Microsoft/TypeScript

TypeScript is a superset of JavaScript that compiles to clean JavaScript output.

AnyhowStep

@AnyhowStep

Possible with another type guard, though

It's type guards all the way down!

Bruce Pascoe

@fatcerberus

@AnyhowStep I like that yours is basically a type guard factory

for some reason I didn’t think you could curry them but when I think about it... there’s no reason why it shouldn’t work

AnyhowStep

@AnyhowStep

You'll notice I hecked up the factory, though

The keys should go into the factory function

Instead, the keys are being passed when invoked

And I could be caching it and reusing it but I'm not

Derek Wickern

@dwickern

is there a type for something which can be imported?

import 'foo' // good
import 'bar' // error

const x: Importable = 'foo' // good
const y: Importable = 'bar' // error

Orta

@orta

That change to add a link to Gitter just got deployed to prod

AnyhowStep

@AnyhowStep

@fatcerberus remember how we were discussing the following?

Where ? denotes the existential type, ? extends ? is true

But ? = ? (assignment) is not allowed

@jack-williams just gave another example of that behavior but it's an actual current behaviour

https://github.com/microsoft/TypeScript/issues/33457#issuecomment-532150946

Not exactly the same

But similar enough that it made me think of that

AnyhowStep

@AnyhowStep

In that issue, (arg : never) => T is assignable to (...args : any) => any but not really. It behaves differently depending on whether it's used to constrain a type parameter, or used in a conditional type

Tõnis Ostrat

@tonisostrat

@VulcanRav, it doesn't, yes, but that technically wasn't your requirement either. if you actually need to access a then use any

AnyhowStep

@AnyhowStep

@orta Gitter really needs a better looking logo

Orta

@orta

Yeah, not much I can do there - gitter got bought now, so it’s kinda on the way out I bet

AnyhowStep

@AnyhowStep

I literally had trouble locating it even though there are only 6 icons!
I had to go Ctrl+F > "Gitter"

Orta

@orta

Hah, yep, them memorable 4 lines

webstrand

@webstrand

Did Gitter get sold again? Or does GitLab still own it?

Orta

@orta

nah, still gitlab

Bruce Pascoe

@fatcerberus

@AnyhowStep I always wondered whether (...args: any) => any was checked structurally or not. Good to have some confirmation one way or the other

Although shouldn’t it be ...args: any[] since the rest param always has to be an array

AnyhowStep

@AnyhowStep

Should be ...args : never >;(

Probably something to do with any being assignable to any[] and the other way around. So it doesn't matter

Less concise than any[], though

Bruce Pascoe

@fatcerberus

...args: never - were you trying to make a top type for functions?

AnyhowStep

@AnyhowStep

Yeap

I added that as a comment at the very bottom

ReturnType<> should be accepting a top type for functions, anyway

Bruce Pascoe

@fatcerberus

I had that issue a while ago. ...args: never[] is no good since you can still call it with no args

Never found a good solution :(

Bruce Pascoe

@fatcerberus

If it’s generic though, what about F extends Function?

AnyhowStep

@AnyhowStep

No good, can't use the infer R syntax if you're using extends Function

Also, my concrete F will still end up having never in the param and will break ReturnType<> =x

Even if I'm using Function as the top type for functions

Keith Layne

@keithlayne

IIRC all function has is a name member.

raghanag

@raghanag

hi all, if the typescript class constructor has too many lines, are we going to stub all of it when we are writing unit tests

AnyhowStep

@AnyhowStep

What does that question even mean

Bruce Pascoe

@fatcerberus

@keithlayne Function doesn’t guarantee that it’s callable?

Because that’s kind of sucky if it doesn’t

Keith Layne

@keithlayne

I must have seen an augmentation instead of the actual definition, my bad

Gareth Jones

@G-Rath

ok want to see something interesting?

interface Mx {
  v: string;
}

const promiseTuple = async <T1, T2>(t1: T1, t2: Promise<T2>): Promise<[T1, T2]> =>
  [t1, await t2];

const doThings = async (): Promise<Array<[string, Mx[]]>> => Promise.all([
  promiseTuple('hello', Promise.resolve([{ v: 'sunshine' }])),
  promiseTuple('world', await [{ v: 'peace' }])
]);

doThings().then(r => r.forEach(console.log));

pretty sure that's a bug :grimacing:

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