[FE] Prohibit expect or actual opt-in annotations

^KT-58554

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

@@ -1172,6 +1172,8 @@ object DIAGNOSTICS_LIST : DiagnosticList("FirErrors") {
         val ACTUAL_MISSING by error<KtNamedDeclaration>(PositioningStrategy.ACTUAL_DECLARATION_NAME)
 
         val NOT_A_MULTIPLATFORM_COMPILATION by error<PsiElement>()
+
+        val EXPECT_ACTUAL_OPT_IN_ANNOTATION by error<KtNamedDeclaration>(PositioningStrategy.EXPECT_ACTUAL_MODIFIER)
     }
 
     val DESTRUCTING_DECLARATION by object : DiagnosticGroup("Destructuring declaration") {

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

@@ -113,6 +113,7 @@ enum class PositioningStrategy(private val strategy: String? = null) {
     REDUNDANT_NULLABLE,
     INLINE_FUN_MODIFIER,
     CALL_ELEMENT_WITH_DOT,
+    EXPECT_ACTUAL_MODIFIER,
     ;
 
     val expressionToCreate get() = "SourceElementPositioningStrategies.${strategy ?: name}"

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

@@ -626,6 +626,7 @@ object FirErrors {
     val NO_ACTUAL_CLASS_MEMBER_FOR_EXPECTED_CLASS by error2<KtNamedDeclaration, FirBasedSymbol<*>, List<Pair<FirBasedSymbol<*>, Map<Incompatible<FirBasedSymbol<*>>, Collection<FirBasedSymbol<*>>>>>>(SourceElementPositioningStrategies.ACTUAL_DECLARATION_NAME)
     val ACTUAL_MISSING by error0<KtNamedDeclaration>(SourceElementPositioningStrategies.ACTUAL_DECLARATION_NAME)
     val NOT_A_MULTIPLATFORM_COMPILATION by error0<PsiElement>()
+    val EXPECT_ACTUAL_OPT_IN_ANNOTATION by error0<KtNamedDeclaration>(SourceElementPositioningStrategies.EXPECT_ACTUAL_MODIFIER)
 
     // Destructuring declaration
     val INITIALIZER_REQUIRED_FOR_DESTRUCTURING_DECLARATION by error0<KtDestructuringDeclaration>()

compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/declaration/FirExpectActualDeclarationChecker.kt

@@ -30,6 +30,8 @@ import org.jetbrains.kotlin.fir.symbols.impl.*
 import org.jetbrains.kotlin.fir.types.coneType
 import org.jetbrains.kotlin.fir.types.toSymbol
 import org.jetbrains.kotlin.lexer.KtTokens
+import org.jetbrains.kotlin.name.StandardClassIds
+import org.jetbrains.kotlin.resolve.checkers.OptInNames
 import org.jetbrains.kotlin.resolve.multiplatform.ExpectActualCompatibility
 import org.jetbrains.kotlin.resolve.multiplatform.ExpectActualCompatibility.*
 
@@ -50,6 +52,7 @@ object FirExpectActualDeclarationChecker : FirBasicDeclarationChecker() {
         }
         if (declaration.isExpect) {
             checkExpectDeclarationModifiers(declaration, context, reporter)
+            checkOptInAnnotation(declaration, declaration.symbol, context, reporter)
         }
         if (declaration.isActual) {
             checkActualDeclarationHasExpected(declaration, context, reporter)
@@ -181,6 +184,7 @@ object FirExpectActualDeclarationChecker : FirBasicDeclarationChecker() {
                 context,
                 reporter,
             )
+            checkOptInAnnotation(declaration, expectedSingleCandidate, context, reporter)
         }
     }
 
@@ -256,4 +260,19 @@ object FirExpectActualDeclarationChecker : FirBasicDeclarationChecker() {
         return !declaration.isAnnotationConstructor(session) &&
                 !declaration.isPrimaryConstructorOfInlineOrValueClass(session)
     }
+
+    private fun checkOptInAnnotation(
+        declaration: FirMemberDeclaration,
+        expectDeclarationSymbol: FirBasedSymbol<*>,
+        context: CheckerContext,
+        reporter: DiagnosticReporter,
+    ) {
+        if (declaration is FirClass &&
+            declaration.classKind == ClassKind.ANNOTATION_CLASS &&
+            !expectDeclarationSymbol.hasAnnotation(StandardClassIds.Annotations.OptionalExpectation, context.session) &&
+            declaration.hasAnnotation(OptInNames.REQUIRES_OPT_IN_CLASS_ID, context.session)
+        ) {
+            reporter.reportOn(declaration.source, FirErrors.EXPECT_ACTUAL_OPT_IN_ANNOTATION, context)
+        }
+    }
 }

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

@@ -230,6 +230,7 @@ import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.EXPOSED_PROPERTY_
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.DEPRECATED_IDENTITY_EQUALS
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.EXPECTED_EXTERNAL_DECLARATION
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.EXPECTED_TAILREC_FUNCTION
+import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.EXPECT_ACTUAL_OPT_IN_ANNOTATION
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.EXPECT_CLASS_AS_FUNCTION
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.FORBIDDEN_BINARY_MOD
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.FORBIDDEN_IDENTITY_EQUALS
@@ -1845,6 +1846,7 @@ object FirErrorsDefaultMessages : BaseDiagnosticRendererFactory() {
         )
         map.put(ACTUAL_MISSING, "Declaration must be marked with 'actual'")
         map.put(NOT_A_MULTIPLATFORM_COMPILATION, "'expect' and 'actual' declarations can be used only in multiplatform projects. Learn more about Kotlin Multiplatform: https://kotl.in/multiplatform-setup")
+        map.put(EXPECT_ACTUAL_OPT_IN_ANNOTATION, "Opt-in annotations are prohibited to be `expect` or `actual`. Instead, declare annotation once in common sources.")
 
         // Destructuring declaration
         map.put(INITIALIZER_REQUIRED_FOR_DESTRUCTURING_DECLARATION, "Initializer required for destructuring declaration")