[After Kotlin Fest 2024 LT Night @ Sansan] もっともっとKotlinを好きになる！K2 Compiler Pluginで遊んでみよう！

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1. After Kotlin Fest 2024 LT Night @Sansan ΋ͬͱ΋ͬͱKotlinΛ޷͖ʹͳΔʂ K2 Compiler PluginͰ༡ΜͰΈΑ͏ @kitakkun_pb
2. 2 ొஃऀϓϩϑΟʔϧ
3. ࠓճ࿩͢͜ͱ
4. FIRνΣοΧʔ֦ுʂʂ
5. ηογϣϯΛݟ͍ͯͳ͍ํ΋ ͍Βͬ͠ΌΔͱࢥ͏ͷͰ
6. 1෼ͰΘ͔Δ Kotlin Compiler Plugin ͷલʹʂ
7. 1෼ͰΘ͔Δ Kotlin Compiler ͋͋͋ P l u g i n
8. Kotlin Compiler 8 ղੳ ࠷దԽɾग़ྗ Frontend Backend ιʔεϓϩάϥϜ ໨తίʔυ .class 0110 1010 JS JVM Native JS
9. தؒදݱʢIR: Intermediate Representationʣ தؒදݱ 
 ɹ= ίϯύΠϧதͷϓϩάϥϜΛ
 ɹ໦ߏ଄Ͱදݱͨ͠΋ͷ • Frontend → FIR • Backend → IR 9 IrClass IrSimpleFunction IrProperty IrExpressionBody IrBlockBody IrConst IrStatement IrStatement
10. 1෼ͰΘ͔Δ Kotlin Compiler Plugin
11. Kotlin Compiler Plugin 11 Frontend Backend ιʔεϓϩάϥϜ ໨తίʔυ .class 0110 1010 JS JVM Native JS
12. Kotlin Compiler Plugin 12 Frontend Backend ιʔεϓϩάϥϜ ໨తίʔυ .class 0110 1010 JS JVM Native JS FIR֦ு IR֦ு FIRνΣοΧʔ
13. FIRνΣοΧʔͰ༡ΜͰΈΑ͏ʂ
14. copy ͸ private ίϯετϥΫλΛ͢Γൈ͚ΔʢBefore 2.0.20-Beta1ʣ 14 data class A private constructor(val a: Int) { companion object { fun create(a: Int) = A(a) } } val a = A.create(10) / / OK val b = a.copy(20) / / OK, but should be an error. ERROR❌
15. 5छྨͷFIR Checker • એݴ FirDeclarationChecker • ࣜ FirExpressionChecker • ܕ FirTypeChecker • ݴޠόʔδϣϯ FirLanguageVersionSettingsChecker • ੍ޚϑϩʔ FirControlFlowChecker 15 ίϯύΠϥ֦ு
 Մೳͳ΋ͷ
16. 5छྨͷFIR Checker • એݴ FirDeclarationChecker • ࣜ FirExpressionChecker • ܕ FirTypeChecker • ݴޠόʔδϣϯ FirLanguageVersionSettingsChecker • ੍ޚϑϩʔ FirControlFlowChecker 16 ίϯύΠϥ֦ு
 Մೳͳ΋ͷ
17. copy Λݕࠪ͢Δ FirFunctionCallChecker 17 object NoCopyFirFunctionCallChecker : FirFunctionCallChecker(MppCheckerKind.Common) { }
18. copy Λݕࠪ͢Δ FirFunctionCallChecker 18 object NoCopyFirFunctionCallChecker : FirFunctionCallChecker(…) { override fun check( expression: FirFunctionCall, context: CheckerContext, reporter: DiagnosticReporter, ) { / / TODO: privateίϯετϥΫλͷΫϥεͷcopy࢖༻Λݕग़ } }
19. copy Λݕࠪ͢Δ FirFunctionCallChecker 19 override fun check( expression: FirFunctionCall, context: CheckerContext, reporter: DiagnosticReporter, ) { // TODO1: copyҎ֎ͷؔ਺ݺͼग़͠Λআ֎ // TODO2: data class Ҏ֎Λআ֎ // TODO3: constructor ͕ private Ͱͳ͍΋ͷΛআ֎ // TODO4: copy ͷ࢖༻ՕॴΛΤϥʔใࠂ }
20. 20 override fun check( expression: FirFunctionCall, context: CheckerContext, reporter: DiagnosticReporter, ) { // TODO1: copyҎ֎ͷؔ਺ݺͼग़͠Λআ֎ if (expression.calleeReference.name != Name.identifier("copy")) { return } // . .. }
21. 21 override fun check( expression: FirFunctionCall, context: CheckerContext, reporter: DiagnosticReporter, ) { // copyҎ֎ͷؔ਺ݺͼग़͠Λআ֎ ✅ // TODO2: data class Ҏ֎Λআ֎ val classSymbol = expression.resolvedType .toRegularClassSymbol(context.session) ? : return if (!classSymbol.isData) return // .. . }
22. 22 override fun check( expression: FirFunctionCall, context: CheckerContext, reporter: DiagnosticReporter, ) { // copyҎ֎ͷؔ਺ݺͼग़͠Λআ֎ ✅ // data class Ҏ֎Λআ֎ ✅ // TODO3: constructor ͕ private Ͱͳ͍΋ͷΛআ֎ val constructorVisibility = classSymbol .primaryConstructorSymbol(context.session) .visibility ? : return if (constructorVisibility ! = Visibilities.Private) return // … }
