Support for `structuredClone`

New DOM api structuredClone should be added.

MDN: https://developer.mozilla.org/en-US/docs/Web/API/structuredClone

[cawa-93]

This type declaration works for me:

type Cloneable<T> = T extends Function | Symbol
  ? never 
  : T extends Record<any, any> 
    ? {-readonly [k in keyof T]: Cloneable<T[k]>}
    : T

declare function structuredClone<T>(value: Cloneable<T>, options?: StructuredSerializeOptions | undefined): Cloneable<T>

1. Return type = value type
2. In the returned type, all fields are writable. But maybe returned type should keep readonly?
3. Will throw a type error if the passed object at any depth contains data that cannot be cloned (function or symbol). This is most important, in my opinion.

const value = {foo: 1} as const
structuredClone(value) // { foo: 1 } Note, foo now writable

const value = {foo: 1, fn() {}} as const
structuredClone(value) // expect type error because function can't be cloned and it will throw DOMException in runtime

Playground

[GabrielDelepine]

Any chance we could get a typed return value in the future?

Something like declare function structuredClone(value: T, options?: StructuredSerializeOptions): T; ?

I know that structuredClone is not returning a strictly identical object (functions are silently removed for instance). Maybe that’s the reason to use : any here?