Adding class properties using stage 3 decorators

[indigo relic]

In TS5 with legacy decorators off, how can I add properties to a class using a decorator such that the type system recognizes it?

Playground link to an attempt that doesn't work:
https://www.typescriptlang.org/play?&experimentalDecorators=false#code/JYOwLgpgTgZghgYwgAgKIA8xTgBSgewAdoxgIBnZAbwChlkJNs8iSBPALmXK1AHMA3DQC+NGgnwgeyAIIATOS2JRSFZAF5kAHgAqDTBBBzKICAHdkACgB0tuFD7kucEGwDaAXQCUGgHzVhX0s6ZAkpLABXBDB8KC4dABoQsMhMLgBhABs4cnIAEQgJbBiodMlUsBofdX9aeigIMAioEFDs3P1II0ownigokuRgAFtCTIhhwzBKDCxcAmVVSjr6TuYF9g1kACJZ7GRCDZU2baF6YSFRGgABeUUjpfF2yh0KMCyc5avesCHwlyQW1MFlePA+uUsXiEvXw42smXwfEsoB4AIg1kYcyU7ChyAA9HjkDoABbASjwYCZShwX4SUaUlCkSZAA

Notably an example decorator from the proposal (https://github.com/tc39/proposal-decorators#classes) also fails:
https://www.typescriptlang.org/play?#code/GYVwdgxgLglg9mABAGzgczQUwCYAoBuAhsiJgFyKFgCeANIhAlJgB5QUDCyhAzjwCKZGAJ0JQ4wjk1ZQAlIgDeAKESJhmKCGFII3PohmYw2HoiIlMilaoYIeUYSGgTcAOneFhaHhSrUA2gC68so2NjwgAA6Ywm4eXjyyANzWYYxgPHDImK6oaLgABun2jtAwYGiUSOX2VBCWcMCIACQKYIQAtpgAvogA7jBQABaUXiBdYFCmrZ7ergBWcOW4AET0K7LdBcmpiN3W+9YA9EeI7q5KhwACeVjYSrq8phyKh2CYfYgcuACMyUA

[safe temple]

@indigo relic Here's a shortened URL of your playground link! You can remove the full link from your message.

blodir#0

Playground Link

Preview:```ts
interface ExtraProperties {
extraProperty: string
}

const AddProperties = <
T extends new (...args: any[]) => {}

(
constructor: T,
context: ClassDecoratorContext
) => {
return class
extends constructor
implements ExtraProperties
{
extraProperty = "Extra property
...```

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[random sundial]

Decorators cannot modify types by definition iirc