Upgrade TypeScript to 2.9

[webmaster128]

With TypeScript 2.9, our code does not compile anymore. The problematic piece is

  constructor(data?: KeyDataString) {
    const identities: PublicIdentity[] = [];
    const privkeys = new Map<string, Ed25519Keypair>();
    if (data) { // data is always of type undefined
      const decodedData = JSON.parse(data); // data is always of type undefined

Both constructor(data?: KeyDataString) and constructor(data: KeyDataString | undefined) do not work anymore, while constructor(data?: string) and constructor(data: string | undefined) are not problem.

I guess this is a bug in Typescript, so the next steps would be to write a minimal example and file a bugreport.

[webmaster128]

microsoft/TypeScript#25268

[webmaster128]

Looks like out types like

declare const AddressSymbol: unique symbol;
type AddressString = typeof AddressSymbol & string;

are hacks because the type typeof unique symbol & something is always never (see bugreport above).

Any other ideas to get typesafe aliases? @will-iov @ethanfrey

In another project I used composition for type safety, but this required calling the .data member all the time when accessing the data. E.g.

export class Pubkey {
  private makeTypeIncompatible: void;

  constructor(public readonly data: Uint8Array) {
  }
}

[ethanfrey]

There were a few ways mentioned on the same thread it boiled down to something like...

Number & {"Foo" : string}

Or maybe {"__" :"Foo"}

Does that work with the new typescript?
If one compiles we can see how to clean it up

[webmaster128]

I guess the core issue persists: those kind of things can never be constructed and it is a matter of time until TypeScript finds that and reduces the type to never.

[ethanfrey]

Random, but interesting, link on more types....
https://www.infoq.com/news/2018/04/typescript-2-8-conditional-types

[ethanfrey]

This was the original thread with people discussing tag types. Maybe one of those suggestions work.
microsoft/TypeScript#4895

I will link the two typescript issues....

[webmaster128]

Great discussion you linked there. I'm trying this one now:

declare class As<Tag extends string> { private ' _ _ _ ': Tag; }
type UserId = string & As<'user-id'>