[FIR, Tests] Deprecate property references to ::javaClass

analysis/analysis-api-fir/gen/org/jetbrains/kotlin/analysis/api/fir/diagnostics/KaFirDataClassConverters.kt

@@ -1126,6 +1126,12 @@ private fun KaDiagnosticConverterBuilder.addConversions20() {
             token,
         )
     }
+    add(FirJvmErrors.JAVA_CLASS_PROPERTY_REFERENCE.warningFactory) { firDiagnostic ->
+        JavaClassPropertyReferenceWarningImpl(
+            firDiagnostic as KtPsiDiagnostic,
+            token,
+        )
+    }
     add(FirWebCommonErrors.NESTED_JS_EXPORT) { firDiagnostic ->
         NestedJsExportImpl(
             firDiagnostic as KtPsiDiagnostic,
@@ -6580,6 +6586,12 @@ private fun KaDiagnosticConverterBuilder.addConversions144() {
             token,
         )
     }
+    add(FirJvmErrors.JAVA_CLASS_PROPERTY_REFERENCE.errorFactory) { firDiagnostic ->
+        JavaClassPropertyReferenceErrorImpl(
+            firDiagnostic as KtPsiDiagnostic,
+            token,
+        )
+    }
 }
 
 private fun KaDiagnosticConverterBuilder.addConversions145() {

analysis/analysis-api-fir/gen/org/jetbrains/kotlin/analysis/api/fir/diagnostics/KaFirDiagnostics.kt

@@ -4985,6 +4985,14 @@ sealed interface KaFirDiagnostic<PSI : PsiElement> : KaDiagnosticWithPsi<PSI> {
         val expectedType: KaType
     }
 
+    interface JavaClassPropertyReferenceError : KaFirDiagnostic<PsiElement> {
+        override val diagnosticClass get() = JavaClassPropertyReferenceError::class
+    }
+
+    interface JavaClassPropertyReferenceWarning : KaFirDiagnostic<PsiElement> {
+        override val diagnosticClass get() = JavaClassPropertyReferenceWarning::class
+    }
+
     interface UnexhaustiveWhenBasedOnJavaAnnotations : KaFirDiagnostic<PsiElement> {
         override val diagnosticClass get() = UnexhaustiveWhenBasedOnJavaAnnotations::class
         val subjectType: KaType

analysis/analysis-api-fir/gen/org/jetbrains/kotlin/analysis/api/fir/diagnostics/KaFirDiagnosticsImpl.kt

@@ -5986,6 +5986,16 @@ internal class JavaClassOnCompanionImpl(
     token: KaLifetimeToken,
 ) : KaAbstractFirDiagnostic<PsiElement>(firDiagnostic, token), KaFirDiagnostic.JavaClassOnCompanion
 
+internal class JavaClassPropertyReferenceErrorImpl(
+    firDiagnostic: KtPsiDiagnostic,
+    token: KaLifetimeToken,
+) : KaAbstractFirDiagnostic<PsiElement>(firDiagnostic, token), KaFirDiagnostic.JavaClassPropertyReferenceError
+
+internal class JavaClassPropertyReferenceWarningImpl(
+    firDiagnostic: KtPsiDiagnostic,
+    token: KaLifetimeToken,
+) : KaAbstractFirDiagnostic<PsiElement>(firDiagnostic, token), KaFirDiagnostic.JavaClassPropertyReferenceWarning
+
 internal class UnexhaustiveWhenBasedOnJavaAnnotationsImpl(
     override val subjectType: KaType,
     firDiagnostic: KtPsiDiagnostic,

compiler/fir/checkers/checkers-component-generator/src/org/jetbrains/kotlin/fir/checkers/generator/diagnostics/FirJvmDiagnosticsList.kt

