Confused about the way injected values are resolved when they share common type

[g00fy-]

class Database{
}

class MySql extends Database {}
class PostgreSql extends Database {}

@Inject(Database,Database)
class DatabaseSyncService {
    constructor(sourceDatabase: Database, destinationDatabase: Database){}
}

function main(){
    var injector = new Injector([PostgreSql,MySql]);
    var syncService = injector.get(DatabaseSyncService);
}

What will be provided to the syncService instance?