[FE 1.0] Implement deprecation warning for private constructors of sealed classes

^KT-44866
^KT-49729 Fixed

compiler/frontend/src/org/jetbrains/kotlin/diagnostics/Errors.java

@@ -810,6 +810,8 @@ public interface Errors {
 
     DiagnosticFactory0<KtParenthesizedExpression> PARENTHESIZED_COMPANION_LHS_DEPRECATION = DiagnosticFactory0.create(WARNING);
 
+    DiagnosticFactory0<PsiElement> RESOLUTION_TO_PRIVATE_CONSTRUCTOR_OF_SEALED_CLASS = DiagnosticFactory0.create(WARNING);
+
     // Type inference
 
     DiagnosticFactory0<KtParameter> CANNOT_INFER_PARAMETER_TYPE = DiagnosticFactory0.create(ERROR);

compiler/frontend/src/org/jetbrains/kotlin/diagnostics/rendering/DefaultErrorMessages.java

@@ -450,6 +450,8 @@ public class DefaultErrorMessages {
 
         MAP.put(PARENTHESIZED_COMPANION_LHS_DEPRECATION, "Access to companion object through parenthesized class name is deprecated. Please, add explicit Companion qualifier.");
 
+        MAP.put(RESOLUTION_TO_PRIVATE_CONSTRUCTOR_OF_SEALED_CLASS, "Resolution to private constructor of sealed class. In future it will be allowed to use this constructor only inside declaring sealed class");
+
         MAP.put(LOCAL_EXTENSION_PROPERTY, "Local extension properties are not allowed");
         MAP.put(LOCAL_VARIABLE_WITH_GETTER, "Local variables are not allowed to have getters");
         MAP.put(LOCAL_VARIABLE_WITH_SETTER, "Local variables are not allowed to have setters");

compiler/frontend/src/org/jetbrains/kotlin/resolve/PlatformConfiguratorBase.kt

@@ -63,6 +63,7 @@ private val DEFAULT_CALL_CHECKERS = listOf(
     UnitConversionCallChecker, FunInterfaceConstructorReferenceChecker, NullableExtensionOperatorWithSafeCallChecker,
     ReferencingToUnderscoreNamedParameterOfCatchBlockChecker, VarargWrongExecutionOrderChecker, SelfCallInNestedObjectConstructorChecker,
     NewSchemeOfIntegerOperatorResolutionChecker, EnumEntryVsCompanionPriorityCallChecker, CompanionInParenthesesLHSCallChecker,
+    ResolutionToPrivateConstructorOfSealedClassChecker,
 )
 private val DEFAULT_TYPE_CHECKERS = emptyList<AdditionalTypeChecker>()
 private val DEFAULT_CLASSIFIER_USAGE_CHECKERS = listOf(

compiler/frontend/src/org/jetbrains/kotlin/resolve/calls/checkers/ResolutionToPrivateConstructorOfSealedClassChecker.kt

@@ -0,0 +1,30 @@
+/*
+ * Copyright 2010-2021 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.resolve.calls.checkers
+
+import com.intellij.psi.PsiElement
+import org.jetbrains.kotlin.config.LanguageFeature
+import org.jetbrains.kotlin.descriptors.ConstructorDescriptor
+import org.jetbrains.kotlin.descriptors.DescriptorVisibilities
+import org.jetbrains.kotlin.descriptors.isSealed
+import org.jetbrains.kotlin.diagnostics.Errors
+import org.jetbrains.kotlin.resolve.calls.model.ResolvedCall
+
+object ResolutionToPrivateConstructorOfSealedClassChecker : CallChecker {
+    override fun check(resolvedCall: ResolvedCall<*>, reportOn: PsiElement, context: CallCheckerContext) {
+        // If AllowSealedInheritorsInDifferentFilesOfSamePackage disabled then all sealed constructors are private by default
+        if (!context.languageVersionSettings.supportsFeature(LanguageFeature.AllowSealedInheritorsInDifferentFilesOfSamePackage)) return
+        if (context.languageVersionSettings.supportsFeature(LanguageFeature.UseConsistentRulesForPrivateConstructorsOfSealedClasses)) return
+        val descriptor = resolvedCall.resultingDescriptor as? ConstructorDescriptor ?: return
+        if (descriptor.visibility != DescriptorVisibilities.PRIVATE) return
+        if (!descriptor.constructedClass.isSealed()) return
+        val containingDescriptor = context.scope.ownerDescriptor
+        val receiver = resolvedCall.dispatchReceiver ?: DescriptorVisibilities.ALWAYS_SUITABLE_RECEIVER
+        if (DescriptorVisibilities.findInvisibleMember(receiver, descriptor, containingDescriptor, false) != null) {
+            context.trace.report(Errors.RESOLUTION_TO_PRIVATE_CONSTRUCTOR_OF_SEALED_CLASS.on(reportOn))
+        }
+    }
+}