@@ -117,6 +117,10 @@ object JVM_DIAGNOSTICS_LIST : DiagnosticList("FirJvmErrors") {
             parameter<ConeKotlinType>("actualType")
             parameter<ConeKotlinType>("expectedType")
         }
+        val JAVA_CLASS_PROPERTY_REFERENCE by deprecationError<PsiElement>(
+            featureForError = ForbidJavaClassPropertyReferences,
+            positioningStrategy = PositioningStrategy.REFERENCED_NAME_BY_QUALIFIED,
+        )
 
         val UNEXHAUSTIVE_WHEN_BASED_ON_JAVA_ANNOTATIONS by warning<PsiElement>(PositioningStrategy.WHEN_EXPRESSION) {
             parameter<ConeKotlinType>("subjectType")

compiler/fir/checkers/checkers.jvm/gen/org/jetbrains/kotlin/fir/analysis/diagnostics/jvm/FirJvmErrors.kt

@@ -7,6 +7,7 @@ package org.jetbrains.kotlin.fir.analysis.diagnostics.jvm
 
 import com.intellij.psi.PsiElement
 import org.jetbrains.kotlin.config.LanguageFeature.ForbidImplementationByDelegationWithDifferentGenericSignature
+import org.jetbrains.kotlin.config.LanguageFeature.ForbidJavaClassPropertyReferences
 import org.jetbrains.kotlin.config.LanguageFeature.ForbidJvmAnnotationsOnAnnotationParameters
 import org.jetbrains.kotlin.config.LanguageFeature.ForbidJvmSerializableLambdaOnInlinedFunctionLiterals
 import org.jetbrains.kotlin.config.LanguageFeature.ProhibitSynchronizationByValueClassesAndPrimitives
@@ -86,6 +87,7 @@ object FirJvmErrors : KtDiagnosticsContainer() {
     val NULLABILITY_MISMATCH_BASED_ON_EXPLICIT_TYPE_ARGUMENTS_FOR_JAVA: KtDiagnosticFactory3<ConeKotlinType, ConeKotlinType, String> = KtDiagnosticFactory3("NULLABILITY_MISMATCH_BASED_ON_EXPLICIT_TYPE_ARGUMENTS_FOR_JAVA", WARNING, SourceElementPositioningStrategies.DEFAULT, PsiElement::class, getRendererFactory())
     val TYPE_MISMATCH_WHEN_FLEXIBILITY_CHANGES: KtDiagnosticFactory2<ConeKotlinType, ConeKotlinType> = KtDiagnosticFactory2("TYPE_MISMATCH_WHEN_FLEXIBILITY_CHANGES", WARNING, SourceElementPositioningStrategies.DEFAULT, PsiElement::class, getRendererFactory())
     val JAVA_CLASS_ON_COMPANION: KtDiagnosticFactory2<ConeKotlinType, ConeKotlinType> = KtDiagnosticFactory2("JAVA_CLASS_ON_COMPANION", WARNING, SourceElementPositioningStrategies.SELECTOR_BY_QUALIFIED, PsiElement::class, getRendererFactory())
+    val JAVA_CLASS_PROPERTY_REFERENCE: KtDiagnosticFactoryForDeprecation0 = KtDiagnosticFactoryForDeprecation0("JAVA_CLASS_PROPERTY_REFERENCE", ForbidJavaClassPropertyReferences, SourceElementPositioningStrategies.REFERENCED_NAME_BY_QUALIFIED, PsiElement::class, getRendererFactory())
     val UNEXHAUSTIVE_WHEN_BASED_ON_JAVA_ANNOTATIONS: KtDiagnosticFactory1<ConeKotlinType> = KtDiagnosticFactory1("UNEXHAUSTIVE_WHEN_BASED_ON_JAVA_ANNOTATIONS", WARNING, SourceElementPositioningStrategies.WHEN_EXPRESSION, PsiElement::class, getRendererFactory())
 
     // Type parameters

compiler/fir/checkers/checkers.jvm/src/org/jetbrains/kotlin/fir/analysis/diagnostics/jvm/FirJvmErrorsDefaultMessages.kt

