instantiable property
Whether the Built Value is instantiable. Defaults to true.
A non-instantiable Built Value has no constructor or factory. No implementation will be generated. But, an abstract builder will be generated, or you may write one yourself.
Other Built Values may choose to implement a non-instantiable Built
Value, pulling in fields and methods from it. Their generated builders
will automatically implement the corresponding builder, so you can
access and modify the common inherited fields without knowing the
concrete type.
Implementation
final bool instantiable;