[FIR] Implement CLASS_CANNOT_BE_EXTENDED_DIRECTLY

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

@@ -124,6 +124,9 @@ object DIAGNOSTICS_LIST : DiagnosticList("FirErrors") {
         val SUPERTYPE_INITIALIZED_IN_INTERFACE by error<KtTypeReference>()
         val INTERFACE_WITH_SUPERCLASS by error<KtTypeReference>()
         val FINAL_SUPERTYPE by error<KtTypeReference>()
+        val CLASS_CANNOT_BE_EXTENDED_DIRECTLY by error<KtTypeReference> {
+            parameter<FirRegularClassSymbol>("classSymbol")
+        }
         val SUPERTYPE_IS_EXTENSION_FUNCTION_TYPE by error<KtTypeReference>()
         val SINGLETON_IN_SUPERTYPE by error<KtTypeReference>()
         val NULLABLE_SUPERTYPE by error<KtTypeReference>(PositioningStrategy.QUESTION_MARK_BY_TYPE)

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

@@ -134,6 +134,7 @@ object FirErrors {
     val SUPERTYPE_INITIALIZED_IN_INTERFACE by error0<KtTypeReference>()
     val INTERFACE_WITH_SUPERCLASS by error0<KtTypeReference>()
     val FINAL_SUPERTYPE by error0<KtTypeReference>()
+    val CLASS_CANNOT_BE_EXTENDED_DIRECTLY by error1<KtTypeReference, FirRegularClassSymbol>()
     val SUPERTYPE_IS_EXTENSION_FUNCTION_TYPE by error0<KtTypeReference>()
     val SINGLETON_IN_SUPERTYPE by error0<KtTypeReference>()
     val NULLABLE_SUPERTYPE by error0<KtTypeReference>(SourceElementPositioningStrategies.QUESTION_MARK_BY_TYPE)

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

@@ -22,6 +22,7 @@ import org.jetbrains.kotlin.fir.resolve.fullyExpandedType
 import org.jetbrains.kotlin.fir.resolve.toSymbol
 import org.jetbrains.kotlin.fir.symbols.impl.FirRegularClassSymbol
 import org.jetbrains.kotlin.fir.types.*
+import org.jetbrains.kotlin.name.StandardClassIds
 import org.jetbrains.kotlin.utils.addToStdlib.safeAs
 
 object FirSupertypesChecker : FirClassChecker() {
@@ -106,6 +107,10 @@ object FirSupertypesChecker : FirClassChecker() {
                         }
                     }
                 }
+
+                if (symbol is FirRegularClassSymbol && symbol.classId == StandardClassIds.Enum) {
+                    reporter.reportOn(superTypeRef.source, FirErrors.CLASS_CANNOT_BE_EXTENDED_DIRECTLY, symbol, context)
+                }
             }
         }
 

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

@@ -65,6 +65,7 @@ import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.CAN_BE_VAL
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.CAPTURED_MEMBER_VAL_INITIALIZATION
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.CAPTURED_VAL_INITIALIZATION
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.CATCH_PARAMETER_WITH_DEFAULT_VALUE
+import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.CLASS_CANNOT_BE_EXTENDED_DIRECTLY
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.CLASS_IN_SUPERTYPE_FOR_ENUM
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.CLASS_LITERAL_LHS_NOT_A_CLASS
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.COMPONENT_FUNCTION_AMBIGUITY
@@ -453,6 +454,7 @@ class FirDefaultErrorMessages {
             map.put(SUPERTYPE_INITIALIZED_IN_INTERFACE, "Interfaces cannot initialize supertypes")
             map.put(INTERFACE_WITH_SUPERCLASS, "An interface cannot inherit from a class")
             map.put(FINAL_SUPERTYPE, "This type is final, so it cannot be inherited from")
+            map.put(CLASS_CANNOT_BE_EXTENDED_DIRECTLY, "Class {0} cannot be extended directly", SYMBOL)
             map.put(SUPERTYPE_IS_EXTENSION_FUNCTION_TYPE, "Extension function type is not allowed as supertypes")
             map.put(SINGLETON_IN_SUPERTYPE, "Cannot inherit from a singleton")
             map.put(NULLABLE_SUPERTYPE, "A supertype cannot be nullable")

compiler/testData/diagnostics/tests/enum/extendingEnumDirectly.fir.kt

@@ -1,9 +0,0 @@
-class Test1 : Enum<Test1>("", 0)
-
-class Outer {
-    class Test2 : Enum<Test2>("", 0)
-}
-
-fun outer() {
-    class Test3 : Enum<Test3>("", 0)
-}

compiler/testData/diagnostics/tests/enum/extendingEnumDirectly.kt

@@ -1,3 +1,4 @@
+// FIR_IDENTICAL
 class Test1 : <!CLASS_CANNOT_BE_EXTENDED_DIRECTLY!>Enum<Test1><!>("", 0)
 
 class Outer {

idea/idea-frontend-fir/src/org/jetbrains/kotlin/idea/frontend/api/fir/diagnostics/KtFirDataClassConverters.kt

@@ -351,6 +351,13 @@ internal val KT_DIAGNOSTIC_CONVERTER = KtDiagnosticConverterBuilder.buildConvert
             token,
         )
     }
+    add(FirErrors.CLASS_CANNOT_BE_EXTENDED_DIRECTLY) { firDiagnostic ->
+        ClassCannotBeExtendedDirectlyImpl(
+            firSymbolBuilder.classifierBuilder.buildClassLikeSymbol(firDiagnostic.a.fir),
+            firDiagnostic as FirPsiDiagnostic,
+            token,
+        )
+    }
     add(FirErrors.SUPERTYPE_IS_EXTENSION_FUNCTION_TYPE) { firDiagnostic ->
         SupertypeIsExtensionFunctionTypeImpl(
             firDiagnostic as FirPsiDiagnostic,

idea/idea-frontend-fir/src/org/jetbrains/kotlin/idea/frontend/api/fir/diagnostics/KtFirDiagnostics.kt

@@ -266,6 +266,11 @@ sealed class KtFirDiagnostic<PSI: PsiElement> : KtDiagnosticWithPsi<PSI> {
         override val diagnosticClass get() = FinalSupertype::class
     }
 
+    abstract class ClassCannotBeExtendedDirectly : KtFirDiagnostic<KtTypeReference>() {
+        override val diagnosticClass get() = ClassCannotBeExtendedDirectly::class
+        abstract val classSymbol: KtClassLikeSymbol
+    }
+
     abstract class SupertypeIsExtensionFunctionType : KtFirDiagnostic<KtTypeReference>() {
         override val diagnosticClass get() = SupertypeIsExtensionFunctionType::class
     }

idea/idea-frontend-fir/src/org/jetbrains/kotlin/idea/frontend/api/fir/diagnostics/KtFirDiagnosticsImpl.kt

@@ -408,6 +408,14 @@ internal class FinalSupertypeImpl(
     override val firDiagnostic: FirPsiDiagnostic by weakRef(firDiagnostic)
 }
 
+internal class ClassCannotBeExtendedDirectlyImpl(
+    override val classSymbol: KtClassLikeSymbol,
+    firDiagnostic: FirPsiDiagnostic,
+    override val token: ValidityToken,
+) : KtFirDiagnostic.ClassCannotBeExtendedDirectly(), KtAbstractFirDiagnostic<KtTypeReference> {
+    override val firDiagnostic: FirPsiDiagnostic by weakRef(firDiagnostic)
+}
+
 internal class SupertypeIsExtensionFunctionTypeImpl(
     firDiagnostic: FirPsiDiagnostic,
     override val token: ValidityToken,