@@ -49,6 +49,7 @@ import org.jetbrains.kotlin.fir.analysis.diagnostics.jvm.FirJvmErrors.INNER_JVM_
 import org.jetbrains.kotlin.fir.analysis.diagnostics.jvm.FirJvmErrors.INTERFACE_CANT_CALL_DEFAULT_METHOD_VIA_SUPER
 import org.jetbrains.kotlin.fir.analysis.diagnostics.jvm.FirJvmErrors.JAVA_CLASS_INHERITS_KT_PRIVATE_CLASS
 import org.jetbrains.kotlin.fir.analysis.diagnostics.jvm.FirJvmErrors.JAVA_CLASS_ON_COMPANION
+import org.jetbrains.kotlin.fir.analysis.diagnostics.jvm.FirJvmErrors.JAVA_CLASS_PROPERTY_REFERENCE
 import org.jetbrains.kotlin.fir.analysis.diagnostics.jvm.FirJvmErrors.JAVA_FIELD_SHADOWED_BY_KOTLIN_PROPERTY
 import org.jetbrains.kotlin.fir.analysis.diagnostics.jvm.FirJvmErrors.JAVA_MODULE_DOES_NOT_DEPEND_ON_MODULE
 import org.jetbrains.kotlin.fir.analysis.diagnostics.jvm.FirJvmErrors.JAVA_MODULE_DOES_NOT_EXPORT_PACKAGE
@@ -185,6 +186,10 @@ object FirJvmErrorsDefaultMessages : BaseDiagnosticRendererFactory() {
             RENDER_TYPE,
             RENDER_TYPE,
         )
+        map.put(
+            JAVA_CLASS_PROPERTY_REFERENCE,
+            "Property references to 'javaClass' are error-prone: '::javaClass' creates a property reference, not the Java class of the receiver. Use '.javaClass' or '::class.java' instead.",
+        )
 
         map.put(
             UNEXHAUSTIVE_WHEN_BASED_ON_JAVA_ANNOTATIONS,

compiler/fir/checkers/checkers.jvm/src/org/jetbrains/kotlin/fir/analysis/jvm/checkers/JvmExpressionCheckers.kt

@@ -38,6 +38,7 @@ object JvmExpressionCheckers : ExpressionCheckers() {
             FirUnsupportedSyntheticCallableReferenceChecker,
             FirFieldReferenceShadowedByInvisibleKotlinProperty,
             FirJavaSamInterfaceConstructorReferenceChecker,
+            FirJavaClassPropertyReferenceChecker,
         )
 
     override val functionCallCheckers: Set<FirFunctionCallChecker>

compiler/fir/checkers/checkers.jvm/src/org/jetbrains/kotlin/fir/analysis/jvm/checkers/expression/FirJavaClassPropertyReferenceChecker.kt

@@ -0,0 +1,27 @@
+/*
+ * Copyright 2010-2026 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+
+package org.jetbrains.kotlin.fir.analysis.jvm.checkers.expression
+
+import org.jetbrains.kotlin.diagnostics.DiagnosticReporter
+import org.jetbrains.kotlin.diagnostics.reportOn
+import org.jetbrains.kotlin.fir.analysis.checkers.MppCheckerKind
+import org.jetbrains.kotlin.fir.analysis.checkers.context.CheckerContext
+import org.jetbrains.kotlin.fir.analysis.checkers.expression.FirCallableReferenceAccessChecker
+import org.jetbrains.kotlin.fir.analysis.diagnostics.jvm.FirJvmErrors
+import org.jetbrains.kotlin.fir.expressions.FirCallableReferenceAccess
+import org.jetbrains.kotlin.fir.expressions.toResolvedCallableReference
+import org.jetbrains.kotlin.fir.symbols.impl.FirCallableSymbol
+import org.jetbrains.kotlin.name.JvmStandardClassIds
+
+object FirJavaClassPropertyReferenceChecker : FirCallableReferenceAccessChecker(MppCheckerKind.Common) {
+    context(context: CheckerContext, reporter: DiagnosticReporter)
+    override fun check(expression: FirCallableReferenceAccess) {
+        val resolvedSymbol = expression.toResolvedCallableReference()?.resolvedSymbol as? FirCallableSymbol<*> ?: return
+        if (resolvedSymbol.callableId != JvmStandardClassIds.Callables.JavaClass) return
+
+        reporter.reportOn(expression.calleeReference.source, FirJvmErrors.JAVA_CLASS_PROPERTY_REFERENCE)
+    }
+}

compiler/fir/checkers/gen/org/jetbrains/kotlin/fir/analysis/diagnostics/FirNonSuppressibleErrorNames.kt

