Got something like that in practice with backup recovery - IRL most probably the sequence of events leading to that discrepancy was different (not clear yet).

```sql
drop table enum_alter_issue;
create table enum_alter_issue (a Enum8('one' = 1, 'two' = 2)) engine = ReplicatedMergeTree('/clickhouse/tables/enum_alter_issue', 'test') ORDER BY a;

-- backup / move part aside or similar operation 
insert into enum_alter_issue values ('one'), ('two');
alter table enum_alter_issue detach partition id 'all';

-- schema evolution (enum get extended)
alter table enum_alter_issue modify column a Enum8('one' = 1, 'two' = 2, 'three' = 3);
insert into enum_alter_issue values ('one'), ('two');
alter table enum_alter_issue detach partition id 'all';

-- attempt to attach back all the parts (new generation and old generation)
alter table enum_alter_issue attach partition id 'all';

Received exception from server (version 21.9.1):
Code: 53. DB::Exception: Received from localhost:9000. DB::Exception: Type mismatch for column a. Column has type Enum8('one' = 1, 'two' = 2, 'three' = 3), got type Enum8('one' = 1, 'two' = 2). 
```
{
    return primary_key.definition_ast != nullptr;
}
bool StorageInMemoryMetadata::hasPrimaryKey() const
{
    return !primary_key.column_names.empty();
}
Names StorageInMemoryMetadata::getColumnsRequiredForPrimaryKey() const
{
    if (hasPrimaryKey())
        return primary_key.expression->getRequiredColumns();
    return {};
}
Names StorageInMemoryMetadata::getPrimaryKeyColumns() const
{
    if (!primary_key.column_names.empty())
        return primary_key.column_names;
    return {};
}
ASTPtr StorageInMemoryMetadata::getSettingsChanges() const
{
    if (settings_changes)
        return settings_changes->clone();
    return nullptr;
}
const SelectQueryDescription & StorageInMemoryMetadata::getSelectQuery() const
{
    return select;
}
bool StorageInMemoryMetadata::hasSelectQuery() const