StructLike

interface StructLike<
  I = unknown,
  O = unknown,
  OO extends boolean = boolean,
> {
  readonly _struct: StructTypes<I, O, OO>;
}

Anything with a _struct type payload. _struct holds input and output phantom types: StructInput and Infer read input and output from it, and object structs use optionalOut to decide which output fields may be absent.

_struct exists only in the type system. Structs have no _struct property at runtime, and a plain object with that type is not a valid struct. input and output are the phantom types. optionalOut is true when the third type argument is true, and undefined otherwise.