@@ -776,6 +776,7 @@ val FIR_NON_SUPPRESSIBLE_ERROR_NAMES: Set<String> = setOf(
     "IMPLEMENTATION_BY_DELEGATION_WITH_DIFFERENT_GENERIC_SIGNATURE_ERROR",
     "NOT_YET_SUPPORTED_LOCAL_INLINE_FUNCTION",
     "JAVA_TYPE_MISMATCH",
+    "JAVA_CLASS_PROPERTY_REFERENCE_ERROR",
     "UPPER_BOUND_CANNOT_BE_ARRAY",
     "STRICTFP_ON_CLASS",
     "SYNCHRONIZED_ON_ABSTRACT",

compiler/testData/diagnostics/testsWithStdLib/callableReferences/javaClassPropertyReference.kt

@@ -0,0 +1,16 @@
+// RUN_PIPELINE_TILL: FRONTEND
+// ISSUE: KTLC-375, KT-81931
+// LATEST_LV_DIFFERENCE
+
+fun test(x: Any) {
+    val a = x::<!JAVA_CLASS_PROPERTY_REFERENCE_WARNING!>javaClass<!>
+    val b = Any()::<!JAVA_CLASS_PROPERTY_REFERENCE_WARNING!>javaClass<!>
+    val c = 2::<!JAVA_CLASS_PROPERTY_REFERENCE_WARNING!>javaClass<!>
+    val d = x::<!JAVA_CLASS_PROPERTY_REFERENCE_WARNING!>javaClass<!>.get()
+
+    val direct = x.javaClass
+    val literal = Any::class.java
+}
+
+/* GENERATED_FIR_TAGS: callableReference, classReference, functionDeclaration, integerLiteral, localProperty,
+propertyDeclaration */

compiler/testData/diagnostics/testsWithStdLib/callableReferences/javaClassPropertyReference.latestLV.kt

@@ -0,0 +1,16 @@
+// RUN_PIPELINE_TILL: FRONTEND
+// ISSUE: KTLC-375, KT-81931
+// LATEST_LV_DIFFERENCE
+
+fun test(x: Any) {
+    val a = x::<!JAVA_CLASS_PROPERTY_REFERENCE_ERROR!>javaClass<!>
+    val b = Any()::<!JAVA_CLASS_PROPERTY_REFERENCE_ERROR!>javaClass<!>
+    val c = 2::<!JAVA_CLASS_PROPERTY_REFERENCE_ERROR!>javaClass<!>
+    val d = x::<!JAVA_CLASS_PROPERTY_REFERENCE_ERROR!>javaClass<!>.get()
+
+    val direct = x.javaClass
+    val literal = Any::class.java
+}
+
+/* GENERATED_FIR_TAGS: callableReference, classReference, functionDeclaration, integerLiteral, localProperty,
+propertyDeclaration */

core/language.version-settings/src/org/jetbrains/kotlin/config/LanguageVersionSettings.kt

@@ -552,6 +552,7 @@ enum class LanguageFeature(
     // 2.6
 
     ReportReificationProblemsInDnnAndFlexible(sinceVersion = KOTLIN_2_6, enabledInProgressiveMode = true, "KTLC-399"),
+    ForbidJavaClassPropertyReferences(sinceVersion = KOTLIN_2_6, enabledInProgressiveMode = true, "KTLC-375"),
 
     // End of 2.* language features --------------------------------------------------