FIR: add getter visibility and setter return type checks

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

@@ -1581,6 +1581,18 @@ internal val KT_DIAGNOSTIC_CONVERTER = KtDiagnosticConverterBuilder.buildConvert
             token,
         )
     }
+    add(FirErrors.GETTER_VISIBILITY_DIFFERS_FROM_PROPERTY_VISIBILITY) { firDiagnostic ->
+        GetterVisibilityDiffersFromPropertyVisibilityImpl(
+            firDiagnostic as FirPsiDiagnostic<*>,
+            token,
+        )
+    }
+    add(FirErrors.WRONG_SETTER_RETURN_TYPE) { firDiagnostic ->
+        WrongSetterReturnTypeImpl(
+            firDiagnostic as FirPsiDiagnostic<*>,
+            token,
+        )
+    }
     add(FirErrors.EXPECTED_DECLARATION_WITH_BODY) { firDiagnostic ->
         ExpectedDeclarationWithBodyImpl(
             firDiagnostic as FirPsiDiagnostic<*>,

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

@@ -1112,6 +1112,14 @@ sealed class KtFirDiagnostic<PSI: PsiElement> : KtDiagnosticWithPsi<PSI> {
         abstract val actual: KtType
     }
 
+    abstract class GetterVisibilityDiffersFromPropertyVisibility : KtFirDiagnostic<KtModifierListOwner>() {
+        override val diagnosticClass get() = GetterVisibilityDiffersFromPropertyVisibility::class
+    }
+
+    abstract class WrongSetterReturnType : KtFirDiagnostic<KtProperty>() {
+        override val diagnosticClass get() = WrongSetterReturnType::class
+    }
+
     abstract class ExpectedDeclarationWithBody : KtFirDiagnostic<KtDeclaration>() {
         override val diagnosticClass get() = ExpectedDeclarationWithBody::class
     }

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

@@ -1803,6 +1803,20 @@ internal class InitializerTypeMismatchImpl(
     override val firDiagnostic: FirPsiDiagnostic<*> by weakRef(firDiagnostic)
 }
 
+internal class GetterVisibilityDiffersFromPropertyVisibilityImpl(
+    firDiagnostic: FirPsiDiagnostic<*>,
+    override val token: ValidityToken,
+) : KtFirDiagnostic.GetterVisibilityDiffersFromPropertyVisibility(), KtAbstractFirDiagnostic<KtModifierListOwner> {
+    override val firDiagnostic: FirPsiDiagnostic<*> by weakRef(firDiagnostic)
+}
+
+internal class WrongSetterReturnTypeImpl(
+    firDiagnostic: FirPsiDiagnostic<*>,
+    override val token: ValidityToken,
+) : KtFirDiagnostic.WrongSetterReturnType(), KtAbstractFirDiagnostic<KtProperty> {
+    override val firDiagnostic: FirPsiDiagnostic<*> by weakRef(firDiagnostic)
+}
+
 internal class ExpectedDeclarationWithBodyImpl(
     firDiagnostic: FirPsiDiagnostic<*>,
     override val token: ValidityToken,