[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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After Kotlin Fest 2024 LT Night @Sansan ΋ͬͱ΋ͬͱKotlinΛ޷͖ʹͳΔʂ K2 Compiler PluginͰ༡ΜͰΈΑ͏ @kitakkun_pb

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2 ొஃऀϓϩϑΟʔϧ

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ࠓճ࿩͢͜ͱ

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FIRνΣοΧʔ֦ுʂʂ

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ηογϣϯΛݟ͍ͯͳ͍ํ΋ ͍Βͬ͠ΌΔͱࢥ͏ͷͰ

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1෼ͰΘ͔Δ Kotlin Compiler Plugin ͷલʹʂ

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1෼ͰΘ͔Δ Kotlin Compiler ͋͋͋ P l u g i n

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Kotlin Compiler 8 ղੳ ࠷దԽɾग़ྗ Frontend Backend ιʔεϓϩάϥϜ ໨తίʔυ .class 0110 1010 JS JVM Native JS

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தؒදݱʢIR: Intermediate Representationʣ தؒදݱ   ɹ= ίϯύΠϧதͷϓϩάϥϜΛ  ɹ໦ߏ଄Ͱදݱͨ͠΋ͷ • Frontend → FIR • Backend → IR 9 IrClass IrSimpleFunction IrProperty IrExpressionBody IrBlockBody IrConst IrStatement IrStatement

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1෼ͰΘ͔Δ Kotlin Compiler Plugin

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Kotlin Compiler Plugin 11 Frontend Backend ιʔεϓϩάϥϜ ໨తίʔυ .class 0110 1010 JS JVM Native JS

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Kotlin Compiler Plugin 12 Frontend Backend ιʔεϓϩάϥϜ ໨తίʔυ .class 0110 1010 JS JVM Native JS FIR֦ு IR֦ு FIRνΣοΧʔ

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FIRνΣοΧʔͰ༡ΜͰΈΑ͏ʂ

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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❌

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5छྨͷFIR Checker • એݴ FirDeclarationChecker • ࣜ FirExpressionChecker • ܕ FirTypeChecker • ݴޠόʔδϣϯ FirLanguageVersionSettingsChecker • ੍ޚϑϩʔ FirControlFlowChecker 15 ίϯύΠϥ֦ு  Մೳͳ΋ͷ

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5छྨͷFIR Checker • એݴ FirDeclarationChecker • ࣜ FirExpressionChecker • ܕ FirTypeChecker • ݴޠόʔδϣϯ FirLanguageVersionSettingsChecker • ੍ޚϑϩʔ FirControlFlowChecker 16 ίϯύΠϥ֦ு  Մೳͳ΋ͷ

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copy Λݕࠪ͢Δ FirFunctionCallChecker 17 object NoCopyFirFunctionCallChecker : FirFunctionCallChecker(MppCheckerKind.Common) { }

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copy Λݕࠪ͢Δ FirFunctionCallChecker 18 object NoCopyFirFunctionCallChecker : FirFunctionCallChecker(…) { override fun check( expression: FirFunctionCall, context: CheckerContext, reporter: DiagnosticReporter, ) { / / TODO: privateίϯετϥΫλͷΫϥεͷcopy࢖༻Λݕग़ } }

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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 }

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20 override fun check( expression: FirFunctionCall, context: CheckerContext, reporter: DiagnosticReporter, ) { // TODO1: copyҎ֎ͷؔ਺ݺͼग़͠Λআ֎ if (expression.calleeReference.name != Name.identifier("copy")) { return } // . .. }

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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 // .. . }

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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 // … }

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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 }

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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") ) }

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Diagnostic Reporter ͷΞʔΩςΫνϟ 25 DiagnosticRendererFactory ʓʓErrors DiagnosticReporter CheckerContext ਍அ৘ใͷఆٛ ਍அ৘ใͷ  දࣔํ๏Λܾఆ νΣοΧʔ͕ѻ͏  શͯͷ৘ใΛอ࣋ ਍அ৘ใͷใࠂ

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ʓʓErrorsͷ࣮૷ʢΤϥʔ৘ใͷఆٛʣ 26 object NoCopyFirErrors { val COPY_CALL_FOR_DATA_CLASS_WITH_PRIVATE_CONSTRUCTOR by error1() init { RootDiagnosticRendererFactory.registerFactory( NoCopyErrorMessages ) } }

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ʓʓErrorsͷ࣮૷ʢΤϥʔ৘ใͷఆٛʣ 27 object NoCopyFirErrors { val COPY_CALL_AGAINST_PRIVATE_CONSTRUCTOR_DATA_CLASS by error1() init { RootDiagnosticRendererFactory.registerFactory( NoCopyErrorMessages ) } }

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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, ) } }

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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") ) }

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30 / / TODO4: copyͷ࢖༻ՕॴΛΤϥʔใࠂ reporter.reportOn( context = context, source = TODO("Ͳͷએݴʹର͢Δ΋ͷʁ"), factory = TODO("ରԠ͢ΔΤϥʔఆٛ͸ʁ"), a = TODO("Τϥʔใࠂ༻ͷ෇Ճ৘ใ") )

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31 / / TODO4: copyͷ࢖༻ՕॴΛΤϥʔใࠂ reporter.reportOn( context = context, source = expression.calleeReference.source, factory = TODO("ରԠ͢ΔΤϥʔఆٛ͸ʁ"), a = TODO("Τϥʔใࠂ༻ͷ෇Ճ৘ใ") )

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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") )

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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() )

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Checkerͷ࣮૷͸͓͠·͍ʂ

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ࡉ͔͍࢒Γͷ࣮૷͸ ׂѪ͠·ͯ͠ɾɾ

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ಈ࡞σϞΛ͓ݟͤ͠·͢

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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

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ࢿྉɾαϯϓϧϦϙδτϦڞ༗ https://github.com/kitakkun/NoCopy-Compiler-Plugin

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͝ਗ਼ௌ͋Γ͕ͱ͏͍͟͝·ͨ͠ʂ