OptionalequalsOptionalextendsOptionalisJS constructor (or its global name).
OptionalnameRegistry key for abstract types with no is.
OptionalparseOptionalstringifyOptionalsubSpec keys whose values are sub-type specs, resolved to PropType instances at construction. A child's list replaces (not extends) the parent's. Unspecified keys default to PropType.any.
Explicit parent in the chain — used when the parent differs from
registry.get(is)(e.g. concrete types extending an abstract).