    toTypeName(uniq),
+    arraySort(groupArray(val)) AS arr,
+    toTypeName(arr)
+FROM
+(
+    SELECT CAST(number % 2, 'Enum(\'hello\' = 1, \'world\' = 0)') AS val
+    FROM numbers(2)
+);