RK, RV> method Null safety
Provides a view of this map as having
RK keys and
If this map is already a
Map<RK, RV>, it is returned unchanged.
If this set contains only keys of type
RK and values of type
all read operations will work correctly.
If any operation exposes a non-
RK key or non-
the operation will throw instead.
Entries added to the map must be valid for both a
Map<K, V> and a
Map<RK, RV> cast<RK, RV>() => Map.castFrom<K, V, RK, RV>(this);