heyo, I pushed it a bit further last two evenings ...

# pattern-matching

[shikasd]

heyo, I pushed it a bit further last two evenings and got basic support for sealed classes working in this PR
for now only it supports data class with one parameter, because I need to pass the info about index of parameter to IR level somehow. (Problem for tomorrow)

I also had to rewrite some parts of analysis. Now we go through contents of all files and check when expressions directly instead of relying on diagnostics to detect them.

And the last change, we also have a todo property in the prelude which serves as a placeholder to complete calls in PSI.

(also merged master, so sorry for a bit messy changeset)

[shikasd]

@mattmoore pinging you as usual 🙂

[mattmoore]

Nice! I'll take a look soon 🙂

[mattmoore]

@shikasd Just updated upstream pattern-matching branch with master. Can you try rebasing on upstream pattern-matching branch?

[shikasd]

thanks, just did this
seems like tests got merged a bit weirdly, will fix this now

[shikasd]

seems alright now

[mattmoore]

👍

[mattmoore]

@shikasd This is really neat. I didn't know you could create your own slice with custom types:

val PATTERN_EXPRESSION = Slices.createSimpleSlice<KtWhenEntry, PatternExpression>()
val PATTERN_EXPRESSION_CAPTURED_PARAMS = Slices.createCollectiveSetSlice<KtNameReferenceExpression>()
val PATTERN_EXPRESSION_BODY_PARAMS = Slices.createCollectiveSetSlice<KtSimpleNameExpression>()

[shikasd]

Yeah, I learned it from kotlinx.serialiaztion long time ago

[shikasd]

Unfortunately, toString doesn't work well with those :)

[shikasd]

@mattmoore Updated my PR, now all tests pass
No need for a todo property anymore, I decided to create them on the fly kinda like compose does, so I could keep track of which component function to call

Also it now supports other expressions as captured params, so test const strings work correctly as well.
To achieve that, I have written a simple transform which basically converts
case(Person("Matt", "Moore")) into subject is Person && subject.component1() == "Matt" && subject.component2() == "Moore"

[mattmoore]

This looks great! I merged your PR.

[raulraja]

awesome stuff @shikasd 👏

[raulraja]

Some of those component methods are unsafe in the std lib and would cause the pattern to blow up

[raulraja]

like destructuring a list

[raulraja]

that is empty. We need to ensure the desugaring is safe in those cases because a user always expect the match to be a partial function. This is why unapply in Scala returns an Option tupled

[raulraja]

that is if any of those result in the match results on an exception by invoking componentN it needs to go towards false in the desugar in such a way that it does not blow up

[raulraja]

ideally it detects if it’s a data class then it’s safe to not try catch

[raulraja]

but any component1 declared in interfaces have to be safe wrapped and non fatal exceptions coerced to false or the cases won’t form partial functions.

[shikasd]

For now I check if the call is constructor for class
I think ideally, I would check if parameters of constructor have a corresponding property, so probably we could extend support to more than just data classes
But in general, I think supporting only them is fine