23. 23 override fun check( expression: FirFunctionCall, context: CheckerContext, reporter: DiagnosticReporter, ) { // copyҎ֎ͷؔ਺ݺͼग़͠Λআ֎ ✅ // data class Ҏ֎Λআ֎ ✅ // constructor ͕ private Ͱͳ͍΋ͷΛআ֎ ✅ // TODO4: copy ͷ࢖༻ՕॴΛΤϥʔใࠂ }
24. 24 override fun check( expression: FirFunctionCall, context: CheckerContext, reporter: DiagnosticReporter, ) { // TODO4: copyͷ࢖༻ՕॴΛΤϥʔใࠂ reporter.reportOn( context = context, source = TODO("Ͳͷએݴʹର͢Δ΋ͷʁ"), factory = TODO("ରԠ͢ΔΤϥʔఆٛ͸ʁ"), a = TODO("Τϥʔใࠂ༻ͷ෇Ճ৘ใ") ) }
25. Diagnostic Reporter ͷΞʔΩςΫνϟ 25 DiagnosticRendererFactory ʓʓErrors DiagnosticReporter CheckerContext ਍அ৘ใͷఆٛ ਍அ৘ใͷ
 දࣔํ๏Λܾఆ νΣοΧʔ͕ѻ͏
 શͯͷ৘ใΛอ࣋ ਍அ৘ใͷใࠂ
26. ʓʓErrorsͷ࣮૷ʢΤϥʔ৘ใͷఆٛʣ 26 object NoCopyFirErrors { val COPY_CALL_FOR_DATA_CLASS_WITH_PRIVATE_CONSTRUCTOR by error1<PsiElement, String>() init { RootDiagnosticRendererFactory.registerFactory( NoCopyErrorMessages ) } }
27. ʓʓErrorsͷ࣮૷ʢΤϥʔ৘ใͷఆٛʣ 27 object NoCopyFirErrors { val COPY_CALL_AGAINST_PRIVATE_CONSTRUCTOR_DATA_CLASS by error1<PsiElement, String>() init { RootDiagnosticRendererFactory.registerFactory( NoCopyErrorMessages ) } }
28. DiagnosticRendererFactoryͷ࣮૷ʢΤϥʔͷදࣔํ๏ͷܾఆʣ 28 object NoCopyErrorMessages : BaseDiagnosticRendererFactory() { override val MAP = KtDiagnosticFactoryToRendererMap("NoCopy").apply { put( NoCopyFirErrors.COPY_CALL_FOR_DATA_CLASS_WITH_PRIVATE_CONSTRUCTOR, "data class {0} has a private constructor." + "The use of copy method is not allowed", rendererA = TO_STRING, ) } }
29. 29 override fun check( expression: FirFunctionCall, context: CheckerContext, reporter: DiagnosticReporter, ) { // TODO4: copyͷ࢖༻ՕॴΛΤϥʔใࠂ reporter.reportOn( context = context, source = TODO("Ͳͷએݴʹର͢Δ΋ͷʁ"), factory = TODO("ରԠ͢ΔΤϥʔఆٛ͸ʁ"), a = TODO("Τϥʔใࠂ༻ͷ෇Ճ৘ใ") ) }
30. 30 / / TODO4: copyͷ࢖༻ՕॴΛΤϥʔใࠂ reporter.reportOn( context = context, source = TODO("Ͳͷએݴʹର͢Δ΋ͷʁ"), factory = TODO("ରԠ͢ΔΤϥʔఆٛ͸ʁ"), a = TODO("Τϥʔใࠂ༻ͷ෇Ճ৘ใ") )
31. 31 / / TODO4: copyͷ࢖༻ՕॴΛΤϥʔใࠂ reporter.reportOn( context = context, source = expression.calleeReference.source, factory = TODO("ରԠ͢ΔΤϥʔఆٛ͸ʁ"), a = TODO("Τϥʔใࠂ༻ͷ෇Ճ৘ใ") )
32. 32 // TODO4: copyͷ࢖༻ՕॴΛΤϥʔใࠂ reporter.reportOn( context = context, source = expression.calleeReference.source, factory = NoCopyFirErrors. COPY_CALL_FOR_DATA_CLASS_WITH_PRIVATE_CONSTRUCTOR, a = TODO("Τϥʔใࠂ༻ͷ෇Ճ৘ใ") )
33. 33 // TODO4: copyͷ࢖༻ՕॴΛΤϥʔใࠂ reporter.reportOn( context = context, source = expression.calleeReference.source, factory = NoCopyFirErrors. COPY_CALL_FOR_DATA_CLASS_WITH_PRIVATE_CONSTRUCTOR, a = classSymbol.classId.asString() )
34. Checkerͷ࣮૷͸͓͠·͍ʂ
35. ࡉ͔͍࢒Γͷ࣮૷͸ ׂѪ͠·ͯ͠ɾɾ
36. ಈ࡞σϞΛ͓ݟͤ͠·͢
38. ࢀߟจݙ • νΣοΧʔΛ௥Ճ͢ΔFIR֦ு • https://github.com/JetBrains/kotlin/blob/master/docs/ fi r/ fi r- plugins.md# fi radditionalcheckersextension • FIRνΣοΧʔͷࡉ͔͍࢓༷ • https://github.com/JetBrains/kotlin/blob/master/compiler/ fi r/checkers/ module.md 38
39. ࢿྉɾαϯϓϧϦϙδτϦڞ༗ https://github.com/kitakkun/NoCopy-Compiler-Plugin
40. ͝ਗ਼ௌ͋Γ͕ͱ͏͍͟͝·ͨ͠ʂ