Is true iff T is a type with a member null value.
Is true iff T is a type with a standardized null (zero address) value.
Default null key of type T,
Is true iff T is a type with a standardized null (zero address) value.
Is true iff T is type with a predefined undefined (null) value.
Traits for introspection the nullability (undefinedness) of a type.
If a type is nullable it has a special value reserved in its set of possible which is to indicated that the value is undefined.