Match multiple patterns simultaneously

[TmLev]

Hi!

Thanks for this useful package.

I was wondering whether it is possible to match multiple patterns simultaneously? Like so:

const LoadState = makeTaggedUnion({
  Unstarted: none,
  Loading: (percentLoaded: number) => percentLoaded,
  Loaded: (response: Buffer) => response,
  Error: (error: Error) => error,
});

type LoadState = MemberType<typeof LoadState>;

const state: LoadState = LoadState.Unstarted;

console.log("State is ", state.match({
  Unstarted | Error: () => "unavailable", // `Unstarted` AND `Error` simultaneously.
  _: () => "available", 
}));

I'm assuming it's not possible since it requires changes to how TypeScript treats Something | AnotherThing syntax, but maybe I'm wrong.

[suchipi]

Supporting a string key of "Unstarted | Error" is theoretically possible, since you can do some seriously wacky things with TypeScript, but it would be way too complicated for me to want to do :p

While it's not ideal, this is what I do for handling multiple cases:

// definition of LoadState and state omitted; they'd be the same as in your issue description

const unavailable = () => "unavailable";

console.log("State is ", state.match({
  Unstarted: unavailable,
  Error: unavailable,
  _: () => "available", 
}));

For something small like "unavailable" it looks silly, but when the match handler in question is larger, it makes more sense.

[TmLev]

Seems reasonable albeit not very ergonomic. Thought about doing it this way, also. Thanks!

[Evertt]

@suchipi If I, or anyone else for that matter, would offer you a PR that makes this feature possible, would you accept it?

[suchipi]

Yes, provided it was of good quality and etc

[suchipi]

Reopening to better communicate that interest

[cuppachino]

I don't know how much I like the suggested approach with "Unstarted" | Error, but the idea is really cool.

You might need something like PickAll and KeyOf from here to maintain type inference.