Given the way K2 integrates with the IDE, I suppos...

# javascript

[Edoardo Luppi]

Given the way K2 integrates with the IDE, I suppose via a compiler plugin we could get better support for TS unions?

Example:

tsFunction(value: string | number)

Could be translated to

fun tsFunction(value: Union<String, Int>)

And when being called

tsFunction("example")

The plugin could erase the Union type and perform type checking.

I'm dreaming too much?

[turansky]

Overloads works fine in such cases

cc @Sergei Grishchenko

[Edoardo Luppi]

True, but then you have stuff like

Array<string | number>

This can't be nicely expressed unfortunately, as far as I understand Array<Any> is the only solution in Kotlin

[turansky]

Array<Comparable>

[Edoardo Luppi]

That goes only half the way tho

[turansky]

In most cases you can find more strict variant and use it

[Edoardo Luppi]

Also, there is a readability issue.
If I'm creating externals, I can't communicate cleanly to the user the expected types.
Like in the above example a user might understand that all comparables are ok, but that's not true.

[Edoardo Luppi]

A very dumb workaround could be using

typealias Union<First, Second> = Any

But still no type checking for parameters.

[Edoardo Luppi]

So that at least it's clear what types are expected.

[turansky]

If you need strict array - use more useful in your situation

[turansky]

Dumb workarounds has no big sense :(

[turansky]

• Overloads for functions
• Interfaces for opaque aliases
• Interfaces with assign operators for properties

[Edoardo Luppi]

> Dumb workarounds has no big sense 😞
That's true. However, compare these two signatures, which in TS both return Thenable<void> | void

The first one is much clearer when attempting to use it.

[turansky]

Thenable<void> | void -> PromiseResult<Void>