struct OpenHashMap(K, V = void, alias hasher = hashOf, string keyEqualPred = defaultKeyEqualPredOf!(K), alias Allocator = Mallocator.instance, bool borrowChecked = false, bool useSmallLinearSearch = true, bool usePrimeCapacity = false)
enum hasValue =
!is(V == void);
In the hash map case, V is non-void, and a value is stored alongside the key of type K.