Built-in Subclasses

Subclassing behavior is split into two cases.

Undecorated subclasses

Undecorated subclasses of built-in container types keep built-in JSON behavior.

Examples:

• class MyBytes extends Uint8Array {}
• class MyMap extends Map<string, i32> {}
• class MySet extends Set<string> {}
• class MyArray extends Array<i32> {}

These still serialize and deserialize like their built-in bases.

Decorated subclasses

If you decorate the subclass with @json, it is treated like any other generated class.

That means:

• generated __SERIALIZE / __DESERIALIZE methods are created
• inherited public fields can become part of the schema
• custom @serializer(...) / @deserializer(...) hooks can override the wire format

For built-in subclasses, this means inherited fields from the base type may become visible in JSON. If that is not what you want, explicitly mark them with @omit.

Example

@json
class GeneratedBytes extends Uint8Array {
  constructor(length: i32 = 0) {
    super(length);
  }
}

This is different from an undecorated Uint8Array subclass. It participates in transform-generated class serialization.