Hey, just noticed the message in feed channel, qui...

# pattern-matching

[shikasd]

Hey, just noticed the message in feed channel, quite cool to see people interested in implementing lang features as a plugin (especially using meta :D)
I have played around with the PR for an hour or so and managed to make it working for examples you have.
I am still assuming a lot in that code, and also not sure how I can merge it, so will just leave a diff with your upstream here 🙂
It would be great if you could check that it works not only on my machine.

pattern_matching_reference.patch

[shikasd]

@mattmoore tagging you just in case :)

[mattmoore]

This is great! I will pull this down today and try it out. You may have actually helped us get through analysis, it appears 🙂

[shikasd]

It actually generates correct IR, accidentally

[shikasd]

😄

[mattmoore]

Nice! That would save some time then having to do IR transforms.

[shikasd]

essentially, you've been missing a source for this identifier, like where it got assigned from
so I traced it to person.{nth-property}

[shikasd]

I am actually curious how we can make it work with capturing params

[mattmoore]

Me too! With this in place I’ll start taking a look at that today. By the way, feel free to open a PR against the pattern-matching branch on Arrow Meta repo.

[shikasd]

Sure 🙂
Also curious, why you have added case method?

[mattmoore]

Originally, to follow similar to Scala, as well as to have an easy way to find and restrict pattern matching behavior to only what's inside case, given that _ is a reserved Kotlin keyword. However, if we can find a good way to restrict the meaning of _ without case, then we can get rid of that.

I think it's already something I've gotten sufficiently working by checking only for _ where the type is null during analysis phase:

private val BindingTrace.wildcardTypeInfoEntries: List<MutableMap.MutableEntry<KtExpression, KotlinTypeInfo>>
  get() = bindingContext.getSliceContents(BindingContext.EXPRESSION_TYPE_INFO).entries
    .filter { it.value.type == null && it.key.text == "_" }

[mattmoore]

So case can likely go away now.

[shikasd]

Ah, makes sense, thanks

[shikasd]

@mattmoore the pr is here https://github.com/arrow-kt/arrow-meta/pull/690 :)

[mattmoore]

@shikasd I was able to run your patch locally and can confirm it works!

[shikasd]

Amazing, thanks :)